Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Bridging the energy gap of India’s residential buildings by using rooftop solar PV systems for higher energy stars

Bridging the energy gap of India’s residential buildings by using rooftop solar PV systems for... Name: ABC Address: XXX Keywords: ECBC; residential star building; rooftop solar PV; RETScreen this will further increase in the range of 630–940 TWh by Introduction 2032 [4]. India, with a population of >1.3 billion, is the second-most To address energy efficiency in the commercial building populous country in the world and the third-largest economy sector, the Energy Conservation Building Code (ECBC) was in terms of Purchasing Power Parity. India has set a target launched in 2007 [5]. The code applies to buildings with a economy of USD5 trillion by the year 2024–25 with an an- connected load of ≥500 kW or a contact demand of ≥600 nual growth rate of 9%. India’s sustained economic growth kVA. In 2017, ECBC 2007 was modified to ECBC 2017 and in this period will require an enormous energy supply. Key applies to buildings or building complexes that have a indicators of the economy, population and energy between connected load of ≥100 kW or a contract demand of 120 the years 2001 and 2017 are shown in Fig. 1. India intends to kVA. The ECBC provides minimum requirements for the reduce the emissions intensity of its gross domestic product energy-efficient design and construction of buildings. The by 33–35% by 2030 from the 2005 level [1 ]. For achieving this code was extended to the residential buildings through target, improvement in energy efficiency is required in all ECBC 2018-R (Eco-Home guidelines) and it applies to all the sectors, especially in the building sector, as the building residential-use buildings built on a plot area of ≥500 m . sector in India consumes >30% of the total electricity [ ]. 2 The star-labelling programme for all single- and The gross electricity consumption in residential build- multiple-dwelling residential units has been initiated by ings has been rising sharply over the years. Building the Bureau of Energy Efficiency (BEE) [6]. There is no min- energy-consumption figures rose to ~260 TWh in 2016–17, imum requirement for the area or connected load (kW) which was ~55 TWh in 1996–97 [3]. It is estimated that for a building dwelling unit to be covered under this la- belling programme. The Energy Performance Index (EPI) of a building (annual energy consumption in kilowatt-hours per square metre of the building) is taken as an indicator for Legends Index 2001=1 the star label of the building. The EPI includes three com- 3.5 GDP ponents, namely E1, E2 and E3. E1 and E2 include building 3.0 Electricity Generation envelope characteristics, lighting systems and comfort Energy related C02 systems (air conditioners (ACs)). The calculation is made 2.5 TPES with the assumption that 25% of the space in the building 2.0 TFC is air-conditioned with 24°C as the set point (E1) and the 1.5 Population remaining 75% of the space is naturally ventilated (E2). The CO2/kWh 1.0 EPI (E3) for other building appliances such as microwave CO2/GDP ovens, grinders, refrigerators, TVs, water pumps, washing 0.5 machines, etc. is considered to be in the range of 7–9. The 0.0 EPI required for star labelling for different climate regions 2001 2003 2005 2007 2009 2011 2013 2015 2017 is tabulated in Table 1 considering the value of E2 as 8. Years The objective of this research study is to calculate the Fig. 1: Trend in the economy, population and energy [29] energy potential of grid-connected photovoltaic arrays Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Dalal et al. | 425 Table 1: Residential-building EPI (X) for star labelling [6] Consumption of electricity by sectors during 2018–19 Stars Composite Warm and humid Hot and dry Temperate Traction and 1 star 60 < X ≤ 68 66 < X ≤ 72 63 < X ≤ 75 36 < X ≤ 39 Others Agriculture Railways 2% 2 star 53 < X ≤ 60 57 < X ≤ 65 55 < X ≤ 63 32 < X ≤ 36 6% 18% 3 star 45 < X ≤ 53 47 < X ≤ 57 46 < X ≤ 55 29 < X ≤ 32 Commercial 4 star 37 < X ≤ 45 38 < X ≤ 47 37 < X ≤ 46 25 < X ≤ 29 8% 5 star X ≤ 37 X ≤ 38 X ≤ 37 X ≤ 25 on residential-building roofs for achieving the desired five-star energy labelling. The primary data come from a survey of the energy consumption of urban households Industry Domestic located in Delhi and consumers are categorized based on 42% 24% their annual energy consumption. For the selection of ap- propriate rooftop solar PV plants, the energy consumption of the buildings, the electricity tariffs for the residential Fig. 2: Consumption of electricity by sectors during 2018–19 [9] sector, the government subsidy on rooftop solar PV and the BEE’s proposed star labelling for residential buildings growth rate (CAGR) of 6.58%. The per-capita energy con- were considered. We were thus able to estimate the eco- sumption increased from 19  669 Megajoules in 2011–12 nomic potential of rooftop solar PV systems by utilizing to 24  453 Megajoules in 2018–19 with a CAGR of 3.67% the unused roof area of the building. The final section of [8]. Electricity consumption by different sectors of India the article presents the conclusions that can be derived in 2018–19 is given in Fig. 2 and the domestic sector con- from this study. sumes 24% of the total energy [9]. This is probably the first such study to have explored The BEE started the Perform Achieve and Trade (PAT) the star labelling of existing residential buildings in India; programme, which is a regulatory instrument for redu- it was searched in Google Scholar with different combin- cing specific energy consumption in energy-intensive des- ations of words and no such study was found that covered ignated consumers (DCs). It also dovetailed with a market this problem statement. The findings of the study may be mechanism to enhance the cost-effectiveness through the considered for fine-tuning policies and developing rele- certification of excess energy saving that can be traded in vant intervention tools for existing building occupants energy exchanges. The first PAT cycle, which was completed for achieving the building star label through government in March 2015, achieved an energy saving of 8.67 million rooftop solar PV subsidies. tons of oil equivalent (Mtoe), which was ~30% more than the target. The second PAT cycle (2016–19) included three indus- tries in addition to eight industries of the PAT–I cycle and seeks to achieve an energy-saving target of 8.86 Mtoe [10]. 1 Overview: energy conservation Standard and Labeling (S&L) in India works on a model in India in which the vendor provides information related to the India’s basic framework for electricity generation and energy efficiency of the product on the label as prescribed supply was provided by the Electricity Act, 1910. After inde- by the BEE. A  star rating, ranging from one to five in as- pendence in 1947, social progress and development were cending order of energy efficiency, is provided for prod- given impetus and policies were directed for ensuring the ucts registered. An endorsement label is also provided for supply of energy to all stakeholders. Energy-conservation 23 products, of which 10 are mandatory and 13 are vol- measures were started in the year 1970 when the pri- untary. The impact of this programme is visible from the mary focus was to reduce the consumption of petroleum. sale of star-label ACs in the market, as shown in Fig. 3. The In 1981, the Inter-Ministerial Working Group on Energy weighted average of the Indian seasonal energy-efficiency Conservation (IMWG), through 200 energy audits, predicted ratio of ACs increased from 2.80 (in FY 2011) to 3.70 (in FY energy savings of Rs 19.25 billion by investing in energy- 2017–18) [11]. Forty percent of the energy consumed by saving technologies. In 2001, the Energy Conservation Bill room ACs could be saved cost-effectively by enhancing was passed and the Energy Management Centre was re- their efficiency. This translates into a potential energy constituted as the BEE in 2002 [7]. saving of 118 TWh at busbars or a peak-demand saving of The increasing population, energy shortage and aware- 60 GW by 2030 [12]. ness of environment-related issues (such as greenhouse- gas emissions) have raised concerns worldwide about 2 Literature survey current trends in energy consumption. In India, the es- timated electricity consumption in the last 10  years in- The British Petroleum report has indicated that the global creased from 612  645 GWh (2009–10) to 1  158  310 GWh energy demand has grown in the 10 years from 2007 to (2018–19), which corresponds to a compound annual 2017 [13]. Oil consumption will grow by 30% from 2007 Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 426 | Clean Energy, 2021, Vol. 5, No. 3 to 2035, while coal and natural-gas consumption will in- [21]. Florida’s residential energy code has resulted in a de- crease by 50%. The International Energy Agency predicts crease in electricity consumption and a 6% decrease in that with a business-as-usual scenario, the energy-related natural-gas consumption [22]. Energy savings of 31.4% and emissions of carbon dioxide (CO ) will double by 2050 [14]. peak savings of 36.8% were recorded for