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Hindawi Journal of Healthcare Engineering Volume 2019, Article ID 3858560, 14 pages https://doi.org/10.1155/2019/3858560 Research Article Design and Implementation of a Low-Energy-Consumption Air-Conditioning Control System for Smart Vehicle Chien-Lun Weng and Lih-Jen Kau Department of Electronic Engineering, National Taipei University of Technology, No. 1, Sec. 3, Chung-Hsiao E. Rd., Taipei 10608, Taiwan Correspondence should be addressed to Chien-Lun Weng; email@example.com Received 10 February 2019; Revised 23 May 2019; Accepted 13 June 2019; Published 27 August 2019 Academic Editor: Emiliano Schena Copyright © 2019 Chien-Lun Weng and Lih-Jen Kau. ,is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. About 7% of people’s daily time is spent in taking vehicles between oﬃce and home. Besides, with the improvement of the living standard in today’s society, people’s requirements for a comfortable environment inside the car are constantly increasing and this must rely on an eﬀective vehicle air conditioner to maintain the comfort of the cabin environment. In general, a vehicle air conditioner uses the air-mixing mode to regulate the temperature control system. In this mode of operation, the compressor needs to work continuously, which is extremely energy consuming. ,e vehicle’s air conditioner is greatly aﬀected by the inner and outer heat load, which are generated therein. Furthermore, the heat load is instantly changeable. ,erefore, only when the controller can adapt to the feature of heat load, then we can ﬁnd the optimal control method, thus enabling the vehicle’s air conditioner to interact with the actual heat load to supply the balanced cooling capacity and, as a result, create the most comfortable environment inside the cabin with minimum energy consumption. For this purpose, we bring up in this paper a low-energy-consumption smart vehicle air-conditioning control system to detect total heat load, which can change the vehicle’s air-conditioning capacity mode to ° ° maintain the average temperature at 25.2 C∼26.2 C and the average humidity at 46.6%∼54.4% in the cabin. When the inner heat load is stable, the rest times of the compressor can reach 16∼23 times per hour, which attains a rate of fuel saving around 21%∼ 28%. With the proposed architecture, the purpose of the low-energy-consumption vehicle air-conditioning system can be achieved, which, at the same time, creates a comfortable environment inside the cabin. up environmental organizations and signed conventions to 1. Introduction prevent human beings from continuing to undermine the While people are pursuing both economic and technologic Earth’s ecological environment. COP21, which was the ﬁrst development, massive fossil fuels are burnt, which has al- global agreement in history, used to prevent climate change, most used up the energy that have been accumulated for and oﬃcially valid since November 4, 2016. In order to drive centuries and is destroying the environment, making the the COP21 policy, all governments worldwide are com- living condition on Earth deteriorate rapidly. Technologic mitted to developing vehicles with low energy consumption, development results in the air pollution, such as smog, PM low carbon emissions, and low pollution to slow down the 2.5 and CO , etc.; among them, traﬃc exhaust emission con- speed of environmental pollution and destruction. In ad- tributes about 30∼40% of the total air pollutants. In Taiwan, dition, since the vehicle air-conditioning has been the the traﬃc exhaust emission shares up to 37% of total air standard equipment on all modern vehicles, it provides a pollutants . ,ese emissions incur global warming, cli- comfortable in-car environment for driving and passengers; mate change, and formation of extreme climate, which are however, the massive energy consumed by car air condi- the main reasons causing the meteorological disaster to tioners is the major source of vehicle pollution. spread over the entire world. Although in-car space is not big, yet, due to the reason ,ese phenomena force people to focus on the envi- that car is long time exposed in natural environment for ronmental awareness; countries all over the world have set driving, the vehicle air-conditioning heat load has the 2 Journal of Healthcare Engineering instant change feature; the range between maximum and the PM (PM , PM ) environment will induce cardiac 10 2.5 minimum heat load is tremendously large. At present, the contractility and decreased vascular elasticity, resulting in vehicle air-conditioning system is limited by engine rpm, inadequate perfusion, which may be an important factor in and the refrigerating capacity becomes a variable, resulting causing cardiovascular system