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Performance analysis of a floating photovoltaic covering system in an Indian reservoir

Performance analysis of a floating photovoltaic covering system in an Indian reservoir Floating photovoltaic (FPV) systems are one of the globally emerging technologies of renewable energy production that tend to balance the water–energy demand by effectively saving the evaporated water from reservoirs while generating electrical power. This study presents the performance analysis of a model FPV plant in an Indian reservoir. The Mettur dam reservoir located in Tamil Nadu, India with a hydroelectric power plant of 150-MW capacity is considered as a test case. The preliminary design of the FPV plant is proposed based on a detailed study of the key design elements and their suitability for Indian reservoirs. The proposed plant is numerically analysed for various tilt angles, mounting systems and tracking mechanisms in order to assess its potential power generation. A flat-mount system in landscape orientation was found to exhibit a high performance ratio. Further, a fixed-tilt FPV system with a panel slope of 10° and an FPV system with single-axis tracking were found to be suitable for the Mettur reservoir. Further, cost analysis of the FPV system is also presented along with the carbon-footprint estimation to establish the economic and environmental benefits of the system. The results show that the total potential CO saving by a FPV system with tracking is 135 918.87 t CO and it is 12.5% higher 2 2 than that of a fixed-mount FPV system. Received: 30 December 2020; Accepted: 4 March 2021 © The Author(s) 2021. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http:// creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 208 Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 209 Graphical abstract Evaportation in open water reservoirs Gaseous Increase in emissions from energy demand fossil fuels SOLUTION Perfomance analysis Floating model FPV system in photovoltaic Mettur reservoir with (FPV) hydroelectric po wer plant (HEPP) system in India Saves Hybrid FPV-HEPP Combiner 184589 m Prevention system results in box of water of indirect water Central PV modules from 135918.87 saving of 43.99 inverter Transformer Float pontoons evaporation 3.5 MW tons MCM every year every year power carbon Mooring production emission lines at during ther optimum lifetime Anchoring tilt angle Keywords: solar energy; floating photovoltaic system; evaporation loss; hydroelectric power plants With sunlight being the major source of energy pro- Introduction duction, power generation through PV panels is receiving Gaseous emissions due to energy production from fossil worldwide attention. Also, the availability of technically ad- fuels are polluting the atmosphere gradually, which not vanced silicon panels and a cost-effective way of generating only diminishes the purity of the air, but also affects power even in low-light conditions motivate consumers human health. The major pollutants from fossil-fuel com- for self-power generation. However, the unavailability of bustion are the greenhouse gases, which include carbon land for the installation of large-scale land-mounted PV dioxide, methane, benzene and nitrogen oxides. These systems is the major drawback. Thus, achieving the target are the major cause of global warming, air pollution and solar energy production just through land-mounted and water pollution []. 1 In order to combat climate change, rooftop PV systems is quite challenging. One of the alter - moving towards clean energy while generating afford- native solutions to compete with the target framed by the able electricity is necessary. Power generation through nation is FPV, also called floatovoltaics, a floating solar PV renewable energy sources (RES) plays a significant role in (FSPV) or a floating solar covering system (FSCS) [6–8]. This transforming the fossil-fuel-based power sector towards new emerging technology in which the solar panels are zero-carbon green energy by the production of solar, wind, placed on the water surface of ponds, lakes, lagoons, res- hydro and geothermal power []. 2 As per the statistics pro- ervoirs and oceans shows increased efficiency compared vided by the International Renewable Energy Agency, the to land-mounted PV systems [9]. The other significant en- global renewable-energy-generation capacity increased by vironmental impact of placing PV panels on the water is 7.40%, which is equal to 176 GW, from 2018 to 2019 []2 . the reduction in evaporation, which helps in saving fresh- The growth of renewable energy production is spectacular water for domestic and agricultural purposes [10]. Studies particularly in India, where a 27% increase in renewable revealed that covering the water surface has the potential energy production has been achieved in recent years, of to mitigate water loss through evaporation by ≤90% [11]. which 43% is accounted for by the solar photovoltaic (PV) This highly efficient technology had faced real-time imple- sector [3]. The launch of the Jawaharlal Nehru National mentation since 2007; from then, it has shown dramatic Solar Mission (JNNSM) has remarkably increased the de- growth with increased efficiency [12]. ployment of PV systems and resulted in 32.53 GW solar India has a large number of reservoirs and natural and energy production, making the nation the fourth-largest artificial lakes. Due to global warming, the drastic increase generator of renewable energy []. 4 By 2022, JNNSM has a in temperature has increased water loss in open reservoirs target of 175 GW renewable energy production, with 100 due to evaporation [13]. This also affects the hydroelectri- GW from the solar sector as per the report by the Solar city yield from a hydroelectric power plant (HEPP), which Energy Corporation of India (SECI) [5 ]. Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 210 | Clean Energy, 2021, Vol. 5, No. 2 relies mainly on the water stored in the reservoirs. Rather drinking purposes for the district of Salem. Potential evapo- than innovative systems and technologies to reduce transpiration is calculated using Hamon’s method to as- water evaporation, the current need is a simple existing sess the water loss from the reservoir. The model FPV plant system with additional advantages. The FPV technology is designed for a lesser reservoir coverage area to avoid will address this issue in a better way by increasing solar hindrance to the hydropower generation and to maintain power production and preserving the water for future use. water quality. The system is also designed with suitable By deploying FPV in reservoirs with a HEPP, the total en- spacing between every row of the FPV array to maintain ergy output adding to the hydroelectricity can be increased positive ecosystem services [18]. The effects of variation considerably [10]. Studies also confirmed that covering <3% in tilt angle, tracking mechanisms and mounting mechan- of the global reservoir water surfaces can considerably in- isms of the model FPV plants are assessed in detail. In add- crease the power generation from a HEPP to 395.90% with ition, the carbon footprint and cost of the FPV system are 4800 full load hours (FLH) [14]. Thus, installing FPV as the also calculated to understand the environmental and eco- cover system will be helpful in balancing the water–energy nomic feasibility of this technology. Finally, the benefits of demand in water-limited arid and semiarid regions, as it a hybrid HEPP–FPV is assessed by calculating the direct and has been roughly estimated that each MWp can save 25 000 indirect water savings in the reservoir and the FPV model cubic metres of water annually [15]. Experimental investi- plant is compared with the existing FPV plants in India. gations have also proved that the FPV system is technic- As Tamil Nadu Generation and Distribution Corporation ally feasible and economically viable for even covering the (TANGEDCO) is planning to deploy a 100-MW FPV plant in total water surface area of a reservoir [16]. However, the the Mettur reservoir, the key design parameters suggested implementation of large-scale FPV systems covering en- in this study can aid during the design and implemen- tire reservoir surfaces restricts the incoming irradiation to tation stages of the project. The simplified methodology the water body that eventually degrades the water quality followed in the study will also support in assessing the and ecology. Further, the implementation of a large-scale overall performance of FPV plants to be deployed in any FPV system requires minimum water storage in a reservoir reservoir all over the world. to avoid stranding [17]. Thus, considering the hydropower generation and water quality of the reservoir, less reser - 1 Effects of evapotranspiration on voir coverage should be considered during the design of freshwater sources in India FPV systems. In the last two decades, per-capita water availability /(m The cumulative capacity of FPV projects in India has capita/year) has been continuously deteriorating in India. reached 2.70 MW recently and the country aims at produ- Due to the exponential increase in the population and cing 1721 MW of renewable energy through the projects acquisition of water-flow and storage areas for building of the SECI, National Thermal Power Corporation, National construction, freshwater sources are diminishing rapidly Hydroelectric Power Corporation and state-level distribu- in India, which in turn results in high water scarcity in tion companies and city-development authorities [6 8, ]. summer. In addition, the country experiences an annual The first FPV system in India was commissioned in the global horizontal irradiation ranging from 5.0 to 6.0 kW/ year 2014, with 10-kW capacity in West Bengal, following m and rainfall only for 3–4  months in a year. This arid which the implementation of this technology had scaled climatic condition leaves the country experiencing acute up every year to a present cumulative capacity of 2.70 MW freshwater shortages [19]. [2, 6]. According to the combined analysis from the Indian Over the past 100 years, carbon emission from burning Energy Transition Commission (ETC) and the Energy and fossil fuels has adversely increasing the global tempera- Resource Institute (TERI), water bodies with a surface area ture, which in turn increases the potential evapotrans- of ~18  000 km across the states and union territories of piration [19]. Out of 4000 km of water received through India have the potential to implement 280 GW of FPV precipitation in India, 700 km of water are lost through systems [6]. The cumulative tender announced by the evaporation [20]. The evapotranspiration reaches almost Government of India during 2019 for the FPV installations 1000 mm/year in the southern states of India such as Tamil with 1700-MW capacity is in the developmental stage in Nadu and Kerala [21]. These regions are undergoing acute different states of the country. Considering the scope of water scarcity during the lean seasons due to evapor - massive development in this sector, it is mandatory to in- ation loss of water and diminishing water resources. This vestigate the overall performance of the FPV systems as can be clearly seen from the reduction in the per-capita a reservoir cover to arrive at an environmentally friendly availability of water in India from 1950 to 2050 listed in design solution. Table 1 [22]. This also highlights the necessity to conserve In this context, the present study aims at assessing the diminishing freshwater sources like river basins, canals, electrical performance of the FPV model in an Indian res- dams and reservoirs to prevent the larger part of India ervoir. The Mettur dam reservoir with hydroelectric power from ‘water-stressed’ conditions (<1700 m /capita/year) in plants in Tamil Nadu is selected as a test case. The selected the future [19]. reservoir is the major source of water for irrigation and Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 211 Table 1: Per-capita availability of water resources in India [22] Combiner box Annual Per-capita water Average water freshwater Central PV modules 3 3 availability (m / resources (m / requirement inverter Transformer Float pontoons Year capita/year) person/year) (km ) 1951 5177 3008 580–604 Mooring 2001 1820 1283 694–710 lines 2025 1341 814 784–850 2050 1140 687 973–1180 Anchoring The increase in temperature and evapotranspiration Fig. 1: Key design elements for power generation through an FPV is also indirectly affecting hydropower generation in the system [25, 26] country. Hydroelectricity is an efficient source of energy that relies on the amount of water in natural and human- (FRP), high-density polyethylene (HDPE), medium-density made reservoirs, and it is highly advantageous to meet polyethylene (MDPE), polystyrene foam, hydro-elastic instant power-demand fluctuations. As the hydrologic floating membranes or ferro-cements to provide enough and atmospheric water balance is based on the evapo- buoyancy and stability to the total system. Anchoring the transpiration, this water balance is disturbed due to the floating deck with a proper technique is essential for an seasonal rise in temperature, which in turn restricts the FPV system, as the drift in the water level and the action supply of power by a HEPP when the requirement is high. of the wind load can damage the floating platform and the Thus, the increase in the rate of evaporation makes the mooring cables [29, 30]. Various types of mooring systems HEPP system fail in its prime incitement. In this con- suggested for FPV plants include the gravity type, anchor- text, instead of increasing the number of HEPPs, the tension type, semi-rigid type, tension type and modified researchers rely on economical methods to reduce the type [31]. The type of the mooring system is selected based evaporation rate and it has also been found experimen- on the water level and soil type at the location. tally that the implementation of FPV in reservoirs with Further, mechanisms to track the PV panels towards HEPPs aids in increasing hydroelectricity generation by the Sun will increase their power-generation capacity. reducing the water loss due to evaporation [23]. Thus, Accurately focusing the solar radiation perpendicular the installation of FPV plants in Indian reservoirs can be to the PV panels either by a single- or dual-axis tracking seen as a promising solution to all these adverse issues. mechanism will enhance the power density and the effi- ciency of the PV modules. Single-axis tracking is widely used in FPV systems globally, in which the entire desk 2 Overview of key design elements of an with a diameter of <30 m is rotated to receive maximum FPV system radiation [14]. The same mechanism is used in the 500-kW In order to avoid the land acquisition for PV projects, the FPV system in Wayanad, India, where the floating desk is idea of installing PV panels on water resources emerged rotated four times a year by altering the anchoring pos- in the year 2007 and there is an evident growth in this ition [32]. The major disadvantage of the tracking systems technology all over the world due to its significance [24]. is their high cost, as this accounts for 25% of the total cost Apart from the special arrangements required to make of the system, even though it can increase the yield by 25% the system float on the water surface, the FPV system is [14]. In addition, power generation may also be affected quite similar to the conventional PV system. The main due to shading and wind effects when the trackers act all parameters required to design a suitable FPV plant for any day. Also, the installation of dual-axis tracking systems water-storage system includes the type of PV panel, slope makes the FPV system unstable under the action of rela- direction of panels, meteorological conditions of the site, tively modest wind speeds, which tend to cause twisting of support system and moorings. The major key design elem- the mooring lines [9]. ents of FPV systems are shown in Fig. 1. The mounting of PV panels is one of the important Among the different types of PV panels, polycrystal- design factors in determining the amount of radiation line (PC) silicon panels are highly effective for large-scale incident perpendicularly on the fixed solar module solar power production. Recent studies also confirmed throughout the day. Through proper site inspection, the ability of PCs to withstand different environmental the position and direction of the panel can be pre- conditions and the production of a high power output determined in order to track the high-intensity radiation [27, 28]. PCs are also used in the recently deployed FPV for maximum sunlight hours. To further increase the systems in Wayanad and Vishakhapatnam in India. PV power output, tilting of the panels in a suitable direction panels are placed on a floating structure called a pon- is necessary, through which more solar radiation can be toon, which is usually made up of fibre-reinforced plastic captured. It is the key factor that determines the energy Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 212 | Clean Energy, 2021, Vol. 5, No. 2 efficiency per unit area of the panel and the size of the of Salem. It also plays a major role in preventing the area floating deck. As India is in the northern hemisphere, from drought-prone conditions in lean seasons. The view a panel facing in the southern direction (with 180° azi- and geographical location of the Mettur dam reservoir are muth) will improve the radiation interaction and eventu- shown in Fig. 2 [13, 36]. ally increase the output energy of the FPV array [33]. The The dam has a tunnel powerhouse of 200-MW capacity action of waves around the edges of the floating surface and a dam powerhouse of 50-MW capacity. In addition, will tend to move the floating platform [3435 , ]. In this the downstream water gets diverted into four pow -er case, the cables connecting the PV array on the floating houses called lower Mettur hydroelectric power projects desk to the inverters should be provided with sufficient with a total capacity of 120-MW power generation, owned length to withstand this extension. In the 500-kW FPV and operated by Tamil Nadu Generation and Distribution system in Wayanad, India, submerged-type cables are Corporation (TANGEDCO). The details of the HEPPs in the being used to transmit the generated power to the sub- Mettur dam are listed in Table 2. Full power generation of 50 station and floating cables are used in the 2-MW FPV MW from the dam powerhouse can be achieved only when system in Vishakhapatnam, India [6 ]. the water level of the dam is >27.50 m and the power gen- eration from the tunnel powerhouse is possible only when the water level is >16.80 m [36]. The power generation is highly affected when the water inflow is lower, especially 3 Case study in summer during the months of May, June and July. 3.1 Details of study area The hydropower generated from the Mettur HEPP from 2011 to 2019 is shown in Fig. 3. The lowest energy yield is The following section presents the prospects of installing observed during 2016 and the same year is recorded as FPV plants in Indian reservoirs through a detailed per - India’s hottest year of the decade as per the report from formance analysis of an FPV model system in one of the the National Oceanic and Atmospheric Administration existing reservoirs in India. The Mettur dam reservoir (NOAA) [38]. This shows that an increase in the irradiance (Stanley reservoir) in the Salem district of Tamil Nadu, level increases the evaporation rate of the reservoir and India is considered as the test case. The Mettur dam, with drastically affects the net power-generation output from a total height 65 m and length 1.70 km, was built across the HEPP due to less water inflow. Apart from this, the old the river Cauvery in 1934 with a reservoir surface area of equipment and the algal bloom also obstruct the power 42.5 km [36]. The water stored in this largest reservoir in generation. Thus, a reduction in the evaporation rate in the Tamil Nadu is used for hydroelectricity production, irriga- reservoir is highly important to meet the water–energy de- tion and drinking purposes. This has been the main source mand during the summer season and to increase hydro of water for 1096.70 km of farmland around the district TAMIL NADU INDIA SALEM District Boundary State Boundary Taluk Boundary 77°44'0''E 77°52'0''E Legend Locations Highways Reservoir 77°44'0''E 77°52'0''E Fig. 2: Index map of Mettur dam reservoir [37] 11°48'40''N 11°56'50''N 11°48'40''N 11°56'50''N Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 213 Table 2: Hydroelectric power plants in Mettur dam [13, 36] Power-generation Number of Total capacity Power plants capacity (MW) turbine units (MW) Mettur dam powerhouse 12.5 4 50 Mettur tunnel powerhouse 50 4 200 Lower Mettur barrage Powerhouse—I/Chekkanur 15 2 30 Lower Mettur barrage Powerhouse—II/Nerinjipettai 15 2 30 Lower Mettur barrage Powerhouse—III/Kuthirai kalmedu 15 2 30 Lower Mettur barrage Powerhouse—IV/Uratchikottai 15 2 30 2011–12 2012–13 2013–14 2014–15 2015–162016–17 2017–18 2018–19 Fiscal year Fig. 3: Power generation from Mettur hydroelectric power plant from 2011 to 2019 [39] 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year Fig. 4: Daily variation in temperature at Mettur dam from 2010 to 2019 power generation. The implementation of FPV plants in on water bodies is the evapotranspiration, which is the the Mettur reservoir in integration with a HEPP will not sum of the evaporation and transpiration occurring on the only increase the share of renewable energy production in surface. This needs to be estimated accurately for water- the nation, but also fulfil the power energy demand of the resources management. Due to the difficulties associated surrounding locations throughout the year. with the direct estimation of evapotranspiration, potential evapotranspiration (PET) is commonly used to calculate the evapotranspiration occurring from a specific surface 3.2 Potential evapotranspiration in the Mettur with unlimited water supply or from surfaces that are reservoir completely covered with water (like lakes and reservoirs). PET is a useful measure to identify the atmospheric water The meteorological data required for the study were demand of a particular region under study. Further, it also collected from NASA (Prediction of Worldwide Energy helps in understanding the impact of climate change and Resource) for the period 2010–19 [40], from which water loss other human-made installations on water bodies [41]. PET through evaporation over the years is assessed. The tem- is affected by various meteorological conditions and it is perature variation in the Mettur reservoir is shown in Fig. usually measured indirectly from other climate factors 4. An increase in temperature can be clearly seen during such as air temperature, wind speed and solar radiation. the summer (April, May and June) every year. The max- It is usually expressed in depth per unit time (mm/day imum recorded temperature and irradiance are 34.98°C or m/year) and it can be considered as an upper limit of and 7.56 kW/m /day, respectively. One of the important evapotranspiration. parameters that shows the impact of high temperature Temperature (degree celcius) Net power generation (GWh) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 214 | Clean Energy, 2021, Vol. 5, No. 2 In order to predict the water loss in the Mettur reservoir, of the reservoir. Thus, considering the prevailing risks as- daily PET is calculated. Many conventional methods to es- sociated with water-quality management and the eco- timate PET, derived based on the geographical conditions system, the area of the FPV system is considered to be of the location, are available in the literature. One of the <30%. Since the energy generation and water savings are commonly used methods is Hamon’s method, which is a directly connected to the percentage of coverage, the area simple methodology with acceptable accuracy. It is used in of the model FPV plant is chosen close to the existing FPV the present study to estimate PET at the Mettur reservoir. plant in Mudasarlova reservoir in India. This constitutes According to Hamon’s method, PET (mm/day) is expressed ~0.13% of the total reservoir area. using the following relationship [42]: As the initial step, various design solutions to identify the optimum orientation and tilt of the panel to get max- k ∗ 0.165 ∗ 216.7 ∗ N ∗ e imum energy yield are analysed in detail. The potential of (1) PET = T + 273.3 the proposed FPV models is then assessed using a quality factor called the performance ratio (PR), which describes where k is the proportionality coefficient (equal to 1.2), N the potential of FPV systems through the total potential is the daylight hours and e is the saturated vapour pres- energy connected to the grid, which is calculated using the sure at air temperature, T. The daily PET calculated from following expression: the above expression for the Mettur dam is shown in Fig. 5. The maximum value of daily PET obtained was 16.88 mm/ PR = (2) day during the summer of 2016. The minimum value of I POA P × OUT STC the daily evaporation rate is 6.21 mm/day, and thus a min- 5 3 where, E represents the total energy supplied to the grid imum of 9.53  × 10 m of water was lost due to evapor - G (kWh), P is the total power output from the FPV system ation every day during the last 10  years from the Mettur OUT Ä ä kW (kW), I is the plane of array irradiance , and I is the reservoir. POA m STC Ä ä kW From the daily PET at the Mettur dam, the annual evap- irradiance under standard test conditions STC = 1000 . oration rate is calculated and the results are shown in Fig. In the proposed FPV system, PV modules are placed at 6. The maximum value of an annual evaporation rate of a height of 0.3–0.5 m (including the height of the pontoon 3958.74 mm/year is obtained during the year 2016, followed structure) from the water surface. A polycrystalline-type by 3877.46 mm/year in 2019. It is also important to note the PV module of dimensions 196 × 99  × 4  cm and weight increasing trend in the evaporation rate from 2010 to 2019 22.5 kg coated with tempered glass of 3.20 mm and pon- and thus a further increase may be expected in the coming toons made up of MDPE that can support two PV panels years. This highlights the necessity for evaporation-control is considered. The system is designed with a row-to- measures in the Mettur reservoir, which acts as a main row spacing of 0.5 m, necessary for catwalks, and the source of water for drinking and irrigation purposes. modules are placed 0.01 m apart. The output power de- livered by the FPV array is carried through 10 American Wire Gauge copper wires and connected to inverters 3.3 Proposed FPV system for the Mettur to generate AC power. A  string inverter is used in the reservoir FPV model to connect the PV modules in a row. Module- The percentage of FPV system coverage on the reservoir level power electronics systems like power optimizers should be <30% to preserve the water ecology and to avoid are not required in the present system, as the shading losses in hydropower revenues [17]. Large-scale implemen- losses are highly reduced by placing the FPV modules tation covering a greater portion of the reservoir with an in open reservoirs. The system is kept in position using FPV system reduces air–water fluxes and creates physical, the pile-anchoring system. The above-mentioned de- chemical and biological effects on the surface meteorology sign elements of the proposed FPV model in the present 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year Fig. 5: Daily potential evapotranspiration (PET) at Mettur dam from 2010 to 2019 Potential evapotranspiration (mm/day) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 215 Annual average value Linear (Annual average value) 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year Fig. 6: Annual average evaporation rate at Mettur dam from 2010 to 2019 AB Fig. 7: Schematic diagram of the FPV model in Mettur reservoir (a) Location of the FPV system and (b) top view showing the orientation of the panels. study are selected based on its suitability for imple- year of the given location. For the estimation of real-time mentation along with detailed investigation of the ex- power generation for the solar conversion systems, the isting FPV plants in India. The schematic diagram of the irradiation weather file data of the Mettur reservoir from proposed FPV model is shown in Fig. 7. Initial investi- 2010 to 2020 is uploaded in the condition sets of the soft- gations are carried out to assess the suitable PV-panel ware Helioscope [47]. Additionally, the horizontal profile arrangement such as square, rectangle and octagon. of the location over the period of time is obtained from The results show that the octagonal pattern of placing photovoltaic geographical information system (PVGIS) in PV arrays is capable of effectively accommodating the TMY format and uploaded in the condition set to estimate maximum number of PV panels and also provides max- the shading pattern and its associated losses [43]. imum energy yield in both landscape and portrait orien- The other important parameters required in the calcu- tations. Further, this system is found to be feasible while lation of irradiance are the solar angles and surface angles. adjusting the mooring system according to the variation Solar angles include the declination angle (δ), solar eleva- in the reservoir water level and also results in reduced tion angle (α), hour angle (ω), surface azimuth angle (Z) and mooring forces when designed effectively. Detailed ana- solar zenith angle (ϕ), whereas surface angles include the lysis with different FPV system patterns is out of the collector azimuth angle (), Z tilt angle (β) and angle of in- scope of the present investigation. cidence (θ). The variation in the solar elevation angle (α) to the azimuth angle (Z) is useful to predict the length as well as the position of simple shadows like trees, hills, 3.4 Performance analysis poles and buildings lying between the path of the incident The total energy generated by an FPV system with the Sun rays and the panel in the location of the FPV plant. aforementioned design requirements is simulated using The Sun-path diagram determined from these surface- the commercial software Helioscope. For analysing the oriented solar angles helps in identifying the shadows in a annual energy generated from the FPV system, the esti- particular location. The Sun-path chart for the Mettur res- mation of irradiation levels at the location is the initial ervoir in artesian coordinates with hours in Local Standard step. Irradiance can be Direct Normal Irradiance (DNI), Time throughout the year is shown in Fig. 8. Global Horizontal Irradiance (GHI) and Diffuse Horizontal Shading loss due to trees is negligible in water- irradiance (DHI). In order to measure the total irradiation mounted PV systems. The horizon of the PV array is de- incident on the horizontal surface, the GHI, DHI and DNI fined by the solar azimuth angle at a particular location. data for the Mettur reservoir location from 2010 to 2019, Horizontal data of the FPV system with the south-facing obtained from NASA databases in typical methodological PV modules for the Mettur dam were obtained from year format (TMY), are used [40]. TMY is a set of ground- PVGIS and the profile are shown in Fig. 9. The maximum based meteorological data with values for every hour in a horizon height is observed at +90°. This shows that the Evaporation rate (mm/day) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Apr 20 Aug 22 May 21 Jun 21 Jul 21 Jun 21 Sep 22 Oct 21 Mar 20 Nov 21 Dec 21 Dec 21 Feb 20 Feb 20 Jan 21 216 | Clean Energy, 2021, Vol. 5, No. 2 90° (c) Univ. of oregon SRML Sponsor: ETO Lat: 11.78, Long: 77.8 (Standard) time zone: 5.5 80° Sun path diagram Mettur dam 1 PM 70° 11 AM 2 PM 60° 10 AM 12 PM 3 PM 50° 9 AM 40° 4 PM 30° 8 AM 5 PM 20° 7 AM 6 PM 10° 6 AM 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° East Solar azimuth West 90° (c) Univ. of oregon SRML Sponsor: ETO Lat: 11.78, Long: 77.8 (Standard) time zone: 5.5 80° Sun path diagram Mettur dam 1 PM 70° 11 AM 2 PM 60° 10 AM 12 PM 3 PM 50° 9 AM 40° 4 PM 30° 8 AM 5 PM 20° 7 AM 10° 6 PM 6 AM 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° East Solar azimuth West Fig. 8: Sun-path diagram for Mettur dam (a) between solstices from December to June and (b) between solstices from June to December [44]. 5 8 11 2 23 1 67 13 –180 –150 –120 –90 –60 –30 0 30 60 90 120 150 180 Solar azimuth angle (degrees) Fig. 9: Horizontal profile of Mettur reservoir Jul 21 Jun 21 Jun 21 May 21 Solar elevation Solar elevation Horizon height (degrees) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 217 losses from the south-facing PV panels are compara- temperature drops with the wind speed, T is the cell tively lower than those of other orientations. The row- temperature (°C), 𝐸 is the reference solar irradiance on to-row shading can be minimized by providing spacing the PV module (1000 W/m ), WS is the wind speed (m/s) between the individual PV panels and adjacent rows of and Δ𝑇 is the temperature difference between the module panels, and by placing the panels with a minimum tilt and the cell at 𝐸 . angle. Even though the bottom edge of the second row of the PV array will be obstructed by the first row of the PV array, the reflected radiance on the shaded area will 4 Results and discussions help in reducing the losses. The location of the FPV in 4.1 Effect of tilt-angle variation the Mettur reservoir is selected accordingly to avoid the shadow cast by the nearby trees and mountains. The In order to find the optimum tilt angle for the south- possibility of obstruction shadows by the reservoir em- oriented panels of the FPV model, the performance of the bankment on the FPV array may occur only when the system is analysed by varying the tilt angle from 0° to 89° reservoir is empty or <50% of its full water capacity. with 10-degree intervals. The panels are positioned par - The transposition model is used to convert the available allel to the water surface at a 0° tilt angle and the analysis meteorological irradiation data incident on the horizontal is carried out up to 89°. A tilt angle of 90° is not considered surface to the irradiation data incident on the surface in- due to the well-known shading losses associated with clined at a particular angle. The Hays model is used to this position. The results of the performance analyses are calculate the diffuse radiation incident on the solar PV in- listed in Table 3. The results show that the number of mod- clined at an angle [45]. Finally, the reflected radiation in- ules, FPV power output and shading losses increases and cident on the tilted solar module is calculated using the the FPV energy output decreases with the increase in the albedo coefficient (α ) of the location, which is the unitless tilt angle. measure of the amount of irradiance reflected by the sur - The variations in the power and energy of the FPV face. In India, the albedo coefficient for the water reservoir system with varying tilt angles are shown in Fig. 10a. It varies from 0.16 to 0.19 [46]. The local ambient temperature