high-rise apart- Globally, the building sector is responsible for consuming ments in Hong Kong by adopting passive energy-efficient >40% of the total energy consumption [15]. Poor energy strategies [23]. In Greece, the thermal insulation of walls, performance of existing buildings is observed around the roofs and floors, and low-infiltration strategies reduced world [16]. A mix of technologies can enhance the energy energy consumption by 20–40% and 20%, respectively [24]. performance of buildings [17]. Green buildings have proven A  study in Arizona of energy-star buildings before and their performance but still they have not percolated into after the buildings’ certification showed that the occu- the market [18]. pants’ consumed 8% less energy on a monthly basis after As per the US Energy Information Administration, by certification [25]. The effectiveness of the ENERGY STAR the implementation of energy codes and updated effi- programme for residences in Alachua County, Florida, was ciency standards for appliances, the USA could save 3.79 analysed using monthly residential energy-consumption trillion joules [19]. Hong Kong’s building energy code has data between 2000 and 2013; energy savings of 10.9% were improved energy efficiency and also reduced air pollution found under Florida Building Code (FBC) 1997 and 18.6% [20]. Enforcement of Chinese national building standards under FBC 2001 [26]. For the top 25 percentile of buildings led to a 62% energy saving in public buildings and the in Singapore that are eligible for the star label in terms of building code of the UK revealed energy savings of ≤75% an energy-efficiency label, the energy-usage intensity of 178 kWh/m is comparable to the US ENERGY STAR build- ings’ best practice in Californian office buildings [27]. Office Star lable ACs distribution 2017–18 buildings with ENERGY STAR or Leadership in Energy and Environmental Design (LEED) eco-labels get rental pre- 1 star 5 star 2 star 6% miums of ~3–5%. Dual certification fetches an estimated 18% 7% 4 star rental premium of 9%. The sale-price premium for ENERGY 4% STAR- and LEED-labelled office buildings are 18% and 25%, respectively [28]. In 2005, India’s residential and commercial floor area was estimated to be 1.6 and 0.5 billion m , respectively, which in- creased to 3.5 and 1 billion m in 2012. It is also estimated that, by 2030, residential and commercial floor space will increase to 7.0 and 1.5 billion m [18]. The residential sector is the third-largest consumer of electricity and increased by 26% between 2014 and 2017 as shown in Fig. 4 [29]. 3 star 65% By implementing energy-conservation measures re- commended by the ECBC, small buildings can save ≤40% of Fig. 3: Star-label AC distribution 2017–18 [11] the energy used as compared to present buildings in India Energy in TWh Legends Transport Residential Services Industry 1973 77 1981 85 89 1993 97 2001 05 07 201113 2017 Years Fig. 4: Electricity consumption in different sectors (IEA India Report, 2020) [29] Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Dalal et al. | 427 Cumulative Installation of Distribution Roof top solar PV Installation (MW) grid-connected solar PV Residential 14% Public Commercial sector 13% Cumulative Installations 21% in India (GW) Industrial 52% Fig. 5: Grid-integrated solar PV rooftop installations in India (2010–19) [35] [30]. The ECBC could generate a saving of 419 800 GWh in the Gujarat state between 2010 and 2050. Extending the Fig. 6: Distribution of installed rooftop solar PV systems up to ECBC beyond the commercial sector could achieve add- December 2019 [49] itional savings of 193 700 GWh between 2010 and 2050 [31]. A study of six categories of commercial buildings in Jaipur surplus energy of 8450 kWh annually into the grid [43]. city (India) has established that the implementation of the Computer simulation of the installation of the rooftop ECBC can conserve energy by ≤42% [32]. ECBC compliance PV system at five locations in India shows that the en- in hotel buildings in Jaipur results in saving energy in the ergy required for a roof-induced cooling load decreased range of 18.42–37.2% [33]. Another study estimates that by between 73% and 90% [44]. Energy simulation of a buildings in Ahmedabad city (India) could reduce their 110-kWp stand-alone rooftop solar PV system for Bhopal cooling load by 31% by using the ECBC code for envelope (India) demonstrated a payback period of 8.2 years [45]. design [34]. A  grid-connected solar PV system net present cost be- India has a renewable-energy target of 175 GW by 2022. comes 0 at ~1.8 and 3.4 kW, and the cost of energy de- Solar energy will contribute 100 GW; of this, 40 GW would creased with an increase in the capacity addition for the be from rooftop solar PV systems. India had already in- household [46]. stalled 28 GW of solar capacity as of March 2019 [35]. The progress of installation from 2010 to March 2019 is shown 3 Research and collection of data in Fig. 5. Rooftop solar PV installation reached 5.4 GW in The present work is a study on the star labelling of resi- December 2019 and installation is predominately in indus- dential buildings in India that investigates the residential- trial and commercial buildings. The distribution of rooftop building energy consumption and existing gap for star solar PV systems in the different sectors is shown in Fig. 6. labelling promulgated by the BEE. This study also aims to A study of Andalusia (Spain) suggests that rooftop estimate the overall impact of rooftop solar PV system ap- solar PV systems would satisfy 78.89% of the residential plication in a hot-dry climate in achieving a higher star energy demand [36]. In the USA (2015), with residential label. The key objectives of the study are to: solar incentives, 18 of the 51 target cities could reach the break-even point [37]. A  study of the city of Al-Khobar in • quantify the residential-building energy consumption Saudi Arabia suggests that villas and apartment build- (kWh/m /year) through a case study; ings can offset 19% of their electricity demand by utilizing • estimate the energy gap for star labelling and bridging rooftop solar PV systems, when 25% of the building roof this gap through rooftop solar PV systems; for solar PV systems and cooling loads also reduces by 2% • establish the economics of rooftop solar PV systems for due to the shading effect of panels [38]. In the USA, with residential buildings. subsidies, six states have reached socket parity, yet wide- The study has been undertaken for residential buildings in the spread parity has still not been achieved [39]. In Malaysia, Palam area of New Delhi, India. The details of the location are a grid-connected residential solar PV system is found to be given in Table 2. The distribution of flats as per the RETScreen feasible for installation [40]. A  study shows that a 5-kWp version 8 (a software program developed by Natural Resource PV system in Egypt can provide 67.5% of the energy re- Canada [47]) location module is given in Fig. 7. quirement for residential consumers [41]. The residential block is a two-storey structure con- A study of the rooftop solar photovoltaic potential for sisting of four houses with two basements for parking. The Mumbai (India) suggests that it can meet 12.8–20% of the ground coverage of the building block is 314 m and the daily energy demand [42]. Simulation of a 6.4-kW rooftop carpet area is 628 m. The campus has 81 such blocks, ac- solar PV plant for Ujjain (India) demonstrated that it commodating 324 houses. not only meets building energy demand, but also feeds Upto 2010 2010–11 2011–12 2012–13 2013–14 2014–15 2015–16 2016–17 2017–18 2018–19 Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 428 | Clean Energy, 2021, Vol. 5, No. 3 Table 2: Location details (obtained from RETScreen location Table 3: Electricity tariff for Delhi residential houses 2019–20 tab) [51] Sl. no. Energy consumption (kWh) Energy charges (Rs/kWh) Latitude 28.6° N Longitude 77.1° E 1 ≤200 3.00 Climate zone 1B—very hot-dry 2 201–400 4.50 Elevation 217 m 3 401–800 6.50 4 801–1200 7.00 5 >1200 8.00 Table 4: Consumer categorization based on energy consump- tion per annum Energy consumption Group Categorization (E)/annum (kWh) A Low E ≤ 4800 B Moderate 4800 < E ≤ 9600 C High 9600 < E ≤ 14 400 D Very high E > 14 400 Vey High Fig. 7: RETScreen software representation and distribution in the flats High Low 3% 8% 14% Houses Annual Energy Consumption Distribution Moderate 75% kWh Fig. 9: Distribution of consumer-based electricity consumption 2017–18 (author analysis based on a survey of select households) Year 2017-18 Year 2018-19 Fig. 8: Distribution of houses based on annual energy consumption electricity price rates for the year 2019–20 for consumption (analysis based on a survey of households) are categorized into five stages and the same is tabulated in Table 3. Based on the residential energy consumption, con- 4 Material and methods sumers are classified into four groups, which are tabulated 4.1 Step 1: energy-consumption estimation in Table 4. Electricity-consumption data for all of the buildings were Distribution of the consumers based on energy con- collected for the period April 2017 to March 2019 from the so- sumption in 2017–18 and 2018–19 is given in Fig. 9 and Fig. 10, ciety management office. The annual energy-consumption respectively, and it is evident that the majority (>75%) of distribution of these houses is shown in Fig. 8. the end users are moderate energy consumers and that, by The average annual residential energy consumption taking suitable energy substitutions, the desired star label for the year 2017–18 was 7236.72 kWh, which increased to can be achieved. 