damage . Prolonged ex- in unbalance between in-car heat loads and refrigerating posure to environmental air pollution will easily cause al- capacity. At present, the thermostatic control on vehicle lergic reaction of the respiratory system, the most common air-conditioning system makes adjustment by mixing the symptom being asthma, one of the most common chronic warm and cold air, which is extremely energy consuming; diseases in children, mainly caused by the over-reaction of in addition, the in-car relative humidity (RH) is very low trachea that leads to contractions [9–11]. and thus makes in-car passengers dehydrate and easily get tired; also, it increases the car’s energy consumption. In 1.2.2. In-Car Environment. ,e scientiﬁc/technologic de- order to improve this defect, the key point is to adjust velopment and environmental protection awareness are vehicle air-conditioning control system of massive vehicles rising up, and people’s requirements on living quality are that consume massive energy and produce pollution and upgrading too. ,e air-conditioning system is a necessity in enable the vehicle A/C to make optima operation. Except modern life because it provides a comfortable activity providing comfort to in-car passengers, it will also elevate environment and meets people’s most basic physical needs. the energy-consuming eﬃciency and mitigate damage to From the survey report, Americans spend about 89% of Earth’s ecology, as well as contributing to build the sus- their daily time indoors and the remaining 11% are on tainable Earth. transporting vehicles and outdoors . ,e degree of environmental comfort is greatly inﬂuential to people’s work eﬃciency, health, and environment. 1.1. Main Factors )at Aﬀect the Comfort of Human Beings. Related indoor air quality research is not restricted to “Comfortable environment” is an ideal life style that human buildings; it also surveys semiclosed transporting vehicles. beings have been long pursuing. After the Industrial Rev- Studies have found that everyday, people spend much time olution, human life quality has been upgrading rapidly. In on their way between oﬃces and homes by taking trans- order to improve in-door environment and comfort, it also porting tools; approximately 7% of the daily time is spent on has polluted the outer environment in return. With the rapid taking transporting tools . and prosperous scientiﬁc/technologic development, urban Using vehicle air conditioning makes drivers and pas- traﬃcs become more convenient; people use transporting sengers feel comfortable in the car and is an important tools to their destinations. Research shows that people spend indicator of in-car comfort . When starting the vehicle about 7% of their daily time on boarding vehicles ; air conditioning, it cools down and dehumidiﬁes in-car air, therefore, in-car comfort becomes extremely important. bringing the in-car environment into a low-temperature and ,e main factors aﬀecting human being’s comfort are low-humidity state. When a person is in this environment, indoor temperature, relative humidity, wind speed, the body will spread heat loss to the environment through noise, etc. According to the ASHRAE 55-2013 Speciﬁ- conduction and radiate, in which 70% of body heat loss is cation , the metabolic rate of sitting human body is 1.2 caused by conduction and radiate, and 27% is evaporated by Met (1 Met � 58.15 W/m ); under typical clothing con- sweat from the skin . ,erefore, staying in the air- dition, the summer comfort temperature in Taiwan is ° ° ° ° conditioned environment for a long time will easily cause 23 C∼26 C and winter is 18 C∼20 C. Fluctuation of rel- water loss from human body. During long driving, both ative humidity at high or low temperatures becomes very driver and passengers will feel tired . important to human body’s heat balance and thermal sense . In Taiwan, we feel comfortable at 50%∼60% RH. Airﬂow distribution is within 0.15∼0.3 (m/sec) per 1.3. Variation of Vehicle Air-Conditioning Load. Nowadays, minute. Strong air ﬂow will cause discomfort easily; the our living level is elevated. In Taiwan, each family has at least more gentle air ﬂow performed in the indoor air-con- 1∼2 vehicles; to sustain the in-car comfort, it must rely on ditioning environment, the more comfortable human the car’s air-conditioning system. In-car space is not big, but body feel can achieve. during the driving, the car exposes to sunlight and in-car heat is generated, therein causing extremely large heat load. ,e maximum heat load can be 10 times over the minimum 1.2. Inner/Outer Environment Status of Current Vehicle one. For conventional internal combustion engine, the ve- hicle air-conditioning compressor is driven by engine 1.2.1. Out-of-Car Environment. Air pollution is