can be clearly seen that the increase in the tilt angle of the variation and wind speed of the location impact the tem- panels increases the FPV power output from 3440 to 7229.5 perature loss of the FPV system. Further, the temperature kW/year, whereas the FPV energy output increases up to a losses also depend on the variation in the airflow under 20° tilt angle and then decreases. Increasing the tilt angle the PV panel based on the type of racking used. The PV cell of the panel shrinks the area covered by each panel consid- temperature is calculated according to the performance erably, which provides room to deploy panels additionally model given by Sandia National Laboratories using the fol- in the total available area. Thus, a large number of PV mod- lowing mathematical equations [47]: ules can be placed in the available area and this results in (a+b∗WS) an increase in the FPV power with the increase in tilt angle. (3) T = E ∗ e + T M A The FPV energy at a 89° tilt angle is 38% less than the en- ergy at a 20° tilt angle. This occurs due to the increase in T = T + ∗ΔT (4) C M the row-to-row shading of panels leading to a non-uniform panel of array (POA) irradiance at higher tilt angles. The where T is the module temperature (°C), T is the am- M A variation in shading and temperature losses for different bient air temperature (°C), is the solar irr 𝐸 adiance inci- tilt angles is shown in Fig. 10b . The maximum shading loss dent on the module surface (W/m), α is the empirically of 39.10% is observed at a 89° tilt angle, whereas a com- determined coefficient for the upper limit of the module paratively less significant variation in the temperature loss temperature at low wind speed, is b the empirically de- is observed with an increase in the tilt angle. termined coefficient for the rate at which the module Table 3: Performance of the FPV system in Mettur reservoir under varying tilt angles Tilt FPV power FPV energy FPV potential POA irradiance Number of Shading Temperature (degrees) (KW) (MWh/year) PR (%) (kWh/kW) (kW/m ) modules loss (%) loss (%) 0 3440 5586 80.7 1625 2016.5 13 742 0.01 9.3 10 3472 5799 80.4 1670.3 2078.4 13 888 0.4 9.6 20 3564 5939 79.6 1666.2 2092.9 14 258 1.5 9.6 30 3707 5932 77.7 1600.1 2059.4 14 258 3.9 9.5 40 3936 5906 75.9 1500.2 1977.1 15 746 6.2 9.2 50 4258 5689 72.3 1336.4 1849.0 17 032 10.8 8.6 60 4689 5376 68.3 1148.3 1608.8 18 758 15.4 7.9 70 5299.5 4897 62.4 924.0 1479.0 21 198 22.1 7.1 80 6153.5 4334 55.7 704.3 1263.8 24 614 29.5 6.2 89 7229.5 3675 46.9 508.0 1083.9 28 918 39.1 5.2 Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 218 | Clean Energy, 2021, Vol. 5, No. 2 A 10 000 B FPV power (kW) Shading loss FPV energy (kWh) Temperature loss 4000 20 2000 10 0 0 0 10 20 30 40 50 60 70 80 90 01020304050 60 70 80 90 Tilt angle (Degrees) Tilt angle (Degrees) × 10 CD 2.7 2.4 2.1 1.8 1.5 1.2 40 01020304050 60 70 80 90 01020304050 60 70 80 90 Tilt angle (Degrees) Tilt angle (Degrees) Fig. 10: Effect of tilt-angle variation on the performance of the FPV model (a) Power and energy output, (b) losses, (c) number of modules and (d) performance ratio. The number of panels required for the FPV system in- and carport mounting systems to identify the best FPV creases by 50% with the increase in the tilt angle from 0° model system for better output in the Mettur reservoir. In a to 89° as seen from Fig. 10c, which will result in increased flat-mount type of racking system, the PV modules are ar - cost of the system. Thus, considering the number of ranged at a fixed tilt angle on a flat surface. Each module in panels required and the yield of the FPV system, it is ad- the array is arranged with sufficient row spacing between vantageous to position the panels with a lower tilt angle. them to reduce the shading losses. Also, the space behind Further, the PR of the FPV system is also high for the the PV panel in this type of arrangement ensures good ven- lower tilt angles, as seen from Fig. 10d. In addition, the tilation that results in less temperature loss even at high lower tilt angle of panels also results in high PV poten- temperatures. In flush-mount racking, the PV modules are tial. This will tend to reduce the magnitude of the drag placed in such a way that the tilt angle is equal to the in- force acting on the PV array and thus avoids damage clination of the surface with zero row spacing. Therefore, to the panels due to high winds. A  lower tilt angle also losses due to shade from adjacent panels can be effectively helps in reducing the evaporation rate in the reservoir neglected whereas the absence of any space between the and provides evaporative cooling to maintain the panel modules and the surface leads to poor ventilation and in- temperature. Thus, a tilt angle of 10° has been identified creased temperature loss. In an East–West type of racking as being more suitable for this FPV model in the Mettur system, PV panels are positioned at 90° and 270° at an reservoir due to its good electrical, structural and oper - azimuth angle of 180°. The row, module, frame and peak ational performances. spacing of the panels in this dual-tilt racking arrangement provides sufficient ventilation to each module in the PV array. Thus, lower temperature and shading losses of the 4.2 Effect of panel orientation and system provide higher energy yield than flat- and flush- mounting systems mount racking. In a carport mounting type, the entire PV The performance of the proposed model is then analysed array is placed at a particular tilt angle to the flat sur - by varying the orientation of the panels and the mounting face area without row spacing. Thus, the panels arranged systems, by maintaining the optimum tilt angle of 10°. in a carport type of racking is similar to the flush-mount Portrait and landscape orientations of the panels are con- racking system with reduced temperature losses equal to sidered along with flat-mount, flush-mount, East–West those of the flat-mount racking system [47]. The schematic Output Number of modules Performance ratio (%) Loss (%) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 219 AB C Fig. 11: Schematic diagram of FPV models with different mounting systems (a) Flat mount, (b) East–West and (c) carport and flush mount. Table 4: Performance of the FPV model under varying orientations and mounting systems FPV power FPV energy FPV potential Number of Orientation Mounting system (KW/year) (MWh/year) PR (%) (kWh/kW) modules Portrait Flat-mount 4138.5 6909.9 80.3 1669.5 16 554 Flush-mount 4140.0 6325.0 73.5 1528.3 16 654 East–West 5240.0 7866.6 76.2 1506.6 20 968 Carport 3460.0 5820.0 80.2 1683.6 16 554 Landscape Flat-mount 3380.0 5155.0 73.4 1526.0 13 822 Flush-mount 3380.0 5645.0 80.4 1671.7 13 822 East–West 3730.0 6973.0 76.2 1502.4 18 564 Carport 3460.0 5818.0 80.4 1683.6 13 822 diagrams of different mounting systems considered in the East–West and carport-mount systems, respectively. present study are shown in Fig. 11. However, the variation in PR of the FPV systems under Carport and flush-mount structures are common in different orientations is not similar to the trend ob- land-based fixed PV systems; however, these structures served in FPV power and energy outputs. The PR of the have not been practically used or theoretically analysed in flat-mount system in portrait orientation is higher than a water-based fixed PV system [48–50]. These systems are that of landscape orientation by 8.60%, but the value is included in the present study to understand the tempera- less in the case of a flush-mount system. The variation ture and shading losses in the systems. The geometry of in PR between the landscape and portrait orientations the carport structure is configured according to the orien- under other mounting systems is found to be negligible. tation of the PV array and the optimal angle of the slope is Despite the high FPV power and energy output of the identified using the PVGIS application [43]. The perform- East–West mount system, its PR is comparatively lower ances of the FPV model under varying orientations and due to the requirement for a large number of PV modules. mounting systems are listed in Table 4. Portrait orientation In the case of the flush and carport mounts, these systems of the panels results in higher power output compared to are specialized types for PV models in rooftops with slopes. landscape orientation. Under portrait orientation, the max- They may not be highly advantageous when implemented imum power output of 5240 kW/year is obtained from the in FPV models due to the increase in the distance between East–West mounting system, followed by flush-mount and one side of the FPV array and the water surface, which af- flat-mount systems with an almost equal power output of fects the uniform cooling effect on the panels and thereby 4140 kW/year. The same trend is also observed under land- affects the overall panel efficiency. Considering the overall scape orientation. performance of FPV model cases, the flat-mount FPV A comparison of FPV power, energy and PR under dif- system was found to be the most suitable for the Mettur ferent conditions considered in the study is shown in reservoir. Though there exists a significant difference in Fig. 12. The FPV power produced using the East–West the PR of the portrait and landscape orientations of flat- mounting in landscape orientation is 28.80% less than mount systems, the variation in the FPV potential is only that in portrait orientation. In the case of the flat-mount 8.50%. From an economic perspective, a flat-mount system and flush-mount systems, the power reduction in land- with landscape orientation will be advantageous due to scape orientation is ~18%. The power output remains the the smaller number of modules required. same under both orientations when carport tracking is used. The FPV energy output of the portrait orientation 4.3 Effect of tracking mechanisms is higher than that of the landscape orientation under FPV systems with tracking mechanisms tend to result in all mounting systems, with variations of 25.40%, 10.75%, high energy yield compared to fixed-tilt FPV systems in 11.35% and 0.03% under flat-mount, flush-mount, Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 220 | Clean Energy, 2021, Vol. 5, No. 2 Portrait Landscape Portrait Landscape 6000 10 000 8000 1 1 2 2 3 4 4 4 4 1 2 1 0 0 Flat Flush East West Carport Flat Flush East West Carport Mounting system Mounting system Portrait Landscape 1 2 4 4 3 3 1 2 Flat Flush East West Carport Mounting system Fig. 12: Performance of the FPV model with varying panel orientations and mounting systems Table 5: Performance of the FPV system with and without tracking POA FPV power FPV energy FPV potential irradiance Number of Shading Temperature Orientation Tracking (KW/year) (MWh/year) PR (%) (kWh/kW) (kW/m ) modules loss (%) loss (%) Portrait Single-axis 3459 6713 79.2 1937.6 2447.2 13 858 2.4 10.6 Fixed 3472 5851 81.1 1685.2 2078.4 13 888 0.5 9.7 Landscape Single-axis 2676 5358 79.1 1998.6 2527.5 10 724 2.3 10.7 Fixed 2701 4512 81.2 1674.2 1999.7 10 780 0.2 9.7 both portrait and landscape orientations. One of the com- irradiance due to tracking especially during the summer monly deployed tracking mechanisms in FPV systems is in the months of March, April and May. However, the single-axis tracking. Thus, the performance of the FPV cost associated with the installation and maintenance model in the Mettur reservoir with single-axis tracking of tracking mechanisms is a major issue. Thus, a suitable is assessed and the results are compared with the op- trade-off is necessary before deciding on the tracking timum fixed flat-mount tilt system. The comparison of mechanism for the FPV model. Both fixed-tilt FPV sys- outputs of FPV models with single-axis tracking and tems with a panel slope of 10° and FPV with single-axis fixed-mount systems in landscape and portrait orienta- tracking are found to be suitable for the Mettur reservoir. tions are listed in Table 5. The tracking mechanism in- The inclusion of the tracking mechanism solely depends creases the FPV energy yield of models with portrait and upon the project cost. landscape orientations by 12.80% and 15.80%, respect- ively. In addition, the tracking mechanism also increases 4.4 Carbon footprint the FPV potential of landscape- and portrait-oriented FPV models by 15% and 20%, respectively. It is important According to the UN human development report (2016), to note that FPV systems with single-axis tracking can the per-capita CO emission in India is 1.60 tons and India provide high energy output even with an 80% increase in stands as the third-largest contributor of carbonaceous the shading loss compared to the fixed flat-mount sys- emission from fossil fuels, of which 50% of the emissions tems without tracking. are from the power sector [51]. The National Electricity Plan A comparison of the average POA irradiance of FPV of the Central Electricity Authority (CEA) reported in 2018 systems with and without tracking in portrait and that solar power generation in India will increase to 162 landscape orientations with the GHI of Mettur reser - GW in 2021, through which 130 million tons of CO emis- voir throughout the year is shown in Fig. 13a and , r b e- sion can be avoided [39]. The average CO -emission factor spectively. This clearly shows the increase in the POA in India including the RES for the year 2015–16 (0.721  kg FPV power (kW/year) Performance ratio (%) FPV energy (MWh/year) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 221 POA irradiance without tracking (kWh/m ) POA irradiance with tracking (kWh/m ) Global Horizontal Irradiation (kWh/m ) 250 3 5 9 11 3 4 5 10 200 8 4 11 1 6 9 2 5 8 11 B POA irradiance without tracking (kWh/m ) POA irradiance with tracking (kWh/m ) Global Horizontal Irradiation (kWh/m ) 1 4 250 3 2 4 9 11 5 8 10 200 7 4 11 1 9 2 8 6 10 150 9 Fig. 13: Comparison of monthly POA irradiance of FPV systems with and without tracking (a) Portrait orientation; (b) landscape orientation. Power Station I Power Station II 1.2 1.15 1 6 1.1 1.05 1 4 8 0.95 0.9 2011–12 2012–13 2013–14 2014–15 2015–16 2016–172017–18 2018–19 Fiscal year Fig. 14: Specific carbon emission per KW power generated from the Mettur thermal power plants from 2011 to 2019 Source: CEA, 2019. CO /kWh) is expected to reduce by 16% (0.604 kg CO/kWh) equivalent amount of carbon emission while deploying 2 2 by the end of the year 2021–22 [39]. Also, the Intended FPV systems. Studies have also reported that the annual Nationally Determined Contributions (INDCs) of India in- carbon footprint of a PV system can be estimated by sub- sist on reducing the emission intensity to 35% by the year tracting the direct and indirect energy consumption of 2030 in comparison with the 2005 level to diminish the the PV system from the gross energy injected into the equivalent carbon emission of 2.5 billion tons [2]. India grid by the total PV system [52], and it is found that the needs to pay more attention to minimizing the use of ex- potential of a 20-kWp FPV system has carbon savings isting coal-fired power plants in order to meet the INDC of 1454.19 t CO over a lifetime of 20  years [10]. The CO 2 2 target with future security and reliability of power supply. emission per kW power generated in India has been in The solar energy sector plays a major role in pollution- the range of 0.841–1.055 kg over the past two decades. In free electricity production by avoiding carbon emissions particular, the CO emission per kW power generated in to a greater extent. Thus, it is important to estimate the the Mettur thermal power plants is shown in Fig. 14. The January February March April May June January July February August March September April October May November June December July August September October November December CO emission (kg/kW) 2 2 2 Irradiance (kWh/m ) Irradiance (kWh/m ) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 222 | Clean Energy, 2021, Vol. 5, No. 2 Table 6: Lifetime CO saving from fixed-mount and single-axis tracking FPV systems FPV energy CO saving from solar energy CO saving from reduction in Total CO 2 2 2 FPV system (MWh/year) production (tons) evaporation (tons) saving (tons) Single-axis 6713 132 246.10 3672.77 135 918.87 tracking Fixed-mount 5851 115 264.70 3672.77 118 937.47 average specific carbon emission from the Mettur region is than the per kW installation cost of the country in 2010. ~0.985 kg CO /kWh [53]. Also, the nation’s levelized cost of electricity was reduced The CO savings from the FPV fixed-mount system and by 85% from 2010 to 2019 [2]. This cost reduction in recent FPV system with single-axis tracking in portrait orienta- years is one of the major advantages that promote the in- tion are calculated for a service life of 20  years and the stallation of PV systems. However, the cost associated with values are listed in Table 6. In addition to the quantification the additional components of the floating platform should of the potential net loss in the carbon emissions from the also be considered in the case of FPV systems [10, 16, 24]. installation of FPV systems, the effects due to the reduc- The cost analysis of the fixed-mount FPV system is tion in water evaporation should also be considered while presented in the following section. The number of floating calculating the CO balance. This can be calculated using modules required to accommodate 13  858 PV panels in specific electricity consumption (SEC), which is the ratio portrait orientation is 6930 while 10  780 PV panels in of the consumed energy to the volume of water supplied landscape orientation require an equivalent number of [39]. It is a key indicator for estimating the environmental pontoons. The