8101.34 kWh in the year 2018–19. The sole source of energy The energy consumption of the residential consumers for the buildings is electricity supplied by BSES Rajdhani under study increased from 2017–18 to 2018–19 and, as a Power Limited (BRPL), a distributor for south and west Delhi, result, the moderate and low energy consumer category and no other source of energy is deployed by the society percentage reduced from 75% and 14% to 65% and 10%, re- or building occupants. The electricity tariff for the residen- spectively, whereas the high energy consumer category in- tial building in Delhi is based on energy consumption. The creased from 8% to 23%. 3501–4500 5501–6500 7501–8500 9501–10500 12501–13500 15501–16500 17501–18500 No. of Houses Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Temperature Dalal et al. | 429 solar PV plants rating ≤3 kW and a 20% subsidy for solar PV 4.2 Step 2: calculation of the technical performance of rooftop solar PV systems plants rating >3 kW up to 10 kW. The selected site receives an average of 5.06 kWh/m /day solar radiation horizontal Three rooftop solar scenarios are considered for residen- and its monthly availability is given in Fig. 11. tial buildings based on the present energy consumption and available area on the rooftop. The calculation for these three scenarios is carried out using a solar rooftop financial 4.3 Step 3: simulation and economic analysis of calculator hosted on the Ministry of New and Renewable solar rooftop PV plants Energy (MNRE) website (https://mnre.gov.in/) and is tabu- The electricity generated from the PV system that was cal- lated in Table 5. culated in Table 5 was validated by using RETScreen ver - The cost of the proposed solar PV plant is based on the sion 8 [48]. The energy output obtained from RETScreen is MNRE benchmark cost that also includes subsidies ex- within a tolerance of 5% as compared to results obtained tended by the MNRE. The MNRE gives a flat 40% subsidy on from the MNRE solar PV rooftop calculator (Tabl ).e 6 Analysing the residential electricity tariff (Tabl),e a 3 flat 40% subsidy extended up to a 3-kW rooftop solar PV Very High Low 2% system, the distribution of consumers based on energy High 10% 23% consumption (Figs 10 and 11) and the energy gap for the star label by solar power (Tables 1 and 7) of a 3-kW rooftop solar PV are considered for the case study. Eighty to 90% of the houses could achieve a five-star label by employing a 3-kW rooftop solar PV. The distribution of star labels for 2017–18 and 2018–19 for the buildings as per consumption is shown in Figs 12 and 13, respectively. Low and moderate energy consumers (Table 4 ) could achieve a high five-star label by employing a rooftop solar PV system whereas high energy consumers could achieve an additional two-star label by this measure. Moderate The economic viability of a rooftop solar PV system for 65% the buildings under consideration was also ascertained Fig. 10: Distribution of consumer-based electricity consumption 2018– by using RETScreen. The net present value (NPV) based on 19 (analysis based on a survey of select households) discounted cash flow was used as an analysis approach using the RETScreen cost and finance module. The analysis Table 5: Residential solar rooftop PV evaluation [47] period was assumed to be 25 years based on the useful life and warranty period of solar PV panels. Financial param- Roof area (150 Roof area util- Solar The energy MNRE eters used in the RETScreen finance module for ascer- m ) utilization ized by solar plant produced benchmark percentage PV plant (m) (kW ) (kWh)/year cost (Rs) taining the economic viability of the two scenarios are given in Table 7 and the simulation results obtained are 20 30 3 4140 75 600 tabulated in Table 8. 26 40 4 5520 106 600 To explore rooftop solar PV systems for other climatic 33 50 5 6900 139 400 zones, an exercise akin to that undertaken in Delhi was KWh/m2/day Celcius 7 35 6 30 5 25 4 20 3 15 2 10 1 5 0 0 Jan Feb Mar Apr MayJun JulAug Sep Oct Nov Dec Months Fig 11: Monthly solar radiation horizontal availability at the site (analysis based on RETScreen simulation) [48] Solar radiation Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 430 | Clean Energy, 2021, Vol. 5, No. 3 Table 6: Technical evaluation of residential solar PV rooftop Table 8: Economics of a 3-kW rooftop solar PV system at the using RETScreen energy module study site Roof area Energy NPV with 4% annual Roof area (150 utilized by Solar produced Rooftop solar Simple escalation of electricity m ) utilization solar PV plant (kWh)/ PV (rating) payback period tariff (Rs) percentage plant (m) (kW ) year 3 kW 6.5 years 140 000 20 30 3 4320 26 40 4 5760 Table 9: Electricity tariff and solar-radiation availability in 33 50 5 7200 Indian cities Daily solar Electricity tariff Table 7: Financial parameters considered for the viability of a radiation for consumption solar PV rooftop system Coordinates horizontal for >400 kWh/ Parameter Description Source (latitude (°)/ (kWh/m / month (Rs/kWh) City longitude (°)) day) [55] Electricity escalation rate 15% [51] Inflation rate 5% [51] Mumbai 19.1/72.9 5.12 7.51 Discount rate 9.36% [52] Chennai 12.8/80.1 5.37 6.10 Project life 25 years [53] Kolkata 22.5/88.3 4.86 8.92 Debt ratio 70:30 [53] Bengaluru 13/77.6 5.32 7.80 Debt interest ratio 11% [54] Hyderabad 17.5/78.5 5.00 9.00 Debt terms 10 years [48] Ahmedabad 23.1/72.6 5.50 5.20 Pune 18.5/73.8 5.52 11.54 Distribution of star building by employing rooftop solar PV (2017–18) Table 10: RETScreen simulation of 3-kWp solar rooftop PV systems for selected cities of India 0.5% 1% One Star 25% 4% NPV with 4% Two Annual Simple annual energy payback escalation Three Star generation period of electricity Four Star City (kWh) (years) tariff (Rs) 92% Five Star Mumbai 4274 3.5 375 956 Chennai 4330 7.3 90 872 No Star Kolkata 4082 6.5 124 625 Bengaluru 4334 5.2 200 711 Hyderabad 4127 4.6 242 970 Fig. 12: Distribution of star buildings employing rooftop solar PV sys- Ahmedabad 4646 9.2 –12 174 tems (2017–18) Pune 4614 3 432 126 Distribution of Star building by employing rooftop solar PV (2018–19) 5 Conclusion Rooftop grid-integrated 3-kW solar PV systems can 1% 2%1% 7% One Star bridge a building’s existing energy gap for the five-star 8% label. The study indicates that a grid-connected 3-kWp Two Star solar PV system is suitable for rooftop residential instal- Three Star lation in most Indian cities and this retrofit improves the EPI of a building and thus provides two additional en- Four Star ergy stars to the building. The payback period of grid- connected rooftop solar PV systems varies from 3 to Five Star 7  years. However, the payback period varies widely for No Star different Indian cities; for Pune and Ahmedabad, des- 81% pite having the same annual solar radiation, the payback period is 3 and 9  years, respectively. This is primarily Fig. 13: Distribution of star buildings employing rooftop solar PV sys- due to different residential electricity tariff rates in the tems (2018–19) states of India and it is the most important factor to af- carried out for other cities of India, which are tabulated in fect the finances of rooftop solar PV systems. Therefore, Table 9. RETScreen simulation results for these cities are rooftop solar PV systems are not recommended as an in- tabulated in Table 10. strument for achieving a higher star label for the states Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Dalal et al. | 431 [12] Phadke A, Abhyankar N, Shah N. Avoiding 100 New Power like Gujarat where the residential electricity tariff is low. Plants by Increasing Efficiency of Room Air Conditioners in India: The installation of a 3-kWp grid-integrated rooftop solar Opportunities and Challenges. Report LBNL-6674E. Berkeley, CA: PV by low and moderate energy consumers is sufficient Lawrence Berkeley National Lab, 2014. for achieving the five-star energy label for the building [13] British Petroleum. Statistical Review of World Energy, 2018. whereas high and very high energy consumers need to https://www.bp.com/en/global/corporate/energy-economics/ take additional measures for getting five-star energy statistical-review-of-world-energy.html (30 June 2020, date labels for their buildings. The reduction in energy pur - last accessed). [14] U.S. Energy Information Administration. International Energy chases from the grid increases the saving of energy for Outlook 2020. https://www.eia.gov/outlooks/ieo/ (5 May 2021, end consumers and thus reduces emissions because date last accessed). grid electricity in India is predominately coal-based. This [15] International Energy Agency Modernizing . Building Energy Codes, study can be further extended for the normalization of 2013. https://unfccc.int/files/documentation/submissions_ rooftop solar PV subsidies for different states so that and_statements/application/pdf/international_energy_ this energy substitution can match the grid parity in re- agency_-_unep._modernising_building_energy_codes_to_se- spective Indian states. Further passive retrofit measures, cure_our_global_energy_future_-_submitted_by_the_u.s..pdf (5 May 2021, date last accessed). which include improvement in the envelopes of existing [16] Roberts S. Altering existing buildings in the UK. Energy Policy, residential buildings and active retrofit measures, such 2008, 36:4482–4486. as the installation of grid-integrated rooftop solar PV sys- [17] Chua KJ, Chou SK, Yang WM, et  al. Achieving better tems, can be optimized for a building based on life-cycle energy-efficient air conditioning—a review of technologies costing so that the cost of energy stars is minimized. and strategies. Applied Energy, 2013, 104:87–104. [18] Zuo  J, Zhao  ZY. Green building research-current status and future agenda: a review. Renewable and Sustainable Energy Funding Reviews, 2014, 30:271–281. [19] American Council for an Energy-Efficient Economy (ACEEE). Study is not funded by any agency/organization. Data gathered by The 2013 State Energy Efficiency Scorecard. Report E13K. https:// self for the study undertaken. Other sources cited as applicable. www.aceee.org/research-report/e13k (30 June 2020, date last accessed). Conflict of Interest [20] Chan AT, Yeung VCH. Implementing building energy codes in Hong Kong: energy saving, environmental impacts and cost. None declared. Energy and Buildings, 2005, 37:631–642. [21] Xu L, Liu J, Pein J, et al. Building energy saving potential in Hot References Summer and Cold Winter (HSCW) Zone, China: influence of building energy efficiency standards and implications.Ener gy [1] India’s Intended Nationally Determined Contribution. http:// Policy, 2013, 57:253–262. www4.unfccc.int/submissions/INDC (15 May 2019, date last [22] Jacobsen  GD, Kotchen  MJ. Are building codes effective at accessed). saving energy? Evidence from residential billing data in [2] EnergyStatistics2020.http://mospi.nic.in/sites/default/files/ Florida. Working Paper 16194. http://www.nber.org/papers/ publication_reports/Energy%20Statistics%202019-final.pdf (5 w16194 (20 June 2020, date last accessed). July 2021, date last accessed). [23] Cheung  CK, Fuller  RJ, Luther  MB. Energy-efficient envelope [3] Central Electricity Authority (CEA). Growth of Electricity Sector design for high-rise apartments. Energy and Buildings, 2005, in India from 1947–2017. New Delhi: CEA, Government of India, 37:37–48. [24] Balaras CA, Droutsa K, Argiriou AA, et  al. Potential for energy [4] NITI Aayog. India Energy Security Scenario, 2047. http:// conservation in apartment buildings. Energy and Buildings, indiaenergy.gov.in/iess/default.php (16 May 2020, date last 2000, 31:143–154. accessed). [25] Qiu  Y, Kahn  ME. Impact of voluntary green certification on [5] Bureau of Energy Efficiency. Energy Conservation Building Code building energy performance. Energy Economics, 2019, 80:461–475. User Guide. New Delhi, India: Bureau of Energy Efficiency, 2009. [26] Li  H, Carrión-Flores  CE. An analysis of the ENERGY STAR® https://beeindia.gov.in/sites/default/files/ECBC%20User%20 program in Alachua County, Florida. Ecological Economics, 2017, Guide%20V-0.2%20%28Public%29.pdf (20 January 2020, date 131:98–108. last accessed). [27] Eang  LS, Priyadarsini  R. Building energy efficiency labeling [6] Star Label Program. The star-labelling programme for all single- programme in Singapore. Energy Policy, 2008, 36:3982–3992. and multiple-dwelling residential units has been initiated by the [28] Fuerst F, McAllister P. Eco-labeling in commercial office mar - Bureau of Energy Efficiency (BEE). https://www.beestarlabel. kets: do LEED and Energy Star offices obtain multiple pre- com/ (2 August 2020, date last accessed). miums? Ecological Economics, 2011, 70:1220–1230. [7] Vasudevan R, Cherail K, Bhatia R, et alEner . gy Efficiency in India. [29] India Report, 2020. https://niti.gov.in/IEA (6 August 2020, date New Delhi: Alliance for an Energy Efficient Economy, 2011. last accessed). [8] http://www.mospi.gov.in/sites/default/files/publication/ (31 [30] USAID and BEE. HVAC Market Assessment and Transformation July 2020, date last accessed). Approach for India, PACE-D Technical Assistance Programme, [9] CEA Annual Report 2019. https://cea.nic.in/annual-report (30 2014. https://www.climatelinks.org/ resources/hvac-market- Jun 2020, date last accessed). Assessment-and-Transformation-Approach-India (30 June [10] BEE Annual Report. https://beeindia.gov.in/content/annual- 2020, date last accessed). report (30 June 2020, date last accessed). [31] Dhaka  S, Mathur  J, Garg  V. Combined effect of energy effi- [11] BEE Report. https://www.beestarlabel.com/viewMeeting/Doc ciency measures and thermal adaptation on air conditioned (30 June 2020, date last accessed). Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 432 | Clean Energy, 2021, Vol. 5, No. 3 building in warm climatic conditions of India.Ener gy and [42] Singh R, Banerjee R. Estimation of rooftop solar photovoltaic Buildings, 2012, 55:351–360. potential of a city. Solar Energy, 2015, 115:589–602. [32] Tulsyan A, Dhaka S, Mathur J, et al. Potential of energy savings [43] Dondariya C, Porwal D, Awasthi A, et  al. Performance simu- through implementation of Energy Conservation Building lation of grid-connected rooftop solar PV system for small Code in Jaipur city, India. Energy and Buildings, 2013, 58:123–130. households: a case study of Ujjain, India. Energy Reports, 2018, [33] Chedwal R, Mathur J, Agarwal GD et , al. Energy saving poten- 4:546–553. tial through Energy Conservation Building Code and advance [44] Kotak  Y, Gago  EJ, Mohanty  P, et  al. Installation of roof-top energy efficiency measures in hotel buildings of Jaipur city, solar PV modules and their impact on building cooling load. India. Energy and Buildings, 2015, 92:282–295. Building Services Engineering Research and Technology, 2014, [34] Jayswal  M. To examine the energy conservation potential of 35:613–633. passive & hybrid downdraught evaporative cooling: a study [45] Shukla  AK, Sudhakar  K, Baredar  P. Design, simulation and for commercial building sector in hot and dry climate of economic analysis of standalone roof top solar PV system in Ahmedabad. Energy Procedia, 2012, 30:1131–1142. India. Solar Energy, 2016, 136:437–449. [35] MNRE. Solar On-grid. https://mnre.gov.in/solar/solar-ongrid (7 [46] Tomar V, Tiwari GN. Techno-economic evaluation of grid con- August 2020, date last accessed). nected PV system for households with feed in tariff and time [36] Ordonez J, Jadraque E, Alegre J,et  al. Analysis of the photovol- of day tariff regulation in New DelhiP: a sustainable approach. taic solar energy capacity of residential rooftops in Andalusia Renewable and Sustainable Energy Reviews, 2017, 70:822–835. (Spain). Renewable and Sustainable Energy Reviews, 2010, [47] Rooftop Solar Calculator. https://solarrooftop.gov.in/rooftop_ 14:2122–2130. calculator (10 August 2020, date last accessed). [37] Lee M, Hong T, Koo C, et al. A break-even analysis and impact [48] RETScreen Software. https://www.nrcan.gc.ca/maps-tools- analysis of residential solar photovoltaic systems considering publications/tools/data-analysis-software-modelling/ state solar incentives. Technological and Economic Development retscreen/7465 (10 January 2021, date last accessed). of Economy, 2018, 24:358–382. [49] Bridge to India. Rooftop Solar Installation. https://bridgetoindia. [38] Dehwah AH, Asif M. Assessment of net energy contribution to com/ (7 August 2020, date last accessed). buildings by rooftop photovoltaic systems in hot-humid cli- [50] Electricity Tariff Delhi. http://www.derc.gov.in (10 August 2020, mates. Renewable Energy, 2019, 131:1288–1299. date last accessed). [39] Hagerman  S, Jaramillo  P, Morgan  MG. Is rooftop solar PV at [51] https://www.statista.com/statistics/ (10 August 2020, date last socket parity without subsidies? Energy Policy, 2016, 89:84–94. accessed). [40] Abul SB, Muhammad EH, Tabassum M, et al. Feasibility study [52] Renewable Tariff Order. https://Cercind.gov.in/2019/orders (10 of solar power system in residential area. International Journal August 2020, date last accessed). of Innovation in Computational Science and Engineering (IJICSE), [53] Renewable Tariff Calculations. http://www.cercind.gov.in/2020/ 2020, 1:10–17. draft_reg/DEM-RE-Tariff-Regulations2020.pdf (10 August [41] Gabr AZ, Helal AA, Abbasy NH. Economic evaluation of rooftop 2020, date last accessed). grid-connected photovoltaic systems for residential building [54] https://mercomindia.com/ (10 August 2020, date last accessed). in Egypt. International Transactions on Electrical Energy Systems, [55] Residential Electricity Tariff. https://www.bijlibachao.com/ (10 2020, 30:e12379. August 2020, date last accessed). http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Clean Energy Oxford University Press

Bridging the energy gap of India’s residential buildings by using rooftop solar PV systems for higher energy stars

Clean Energy , Volume 5 (3) – Sep 1, 2021

Loading next page...