caused not only by the pollutants emitted from factories and vehicles, crankshaft and the cooling capacity is restricted to engine but dust storms from the Gobi Desert, plant’s dust, volatile speed and is proportional to engine rpm; the ratio of max/ organic compounds (VOCs), and photochemical smog re- min output capacity is over 3 times . Although the air- actions are all part of air pollution as well . conditioning system of electric vehicle runs independently Gases exhausted from traﬃc tools contain the hazardous and since it is limited to the battery jar capacity, it has to particulate matters (PM), SO , NO , CO, and ozone (O ) reduce the energy consumption from the air-conditioning 2 X 3 system to elevate car’s durability [17–21]. ,us, the ﬁt of [5–7], closely related to the human respiratory system and cardiovascular disease. Long-term or short-term exposure in vehicle air-conditioning demand and energy supply is Journal of Healthcare Engineering 3 temperature control system. However, in this mode of extremely important; when the car is starting up or at low- speed state, in-car space temperature may rise up to 60 C due operation, the compressor needs to work continuously, which is extremely energy consuming. Moreover, the ve- to being exposed to sunlight; yet, output of car air-condi- tioning refrigerating capacity is low due to low engine speed, hicle air-conditioning matter is against both inner and and the heat load input/output is unbalanced, which will outer big heat loads, which have “instantly change” feature. make in-car passengers feel too warm and uncomfortable ,us, if we can adapt to the load characteristics and ﬁnd out . After the car drives for a while, in-car temperature the optimal control method and enable vehicle A/C to reduces gradually and heat load is down. Since the car is at supply cold energy per actual heat load required, then we high-speed state, supply of refrigerating capacity is high and can achieve a balance between supply and demand and too much cool air is supplied and passengers feel too cold create the most comfortable in-car environment with the and uncomfortable again. Since normally the vehicle air- lowest energy consumption. Motivation of performing this study is to seek the optima conditioning system mixes warm and cold air to adjust the cooling state, which makes in-car temperature approaches control method of the vehicle air-conditioning system. Regarding the “instantly change” feature in vehicle air- the setting one, driver and passengers can feel comfortable. ,is unbalanced air-conditioning system is not only conditioning load, we studied to eliminate the existed defects unable to provide comfort to people, when in-car passengers that include too low temperature/humidity and high oil feel comfortable by means of mixing of warm and cold air to consumption. ,e main purpose is to follow the heat load regulate air temperature, the system will also dehumidify the characteristics and adjust/control the air-conditioning ca- in-car air that reduces the relative humidity (RH) to as low as pacity per load demand, create the optimal energy-saving below 40% too. It thus makes in-car passengers dehydrate operation mode that supplies the exactly required in-car cooling capacity, stably maintain the in-car most comfort- and easily get tired and increases the driving danger. In addition, it is an extremely energy-consuming air-condi- able environment with low-energy consumption, and ef- fectively reduce the environmental pollution and tioning control method. Heat sources that aﬀect vehicle’s heat load are divided destruction. ,is article’s structure is illustrated as follows: Section 2 into two categories: illustrates the innovative low-energy-consumption vehicle In-car generated heat load: this includes heat coming air-conditioning control system structure; Section 3 performs from the engine and human body. tests and comparison on the experimental conﬁguration and Heat load coming from the outer ambient atmosphere: performance of designed innovative system; and Section 4 heat load coming from car top, side doors, chassis, and gives the conclusion. glass windows (heat of radiation, approx. 