cost of transporting and assembling the benefit of reducing the rate of evaporation. The average required materials of the floating platform (USD/Wp) SEC in India is 1.01 kWh/m for the recycled water of de- along with the cost of the mooring system are estimated centralized wastewater treatment plants [54]. The model and listed in Table 7 with the components cost given in FPV array consists of polymeric floating modules and US dollars equivalent to its Indian rate conversion in metal net catwalks. A small amount of air–water flux and the year 2019. The total cost of the FPV support system irradiation is available for the water surface through these is 0.963 USD/Wp. The cost of PV panels and other elec- catwalks and the space between each floating module. trical components used in the installation of the FPV Due to the possibility of water loss through these available system is 0.526 USD/Wp [2]. Table 8 provides the installa- spaces in the FPV system, complete eradication of water tion and soft and hardware costs of the components in- evaporation cannot be achieved. Hence, an evaporation volved in the utility-scale PV system in India in the year coefficient of 0.896 is assumed for calculating the direct 2019. Thus, the total cost of the model FPV system in water saving using HDPE pontoons. This indicates that Mettur reservoir without a tracking system is 1.49 USD/ 10.40% water loss occurs through the openings in the FPV Wp for the portrait-oriented and 2.329 USD/Wp for the system [55, 56]. The amount of water saved due to the re- landscape-oriented FPV plant. The cost breakdown of the duction in evaporation by the model FPV system is 184 589 FPV system components is shown in Fig. 15. This clearly m /year. Taking all this into account, the total potential CO shows the high cost associated with the construction saving by FPV systems with tracking is 135 918.87 t CO and and installation of the floating platform, which is ~35% it is 12.5% higher than the fixed-mount FPV system for a of the total cost of the FPV system. However, the cost of lifespan of 20 years. buying and levelling large hectares of land is avoided in Apart from the CO savings, it is also important to this water infrastructure system when compared to con- record the CO emission associated with the production of ventional PV systems. In addition, FPV coupled with a the polymeric floating modules. The total carbon footprint HEPP also eliminates the need for grid connection and of the PV floating module considered in the study will re- the water-saving effect also provides additional advan- sult in CO emission of 23.1 kg CO /m [10]. Thus, the model tage to meet the required power demand. 2 2 FPV system will have embodied carbon of 1108.80 t CO . In the case of FPV systems with single-axis tracking, the Hence, a large-scale FPV system using a different floating cost of the tracking mechanisms increases the total cost of platform having a zero carbon footprint will further reduce the plant. A  comparison of utility-scale fixed-mount and the carbon emission, making this technology more envir - single-axis tracking FPV systems is listed in Table 9 [57]. The onmentally suitable. hardware cost includes the cost of the modules, inverters, racking and all balance-of-system (BoS) hardware, which is 7.35% higher for the FPV system with single-axis tracking in comparison with the fixed-mount system. The soft cost 4.5 Cost analysis is the installation labour, which is equal for both systems. The total installation cost per kW for the PV system in However, the other soft-cost category that includes the India was 0.618 USD in the year 2019, which was 88% less non-hardware and non-installation labour costs, primarily Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 223 Table 7: Estimated cost of the floating platform and mooring system Cost of portrait-oriented Cost of landscape-oriented Sl no. Item FPV system FPV system 1 Floating module (USD) 2036.034 3150.711 2 Structure (USD) 574.266 888.6621 3 Platforms transport (USD) 52.206 80.78747 4 Tensors (USD) 83.530 129.2599 5 Screws and rivets (USD) 20.882 32.31499 6 Assembly (USD) 208.824 323.1499 7 Total cost of the floating module (USD) 2975.742 4604.886 Cost estimation per Wp 8 Cost of the floating module (USD/m ) 0.062 0.096 9 FPV power produced (Wp/m ) 0.072 0.056 10 Total cost of the floating module (USD/Wp) 0.861 1.713 11 Elastic joints (USD/Wp) 0.068 0.068 12 Pilot foundation (USD/Wp) 0.034 0.034 13 Total cost of the floating system (USD/Wp) 0.963 1.803 Table 8: Cost components of the utility-scale PV system in India in 2019 [2] Utility-scale solar PV installed Sl no. Category Cost component cost in India in 2019 (USD/kW) 1. Module and inverter hardware Modules 277.9 Inverters 44.4 2. Balance-of-system (BoS) hardware Cabling/wiring 29.3 Safety and security 21.3 Monitoring and control 0.7 3. Installation Inspection 3.7 Electrical installation 14.6 4. Soft costs Margin 25.6 Financing costs 40.6 System design 19.9 Permitting 14.2 Incentive application 21.9 Costumer acquisition 12.2 PV Modules Floating Cables Inverter Soft Cost BoS Anchoring Installation Platform Hardware & Mooring FPV system components Fig. 15: Cost breakdown of fixed-mount FPV-system components in Mettur reservoir Table 9: Cost comparison of utility-scale fixed-mount and single-axis tracking FPV systems [57] FPV system Hardware cost (USD/Wp) Soft cost (USD/Wp) Other soft cost (USD/Wp) Total cost (USD/Wp) Fixed-mount 0.68 0.10 0.28 1.06 Single-axis tracking 0.73 0.10 0.35 1.18 Total cost (%) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 224 | Clean Energy, 2021, Vol. 5, No. 2 EPC (Engineering, Procurement and Construction), is 25% which is the direct water-saving effect of the hybrid HEPP– higher for the tracking PV system. Hence, the total cost of FPV system. The saved water can be suitably used for ei- the tracking FPV system is 11.30% higher than that of the ther generating hydropower or domestic and agricultural fixed-mount system. purposes. The indirect water-saving effect is calculated by To identify the time required to offset the carbon emis- converting the power generated from the FPV system into sions during the production of the floating modules, the the volume of water (V) using the following expression payback time PB of the FPV system is calculated using [56]: time the following equation: 0.75 ∗ 3600 ∗ E ∗ [1 ε] PV V = (6) C ρ ∗ g ∗ ΔH PV PB = (5) time PV where E is the total amount of electricity generated by PV where C is the total cost of the FPV system that in- PV the FPV plant (Wh), ∆H is the water head (36.57 m), g is cludes the BoS and hard and soft costs, and S is the PV the gravitational acceleration (9.8 m /s), ρ is the density of total saving from the FPV system after its installation. the water (1000 kg/m) and ε is the discarding rate of the The FPV system in the present study gives good elec- PV power, which is the ratio of the discarded PV output to trical and economic performance when it is placed in the total power generated from the FPV. Based on this, the portrait orientation and the same is considered for ana- power generated from the FPV model system will corres- lysing the PB . The selling cost of solar power in India time pond to indirect water savings of 43.99 millions of cubic was ~0.27 USD/kWh in the year 2019 [58]. The total cost metres every year. This water saved indirectly can be ef- of the fixed FPV system with portrait orientation is 5.17 fectively used for irrigation. million USD and the total annual savings after installa- tion of the FPV system on Mettur reservoir is 0.7 million USD. Thus, the payback time is 7.3  years and the sav- 4.7 Comparison of the Mettur FPV model with ings from the FPV system by the end of 7.5  years and existing FPV plants in India 10  years is 0.09 million USD and 1.85 million USD, re- The two largest FPV plants in India, with 500- and 2000- spectively. The additional cost to implement the tracking kW capacity, are located in Banasura Sagar dam reservoir mechanism into the FPV system is 0.07 USD/W. Thus, the in Kerala [61, 62] and Mudasarlova reservoir in Andhra total cost of the FPV system in portrait orientation with Pradesh [63], respectively. Comparisons of the existing FPV a tracking mechanism is 5.38 million USD with annual plants with the FPV model proposed in the present study savings of 0.8 million USD after installation. Hence, the for Mettur reservoir are given in Table 10. The energy pro- payback time of the FPV system with a tracking mech- duced in the FPV plants increases with the increase in the anism is 6.3 years and results in a saving of 3.1 million FPV size and varies also with respect to the orientation of USD after 10 years. the panels. Hence, the electrical performance of the pro- posed FPV model in both portrait and landscape orienta- 4.6 Benefits of the hybrid HEPP–FPV system tions is considered for comparison. In Banasura Sagar reservoir FPV plant, PV arrays are pro- The major advantages of the hybrid HEPP–FPV configur- vided in two layers piled one above the other (see Fig. 16a). ation are the prevention of water loss due to evaporation, In the case of the Mudasarlova reservoir FPV system, only the available grid connectivity and high efficiency in com- one layer of PV array is positioned in landscape orientation parison with land-based PV systems [59]. In addition, this (see Fig. 16b). The difference in the energy production be- integration aids the intermittent operation of the HEPP in tween the FPV systems can be attributed to this variation regions with good solar-radiation levels [60]. Intermittent in the PV-panel arrangement. The power density (W/m ) of operation refers to the power generation through solar the FPV plant at Banasura Sagar dam is 75.02% higher than PV during high irradiation times and hydropower gener - that of Mudasarlova reservoir, i.e. the former effectively ation during low or absence of irradiation for continuous utilizes a minimum-area two-layer arrangement when power supply. Further, the amount of water saved by the compared to the latter. The variation in the cost of the FPV FPV covering system through preventing evaporation is systems is due to the different type of floating platforms also directed to generate hydroelectricity. Thus, the FPV used, the PV-panel arrangement and the difference in the system in a reservoir saves water by reducing the evap- installation costs. For example, ferrocement platforms oration rate, which is the direct water-saving effect. The are used to accommodate the PV panels and inverters electricity generated by the FPV is used as a substitute in Banasura Sagar dam FPV plant, whereas metal rafts for the hydropower and this is equivalent to the water and aluminium bars are used in Mudasarlova FPV plant. consumed by the HEPP for generating the same amount Further, the installation costs of these systems were 1.12 of electricity. This is an indirect water-saving effect of the USD/W in 2016 and 0.79 USD/W in 2018. In Mudasarlova FPV system [56]. reservoir, the FPV system is installed close to the land sur - As mentioned earlier, the FPV model system proposed face. Hence, a land substation is used, as shown in Fig. 17. in the present study saves 184  589 m of water per year, Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 225 Table 10: Comparison of proposed FPV model and existing FPV plants in India [61–63] Present study Mettur reservoir, Tamil Nadu Mudasarlova reservoir Banasura Sagar dam, Vishakhapatnam-Andhra Portrait Landscape Sl no. Parameters Wayanad-Kerala Pradesh orientation orientation 1. Floating PV size (MW) 0.5 2 3.5 2.8 2. Energy produced per 0.130 0.074 0.122 0.094 year (MWh/m ) 3. Area (m ) 6000 42 000 48 000 48 000 4. Power density (W/m ) 83.33 47.61 72.33 56.27 5. Specific yield (kWh/kW) 1556 1555 1685.2 1674.2 6. Floating desk Ferrocement Metal raft-type, aluminium, HDPE HDPE pontoon-type HDPE and fibre materials pontoon-type pontoon-type 7. Total number of panels 370 6250 13 888 10 780 8. Type of panel Polycrystalline Polycrystalline Polycrystalline Polycrystalline 9. Orientation Portrait Landscape Portrait Landscape 10. Cost (USD/W) 1.68 3.95 1.49 2.33 11. Water evaporation NA 20 31.1 31.1 reduction (%) 12. Land area required for 10 117 40 468 70 256 54 655 the equivalent power rating (m) 13. Substation Floating substation Land-based substation HEPP integrated HEPP integrated AB Fig. 16: Exiting FPV plants in India (a) 500-kW plant in Wayanad, Kerala and (b) 2-MW plant in Vishakhapatnam, Andhra Pradesh [32, 63]. The major differences between the existing FPV sys- similar orientation to the respective FPV plants. While tems can be seen from the type of floating platforms, comparing the power density of the 500-kW FPV plant PV-panel arrangement, mooring system and installation and the proposed FPV model in portrait orientation, a cost. In the present study, pontoon-based FPV systems lower power density (by 13.20%) is observed in the pro- with pile-anchoring systems are considered for the pre- posed model. The reduction in the power density of the liminary design of the demonstrative FPV plant in Mettur Mettur FPV model can be attributed to the absence of reservoir. The FPV parameters are carefully selected on the the two layers of PV module used in the 500-kW plant. basis of the economic perspective and feasibility of the This configuration of the piled PV module layers is not selected parameters for the location. considered in the present study to avoid shading losses. As mentioned earlier, polycrystalline PV modules are The power density of the Mettur FPV model in landscape used in present FPV models that are similar to the two orientation is 15.30% higher than that of the 2000-kW existing FPV plants. Regarding the orientation of the FPV plant. Despite the equivalent range of irradiance panels, portrait and landscape orientations are used in levels in Mudasarlova reservoir and Mettur reservoir, the 500- and 2000-kW FPV plants, respectively. Hence, it is proposed FPV model has high power density due to the reasonable to compare the proposed FPV model with a effective installation of a large number of PV modules Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 226 | Clean Energy, 2021, Vol. 5, No. 2 Substation Floating carles 2MW floating PV ARRAY Fig. 17: Location of the substation in Mudasarlova reservoir with a pontoon-type floating desk rather than the raft A tilt angle of 10° was found to be more suitable for the type, which needs large spacing between the panels, as Mettur location. used in 2000-kW FPV plant. The land-area requirements (ii) Considering the power output, energy output and PR for the FPV plants are calculated based on the rule of of FPV systems with different mounting systems, a thumb of 9.29 m area required for every 1-kW panel. flat-mount system has been identified as being more Thus, a 1-MW land-based PV system requires 20  234.30 suitable for Mettur reservoir. m of land area, which includes the area for the installa- (iii) Landscape orientation of the panels is more econom- tion of panels and spacing between them [64]. Through ical due to the reduced number of panels required in effective utilization of the available area, the proposed comparison with portrait orientation. FPV model for Mettur reservoir produces better energy (iv) An FPV system with single-axis tracking yields 15.80% output without exceeding the equivalent land require- more energy in comparison with a fixed-tilt system ment, even in landscape orientation. without tracking. But the inclusion of a tracking mechanism is not advantageous from an economic perspective. 5 Conclusion Following the assessment of electrical performance, the Floating photovoltaic installation has grown tremen- carbon footprint and cost analysis of the FPV system were dously in the last 3 years with a global installed capacity also carried out. The results show that an FPV system with of 1314 MW. India, being in the development stage, has in- single-axis tracking in the Mettur reservoir will help in re- creased its FPV implementation from kW to MW scales in ducing 135  918.87 tons of CO emission annually. Based the last 5  years. With proper technological development on the cost-analysis study, it is estimated that 35% of the in the FPV sector, India has the potential to implement total cost of the project is associated with the construction ≤280 GW of capacity with its available water resources. of the floating platforms. However, this can be effectively This study presents a detailed numerical analysis of a compensated for by the cost reduction due to the existing model FPV system in Mettur reservoir. It is observed that grid connection of the HEPP. This small-scale methodology the FPV cover will save 184 589 m of water annually from exemplified for the Mettur reservoir outlining key design evaporation. The demonstrative plant in this study is also factors will support the 100-MW FPV target plan of Tamil analysed for various angles of inclination, mounting sys- Nadu government in Mettur reservoir. As India is a tropical tems and tracking mechanisms. The main outcomes are country with high solar irradiance throughout the nation, listed below: the installation of FPV systems in similar reservoirs with (i) The lower tilt angle will result in a reduced number existing HEPPs will enhance the solar power production of PV panels, high PR and high PV potential, and also and also help in reducing water evaporation. Similarly, the helps in maintaining the optimum panel temperature. parametric investigations presented in the study will also Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 227 [16] Ferrer-Gisbert C, Ferrán-Gozálvez JJ, Redón-Santafé M, et al. A help in deciding the suitable configuration of FPV systems new photovoltaic floating cover system for water reservoirs. in several other locations all over the world. As the advan- Renewable Energy, 2013, 60:63–70. tages of FPV systems have been established based on the [17] Haas J, Khalighi J, de la Fuente A, et  al. 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Performance analysis of a floating photovoltaic covering system in an Indian reservoir