 
/lp/oxford-university-press/bridging-the-energy-gap-of-india-s-residential-buildings-by-using-f3t0f4fXa0
Publisher
Oxford University Press
Copyright
Copyright © 2021 National Institute of Clean-and-Low-Carbon Energy
ISSN
2515-4230
eISSN
2515-396X
DOI
10.1093/ce/zkab017
Publisher site
See Article on Publisher Site

Abstract

Name: ABC Address: XXX Keywords: ECBC; residential star building; rooftop solar PV; RETScreen this will further increase in the range of 630–940 TWh by Introduction 2032 [4]. India, with a population of >1.3 billion, is the second-most To address energy efficiency in the commercial building populous country in the world and the third-largest economy sector, the Energy Conservation Building Code (ECBC) was in terms of Purchasing Power Parity. India has set a target launched in 2007 [5]. The code applies to buildings with a economy of USD5 trillion by the year 2024–25 with an an- connected load of ≥500 kW or a contact demand of ≥600 nual growth rate of 9%. India’s sustained economic growth kVA. In 2017, ECBC 2007 was modified to ECBC 2017 and in this period will require an enormous energy supply. Key applies to buildings or building complexes that have a indicators of the economy, population and energy between connected load of ≥100 kW or a contract demand of 120 the years 2001 and 2017 are shown in Fig. 1. India intends to kVA. The ECBC provides minimum requirements for the reduce the emissions intensity of its gross domestic product energy-efficient design and construction of buildings. The by 33–35% by 2030 from the 2005 level [1 ]. For achieving this code was extended to the residential buildings through target, improvement in energy efficiency is required in all ECBC 2018-R (Eco-Home guidelines) and it applies to all the sectors, especially in the building sector, as the building residential-use buildings built on a plot area of ≥500 m . sector in India consumes >30% of the total electricity [ ]. 2 The star-labelling programme for all single- and The gross electricity consumption in residential build- multiple-dwelling residential units has been initiated by ings has been rising sharply over the years. Building the Bureau of Energy Efficiency (BEE) [6]. There is no min- energy-consumption figures rose to ~260 TWh in 2016–17, imum requirement for the area or connected load (kW) which was ~55 TWh in 1996–97 [3]. It is estimated that for a building dwelling unit to be covered under this la- belling programme. The Energy Performance Index (EPI) of a building (annual energy consumption in kilowatt-hours per square metre of the building) is taken as an indicator for Legends Index 2001=1 the star label of the building. The EPI includes three com- 3.5 GDP ponents, namely E1, E2 and E3. E1 and E2 include building 3.0 Electricity Generation envelope characteristics, lighting systems and comfort Energy related C02 systems (air conditioners (ACs)). The calculation is made 2.5 TPES with the assumption that 25% of the space in the building 2.0 TFC is air-conditioned with 24°C as the set point (E1) and the 1.5 Population remaining 75% of the space is naturally ventilated (E2). The CO2/kWh 1.0 EPI (E3) for other building appliances such as microwave CO2/GDP ovens, grinders, refrigerators, TVs, water pumps, washing 0.5 machines, etc. is considered to be in the range of 7–9. The 0.0 EPI required for star labelling for different climate regions 2001 2003 2005 2007 2009 2011 2013 2015 2017 is tabulated in Table 1 considering the value of E2 as 8. Years The objective of this research study is to calculate the Fig. 1: Trend in the economy, population and energy [29] energy potential of grid-connected photovoltaic arrays Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Dalal et al. | 425 Table 1: Residential-building EPI (X) for star labelling [6] Consumption of electricity by sectors during 2018–19 Stars Composite Warm and humid Hot and dry Temperate Traction and 1 star 60 < X ≤ 68 66 < X ≤ 72 63 < X ≤ 75 36 < X ≤ 39 Others Agriculture Railways 2% 2 star 53 < X ≤ 60 57 < X ≤ 65 55 < X ≤ 63 32 < X ≤ 36 6% 18% 3 star 45 < X ≤ 53 47 < X ≤ 57 46 < X ≤ 55 29 < X ≤ 32 Commercial 4 star 37 < X ≤ 45 38 < X ≤ 47 37 < X ≤ 46 25 < X ≤ 29 8% 5 star X ≤ 37 X ≤ 38 X ≤ 37 X ≤ 25 on residential-building roofs for achieving the desired five-star energy labelling. The primary data come from a survey of the energy consumption of urban households Industry Domestic located in Delhi and consumers are categorized based on 42% 24% their annual energy consumption. For the selection of ap- propriate rooftop solar PV plants, the energy consumption of the buildings, the electricity tariffs for the residential Fig. 2: Consumption of electricity by sectors during 2018–19 [9] sector, the government subsidy on rooftop solar PV and the BEE’s proposed star labelling for residential buildings growth rate (CAGR) of 6.58%. The per-capita energy con- were considered. We were thus able to estimate the eco- sumption increased from 19  669 Megajoules in 2011–12 nomic potential of rooftop solar PV systems by utilizing to 24  453 Megajoules in 2018–19 with a CAGR of 3.67% the unused roof area of the building. The final section of [8]. Electricity consumption by different sectors of India the article presents the conclusions that can be derived in 2018–19 is given in Fig. 2 and the domestic sector con- from this study. sumes 24% of the total energy [9]. This is probably the first such study to have explored The BEE started the Perform Achieve and Trade (PAT) the star labelling of existing residential buildings in India; programme, which is a regulatory instrument for redu- it was searched in Google Scholar with different combin- cing specific energy consumption in energy-intensive des- ations of words and no such study was found that covered ignated consumers (DCs). It also dovetailed with a market this problem statement. The findings of the study may be mechanism to enhance the cost-effectiveness through the considered for fine-tuning policies and developing rele- certification of excess energy saving that can be traded in vant intervention tools for existing building occupants energy exchanges. The first PAT cycle, which was completed for achieving the building star label through government in March 2015, achieved an energy saving of 8.67 million rooftop solar PV subsidies. tons of oil equivalent (Mtoe), which was ~30% more than the target. The second PAT cycle (2016–19) included three indus- tries in addition to eight industries of the PAT–I cycle and seeks to achieve an energy-saving target of 8.86 Mtoe [10]. 1 Overview: energy conservation Standard and Labeling (S&L) in India works on a model in India in which the vendor provides information related to the India’s basic framework for electricity generation and energy efficiency of the product on the label as prescribed supply was provided by the Electricity Act, 1910. After inde- by the BEE. A  star rating, ranging from one to five in as- pendence in 1947, social progress and development were cending order of energy efficiency, is provided for prod- given impetus and policies were directed for ensuring the ucts registered. An endorsement label is also provided for supply of energy to all stakeholders. Energy-conservation 23 products, of which 10 are mandatory and 13 are vol- measures were started in the year 1970 when the pri- untary. The impact of this programme is visible from the mary focus was to reduce the consumption of petroleum. sale of star-label ACs in the market, as shown in Fig. 3. The In 1981, the Inter-Ministerial Working Group on Energy weighted average of the Indian seasonal energy-efficiency Conservation (IMWG), through 200 energy audits, predicted ratio of ACs increased from 2.80 (in FY 2011) to 3.70 (in FY energy savings of Rs 19.25 billion by investing in energy- 2017–18) [11]. Forty percent of the energy consumed by saving technologies. In 2001, the Energy Conservation Bill room ACs could be saved cost-effectively by enhancing was passed and the Energy Management Centre was re- their efficiency. This translates into a potential energy constituted as the BEE in 2002 [7]. saving of 118 TWh at busbars or a peak-demand saving of The increasing population, energy shortage and aware- 60 GW by 2030 [12]. ness of environment-related issues (such as greenhouse- gas emissions) have raised concerns worldwide about 2 Literature survey current trends in energy consumption. In India, the es- timated electricity consumption in the last 10  years in- The British Petroleum report has indicated that the global creased from 612  645 GWh (2009–10) to 1  158  310 GWh energy demand has grown in the 10 years from 2007 to (2018–19), which corresponds to a compound annual 2017 [13]. Oil consumption will grow by 30% from 2007 Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 426 | Clean Energy, 2021, Vol. 5, No. 3 to 2035, while coal and natural-gas consumption will in- [21]. Florida’s residential energy code has resulted in a de- crease by 50%. The International Energy Agency predicts crease in electricity consumption and a 6% decrease in that with a business-as-usual scenario, the energy-related natural-gas consumption [22]. Energy savings of 31.4% and emissions of carbon