30% of it will become in-car heat load) and warm wind from outer 2. Structure of Low-Energy-Consumption ambient environment. Vehicle Air-Conditioning Control System As illustrated above, the purpose of this study is to achieve 1.4. Improve Vehicle Air-Conditioning’s Comfort Eﬀect by Low the optima control of low-energy-consumption vehicle air- Energy Consumption. Vehicle air conditioning now has conditioning system, interpret the structure and features of become the standard equipment of modern vehicles. It can conventional vehicle air-conditioning system and bring up provide drivers and passengers a comfortable in-car envi- the structure of low-energy-consumption vehicle air-con- ronment. Yet, turning on the air-conditioning system will ditioning control system studied to improve the defects and increase engine loading and energy loss. Factors that aﬀect problems on the conventional system. In this section, we are vehicle’s energy consumption are the driving habit, weather interpreting the structure of the planned system in detail. status, traﬃc status, vehicle status, etc. Among them, the one inﬂuencing the oil consumption most is initiating the vehicle air conditioning, and average oil consumption will increase 2.1. Structure of Vehicle Air-Conditioning System. Along with up to 21% from it ; for an electric vehicle, after initiating the higher requirement of in-car comfort, the vehicle air- the air-conditioning system or electric-heating system, the conditioning system can provide cooled, heated, dehu- durability drops over 50% obviously. ,erefore, developing a midiﬁed, and defogged air; ways to drive the vehicle air- low-energy-consumption air-conditioning system becomes conditioning system mainly are two: one is the pulley an important indicator in future vehicle development. compressor system; the other one is the electric compressor Nowadays, the energy-saving control mode of vehicle system, shown in Figure 1 . air conditioners can be achieved by establishing a pre- ,e vehicle air-conditioning structure is shown in diction model for the number of passengers and the am- Figure 2 ; it is mainly conﬁgured by using a com- bient temperature  or with the battery cooling and pressor, condenser, evaporator, and four-way valve. motor waste heat recovery for the management of tem- Among them, the most critical one is the compressor. ,e perature [18, 19]. Air-conditioning performance can also other important structure is the air-mixing box that mixes be improved through refrigerant improvement [20, 21]. For both warm and cold air, as shown in Figure 3 . At both electric vehicles and hybrid electric vehicles, the air present, most vehicle air-conditioning equipment applies conditioner uses the air-mixing mode to regulate the air-mixing way to control in-car temperature eﬀectively. 4 Journal of Healthcare Engineering ACCS Engine Motor EACCS Outside air Compressor Cabin air Condenser Expansion Evaporator valve Figure 1: Structure ﬁgure of air-conditioning circulation in conventional internal combustion engine and electric vehicle . Air conditioning system 1. Compressor 5. Receiver/drier Hot compressed gas - high pressure 2. Compressor clutch 6. Expansion valve Cooled compressed liquid - high pressure Cold liquid/vapour - low pressure 3. Condenser 7. Evaporator 4. Condenser fan 8. Cabin blower motor Cold vapour - low pressure Figure 2: Vehicle air conditioning system . Yet, since vehicle air-conditioning compressor connects to condenser to form cooling eﬀect. Heating eﬀect is made car engine by transmission belt, it normally works at peak over inducing engine’s cooling water into the heat core in capacity, which not only shortens part’s operating lifetime air-conditioning assembly and has the in-car air ﬂow over but also wastes unnecessary energy during the air-condi- the heat core to heat up and is sent to in-car space, as tioning process. shown in Figure 3 . To sustain in-car comfort, it has to mix both the cold and warm air to meet thermostatic eﬀect; yet, the side eﬀect is that the in-car air humidity is too low 2.1.1. Pulley Compressor. At present, the vehicle air-con- and energy consumption is heavy. ditioning system of fuel-oil vehicle is driven by internal Air conditioning on fuel-oil vehicles works by using a combustion engine; the engine rotates to drive the engine-drive compressor, and its cooling eﬀect is pro- portional to the compressor and engine rpm, which in- compressor over belt pulley; after evaporator has absorbed in-car heat, heat is emitted to outer environment via directly increases engine’s load and makes vehicle increase Journal of Healthcare Engineering 5 Damper EA Defogging damper To defogger Evaporator RA Air-mixture door Damper Ventilator Damper Fan motor Heat core To foot-plate Figure 3: Structure of air-mixing box in vehicle air-conditioning system . its oil consumption while the A/C system is initiated. ,e 50% severely. Advantages and disadvantages of the electric advantages and disadvantages of pulley compressors in the compressor air-conditioning system are as follows: vehicle air-conditioning system are as follows: Advantages: the air-conditioning system can run in- Advantage: mature technologies, easy for thermostatic dependently; compressor can run under frequency- control; use engine’s cooling water to provide in-car varying control to elevate the overall air-conditioning heated