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Abstract

Floating photovoltaic (FPV) systems are one of the globally emerging technologies of renewable energy production that tend to balance the water–energy demand by effectively saving the evaporated water from reservoirs while generating electrical power. This study presents the performance analysis of a model FPV plant in an Indian reservoir. The Mettur dam reservoir located in Tamil Nadu, India with a hydroelectric power plant of 150-MW capacity is considered as a test case. The preliminary design of the FPV plant is proposed based on a detailed study of the key design elements and their suitability for Indian reservoirs. The proposed plant is numerically analysed for various tilt angles, mounting systems and tracking mechanisms in order to assess its potential power generation. A flat-mount system in landscape orientation was found to exhibit a high performance ratio. Further, a fixed-tilt FPV system with a panel slope of 10° and an FPV system with single-axis tracking were found to be suitable for the Mettur reservoir. Further, cost analysis of the FPV system is also presented along with the carbon-footprint estimation to establish the economic and environmental benefits of the system. The results show that the total potential CO saving by a FPV system with tracking is 135 918.87 t CO and it is 12.5% higher 2 2 than that of a fixed-mount FPV system. Received: 30 December 2020; Accepted: 4 March 2021 © The Author(s) 2021. Published by Oxford University Press on behalf of National Institute of Clean-and-Low-Carbon Energy This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http:// creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com 208 Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 209 Graphical abstract Evaportation in open water reservoirs Gaseous Increase in emissions from energy demand fossil fuels SOLUTION Perfomance analysis Floating model FPV system in photovoltaic Mettur reservoir with (FPV) hydroelectric po wer plant (HEPP) system in India Saves Hybrid FPV-HEPP Combiner 184589 m Prevention system results in box of water of indirect water Central PV modules from 135918.87 saving of 43.99 inverter Transformer Float pontoons evaporation 3.5 MW tons MCM every year every year power carbon Mooring production emission lines at during ther optimum lifetime Anchoring tilt angle Keywords: solar energy; floating photovoltaic system; evaporation loss; hydroelectric power plants With sunlight being the major source of energy pro- Introduction duction, power generation through PV panels is receiving Gaseous emissions due to energy production from fossil worldwide attention. Also, the availability of technically ad- fuels are polluting the atmosphere gradually, which not vanced silicon panels and a cost-effective way of generating only diminishes the purity of the air, but also affects power even in low-light conditions motivate consumers human health. The major pollutants from fossil-fuel com- for self-power generation. However, the unavailability of bustion are the greenhouse gases, which include carbon land for the installation of large-scale land-mounted PV dioxide, methane, benzene and nitrogen oxides. These systems is the major drawback. Thus, achieving the target are the major cause of global warming, air pollution and solar energy production just through land-mounted and water pollution []. 1 In order to combat climate change, rooftop PV systems is quite challenging. One of the alter - moving towards clean energy while generating afford- native solutions to compete with the target framed by the able electricity is necessary. Power generation through nation is FPV, also called floatovoltaics, a floating solar PV renewable energy sources (RES) plays a significant role in (FSPV) or a floating solar covering system (FSCS) [6–8]. This transforming the fossil-fuel-based power sector towards new emerging technology in which the solar panels are zero-carbon green energy by the production of solar, wind, placed on the water surface of ponds, lakes, lagoons, res- hydro and geothermal power []. 2 As per the statistics pro- ervoirs and oceans shows increased efficiency compared vided by the International Renewable Energy Agency, the to land-mounted PV systems [9]. The other significant en- global renewable-energy-generation capacity increased by vironmental impact of placing PV panels on the water is 7.40%, which is equal to 176 GW, from 2018 to 2019 []2 . the reduction in evaporation, which helps in saving fresh- The growth of renewable energy production is spectacular water for domestic and agricultural purposes [10]. Studies particularly in India, where a 27% increase in renewable revealed that covering the water surface has the potential energy production has been achieved in recent years, of to mitigate water loss through evaporation by ≤90% [11]. which 43% is accounted for by the solar photovoltaic (PV) This highly efficient technology had faced real-time imple- sector [3]. The launch of the Jawaharlal Nehru National mentation since 2007; from then, it has shown dramatic Solar Mission (JNNSM) has remarkably increased the de- growth with increased efficiency [12]. ployment of PV systems and resulted in 32.53 GW solar India has a large number of reservoirs and natural and energy production, making the nation the fourth-largest artificial lakes. Due to global warming, the drastic increase generator of renewable energy []. 4 By 2022, JNNSM has a in temperature has increased water loss in open reservoirs target of 175 GW renewable energy production, with 100 due to evaporation [13]. This also affects the hydroelectri- GW from the solar sector as per the report by the Solar city yield from a hydroelectric power plant (HEPP), which Energy Corporation of India (SECI) [5 ]. Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 210 | Clean Energy, 2021, Vol. 5, No. 2 relies mainly on the water stored in the reservoirs. Rather drinking purposes for the district of Salem. Potential evapo- than innovative systems and technologies to reduce transpiration is calculated using Hamon’s method to as- water evaporation, the current need is a simple existing sess the water loss from the reservoir. The model FPV plant system with additional advantages. The FPV technology is designed for a lesser reservoir coverage area to avoid will address this issue in a better way by increasing solar hindrance to the hydropower generation and to maintain power production and preserving the water for future use. water quality. The system is also designed with suitable By deploying FPV in reservoirs with a HEPP, the total en- spacing between every row of the FPV array to maintain ergy output adding to the hydroelectricity can be increased positive ecosystem services [18]. The effects of variation considerably [10]. Studies also confirmed that covering <3% in tilt angle, tracking mechanisms and mounting mechan- of the global reservoir water surfaces can considerably in- isms of the model FPV plants are assessed in detail. In add- crease the power generation from a HEPP to 395.90% with ition, the carbon footprint and cost of the FPV system are 4800 full load hours (FLH) [14]. Thus, installing FPV as the also calculated to understand the environmental and eco- cover system will be helpful in balancing the water–energy nomic feasibility of this technology. Finally, the benefits of demand in water-limited arid and semiarid regions, as it a hybrid HEPP–FPV is assessed by calculating the direct and has been roughly estimated that each MWp can save 25 000 indirect water savings in the reservoir and the FPV model cubic metres of water annually [15]. Experimental investi- plant is compared with the existing FPV plants in India. gations have also proved that the FPV system is technic- As Tamil Nadu Generation and Distribution Corporation ally feasible and economically viable for even covering the (TANGEDCO) is planning to deploy a 100-MW FPV plant in total water surface area of a reservoir [16]. However, the the Mettur reservoir, the key design parameters suggested implementation of large-scale FPV systems covering en- in this study can aid during the design and implemen- tire reservoir surfaces restricts the incoming irradiation to tation stages of the project. The simplified methodology the water body that eventually degrades the water quality followed in the study will also support in assessing the and ecology. Further, the implementation of a large-scale overall performance of FPV plants to be deployed in any FPV system requires minimum water storage in a reservoir reservoir all over the world. to avoid stranding [17]. Thus, considering the hydropower generation and water quality of the reservoir, less reser - 1 Effects of evapotranspiration on voir coverage should be considered during the design of freshwater sources in India FPV systems. In the last two decades, per-capita water availability /(m The cumulative capacity of FPV projects in India has capita/year) has been continuously deteriorating in India. reached 2.70 MW recently and the country aims at produ- Due to the exponential increase in the population and cing 1721 MW of renewable energy through the projects acquisition of water-flow and storage areas for building of the SECI, National Thermal Power Corporation, National construction, freshwater sources are diminishing rapidly Hydroelectric Power Corporation and state-level distribu- in India, which in turn results in high water scarcity in tion companies and city-development authorities [6 8, ]. summer. In addition, the country experiences an annual The first FPV system in India was commissioned in the global horizontal irradiation ranging from 5.0 to 6.0 kW/ year 2014, with 10-kW capacity in West Bengal, following m and rainfall only for 3–4  months in a year. This arid which the implementation of this technology had scaled climatic condition leaves the country experiencing acute up every year to a present cumulative capacity of 2.70 MW freshwater shortages [19]. [2, 6]. According to the combined analysis from the Indian Over the past 100 years, carbon emission from burning Energy Transition Commission (ETC) and the Energy and fossil fuels has adversely increasing the global tempera- Resource Institute (TERI), water bodies with a surface area ture, which in turn increases the potential evapotrans- of ~18  000 km across the states and union territories of piration [19]. Out of 4000 km of water received through India have the potential to implement 280 GW of FPV precipitation in India, 700 km of water are lost through systems [6]. The cumulative tender announced by the evaporation [20]. The evapotranspiration reaches almost Government of India during 2019 for the FPV installations 1000 mm/year in the southern states of India such as Tamil with 1700-MW capacity is in the developmental stage in Nadu and Kerala [21]. These regions are undergoing acute different states of the country. Considering the scope of water scarcity during the lean seasons due to evapor - massive development in this sector, it is mandatory to in- ation loss of water and diminishing water resources. This vestigate the overall performance of the FPV systems as can be clearly seen from the reduction in the per-capita a reservoir cover to arrive at an environmentally friendly availability of water in India from 1950 to 2050 listed in design solution. Table 1 [22]. This also highlights the necessity to conserve In this context, the present study aims at assessing the diminishing freshwater sources like river basins, canals, electrical performance of the FPV model in an Indian res- dams and reservoirs to prevent the larger part of India ervoir. The Mettur dam reservoir with hydroelectric power from ‘water-stressed’ conditions (<1700 m /capita/year) in plants in Tamil Nadu is selected as a test case. The selected the future [19]. reservoir is the major source of water for irrigation and Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 211 Table 1: Per-capita availability of water resources in India [22] Combiner box Annual Per-capita water Average water freshwater Central PV modules 3 3 availability (m / resources (m / requirement inverter Transformer Float pontoons Year capita/year) person/year) (km ) 1951 5177 3008 580–604 Mooring 2001 1820 1283 694–710 lines 2025 1341 814 784–850 2050 1140 687 973–1180 Anchoring The increase in temperature and evapotranspiration Fig. 1: Key design elements for power generation through an FPV is also indirectly affecting hydropower generation in the system [25, 26] country. Hydroelectricity is an efficient source of energy that relies on the amount of water in natural and human- (FRP), high-density polyethylene (HDPE), medium-density made reservoirs, and it is highly advantageous to meet polyethylene (MDPE), polystyrene foam, hydro-elastic instant power-demand fluctuations. As the hydrologic floating membranes or ferro-cements to provide enough and atmospheric water balance is based on the evapo- buoyancy and stability to the total system. Anchoring the transpiration, this water balance is disturbed due to the floating deck with a proper technique is essential for an seasonal rise in temperature, which in turn restricts the FPV system, as the drift in the water level and the action supply of power by a HEPP when the requirement is high. of the wind load can damage the floating platform and the Thus, the increase in the rate of evaporation makes the mooring cables [29, 30]. Various types of mooring systems HEPP system fail in its prime incitement. In this con- suggested for FPV plants include the gravity type, anchor- text, instead of increasing the number of HEPPs, the tension type, semi-rigid type, tension type and modified researchers rely on economical methods to reduce the type [31]. The type of the mooring system is selected based evaporation rate and it has also been found experimen- on the water level and soil type at the location. tally that the implementation of FPV in reservoirs with Further, mechanisms to track the PV panels towards HEPPs aids in increasing hydroelectricity generation by the Sun will increase their power-generation capacity. reducing the water loss due to evaporation [23]. Thus, Accurately focusing the solar radiation perpendicular the installation of FPV plants in Indian reservoirs can be to the PV panels either by a single- or dual-axis tracking seen as a promising solution to all these adverse issues. mechanism will enhance the power density and the effi- ciency of the PV modules. Single-axis tracking is widely used in FPV systems globally, in which the entire desk 2 Overview of key design elements of an with a diameter of <30 m is rotated to receive maximum FPV system radiation [14]. The same mechanism is used in the 500-kW In order to avoid the land acquisition for PV projects, the FPV system in Wayanad, India, where the floating desk is idea of installing PV panels on water resources emerged rotated four times a year by altering the anchoring pos- in the year 2007 and there is an evident growth in this ition [32]. The major disadvantage of the tracking systems technology all over the world due to its significance [24]. is their high cost, as this accounts for 25% of the total cost Apart from the special arrangements required to make of the system, even though it can increase the yield by 25% the system float on the water surface, the FPV system is [14]. In addition, power generation may also be affected quite similar to the conventional PV system. The main due to shading and wind effects when the trackers act all parameters required to design a suitable FPV plant for any day. Also, the installation of dual-axis tracking systems water-storage system includes the type of PV panel, slope makes the FPV system unstable under the action of rela- direction of panels, meteorological conditions of the site, tively modest wind speeds, which tend to cause twisting of support system and moorings. The major key design elem- the mooring lines [9]. ents of FPV systems are shown in Fig. 1. The mounting of PV panels is one of the important Among the different types of PV panels, polycrystal- design factors in determining the amount of radiation line (PC) silicon panels are highly effective for large-scale incident perpendicularly on the fixed solar module solar power production. Recent studies also confirmed throughout the day. Through proper site inspection, the ability of PCs to withstand different environmental the position and direction of the panel can be pre- conditions and the production of a high power output determined in order to track the high-intensity radiation [27, 28]. PCs are also used in the recently deployed FPV for maximum sunlight hours. To further increase the systems in Wayanad and Vishakhapatnam in India. PV power output, tilting of the panels in a suitable direction panels are placed on a floating structure called a pon- is necessary, through which more solar radiation can be toon, which is usually made up of fibre-reinforced plastic captured. It is the key factor that determines the energy Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 212 | Clean Energy, 2021, Vol. 5, No. 2 efficiency per unit area of the panel and the size of the of Salem. It also plays