dioxide (CO ) will double by 2050 [14]. peak savings of 36.8% were recorded for high-rise apart- Globally, the building sector is responsible for consuming ments in Hong Kong by adopting passive energy-efficient >40% of the total energy consumption [15]. Poor energy strategies [23]. In Greece, the thermal insulation of walls, performance of existing buildings is observed around the roofs and floors, and low-infiltration strategies reduced world [16]. A mix of technologies can enhance the energy energy consumption by 20–40% and 20%, respectively [24]. performance of buildings [17]. Green buildings have proven A  study in Arizona of energy-star buildings before and their performance but still they have not percolated into after the buildings’ certification showed that the occu- the market [18]. pants’ consumed 8% less energy on a monthly basis after As per the US Energy Information Administration, by certification [25]. The effectiveness of the ENERGY STAR the implementation of energy codes and updated effi- programme for residences in Alachua County, Florida, was ciency standards for appliances, the USA could save 3.79 analysed using monthly residential energy-consumption trillion joules [19]. Hong Kong’s building energy code has data between 2000 and 2013; energy savings of 10.9% were improved energy efficiency and also reduced air pollution found under Florida Building Code (FBC) 1997 and 18.6% [20]. Enforcement of Chinese national building standards under FBC 2001 [26]. For the top 25 percentile of buildings led to a 62% energy saving in public buildings and the in Singapore that are eligible for the star label in terms of building code of the UK revealed energy savings of ≤75% an energy-efficiency label, the energy-usage intensity of 178 kWh/m is comparable to the US ENERGY STAR build- ings’ best practice in Californian office buildings [27]. Office Star lable ACs distribution 2017–18 buildings with ENERGY STAR or Leadership in Energy and Environmental Design (LEED) eco-labels get rental pre- 1 star 5 star 2 star 6% miums of ~3–5%. Dual certification fetches an estimated 18% 7% 4 star rental premium of 9%. The sale-price premium for ENERGY 4% STAR- and LEED-labelled office buildings are 18% and 25%, respectively [28]. In 2005, India’s residential and commercial floor area was estimated to be 1.6 and 0.5 billion m , respectively, which in- creased to 3.5 and 1 billion m in 2012. It is also estimated that, by 2030, residential and commercial floor space will increase to 7.0 and 1.5 billion m [18]. The residential sector is the third-largest consumer of electricity and increased by 26% between 2014 and 2017 as shown in Fig. 4 [29]. 3 star 65% By implementing energy-conservation measures re- commended by the ECBC, small buildings can save ≤40% of Fig. 3: Star-label AC distribution 2017–18 [11] the energy used as compared to present buildings in India Energy in TWh Legends Transport Residential Services Industry 1973 77 1981 85 89 1993 97 2001 05 07 201113 2017 Years Fig. 4: Electricity consumption in different sectors (IEA India Report, 2020) [29] Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Dalal et al. | 427 Cumulative Installation of Distribution Roof top solar PV Installation (MW) grid-connected solar PV Residential 14% Public Commercial sector 13% Cumulative Installations 21% in India (GW) Industrial 52% Fig. 5: Grid-integrated solar PV rooftop installations in India (2010–19) [35] [30]. The ECBC could generate a saving of 419 800 GWh in the Gujarat state between 2010 and 2050. Extending the Fig. 6: Distribution of installed rooftop solar PV systems up to ECBC beyond the commercial sector could achieve add- December 2019 [49] itional savings of 193 700 GWh between 2010 and 2050 [31]. A study of six categories of commercial buildings in Jaipur surplus energy of 8450 kWh annually into the grid [43]. city (India) has established that the implementation of the Computer simulation of the installation of the rooftop ECBC can conserve energy by ≤42% [32]. ECBC compliance PV system at five locations in India shows that the en- in hotel buildings in Jaipur results in saving energy in the ergy required for a roof-induced cooling load decreased range of 18.42–37.2% [33]. Another study estimates that by between 73% and 90% [44]. Energy simulation of a buildings in Ahmedabad city (India) could reduce their 110-kWp stand-alone rooftop solar PV system for Bhopal cooling load by 31% by using the ECBC code for envelope (India) demonstrated a payback period of 8.2 years [45]. design [34]. A  grid-connected solar PV system net present cost be- India has a renewable-energy target of 175 GW by 2022. comes 0 at ~1.8 and 3.4 kW, and the cost of energy de- Solar energy will contribute 100 GW; of this, 40 GW would creased with an increase in the capacity addition for the be from rooftop solar PV systems. India had already in- household [46]. stalled 28 GW of solar capacity as of March 2019 [35]. The progress of installation from 2010 to March 2019 is shown 3 Research and collection of data in Fig. 5. Rooftop solar PV installation reached 5.4 GW in The present work is a study on the star labelling of resi- December 2019 and installation is predominately in indus- dential buildings in India that investigates the residential- trial and commercial buildings. The distribution of rooftop building energy consumption and existing gap for star solar PV systems in the different sectors is shown in Fig. 6. labelling promulgated by the BEE. This study also aims to A study of Andalusia (Spain) suggests that rooftop estimate the overall impact of rooftop solar PV system ap- solar PV systems would satisfy 78.89% of the residential plication in a hot-dry climate in achieving a higher star energy demand [36]. In the USA (2015), with residential label. The key objectives of the study are to: solar incentives, 18 of the 51 target cities could reach the break-even point [37]. A  study of the city of Al-Khobar in • quantify the residential-building energy consumption Saudi Arabia suggests that villas and apartment build- (kWh/m /year) through a case study; ings can offset 19% of their electricity demand by utilizing • estimate the energy gap for star labelling and bridging rooftop solar PV systems, when 25% of the building roof this gap through rooftop solar PV systems; for solar PV systems and cooling loads also reduces by 2% • establish the economics of rooftop solar PV systems for due to the shading effect of panels [38]. In the USA, with residential buildings. subsidies, six states have reached socket parity, yet wide- The study has been undertaken for residential buildings in the spread parity has still not been achieved [39]. In Malaysia, Palam area of New Delhi, India. The details of the location are a grid-connected residential solar PV system is found to be given in Table 2. The distribution of flats as per the RETScreen feasible for installation [40]. A  study shows that a 5-kWp version 8 (a software program developed by Natural Resource PV system in Egypt can provide 67.5% of the energy re- Canada [47]) location module is given in Fig. 7. quirement for residential consumers [41]. The residential block is a two-storey structure con- A study of the rooftop solar photovoltaic potential for sisting of four houses with two basements for parking. The Mumbai (India) suggests that it can meet 12.8–20% of the ground coverage of the building block is 314 m and the daily energy demand [42]. Simulation of a 6.4-kW rooftop carpet area is 628 m. The campus has 81 such blocks, ac- solar PV plant for Ujjain (India) demonstrated that it commodating 324 houses. not only meets building energy demand, but also feeds Upto 2010 2010–11 2011–12 2012–13 2013–14 2014–15 2015–16 2016–17 2017–18 2018–19 Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 428 | Clean Energy, 2021, Vol. 5, No. 3 Table 2: Location details (obtained from RETScreen location Table 3: Electricity tariff for Delhi residential houses 2019–20 tab) [51] Sl. no. Energy consumption (kWh) Energy charges (Rs/kWh) Latitude 28.6° N Longitude 77.1° E 1 ≤200 3.00 Climate zone 1B—very hot-dry 2 201–400 4.50 Elevation 217 m 3 401–800 6.50 4 801–1200 7.00 5 >1200 8.00 Table 4: Consumer categorization based on energy consump- tion per annum Energy consumption Group Categorization (E)/annum (kWh) A Low E ≤ 4800 B Moderate 4800 < E ≤ 9600 C High 9600 < E ≤ 14 400 D Very high E > 14 400 Vey High Fig. 7: RETScreen software representation and distribution in the flats High Low 3% 8% 14% Houses Annual Energy Consumption Distribution Moderate 75% kWh Fig. 9: Distribution of consumer-based electricity consumption 2017–18 (author analysis based on a survey of select households) Year 2017-18 Year 2018-19 Fig. 8: Distribution of houses based on annual energy consumption electricity price rates for the year 2019–20 for consumption (analysis based on a survey of households) are categorized into five stages and the same is tabulated in Table 3. Based on the residential energy consumption, con- 4 Material and methods sumers are classified into four groups, which are tabulated 4.1 Step 1: energy-consumption estimation in Table 4. Electricity-consumption data for all of the buildings were Distribution of the consumers based on energy con- collected for the period April 2017 to March 2019 from the so- sumption in 2017–18 and 2018–19 is given in Fig. 9 and Fig. 10, ciety management office. The annual energy-consumption respectively, and it is evident that the majority (>75%) of distribution of these houses is shown in Fig. 8. the end users are moderate energy consumers and that, by The average annual residential energy consumption taking suitable energy substitutions, the desired star label for the year 2017–18 was 7236.72 kWh, which increased to can be achieved. 