air; the heat source supply is stable. eﬃciency; thermostatic control is easy. Disadvantage: thermostatic control has to make ad- Disadvantages: the energy-consuming amount of the justment through mixing the warm/cold air; while at air-conditioning system aﬀects the durability of electric engine’s idling speed state, the cooling/heating eﬀects vehicle. ,e electric-heating system is applied to supply are not good. Since the cooling eﬀect is proportional to heated air; the features of poor eﬃciency of energy engine output capacity, ratio of maximum and mini- conversion on the electric system and high energy mum output capacity is always over three times that of consumption of electric-heating system make the du- rability of electric vehicle down obviously. In addition, waste energy; vehicle cannot normally supply air- conditioning service while vehicle is stationary. the construction cost of the electric compressor and electric-heating system is relatively expensive. ,e vehicle air-conditioning system provides a com- 2.1.2. Electric Compressor. With the rise of environmental fortable in-car environment to the driver and passengers; awareness, vehicle technology focus gradually shifts from yet, from above, we know that the promotion of vehicle air- traditional internal combustion engine to electric motor. conditioning technology still has the energy waste problem With this evolution, the technical development of the dy- while initiating the air-conditioning system on vehicle. namic system and energy storage system of an air-condi- tioning system structure also changes. As shown in Figure 1 , the electric compressor that integrates the drive motor, 2.2. Structure of Planned Innovative Control System. At compressor, and drive circuit has replaced the conventional present, thermostatic control of the vehicle air-conditioning pulley compressor, which enables the air-conditioning system mostly applies mixing of both warm and cold air and system to work independently, and will not increase the load meets the goal of comforting in-car passengers with suitable of dynamical system. ,e system is able to adjust the work temperature. ,is operation is very energy consuming; once status freely per requirement and avoid consuming addi- the target temperature is met, it can also inﬂuenced the in- car air humidity and always result in low relative humidity tional power output; yet, it still is limited by battery jar capacity. Only reducing energy consumption of the air- condition. In this study, the structure of low-energy-con- conditioning system can elevate the durability of electric sumption smart vehicle air-conditioning control system can vehicle eﬀectively . be divided into the sensing unit, set unit, central processing Normally, the electric vehicle is equipped with devices unit (CPU), and output control unit, shown in Figure 4. that can provide stable high-temperature media; the way of ,e most outstanding feature of this study is to build a using engine’s hot cooling water to provide heated air is low-energy-consumption smart air-conditioning control also replaced by electric heating, whereas the conversion of system (Figure 5)  without modifying the devices of the electric heating providing required in-car heated air is vehicle air-conditioning system. ,e system can detect vehicle’s heat load, and control center follows vehicle’s heat always limited by electric-heating conversion and heat conduction eﬃciency. In addition, the electric-heating load to control the refrigerating capacity output from the air-conditioning system; when in-car environment meets system is an extremely high energy-consuming equipment that makes the durability of electric vehicle reduce over the set temperature, it stops compressor’s run at suitable 6 Journal of Healthcare Engineering Sensing unit Central processing unit Outdoor ambient temperature sensor Heat load Air-conditioning capacity Output control unit Air-conditioning return air temperature sensor Compressor Evaporator capacity Fan speed Fan Set unit Compressor speed Frequency conversion Set temperature Figure 4: Structure diagram of low-energy-consumption smart vehicle air-conditioning control system. Low power intelligent vehicle air-conditioning control Fan control Evaporator Expansion valve Compressor control and blower Compressor Return air temperature Drier Condenser and fan High-pressure side, gas Low-pressure side, liquid High-pressure side, liquid Low-pressure side, gas Figure 5: Low-energy-consumption smart vehicle air-conditioning system diagram. timing; it has in-car space maintaining air temperature Temperature sensor A/C power and control lines within the range that comforts human body, it reduces vehicle’s oil consumption, which meets both comfort and environmental protection