a major role in preventing the area floating deck. As India is in the northern hemisphere, from drought-prone conditions in lean seasons. The view a panel facing in the southern direction (with 180° azi- and geographical location of the Mettur dam reservoir are muth) will improve the radiation interaction and eventu- shown in Fig. 2 [13, 36]. ally increase the output energy of the FPV array [33]. The The dam has a tunnel powerhouse of 200-MW capacity action of waves around the edges of the floating surface and a dam powerhouse of 50-MW capacity. In addition, will tend to move the floating platform [3435 , ]. In this the downstream water gets diverted into four pow -er case, the cables connecting the PV array on the floating houses called lower Mettur hydroelectric power projects desk to the inverters should be provided with sufficient with a total capacity of 120-MW power generation, owned length to withstand this extension. In the 500-kW FPV and operated by Tamil Nadu Generation and Distribution system in Wayanad, India, submerged-type cables are Corporation (TANGEDCO). The details of the HEPPs in the being used to transmit the generated power to the sub- Mettur dam are listed in Table 2. Full power generation of 50 station and floating cables are used in the 2-MW FPV MW from the dam powerhouse can be achieved only when system in Vishakhapatnam, India [6 ]. the water level of the dam is >27.50 m and the power gen- eration from the tunnel powerhouse is possible only when the water level is >16.80 m [36]. The power generation is highly affected when the water inflow is lower, especially 3 Case study in summer during the months of May, June and July. 3.1 Details of study area The hydropower generated from the Mettur HEPP from 2011 to 2019 is shown in Fig. 3. The lowest energy yield is The following section presents the prospects of installing observed during 2016 and the same year is recorded as FPV plants in Indian reservoirs through a detailed per - India’s hottest year of the decade as per the report from formance analysis of an FPV model system in one of the the National Oceanic and Atmospheric Administration existing reservoirs in India. The Mettur dam reservoir (NOAA) [38]. This shows that an increase in the irradiance (Stanley reservoir) in the Salem district of Tamil Nadu, level increases the evaporation rate of the reservoir and India is considered as the test case. The Mettur dam, with drastically affects the net power-generation output from a total height 65 m and length 1.70 km, was built across the HEPP due to less water inflow. Apart from this, the old the river Cauvery in 1934 with a reservoir surface area of equipment and the algal bloom also obstruct the power 42.5 km [36]. The water stored in this largest reservoir in generation. Thus, a reduction in the evaporation rate in the Tamil Nadu is used for hydroelectricity production, irriga- reservoir is highly important to meet the water–energy de- tion and drinking purposes. This has been the main source mand during the summer season and to increase hydro of water for 1096.70 km of farmland around the district TAMIL NADU INDIA SALEM District Boundary State Boundary Taluk Boundary 77°44'0''E 77°52'0''E Legend Locations Highways Reservoir 77°44'0''E 77°52'0''E Fig. 2: Index map of Mettur dam reservoir [37] 11°48'40''N 11°56'50''N 11°48'40''N 11°56'50''N Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 213 Table 2: Hydroelectric power plants in Mettur dam [13, 36] Power-generation Number of Total capacity Power plants capacity (MW) turbine units (MW) Mettur dam powerhouse 12.5 4 50 Mettur tunnel powerhouse 50 4 200 Lower Mettur barrage Powerhouse—I/Chekkanur 15 2 30 Lower Mettur barrage Powerhouse—II/Nerinjipettai 15 2 30 Lower Mettur barrage Powerhouse—III/Kuthirai kalmedu 15 2 30 Lower Mettur barrage Powerhouse—IV/Uratchikottai 15 2 30 2011–12 2012–13 2013–14 2014–15 2015–162016–17 2017–18 2018–19 Fiscal year Fig. 3: Power generation from Mettur hydroelectric power plant from 2011 to 2019 [39] 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year Fig. 4: Daily variation in temperature at Mettur dam from 2010 to 2019 power generation. The implementation of FPV plants in on water bodies is the evapotranspiration, which is the the Mettur reservoir in integration with a HEPP will not sum of the evaporation and transpiration occurring on the only increase the share of renewable energy production in surface. This needs to be estimated accurately for water- the nation, but also fulfil the power energy demand of the resources management. Due to the difficulties associated surrounding locations throughout the year. with the direct estimation of evapotranspiration, potential evapotranspiration (PET) is commonly used to calculate the evapotranspiration occurring from a specific surface 3.2 Potential evapotranspiration in the Mettur with unlimited water supply or from surfaces that are reservoir completely covered with water (like lakes and reservoirs). PET is a useful measure to identify the atmospheric water The meteorological data required for the study were demand of a particular region under study. Further, it also collected from NASA (Prediction of Worldwide Energy helps in understanding the impact of climate change and Resource) for the period 2010–19 [40], from which water loss other human-made installations on water bodies [41]. PET through evaporation over the years is assessed. The tem- is affected by various meteorological conditions and it is perature variation in the Mettur reservoir is shown in Fig. usually measured indirectly from other climate factors 4. An increase in temperature can be clearly seen during such as air temperature, wind speed and solar radiation. the summer (April, May and June) every year. The max- It is usually expressed in depth per unit time (mm/day imum recorded temperature and irradiance are 34.98°C or m/year) and it can be considered as an upper limit of and 7.56 kW/m /day, respectively. One of the important evapotranspiration. parameters that shows the impact of high temperature Temperature (degree celcius) Net power generation (GWh) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 214 | Clean Energy, 2021, Vol. 5, No. 2 In order to predict the water loss in the Mettur reservoir, of the reservoir. Thus, considering the prevailing risks as- daily PET is calculated. Many conventional methods to es- sociated with water-quality management and the eco- timate PET, derived based on the geographical conditions system, the area of the FPV system is considered to be of the location, are available in the literature. One of the <30%. Since the energy generation and water savings are commonly used methods is Hamon’s method, which is a directly connected to the percentage of coverage, the area simple methodology with acceptable accuracy. It is used in of the model FPV plant is chosen close to the existing FPV the present study to estimate PET at the Mettur reservoir. plant in Mudasarlova reservoir in India. This constitutes According to Hamon’s method, PET (mm/day) is expressed ~0.13% of the total reservoir area. using the following relationship [42]: As the initial step, various design solutions to identify the optimum orientation and tilt of the panel to get max- k ∗ 0.165 ∗ 216.7 ∗ N ∗ e imum energy yield are analysed in detail. The potential of (1) PET = T + 273.3 the proposed FPV models is then assessed using a quality factor called the performance ratio (PR), which describes where k is the proportionality coefficient (equal to 1.2), N the potential of FPV systems through the total potential is the daylight hours and e is the saturated vapour pres- energy connected to the grid, which is calculated using the sure at air temperature, T. The daily PET calculated from following expression: the above expression for the Mettur dam is shown in Fig. 5. The maximum value of daily PET obtained was 16.88 mm/ PR = (2) day during the summer of 2016. The minimum value of I POA P × OUT STC the daily evaporation rate is 6.21 mm/day, and thus a min- 5 3 where, E represents the total energy supplied to the grid imum of 9.53  × 10 m of water was lost due to evapor - G (kWh), P is the total power output from the FPV system ation every day during the last 10  years from the Mettur OUT Ä ä kW (kW), I is the plane of array irradiance , and I is the reservoir. POA m STC Ä ä kW From the daily PET at the Mettur dam, the annual evap- irradiance under standard test conditions STC = 1000 . oration rate is calculated and the results are shown in Fig. In the proposed FPV system, PV modules are placed at 6. The maximum value of an annual evaporation rate of a height of 0.3–0.5 m (including the height of the pontoon 3958.74 mm/year is obtained during the year 2016, followed structure) from the water surface. A polycrystalline-type by 3877.46 mm/year in 2019. It is also important to note the PV module of dimensions 196 × 99  × 4  cm and weight increasing trend in the evaporation rate from 2010 to 2019 22.5 kg coated with tempered glass of 3.20 mm and pon- and thus a further increase may be expected in the coming toons made up of MDPE that can support two PV panels years. This highlights the necessity for evaporation-control is considered. The system is designed with a row-to- measures in the Mettur reservoir, which acts as a main row spacing of 0.5 m, necessary for catwalks, and the source of water for drinking and irrigation purposes. modules are placed 0.01 m apart. The output power de- livered by the FPV array is carried through 10 American Wire Gauge copper wires and connected to inverters 3.3 Proposed FPV system for the Mettur to generate AC power. A  string inverter is used in the reservoir FPV model to connect the PV modules in a row. Module- The percentage of FPV system coverage on the reservoir level power electronics systems like power optimizers should be <30% to preserve the water ecology and to avoid are not required in the present system, as the shading losses in hydropower revenues [17]. Large-scale implemen- losses are highly reduced by placing the FPV modules tation covering a greater portion of the reservoir with an in open reservoirs. The system is kept in position using FPV system reduces air–water fluxes and creates physical, the pile-anchoring system. The above-mentioned de- chemical and biological effects on the surface meteorology sign elements of the proposed FPV model in the present 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year Fig. 5: Daily potential evapotranspiration (PET) at Mettur dam from 2010 to 2019 Potential evapotranspiration (mm/day) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 215 Annual average value Linear (Annual average value) 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 Year Fig. 6: Annual average evaporation rate at Mettur dam from 2010 to 2019 AB Fig. 7: Schematic diagram of the FPV model in Mettur reservoir (a) Location of the FPV system and (b) top view showing the orientation of the panels. study are selected based on its suitability for imple- year of the given location. For the estimation of real-time mentation along with detailed investigation of the ex- power generation for the solar conversion systems, the isting FPV plants in India. The schematic diagram of the irradiation weather file data of the Mettur reservoir from proposed FPV model is shown in Fig. 7. Initial investi- 2010 to 2020 is uploaded in the condition sets of the soft- gations are carried out to assess the suitable PV-panel ware Helioscope [47]. Additionally, the horizontal profile arrangement such as square, rectangle and octagon. of the location over the period of time is obtained from The results show that the octagonal pattern of placing photovoltaic geographical information system (PVGIS) in PV arrays is capable of effectively accommodating the TMY format and uploaded in the condition set to estimate maximum number of PV panels and also provides max- the shading pattern and its associated losses [43]. imum energy yield in both landscape and portrait orien- The other important parameters required in the calcu- tations. Further, this system is found to be feasible while lation of irradiance are the solar angles and surface angles. adjusting the mooring system according to the variation Solar angles include the declination angle (δ), solar eleva- in the reservoir water level and also results in reduced tion angle (α), hour angle (ω), surface azimuth angle (Z) and mooring forces when designed effectively. Detailed ana- solar zenith angle (ϕ), whereas surface angles include the lysis with different FPV system patterns is out of the collector azimuth angle (), Z tilt angle (β) and angle of in- scope of the present investigation. cidence (θ). The variation in the solar elevation angle (α) to the azimuth angle (Z) is useful to predict the length as well as the position of simple shadows like trees, hills, 3.4 Performance analysis poles and buildings lying between the path of the incident The total energy generated by an FPV system with the Sun rays and the panel in the location of the FPV plant. aforementioned design requirements is simulated using The Sun-path diagram determined from these surface- the commercial software Helioscope. For analysing the oriented solar angles helps in identifying the shadows in a annual energy generated from the FPV system, the esti- particular location. The Sun-path chart for the Mettur res- mation of irradiation levels at the location is the initial ervoir in artesian coordinates with hours in Local Standard step. Irradiance can be Direct Normal Irradiance (DNI), Time throughout the year is shown in Fig. 8. Global Horizontal Irradiance (GHI) and Diffuse Horizontal Shading loss due to trees is negligible in water- irradiance (DHI). In order to measure the total irradiation mounted PV systems. The horizon of the PV array is de- incident on the horizontal surface, the GHI, DHI and DNI fined by the solar azimuth angle at a particular location. data for the Mettur reservoir location from 2010 to 2019, Horizontal data of the FPV system with the south-facing obtained from NASA databases in typical methodological PV modules for the Mettur dam were obtained from year format (TMY), are used [40]. TMY is a set of ground- PVGIS and the profile are shown in Fig. 9. The maximum based meteorological data with values for every hour in a horizon height is observed at +90°. This shows that the Evaporation rate (mm/day) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Apr 20 Aug 22 May 21 Jun 21 Jul 21 Jun 21 Sep 22 Oct 21 Mar 20 Nov 21 Dec 21 Dec 21 Feb 20 Feb 20 Jan 21 216 | Clean Energy, 2021, Vol. 5, No. 2 90° (c) Univ. of oregon SRML Sponsor: ETO Lat: 11.78, Long: 77.8 (Standard) time zone: 5.5 80° Sun path diagram Mettur dam 1 PM 70° 11 AM 2 PM 60° 10 AM 12 PM 3 PM 50° 9 AM 40° 4 PM 30° 8 AM 5 PM 20° 7 AM 6 PM 10° 6 AM 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° East Solar azimuth West 90° (c) Univ. of oregon SRML Sponsor: ETO Lat: 11.78, Long: 77.8 (Standard) time zone: 5.5 80° Sun path diagram Mettur dam 1 PM 70° 11 AM 2 PM 60° 10 AM 12 PM 3 PM 50° 9 AM 40° 4 PM 30° 8 AM 5 PM 20° 7 AM 10° 6 PM 6 AM 30° 60° 90° 120° 150° 180° 210° 240° 270° 300° 330° 360° East Solar azimuth West Fig. 8: Sun-path diagram for Mettur dam (a) between solstices from December to June and (b) between solstices from June to December [44]. 