8101.34 kWh in the year 2018–19. The sole source of energy The energy consumption of the residential consumers for the buildings is electricity supplied by BSES Rajdhani under study increased from 2017–18 to 2018–19 and, as a Power Limited (BRPL), a distributor for south and west Delhi, result, the moderate and low energy consumer category and no other source of energy is deployed by the society percentage reduced from 75% and 14% to 65% and 10%, re- or building occupants. The electricity tariff for the residen- spectively, whereas the high energy consumer category in- tial building in Delhi is based on energy consumption. The creased from 8% to 23%. 3501–4500 5501–6500 7501–8500 9501–10500 12501–13500 15501–16500 17501–18500 No. of Houses Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Temperature Dalal et al. | 429 solar PV plants rating ≤3 kW and a 20% subsidy for solar PV 4.2 Step 2: calculation of the technical performance of rooftop solar PV systems plants rating >3 kW up to 10 kW. The selected site receives an average of 5.06 kWh/m /day solar radiation horizontal Three rooftop solar scenarios are considered for residen- and its monthly availability is given in Fig. 11. tial buildings based on the present energy consumption and available area on the rooftop. The calculation for these three scenarios is carried out using a solar rooftop financial 4.3 Step 3: simulation and economic analysis of calculator hosted on the Ministry of New and Renewable solar rooftop PV plants Energy (MNRE) website (https://mnre.gov.in/) and is tabu- The electricity generated from the PV system that was cal- lated in Table 5. culated in Table 5 was validated by using RETScreen ver - The cost of the proposed solar PV plant is based on the sion 8 [48]. The energy output obtained from RETScreen is MNRE benchmark cost that also includes subsidies ex- within a tolerance of 5% as compared to results obtained tended by the MNRE. The MNRE gives a flat 40% subsidy on from the MNRE solar PV rooftop calculator (Tabl ).e 6 Analysing the residential electricity tariff (Tabl),e a 3 flat 40% subsidy extended up to a 3-kW rooftop solar PV Very High Low 2% system, the distribution of consumers based on energy High 10% 23% consumption (Figs 10 and 11) and the energy gap for the star label by solar power (Tables 1 and 7) of a 3-kW rooftop solar PV are considered for the case study. Eighty to 90% of the houses could achieve a five-star label by employing a 3-kW rooftop solar PV. The distribution of star labels for 2017–18 and 2018–19 for the buildings as per consumption is shown in Figs 12 and 13, respectively. Low and moderate energy consumers (Table 4 ) could achieve a high five-star label by employing a rooftop solar PV system whereas high energy consumers could achieve an additional two-star label by this measure. Moderate The economic viability of a rooftop solar PV system for 65% the buildings under consideration was also ascertained Fig. 10: Distribution of consumer-based electricity consumption 2018– by using RETScreen. The net present value (NPV) based on 19 (analysis based on a survey of select households) discounted cash flow was used as an analysis approach using the RETScreen cost and finance module. The analysis Table 5: Residential solar rooftop PV evaluation [47] period was assumed to be 25 years based on the useful life and warranty period of solar PV panels. Financial param- Roof area (150 Roof area util- Solar The energy MNRE eters used in the RETScreen finance module for ascer- m ) utilization ized by solar plant produced benchmark percentage PV plant (m) (kW ) (kWh)/year cost (Rs) taining the economic viability of the two scenarios are given in Table 7 and the simulation results obtained are 20 30 3 4140 75 600 tabulated in Table 8. 26 40 4 5520 106 600 To explore rooftop solar PV systems for other climatic 33 50 5 6900 139 400 zones, an exercise akin to that undertaken in Delhi was KWh/m2/day Celcius 7 35 6 30 5 25 4 20 3 15 2 10 1 5 0 0 Jan Feb Mar Apr MayJun JulAug Sep Oct Nov Dec Months Fig 11: Monthly solar radiation horizontal availability at the site (analysis based on RETScreen simulation) [48] Solar radiation Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 430 | Clean Energy, 2021, Vol. 5, No. 3 Table 6: Technical evaluation of residential solar PV rooftop Table 8: Economics of a 3-kW rooftop solar PV system at the using RETScreen energy module study site Roof area Energy NPV with 4% annual Roof area (150 utilized by Solar produced Rooftop solar Simple escalation of electricity m ) utilization solar PV plant (kWh)/ PV (rating) payback period tariff (Rs) percentage plant (m) (kW ) year 3 kW 6.5 years 140 000 20 30 3 4320 26 40 4 5760 Table 9: Electricity tariff and solar-radiation availability in 33 50 5 7200 Indian cities Daily solar Electricity tariff Table 7: Financial parameters considered for the viability of a radiation for consumption solar PV rooftop system Coordinates horizontal for >400 kWh/ Parameter Description Source (latitude (°)/ (kWh/m / month (Rs/kWh) City longitude (°)) day) [55] Electricity escalation rate 15% [51] Inflation rate 5% [51] Mumbai 19.1/72.9 5.12 7.51 Discount rate 9.36% [52] Chennai 12.8/80.1 5.37 6.10 Project life 25 years [53] Kolkata 22.5/88.3 4.86 8.92 Debt ratio 70:30 [53] Bengaluru 13/77.6 5.32 7.80 Debt interest ratio 11% [54] Hyderabad 17.5/78.5 5.00 9.00 Debt terms 10 years [48] Ahmedabad 23.1/72.6 5.50 5.20 Pune 18.5/73.8 5.52 11.54 Distribution of star building by employing rooftop solar PV (2017–18) Table 10: RETScreen simulation of 3-kWp solar rooftop PV systems for selected cities of India 0.5% 1% One Star 25% 4% NPV with 4% Two Annual Simple annual energy payback escalation Three Star generation period of electricity Four Star City (kWh) (years) tariff (Rs) 92% Five Star Mumbai 4274 3.5 375 956 Chennai 4330 7.3 90 872 No Star Kolkata 4082 6.5 124 625 Bengaluru 4334 5.2 200 711 Hyderabad 4127 4.6 242 970 Fig. 12: Distribution of star buildings employing rooftop solar PV sys- Ahmedabad 4646 9.2 –12 174 tems (2017–18) Pune 4614 3 432 126 Distribution of Star building by employing rooftop solar PV (2018–19) 5 Conclusion Rooftop grid-integrated 3-kW solar PV systems can 1% 2%1% 7% One Star bridge a building’s existing energy gap for the five-star 8% label. The study indicates that a grid-connected 3-kWp Two Star solar PV system is suitable for rooftop residential instal- Three Star lation in most Indian cities and this retrofit improves the EPI of a building and thus provides two additional en- Four Star ergy stars to the building. The payback period of grid- connected rooftop solar PV systems varies from 3 to Five Star 7  years. However, the payback period varies widely for No Star different Indian cities; for Pune and Ahmedabad, des- 81% pite having the same annual solar radiation, the payback period is 3 and 9  years, respectively. This is primarily Fig. 13: Distribution of star buildings employing rooftop solar PV sys- due to different residential electricity tariff rates in the tems (2018–19) states of India and it is the most important factor to af- carried out for other cities of India, which are tabulated in fect the finances of rooftop solar PV systems. Therefore, Table 9. RETScreen simulation results for these cities are rooftop solar PV systems are not recommended as an in- tabulated in Table 10. strument for achieving a higher star label for the states Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 Dalal et al. | 431 [12] Phadke A, Abhyankar N, Shah N. Avoiding 100 New Power like Gujarat where the residential electricity tariff is low. Plants by Increasing Efficiency of Room Air Conditioners in India: The installation of a 3-kWp grid-integrated rooftop solar Opportunities and Challenges. Report LBNL-6674E. Berkeley, CA: PV by low and moderate energy consumers is sufficient Lawrence Berkeley National Lab, 2014. for achieving the five-star energy label for the building [13] British Petroleum. Statistical Review of World Energy, 2018. whereas high and very high energy consumers need to https://www.bp.com/en/global/corporate/energy-economics/ take additional measures for getting five-star energy statistical-review-of-world-energy.html (30 June 2020, date labels for their buildings. The reduction in energy pur - last accessed). [14] U.S. Energy Information Administration. International Energy chases from the grid increases the saving of energy for Outlook 2020. https://www.eia.gov/outlooks/ieo/ (5 May 2021, end consumers and thus reduces emissions because date last accessed). grid electricity in India is predominately coal-based. This [15] International Energy Agency Modernizing . Building Energy Codes, study can be further extended for the normalization of 2013. https://unfccc.int/files/documentation/submissions_ rooftop solar PV subsidies for different states so that and_statements/application/pdf/international_energy_ this energy substitution can match the grid parity in re- agency_-_unep._modernising_building_energy_codes_to_se- spective Indian states. Further passive retrofit measures, cure_our_global_energy_future_-_submitted_by_the_u.s..pdf (5 May 2021, date last accessed). which include improvement in the envelopes of existing [16] Roberts S. Altering existing buildings in the UK. Energy Policy, residential buildings and active retrofit measures, such 2008, 36:4482–4486. as the installation of grid-integrated rooftop solar PV sys- [17] Chua KJ, Chou SK, Yang WM, et  al. Achieving better tems, can be optimized for a building based on life-cycle energy-efficient air conditioning—a review of technologies costing so that the cost of energy stars is minimized. and strategies. Applied Energy, 2013, 104:87–104. [18] Zuo  J, Zhao  ZY. Green building research-current status and future agenda: a review. Renewable and Sustainable Energy Funding Reviews, 2014, 30:271–281. [19] American Council for an Energy-Efficient Economy (ACEEE). Study is not funded by any agency/organization. Data gathered by The 2013 State Energy Efficiency Scorecard. Report E13K. https:// self for the study undertaken. Other sources cited as applicable. www.aceee.org/research-report/e13k (30 June 2020, date last accessed). Conflict of Interest [20] Chan AT, Yeung VCH. Implementing building energy codes in Hong Kong: energy saving, environmental impacts and cost. None declared. Energy and Buildings, 2005, 37:631–642. [21] Xu L, Liu J, Pein J, et al. Building energy saving potential in Hot References Summer and Cold Winter (HSCW) Zone, China: influence of building energy efficiency standards and implications.Ener gy [1] India’s Intended Nationally Determined Contribution. http:// Policy, 2013, 57:253–262. www4.unfccc.int/submissions/INDC (15 May 2019, date last [22] Jacobsen  GD, Kotchen  MJ. Are building codes effective at accessed). saving energy? Evidence from residential billing data in [2] EnergyStatistics2020.http://mospi.nic.in/sites/default/files/ Florida. Working Paper 16194. http://www.nber.org/papers/ publication_reports/Energy%20Statistics%202019-final.pdf (5 w16194 (20 June 2020, date last accessed). July 2021, date last accessed). [23] Cheung  CK, Fuller  RJ, Luther  MB. Energy-efficient envelope [3] Central Electricity Authority (CEA). Growth of Electricity Sector design for high-rise apartments. Energy and Buildings, 2005, in India from 1947–2017. New Delhi: CEA, Government of India, 37:37–48. [24] Balaras CA, Droutsa K, Argiriou AA, et  al. Potential for energy [4] NITI Aayog. India Energy Security Scenario, 2047. http:// conservation in apartment buildings. Energy and Buildings, indiaenergy.gov.in/iess/default.php (16 May 2020, date last 2000, 31:143–154. accessed). [25] Qiu  Y, Kahn  ME. Impact of voluntary green certification on [5] Bureau of Energy Efficiency. Energy Conservation Building Code building energy performance. Energy Economics, 2019, 80:461–475. User Guide. New Delhi, India: Bureau of Energy Efficiency, 2009. [26] Li  H, Carrión-Flores  CE. An analysis of the ENERGY STAR® https://beeindia.gov.in/sites/default/files/ECBC%20User%20 program in Alachua County, Florida. Ecological Economics, 2017, Guide%20V-0.2%20%28Public%29.pdf (20 January 2020, date 131:98–108. last accessed). [27] Eang  LS, Priyadarsini  R. Building energy efficiency labeling [6] Star Label Program. The star-labelling programme for all single- programme in Singapore. Energy Policy, 2008, 36:3982–3992. and multiple-dwelling residential units has been initiated by the [28] Fuerst F, McAllister P. Eco-labeling in commercial office mar - Bureau of Energy Efficiency (BEE). https://www.beestarlabel. kets: do LEED and Energy Star offices obtain multiple pre- com/ (2 August 2020, date last accessed). miums? Ecological Economics, 2011, 70:1220–1230. [7] Vasudevan R, Cherail K, Bhatia R, et alEner . gy Efficiency in India. [29] India Report, 2020. https://niti.gov.in/IEA (6 August 2020, date New Delhi: Alliance for an Energy Efficient Economy, 2011. last accessed). [8] http://www.mospi.gov.in/sites/default/files/publication/ (31 [30] USAID and BEE. HVAC Market Assessment and Transformation July 2020, date last accessed). Approach for India, PACE-D Technical Assistance Programme, [9] CEA Annual Report 2019. https://cea.nic.in/annual-report (30 2014. https://www.climatelinks.org/ resources/hvac-market- Jun 2020, date last accessed). Assessment-and-Transformation-Approach-India (30 June [10] BEE Annual Report. https://beeindia.gov.in/content/annual- 2020, date last accessed). report (30 June 2020, date last accessed). [31] Dhaka  S, Mathur  J, Garg  V. Combined effect of energy effi- [11] BEE Report. https://www.beestarlabel.com/viewMeeting/Doc ciency measures and thermal adaptation on air conditioned (30 June 2020, date last accessed). Downloaded from https://academic.oup.com/ce/article/5/3/423/6324054 by DeepDyve user on 20 July 2021 432 | Clean Energy, 2021, Vol. 5, No. 3 building in warm climatic conditions of India.Ener gy and [42] Singh R, Banerjee R. Estimation of rooftop solar photovoltaic Buildings, 2012, 55:351–360. potential of a city. Solar Energy, 2015, 115:589–602. [32] Tulsyan A, Dhaka S, Mathur J, et al. Potential of energy savings [43] Dondariya C, Porwal D, Awasthi A, et  al. Performance simu- through implementation of Energy Conservation Building lation of grid-connected rooftop solar PV system for small Code in Jaipur city, India. Energy and Buildings, 2013, 58:123–130. households: a case study of Ujjain, India. Energy Reports, 2018, [33] Chedwal R, Mathur J, Agarwal GD et , al. Energy saving poten- 4:546–553. tial through Energy Conservation Building Code and advance [44] Kotak  Y, Gago  EJ, Mohanty  P, et  al. Installation of roof-top energy efficiency measures in hotel buildings of Jaipur city, solar PV modules and their impact on building cooling load. India. Energy and Buildings, 2015, 92:282–295. Building Services Engineering Research and Technology, 2014, [34] Jayswal  M. To examine the energy conservation potential of 35:613–633. passive & hybrid downdraught evaporative cooling: a study [45] Shukla  AK, Sudhakar  K, Baredar  P. Design, simulation and for commercial building sector in hot and dry climate of economic analysis of standalone roof top solar PV system in Ahmedabad. Energy Procedia, 2012, 30:1131–1142. India. Solar Energy, 2016, 136:437–449. [35] MNRE. Solar On-grid. https://mnre.gov.in/solar/solar-ongrid (7 [46] Tomar V, Tiwari GN. Techno-economic evaluation of grid con- August 2020, date last accessed). nected PV system for households with feed in tariff and time [36] Ordonez J, Jadraque E, Alegre J,et  al. Analysis of the photovol- of day tariff regulation in New DelhiP: a sustainable approach. taic solar energy capacity of residential rooftops in Andalusia Renewable and Sustainable Energy Reviews, 2017, 70:822–835. (Spain). Renewable and Sustainable Energy Reviews, 2010, [47] Rooftop Solar Calculator. https://solarrooftop.gov.in/rooftop_ 14:2122–2130. calculator (10 August 2020, date last accessed). [37] Lee M, Hong T, Koo C, et al. A break-even analysis and impact [48] RETScreen Software. https://www.nrcan.gc.ca/maps-tools- analysis of residential solar photovoltaic systems considering publications/tools/data-analysis-software-modelling/ state solar incentives. Technological and Economic Development retscreen/7465 (10 January 2021, date last accessed). of Economy, 2018, 24:358–382. [49] Bridge to India. Rooftop Solar Installation. https://bridgetoindia. [38] Dehwah AH, Asif M. Assessment of net energy contribution to com/ (7 August 2020, date last accessed). buildings by rooftop photovoltaic systems in hot-humid cli- [50] Electricity Tariff Delhi. http://www.derc.gov.in (10 August 2020, mates. Renewable Energy, 2019, 131:1288–1299. date last accessed). [39] Hagerman  S, Jaramillo  P, Morgan  MG. Is rooftop solar PV at [51] https://www.statista.com/statistics/ (10 August 2020, date last socket parity without subsidies? Energy Policy, 2016, 89:84–94. accessed). [40] Abul SB, Muhammad EH, Tabassum M, et al. Feasibility study [52] Renewable Tariff Order. https://Cercind.gov.in/2019/orders (10 of solar power system in residential area. International Journal August 2020, date last accessed). of Innovation in Computational Science and Engineering (IJICSE), [53] Renewable Tariff Calculations. http://www.cercind.gov.in/2020/ 2020, 1:10–17. draft_reg/DEM-RE-Tariff-Regulations2020.pdf (10 August [41] Gabr AZ, Helal AA, Abbasy NH. Economic evaluation of rooftop 2020, date last accessed). grid-connected photovoltaic systems for residential building [54] https://mercomindia.com/ (10 August 2020, date last accessed). in Egypt. International Transactions on Electrical Energy Systems, [55] Residential Electricity Tariff. https://www.bijlibachao.com/ (10 2020, 30:e12379. August 2020, date last accessed).

Journal

Clean EnergyOxford University Press

Published: Sep 1, 2021

References