requirements. Solid demo dia- gram of the controller used in this study is graphically shown in Figure 6. In this study, we ﬁrst explore the overall heat load of Temperature vehicle. Heat load means all in-car heat sources, including display conduction heat load from vehicle body, solar radiation heat Temperature Temperature load, latent and sensible heat load from out-of-car air, human tuning knob setting button body heat load, and vehicle power-equipment heat load. All heat loads can be detected by the outer environment tem- Figure 6: Solid demo diagram of low-energy-consumption smart perature sensor and return air temperature sensor in the vehicle air-conditioning controller. sensing unit, being sent back to CPU for processing and obtain the total heat load of vehicle. After obtaining total heat load, when initiating the vehicle gets the air-conditioning capacity to be supplied by air-con- ditioning system and immediately decides compressor rpm air-conditioning system, CPU receives the set target-tem- perature signal from set unit simultaneously; CPU calculates and controls the refrigerant ﬂow rate. Meanwhile, it changes through the heat load demand and temperature setting and fan speed per the heat-absorbing amount of evaporator and Journal of Healthcare Engineering 7 keeps the air-conditioning system running at optima oper- Q � V × C × ΔT. (5) Os P ating eﬃciency status with minimum energy consumption. ,e equation of outer fresh air latent heat load calcu- lation is as follows: 2.3. Calculation of Vehicle Air-Conditioning Heat Load. Q � V × C × ΔC. (6) Ol p We study the vehicle air-conditioning heat loads from in-car and out-of-car cases. In-car heat loads mainly come from ,e equation of total outer fresh air heat load calculation human body and inner equipment; out-of-car loads include is as follows: conduction heat load from vehicle body, solar radiation heat Q � Q + Q . (7) load, and latent and sensible heat load from out-of-car warm O Os Ol air. 2.3.4. Solar Radiation Heat Load. From ASHRAE 90.1 2.3.1. Human Body Heat Load. From ASHRAE 55a , Speciﬁcation , vehicle is exposed to sunlight; heat of human body heat load (Q ) can be divided into sensible heat radiation will penetrate through glass windows; yet, part of and latent heat. From in-car passenger amount (n), human radiate light is reﬂected by glass, part of it directly penetrates body heat load can be calculated from equations (1)–(3) . in and is absorbed by in-car articles and human body. ,e equation of human body sensible heat load is ,erefore, solar radiation is also the key inﬂuential factor of Q � n × sensible heat load. (1) Hs air-conditioning load. Equation (8) displays the calculation equation of radiation heat load . Sensible heat load of human body is 128.6 (W). Q is the radiation heat load, Q is the solar radiation Sr c ,e equation of human body latent heat load is strength, τ is the transmittance, a is the glass area, X is the Q � n × latent heat load. (2) inner product in light direction and glass normal direction, Hl and Q is the diﬀused light radiation strength: Latent heat load of human body is 58.1 (W). ,e equation of total human body heat load is Q � Q × τ × a × X + Q × τ × a. (8) Sr c d Q � Q + Q . (3) H Hs Hl Vehicle’s total heat load (Q ) mainly is the sum of human body heat load, vehicle-body conduction heat load, outer fresh air heat load, and solar radiation heat load. Equation (9) displays the calculation of total vehicle heat 2.3.2. Conduction of Heat Load from Vehicle Body. load (9): Temperature diﬀerence between in-car and out-of-car exists; outer environmental heat can ﬂow into in-car or out-of-car Q � Q + Q + Q + Q . (9) T H C O Sr environment, and we have to consider the inﬂuence of heat conduction that aﬀects in-car comfort. Vehicle-body heat- conduction ways can be divided to sheet metal and glass. 3. Experiment Arrangement and Tests of According to ASHRAE 90.1 Speciﬁcation , equation (4) Low-Energy-Consumption Smart Vehicle displays heat conduction calculation equation . AirConditioning Control System Q is the vehicle-body conduction heat load, u is the thermal conductivity of heat-conducting material, a is the As described above, in this study, we bring up the planning heat conduction area, and ΔT is the heat-conduction tem- and design of low-energy-consumption smart vehicle air- perature diﬀerence: conditioning control system structure and follow ASHRAE Q � u × a × ΔT. (4) Speciﬁcation to perform theoretic calculation of vehicle air- conditioning heat load. In this section, we give detailed description on the road-measurement plan of the studied vehicle air-conditioning system and provide performance 2.3.3. Latent and Sensible Heat Load from Out-of-Car Warm verifying and eﬃciency comparison statements. Air. From