5 8 11 2 23 1 67 13 –180 –150 –120 –90 –60 –30 0 30 60 90 120 150 180 Solar azimuth angle (degrees) Fig. 9: Horizontal profile of Mettur reservoir Jul 21 Jun 21 Jun 21 May 21 Solar elevation Solar elevation Horizon height (degrees) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 217 losses from the south-facing PV panels are compara- temperature drops with the wind speed, T is the cell tively lower than those of other orientations. The row- temperature (°C), 𝐸 is the reference solar irradiance on to-row shading can be minimized by providing spacing the PV module (1000 W/m ), WS is the wind speed (m/s) between the individual PV panels and adjacent rows of and Δ𝑇 is the temperature difference between the module panels, and by placing the panels with a minimum tilt and the cell at 𝐸 . angle. Even though the bottom edge of the second row of the PV array will be obstructed by the first row of the PV array, the reflected radiance on the shaded area will 4 Results and discussions help in reducing the losses. The location of the FPV in 4.1 Effect of tilt-angle variation the Mettur reservoir is selected accordingly to avoid the shadow cast by the nearby trees and mountains. The In order to find the optimum tilt angle for the south- possibility of obstruction shadows by the reservoir em- oriented panels of the FPV model, the performance of the bankment on the FPV array may occur only when the system is analysed by varying the tilt angle from 0° to 89° reservoir is empty or <50% of its full water capacity. with 10-degree intervals. The panels are positioned par - The transposition model is used to convert the available allel to the water surface at a 0° tilt angle and the analysis meteorological irradiation data incident on the horizontal is carried out up to 89°. A tilt angle of 90° is not considered surface to the irradiation data incident on the surface in- due to the well-known shading losses associated with clined at a particular angle. The Hays model is used to this position. The results of the performance analyses are calculate the diffuse radiation incident on the solar PV in- listed in Table 3. The results show that the number of mod- clined at an angle [45]. Finally, the reflected radiation in- ules, FPV power output and shading losses increases and cident on the tilted solar module is calculated using the the FPV energy output decreases with the increase in the albedo coefficient (α ) of the location, which is the unitless tilt angle. measure of the amount of irradiance reflected by the sur - The variations in the power and energy of the FPV face. In India, the albedo coefficient for the water reservoir system with varying tilt angles are shown in Fig. 10a. It varies from 0.16 to 0.19 [46]. The local ambient temperature can be clearly seen that the increase in the tilt angle of the variation and wind speed of the location impact the tem- panels increases the FPV power output from 3440 to 7229.5 perature loss of the FPV system. Further, the temperature kW/year, whereas the FPV energy output increases up to a losses also depend on the variation in the airflow under 20° tilt angle and then decreases. Increasing the tilt angle the PV panel based on the type of racking used. The PV cell of the panel shrinks the area covered by each panel consid- temperature is calculated according to the performance erably, which provides room to deploy panels additionally model given by Sandia National Laboratories using the fol- in the total available area. Thus, a large number of PV mod- lowing mathematical equations [47]: ules can be placed in the available area and this results in (a+b∗WS) an increase in the FPV power with the increase in tilt angle. (3) T = E ∗ e + T M A The FPV energy at a 89° tilt angle is 38% less than the en- ergy at a 20° tilt angle. This occurs due to the increase in T = T + ∗ΔT (4) C M the row-to-row shading of panels leading to a non-uniform panel of array (POA) irradiance at higher tilt angles. The where T is the module temperature (°C), T is the am- M A variation in shading and temperature losses for different bient air temperature (°C), is the solar irr 𝐸 adiance inci- tilt angles is shown in Fig. 10b . The maximum shading loss dent on the module surface (W/m), α is the empirically of 39.10% is observed at a 89° tilt angle, whereas a com- determined coefficient for the upper limit of the module paratively less significant variation in the temperature loss temperature at low wind speed, is b the empirically de- is observed with an increase in the tilt angle. termined coefficient for the rate at which the module Table 3: Performance of the FPV system in Mettur reservoir under varying tilt angles Tilt FPV power FPV energy FPV potential POA irradiance Number of Shading Temperature (degrees) (KW) (MWh/year) PR (%) (kWh/kW) (kW/m ) modules loss (%) loss (%) 0 3440 5586 80.7 1625 2016.5 13 742 0.01 9.3 10 3472 5799 80.4 1670.3 2078.4 13 888 0.4 9.6 20 3564 5939 79.6 1666.2 2092.9 14 258 1.5 9.6 30 3707 5932 77.7 1600.1 2059.4 14 258 3.9 9.5 40 3936 5906 75.9 1500.2 1977.1 15 746 6.2 9.2 50 4258 5689 72.3 1336.4 1849.0 17 032 10.8 8.6 60 4689 5376 68.3 1148.3 1608.8 18 758 15.4 7.9 70 5299.5 4897 62.4 924.0 1479.0 21 198 22.1 7.1 80 6153.5 4334 55.7 704.3 1263.8 24 614 29.5 6.2 89 7229.5 3675 46.9 508.0 1083.9 28 918 39.1 5.2 Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 218 | Clean Energy, 2021, Vol. 5, No. 2 A 10 000 B FPV power (kW) Shading loss FPV energy (kWh) Temperature loss 4000 20 2000 10 0 0 0 10 20 30 40 50 60 70 80 90 01020304050 60 70 80 90 Tilt angle (Degrees) Tilt angle (Degrees) × 10 CD 2.7 2.4 2.1 1.8 1.5 1.2 40 01020304050 60 70 80 90 01020304050 60 70 80 90 Tilt angle (Degrees) Tilt angle (Degrees) Fig. 10: Effect of tilt-angle variation on the performance of the FPV model (a) Power and energy output, (b) losses, (c) number of modules and (d) performance ratio. The number of panels required for the FPV system in- and carport mounting systems to identify the best FPV creases by 50% with the increase in the tilt angle from 0° model system for better output in the Mettur reservoir. In a to 89° as seen from Fig. 10c, which will result in increased flat-mount type of racking system, the PV modules are ar - cost of the system. Thus, considering the number of ranged at a fixed tilt angle on a flat surface. Each module in panels required and the yield of the FPV system, it is ad- the array is arranged with sufficient row spacing between vantageous to position the panels with a lower tilt angle. them to reduce the shading losses. Also, the space behind Further, the PR of the FPV system is also high for the the PV panel in this type of arrangement ensures good ven- lower tilt angles, as seen from Fig. 10d. In addition, the tilation that results in less temperature loss even at high lower tilt angle of panels also results in high PV poten- temperatures. In flush-mount racking, the PV modules are tial. This will tend to reduce the magnitude of the drag placed in such a way that the tilt angle is equal to the in- force acting on the PV array and thus avoids damage clination of the surface with zero row spacing. Therefore, to the panels due to high winds. A  lower tilt angle also losses due to shade from adjacent panels can be effectively helps in reducing the evaporation rate in the reservoir neglected whereas the absence of any space between the and provides evaporative cooling to maintain the panel modules and the surface leads to poor ventilation and in- temperature. Thus, a tilt angle of 10° has been identified creased temperature loss. In an East–West type of racking as being more suitable for this FPV model in the Mettur system, PV panels are positioned at 90° and 270° at an reservoir due to its good electrical, structural and oper - azimuth angle of 180°. The row, module, frame and peak ational performances. spacing of the panels in this dual-tilt racking arrangement provides sufficient ventilation to each module in the PV array. Thus, lower temperature and shading losses of the 4.2 Effect of panel orientation and system provide higher energy yield than flat- and flush- mounting systems mount racking. In a carport mounting type, the entire PV The performance of the proposed model is then analysed array is placed at a particular tilt angle to the flat sur - by varying the orientation of the panels and the mounting face area without row spacing. Thus, the panels arranged systems, by maintaining the optimum tilt angle of 10°. in a carport type of racking is similar to the flush-mount Portrait and landscape orientations of the panels are con- racking system with reduced temperature losses equal to sidered along with flat-mount, flush-mount, East–West those of the flat-mount racking system [47]. The schematic Output Number of modules Performance ratio (%) Loss (%) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 219 AB C Fig. 11: Schematic diagram of FPV models with different mounting systems (a) Flat mount, (b) East–West and (c) carport and flush mount. Table 4: Performance of the FPV model under varying orientations and mounting systems FPV power FPV energy FPV potential Number of Orientation Mounting system (KW/year) (MWh/year) PR (%) (kWh/kW) modules Portrait Flat-mount 4138.5 6909.9 80.3 1669.5 16 554 Flush-mount 4140.0 6325.0 73.5 1528.3 16 654 East–West 5240.0 7866.6 76.2 1506.6 20 968 Carport 3460.0 5820.0 80.2 1683.6 16 554 Landscape Flat-mount 3380.0 5155.0 73.4 1526.0 13 822 Flush-mount 3380.0 5645.0 80.4 1671.7 13 822 East–West 3730.0 6973.0 76.2 1502.4 18 564 Carport 3460.0 5818.0 80.4 1683.6 13 822 diagrams of different mounting systems considered in the East–West and carport-mount systems, respectively. present study are shown in Fig. 11. However, the variation in PR of the FPV systems under Carport and flush-mount structures are common in different orientations is not similar to the trend ob- land-based fixed PV systems; however, these structures served in FPV power and energy outputs. The PR of the have not been practically used or theoretically analysed in flat-mount system in portrait orientation is higher than a water-based fixed PV system [48–50]. These systems are that of landscape orientation by 8.60%, but the value is included in the present study to understand the tempera- less in the case of a flush-mount system. The variation ture and shading losses in the systems. The geometry of in PR between the landscape and portrait orientations the carport structure is configured according to the orien- under other mounting systems is found to be negligible. tation of the PV array and the optimal angle of the slope is Despite the high FPV power and energy output of the identified using the PVGIS application [43]. The perform- East–West mount system, its PR is comparatively lower ances of the FPV model under varying orientations and due to the requirement for a large number of PV modules. mounting systems are listed in Table 4. Portrait orientation In the case of the flush and carport mounts, these systems of the panels results in higher power output compared to are specialized types for PV models in rooftops with slopes. landscape orientation. Under portrait orientation, the max- They may not be highly advantageous when implemented imum power output of 5240 kW/year is obtained from the in FPV models due to the increase in the distance between East–West mounting system, followed by flush-mount and one side of the FPV array and the water surface, which af- flat-mount systems with an almost equal power output of fects the uniform cooling effect on the panels and thereby 4140 kW/year. The same trend is also observed under land- affects the overall panel efficiency. Considering the overall scape orientation. performance of FPV model cases, the flat-mount FPV A comparison of FPV power, energy and PR under dif- system was found to be the most suitable for the Mettur ferent conditions considered in the study is shown in reservoir. Though there exists a significant difference in Fig. 12. The FPV power produced using the East–West the PR of the portrait and landscape orientations of flat- mounting in landscape orientation is 28.80% less than mount systems, the variation in the FPV potential is only that in portrait orientation. In the case of the flat-mount 8.50%. From an economic perspective, a flat-mount system and flush-mount systems, the power reduction in land- with landscape orientation will be advantageous due to scape orientation is ~18%. The power output remains the the smaller number of modules required. same under both orientations when carport tracking is used. The FPV energy output of the portrait orientation 4.3 Effect of tracking mechanisms is higher than that of the landscape orientation under FPV systems with tracking mechanisms tend to result in all mounting systems, with variations of 25.40%, 10.75%, high energy yield compared to fixed-tilt FPV systems in 11.35% and 0.03% under flat-mount, flush-mount, Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 220 | Clean Energy, 2021, Vol. 5, No. 2 Portrait Landscape Portrait Landscape 6000 10 000 8000 1 1 2 2 3 4 4 4 4 1 2 1 0 0 Flat Flush East West Carport Flat Flush East West Carport Mounting system Mounting system Portrait Landscape 1 2 4 4 3 3 1 2 Flat Flush East West Carport Mounting system Fig. 12: Performance of the FPV model with varying panel orientations and mounting systems Table 5: Performance of the FPV system with and without tracking POA FPV power FPV energy FPV potential irradiance Number of Shading Temperature Orientation Tracking (KW/year) (MWh/year) PR (%) (kWh/kW) (kW/m ) modules loss (%) loss (%) Portrait Single-axis 3459 6713 79.2 1937.6 2447.2 13 858 2.4 10.6 Fixed 3472 5851 81.1 1685.2 2078.4 13 888 0.5 9.7 Landscape Single-axis 2676 5358 79.1 1998.6 2527.5 10 724 2.3 10.7 Fixed 2701 4512 81.2 1674.2 1999.7 10 780 0.2 9.7 both portrait and landscape orientations. One of the com- irradiance due to tracking especially during the summer monly deployed tracking mechanisms in FPV systems is in the months of March, April and May. However, the single-axis tracking. Thus, the performance of the FPV cost associated with the installation and maintenance model in the Mettur reservoir with single-axis tracking of tracking mechanisms is a major issue. Thus, a suitable is assessed and the results are compared with the op- trade-off is necessary before deciding on the tracking timum fixed flat-mount tilt system. The comparison of mechanism for the FPV model. Both fixed-tilt FPV sys- outputs of FPV models with single-axis tracking and tems with a panel slope of 10° and FPV with single-axis fixed-mount systems in landscape and portrait orienta- tracking are found to be suitable for the Mettur reservoir. tions are listed in Table 5. The tracking mechanism in- The inclusion of the tracking mechanism solely depends creases the FPV energy yield of models with portrait and upon the project cost. landscape orientations by 12.80% and 15.80%, respect- ively. In addition, the tracking mechanism also increases 4.4 Carbon footprint the FPV potential of landscape- and portrait-oriented FPV models by 15% and 20%, respectively. It is important According to the UN human development report (2016), to note that FPV systems with single-axis tracking can the per-capita CO emission in India is 1.60 tons and India provide high energy output even with an 80% increase in stands as the third-largest contributor of carbonaceous the shading loss compared to the fixed flat-mount sys- emission from fossil fuels, of which 50% of the emissions tems without tracking. are from the power sector [51]. The National Electricity Plan A comparison of the average POA irradiance of FPV of the Central Electricity Authority (CEA) reported in 2018 systems with and without tracking in portrait and that solar power generation in India will increase to 162 landscape orientations with the GHI of Mettur reser - GW in 2021, through which 130 million tons of CO emis- voir throughout the year is shown in Fig. 13a and , r b e- sion can be avoided [39]. The average CO -emission factor spectively. This clearly shows the increase in the POA in India including the RES for the year 2015–16 (0.721  kg FPV power (kW/year) Performance ratio (%) FPV energy (MWh/year) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 221 POA irradiance without tracking (kWh/m ) POA irradiance with tracking (kWh/m ) Global Horizontal Irradiation (kWh/m ) 250 3 5 9 11 3 4 5 10 200 8 4 11 1 6 9 2 5 8 11 B POA irradiance without tracking (kWh/m ) POA irradiance with tracking (kWh/m ) Global Horizontal Irradiation (kWh/m ) 1 4 250 3 2 4 9 11 5 8 10 200 7 4 11 1 9 2 8 6 10 150 9 Fig. 13: Comparison of monthly POA irradiance of FPV systems with and without tracking (a) Portrait orientation; (b) landscape orientation. Power Station I Power Station II 1.2 1.15 1 6 1.1 1.05 1 4 8 0.95 0.9 2011–12 2012–13 2013–14 2014–15 2015–16 2016–172017–18 2018–19 Fiscal year Fig. 14: Specific carbon emission per KW power generated from the Mettur thermal power plants from 2011 to 2019 Source: CEA, 2019. CO /kWh) is expected to reduce by 16% (0.604 kg CO/kWh) equivalent amount of carbon emission while deploying 2 2 by the end of the year 2021–22 [39]. Also, the Intended FPV systems. Studies have also reported that the annual Nationally Determined Contributions (INDCs) of India in- carbon footprint of a PV system can be estimated by sub- sist on reducing the emission intensity to 35% by the year tracting the direct and indirect energy consumption of 2030 in comparison with the 2005 level to diminish the the PV system from the gross energy injected into the equivalent carbon emission of 2.5 billion tons [2]. India grid by the total PV system [52], and it is found that the needs to pay more attention to minimizing the use of ex- potential of a 20-kWp FPV system has carbon savings isting coal-fired power plants in order to meet the INDC of 1454.19 t CO over a lifetime of 20  years [10]. The CO 2 2 target with future security and reliability of power supply. emission per kW power generated in India has been in The solar energy sector plays a major role in pollution- the range of 0.841–1.055 kg over the past two decades. In free electricity production by avoiding carbon emissions particular, the CO emission per kW power generated in to a greater extent. Thus, it is important to estimate the the Mettur thermal power plants is shown in Fig. 14. The January February March April May June January July February August March September April October May November June December July August September October November December CO emission (kg/kW) 2 2 2 Irradiance (kWh/m ) Irradiance (kWh/m ) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 222 | Clean Energy, 2021, Vol. 5, No. 2 Table 6: Lifetime CO saving from fixed-mount and single-axis tracking FPV systems FPV energy CO saving from solar energy CO saving from reduction in Total CO 2 2 2 FPV system (MWh/year) production (tons) evaporation (tons) saving (tons) Single-axis 6713 132 246.10 3672.77 135 918.87 tracking Fixed-mount 5851 115 264.70 3672.77 118 937.47 average specific carbon emission from the Mettur region is than the per kW installation cost of the country in 2010. ~0.985 kg CO /kWh [53]. Also, the nation’s levelized cost of electricity was reduced The CO savings from the FPV fixed-mount system and by 85% from 2010 to 2019 [2]. This cost reduction in recent FPV system with single-axis tracking in portrait orienta- years is one of the major advantages that promote the in- tion are calculated for a service life of 20  years and the stallation of PV systems. However, the cost associated with values are listed in Table 6. In addition to the quantification the additional components of the floating platform should of the potential net loss in the carbon emissions from the also be considered in the case of FPV systems [10, 16, 24]. installation of FPV systems, the effects due to the reduc- The cost analysis of the fixed-mount FPV system is tion in water evaporation should also be considered while presented in the following section. The number of floating calculating the CO balance. This can be calculated using modules required to accommodate 13  858 PV panels in specific electricity consumption (SEC), which is the ratio portrait orientation is 6930 while 10  780 PV panels in of the consumed energy to the volume of water supplied landscape orientation require an equivalent number of [39]. It is a key indicator for estimating the environmental pontoons. The cost of transporting and assembling the benefit of reducing the rate of evaporation. The average required materials of the floating platform (USD/Wp) SEC in India is 1.01 kWh/m for the recycled water of de- along with the cost of the mooring system are estimated centralized wastewater treatment plants [54]. The model and listed in Table 7 with the components cost given in FPV array consists of polymeric floating modules and US dollars equivalent to its Indian rate conversion in metal net catwalks. A small amount of air–water flux and the year 2019. The total cost of the FPV support system irradiation is available for the water surface through these is 0.963 USD/Wp. The cost of PV panels and other elec- catwalks and the space between each floating module. trical components used in the installation of the FPV Due to the possibility of water loss through these available system is 0.526 USD/Wp [2]. Table 8 provides the installa- spaces in the FPV system, complete eradication of water tion and soft and hardware costs of the components in- evaporation cannot be achieved. Hence, an evaporation volved in the utility-scale PV system in India in the year coefficient of 0.896 is assumed for calculating the direct 2019. Thus, the total cost of the model FPV system in water saving using HDPE pontoons. This indicates that Mettur reservoir without a tracking system is 1.49 USD/ 10.40% water loss occurs through the openings in the FPV Wp for the portrait-oriented and 2.329 USD/Wp for the system [55, 56]. The amount of water saved due to the re- landscape-oriented FPV plant. The cost breakdown of the duction in evaporation by the model FPV system is 184 589 FPV system components is shown in Fig. 15. This clearly m /year. Taking all this into account, the total potential CO shows the high cost associated with the construction saving by FPV systems with tracking is 135 918.87 t CO and and installation of the floating platform, which is ~35% it is 12.5% higher than the fixed-mount FPV system for a of the total cost of the FPV system. However, the cost of lifespan of 20 years. buying and levelling large hectares of land is avoided in Apart from the CO savings, it is also important to this water infrastructure system when compared to con- record the CO emission associated with the production of ventional PV systems. In addition, FPV coupled with a the polymeric floating modules. The total carbon footprint HEPP also eliminates the need for grid connection and of the PV floating module considered in the study will re- the water-saving effect also provides additional advan- sult in CO emission of 23.1 kg CO /m [10]. Thus, the model tage to meet the required power demand. 2 2 FPV system will have embodied carbon of 1108.80 t CO . In the case of FPV systems with single-axis tracking, the Hence, a large-scale FPV system using a different floating cost of the tracking mechanisms increases the total cost of platform having a zero carbon footprint will further reduce the plant. A  comparison of utility-scale fixed-mount and the carbon emission, making this technology more envir - single-axis tracking FPV systems is listed in Table 9 [57]. The onmentally suitable. hardware cost includes the cost of the modules, inverters, racking and all balance-of-system (BoS) hardware, which is 7.35% higher for the FPV system with single-axis tracking in comparison with the fixed-mount system. The soft cost 4.5 Cost analysis is the installation labour, which is equal for both systems. The total installation cost per kW for the PV system in However, the other soft-cost category that includes the India was 0.618 USD in the year 2019, which was 88% less non-hardware and non-installation labour costs, primarily Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 223 Table 7: Estimated cost of the floating platform and mooring system Cost of portrait-oriented Cost of landscape-oriented Sl no. Item FPV system FPV system 1 Floating module (USD) 2036.034 3150.711 2 Structure (USD) 574.266 888.6621 3 Platforms transport (USD) 52.206 80.78747 4 Tensors (USD) 83.530 129.2599 5 Screws and rivets (USD) 20.882 32.31499 6 Assembly (USD) 208.824 323.1499 7 Total cost of the floating module (USD) 2975.742 4604.886 Cost estimation per Wp 8 Cost of the floating module (USD/m ) 0.062 0.096 9 FPV power produced (Wp/m ) 0.072 0.056 10 Total cost of the floating module (USD/Wp) 0.861 1.713 11 Elastic joints (USD/Wp) 0.068 0.068 12 Pilot foundation (USD/Wp) 0.034 0.034 13 Total cost of the floating system (USD/Wp) 0.963 1.803 Table 8: Cost components of the utility-scale PV system in India in 2019 [2] Utility-scale solar PV installed Sl no. Category Cost component cost in India in 2019 (USD/kW) 1. Module and inverter hardware Modules 277.9 Inverters 44.4 2. Balance-of-system (BoS) hardware Cabling/wiring 29.3 Safety and security 21.3 Monitoring and control 0.7 3. Installation Inspection 3.7 Electrical installation 14.6 4. Soft costs Margin 25.6 Financing costs 40.6 System design 19.9 Permitting 14.2 Incentive application 21.9 Costumer acquisition 12.2 PV Modules Floating Cables Inverter Soft Cost BoS Anchoring Installation Platform Hardware & Mooring FPV system components Fig. 15: Cost breakdown of fixed-mount FPV-system components in Mettur reservoir Table 9: Cost comparison of utility-scale fixed-mount and single-axis tracking FPV systems [57] FPV system Hardware cost (USD/Wp) Soft cost (USD/Wp) Other soft cost (USD/Wp) Total cost (USD/Wp) Fixed-mount 0.68 0.10 0.28 1.06 Single-axis tracking 0.73 0.10 0.35 1.18 Total cost (%) Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 224 | Clean Energy, 2021, Vol. 5, No. 2 EPC (Engineering, Procurement and Construction), is 25% which is the direct water-saving effect of the hybrid HEPP– higher for the tracking PV system. Hence, the total cost of FPV system. The saved water can be suitably used for ei- the tracking FPV system is 11.30% higher than that of the ther generating hydropower or domestic and agricultural fixed-mount system. purposes. The indirect water-saving effect is calculated by To identify the time required to offset the carbon emis- converting the power generated from the FPV system into sions during the production of the floating modules, the the volume of water (V) using the following expression payback time PB of the FPV system is calculated using [56]: time the following equation: 0.75 ∗ 3600 ∗ E ∗ [1 ε] PV V = (6) C ρ ∗ g ∗ ΔH PV PB = (5) time PV where E is the total amount of electricity generated by PV where C is the total cost of the FPV system that in- PV the FPV plant (Wh), ∆H is the water head (36.57 m), g is cludes the BoS and hard and soft costs, and S is the PV the gravitational acceleration (9.8 m /s), ρ is the density of total saving from the FPV system after its installation. the water (1000 kg/m) and ε is the discarding rate of the The FPV system in the present study gives good elec- PV power, which is the ratio of the discarded PV output to trical and economic performance when it is placed in the total power generated from the FPV. Based on this, the portrait orientation and the same is considered for ana- power generated from the FPV model system will corres- lysing the PB . The selling cost of solar power in India time pond to indirect water savings of 43.99 millions of cubic was ~0.27 USD/kWh in the year 2019 [58]. The total cost metres every year. This water saved indirectly can be ef- of the fixed FPV system with portrait orientation is 5.17 fectively used for irrigation. million USD and the total annual savings after installa- tion of the FPV system on Mettur reservoir is 0.7 million USD. Thus, the payback time is 7.3  years and the sav- 4.7 Comparison of the Mettur FPV model with ings from the FPV system by the end of 7.5  years and existing FPV plants in India 10  years is 0.09 million USD and 1.85 million USD, re- The two largest FPV plants in India, with 500- and 2000- spectively. The additional cost to implement the tracking kW capacity, are located in Banasura Sagar dam reservoir mechanism into the FPV system is 0.07 USD/W. Thus, the in Kerala [61, 62] and Mudasarlova reservoir in Andhra total cost of the FPV system in portrait orientation with Pradesh [63], respectively. Comparisons of the existing FPV a tracking mechanism is 5.38 million USD with annual plants with the FPV model proposed in the present study savings of 0.8 million USD after installation. Hence, the for Mettur reservoir are given in Table 10. The energy pro- payback time of the FPV system with a tracking mech- duced in the FPV plants increases with the increase in the anism is 6.3 years and results in a saving of 3.1 million FPV size and varies also with respect to the orientation of USD after 10 years. the panels. Hence, the electrical performance of the pro- posed FPV model in both portrait and landscape orienta- 4.6 Benefits of the hybrid HEPP–FPV system tions is considered for comparison. In Banasura Sagar reservoir FPV plant, PV arrays are pro- The major advantages of the hybrid HEPP–FPV configur- vided in two layers piled one above the other (see Fig. 16a). ation are the prevention of water loss due to evaporation, In the case of the Mudasarlova reservoir FPV system, only the available grid connectivity and high efficiency in com- one layer of PV array is positioned in landscape orientation parison with land-based PV systems [59]. In addition, this (see Fig. 16b). The difference in the energy production be- integration aids the intermittent operation of the HEPP in tween the FPV systems can be attributed to this variation regions with good solar-radiation levels [60]. Intermittent in the PV-panel arrangement. The power density (W/m ) of operation refers to the power generation through solar the FPV plant at Banasura Sagar dam is 75.02% higher than PV during high irradiation times and hydropower gener - that of Mudasarlova reservoir, i.e. the former effectively ation during low or absence of irradiation for continuous utilizes a minimum-area two-layer arrangement when power supply. Further, the amount of water saved by the compared to the latter. The variation in the cost of the FPV FPV covering system through preventing evaporation is systems is due to the different type of floating platforms also directed to generate hydroelectricity. Thus, the FPV used, the PV-panel arrangement and the difference in the system in a reservoir saves water by reducing the evap- installation costs. For example, ferrocement platforms oration rate, which is the direct water-saving effect. The are used to accommodate the PV panels and inverters electricity generated by the FPV is used as a substitute in Banasura Sagar dam FPV plant, whereas metal rafts for the hydropower and this is equivalent to the water and aluminium bars are used in Mudasarlova FPV plant. consumed by the HEPP for generating the same amount Further, the installation costs of these systems were 1.12 of electricity. This is an indirect water-saving effect of the USD/W in 2016 and 0.79 USD/W in 2018. In Mudasarlova FPV system [56]. reservoir, the FPV system is installed close to the land sur - As mentioned earlier, the FPV model system proposed face. Hence, a land substation is used, as shown in Fig. 17. in the present study saves 184  589 m of water per year, Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 Clean Energy | 225 Table 10: Comparison of proposed FPV model and existing FPV plants in India [61–63] Present study Mettur reservoir, Tamil Nadu Mudasarlova reservoir Banasura Sagar dam, Vishakhapatnam-Andhra Portrait Landscape Sl no. Parameters Wayanad-Kerala Pradesh orientation orientation 1. Floating PV size (MW) 0.5 2 3.5 2.8 2. Energy produced per 0.130 0.074 0.122 0.094 year (MWh/m ) 3. Area (m ) 6000 42 000 48 000 48 000 4. Power density (W/m ) 83.33 47.61 72.33 56.27 5. Specific yield (kWh/kW) 1556 1555 1685.2 1674.2 6. Floating desk Ferrocement Metal raft-type, aluminium, HDPE HDPE pontoon-type HDPE and fibre materials pontoon-type pontoon-type 7. Total number of panels 370 6250 13 888 10 780 8. Type of panel Polycrystalline Polycrystalline Polycrystalline Polycrystalline 9. Orientation Portrait Landscape Portrait Landscape 10. Cost (USD/W) 1.68 3.95 1.49 2.33 11. Water evaporation NA 20 31.1 31.1 reduction (%) 12. Land area required for 10 117 40 468 70 256 54 655 the equivalent power rating (m) 13. Substation Floating substation Land-based substation HEPP integrated HEPP integrated AB Fig. 16: Exiting FPV plants in India (a) 500-kW plant in Wayanad, Kerala and (b) 2-MW plant in Vishakhapatnam, Andhra Pradesh [32, 63]. The major differences between the existing FPV sys- similar orientation to the respective FPV plants. While tems can be seen from the type of floating platforms, comparing the power density of the 500-kW FPV plant PV-panel arrangement, mooring system and installation and the proposed FPV model in portrait orientation, a cost. In the present study, pontoon-based FPV systems lower power density (by 13.20%) is observed in the pro- with pile-anchoring systems are considered for the pre- posed model. The reduction in the power density of the liminary design of the demonstrative FPV plant in Mettur Mettur FPV model can be attributed to the absence of reservoir. The FPV parameters are carefully selected on the the two layers of PV module used in the 500-kW plant. basis of the economic perspective and feasibility of the This configuration of the piled PV module layers is not selected parameters for the location. considered in the present study to avoid shading losses. As mentioned earlier, polycrystalline PV modules are The power density of the Mettur FPV model in landscape used in present FPV models that are similar to the two orientation is 15.30% higher than that of the 2000-kW existing FPV plants. Regarding the orientation of the FPV plant. Despite the equivalent range of irradiance panels, portrait and landscape orientations are used in levels in Mudasarlova reservoir and Mettur reservoir, the 500- and 2000-kW FPV plants, respectively. Hence, it is proposed FPV model has high power density due to the reasonable to compare the proposed FPV model with a effective installation of a large number of PV modules Downloaded from https://academic.oup.com/ce/article/5/2/208/6271254 by DeepDyve user on 11 May 2021 226 | Clean Energy, 2021, Vol. 5, No. 2 Substation Floating carles 2MW floating PV ARRAY Fig. 17: Location of the substation in Mudasarlova reservoir with a pontoon-type floating desk rather than the raft A tilt angle of 10° was found to be more suitable for the type, which needs large spacing between the panels, as Mettur location. used in 2000-kW FPV plant. The land-area requirements (ii) Considering the power output, energy output and PR for the FPV plants are calculated based on the rule of of FPV systems with different mounting systems, a thumb of 9.29 m area required for every 1-kW panel. flat-mount system has been identified as being more Thus, a 1-MW land-based PV system requires 20  234.30 suitable for Mettur reservoir. m of land area, which includes the area for the installa- (iii) Landscape orientation of the panels is more econom- tion of panels and spacing between them [64]. Through ical due to the reduced number of panels required in effective utilization of the available area, the proposed comparison with portrait orientation. FPV model for Mettur reservoir produces better energy (iv) An FPV system with single-axis tracking yields 15.80% output without exceeding the equivalent land require- more energy in comparison with a fixed-tilt system ment, even in landscape orientation. without tracking. But the inclusion of a tracking mechanism is not advantageous from an economic perspective. 5 Conclusion Following the assessment of electrical performance, the Floating photovoltaic installation has grown tremen- carbon footprint and cost analysis of the FPV system were dously in the last 3 years with a global installed capacity also carried out. The results show that an FPV system with of 1314 MW. India, being in the development stage, has in- single-axis tracking in the Mettur reservoir will help in re- creased its FPV implementation from kW to MW scales in ducing 135  918.87 tons of CO emission annually. Based the last 5  years. With proper technological development on the cost-analysis study, it is estimated that 35% of the in the FPV sector, India has the potential to implement total cost of the project is associated with the construction ≤280 GW of capacity with its available water resources. of the floating platforms. However, this can be effectively This study presents a detailed numerical analysis of a compensated for by the cost reduction due to the existing model FPV system in Mettur reservoir. It is observed that grid connection of the HEPP. This small-scale methodology the FPV cover will save 184 589 m of water annually from exemplified for the Mettur reservoir outlining key design evaporation. The demonstrative plant in this study is also factors will support the 100-MW FPV target plan of Tamil analysed for various angles of inclination, mounting sys- Nadu government in Mettur reservoir. As India is a tropical tems and tracking mechanisms. 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Clean EnergyOxford University Press

Published: Jun 1, 2021

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