ASHARE 62 Speciﬁcation , each in-car person needs 2.5 L/s fresh air since ventilation will introduce fresh air and thus brings heat to in-car space. ,e calculation 3.1. Road Measurement on Vehicle Air-Conditioning Control of outer air heat load can also be divided to latent and System. In this experiment, we totally selected three models sensible heat load. Formula (5)–(7) display the calculation of cars making tests; car models under tests are listed in equations . Table 1. Q is the outer air heat load, V is the ventilation rate, Q O P ,e experimental speciﬁcation and procedure of low- is the steam latent, C is the air speciﬁc heat capacity, ΔT is energy-consumption smart vehicle air-conditioning system the in-car/out-of-car temperature diﬀerence, and ΔC is the are speciﬁed below: in-car/out-of-car humidity diﬀerence. ,e equation of outer fresh air sensible heat load calculation (1) Refrigerating capacity in the cars under test is cer- is as follows: tiﬁed; when in-car temperature is lower than 28 C, 8 Journal of Healthcare Engineering Table 1: Car models under tests. Table 2: Measuring instruments speciﬁcation table. No. Models Engine displacement Brand Model Detection range 1 A 1600 CC CO : 0∼6000 ppm, diﬀusion 2 B 1600 CC sampling TES-1370 NDIR CO 3 C 1300 CC TES Humidity: 10%∼95% RH meter ° ° Temperature: − 20 C∼+60 C/ − 4℉∼+140℉ cars are run at idling speed; temperature at cooled air outlet shall be below 10 within 10 minutes. Table 3: Outer environment parameters. (2) Each car takes two tests: one was the car which was equipped with the in-car low-energy-consumption Average Average smart vehicle air-conditioning system; the other one Models Route Set temperature temperature humidity was the car which used the original in-car air-con- ° ( C) (%) ditioning control system. Both tests were performed Without at the same start point on road. proposed 30.5 51.8 A Highway controller (3) Drove the car on freeway at 110 km/hr± 5 km/hr. 25 C 32.4 58.8 (4) In the test that the car was equipped with the in-car Without low-energy-consumption smart vehicle air-condi- proposed 31.8 74.2 B Highway tioning system, the car was refueled to full, con- controller trolled temperature at 25 C by the controller making ° 25 C 34.5 63.5 test; A/C wind speed s adjusted to maximum. After Without test run was over, we went back to gas station, proposed 32.5 63.6 C Highway controller refueled to full by autostops for three times, and 25 C 33.8 58 recorded the km driven and refuel amount. (5) For the test of using original in-car air-conditioning control, we performed the test with the procedure can see that cars equipped with the smart control system same as the above one. We applied the original presented in this study can adjust the output of compressor vehicle air-conditioning control mode; A/C wind capacity according to the in-car heat load, sustained the in- speed was adjusted to maximum and after test run car space within the range of comfortable temperature. ,e was over, we went back to gas station, refueled to full compressor rested for 16∼23 times and the smart control by autostops for three times, and recorded the system eﬀectively reduced the compressor load and obtained mileage driven and refuel amount. fuel-save target; fuel-save rate was 21%∼28% and, in par- ticular, was eﬀective to cars with lower emission capacity. (6) During the test runs, we recorded the max/min in- From Table 5 we can see that, while being without the car temperature/humidity. smart control system, when in-car heat load approached After the test cars run at diﬀerent control modes, we stability, Car A (Matrix) in-car temperature ﬂuctuated recorded the mileage driven and refuel amount; equation ° ° within 16.8 C∼20.2 C, and temperature deviation reached (10) is followed to calculate the fuel-save percentage; in-car ° ° 3.4 C and average temperature was 18.8 C; RH ﬂuctuated temperature/humidity was recorded by instruments listed in within 32.3%∼38.9%, average humidity was 34.6%; in-car Table 2. ,e suggested comfort range speciﬁed in ASHRAE environment presented a low temperature/humidity status, 55 is referred . In Taiwan, comfortable temperature is lower than the suggested comfortable range. However, with ° ° ° ° C∼26 C in summer and 18 C∼20 C in winter and hu- the smart control system, when in-car heat load approached midity is within 50%∼60% RH. stability, the in-car temperature ﬂuctuated within ,e equation calculating fuel-save percentage: ° ° ° 24.7 C∼25.5 C, temperature deviation was only 0.8 C, av- erage temperature sustained at 25.2 C; RH ﬂuctuated within S − S i f Fuel − save rate(%) � × 100%. (10) 48.7%∼58.1%, and average humidity was 54.4%; in-car av- erage temperature sustained close to the set one, making in- car driver and passengers feel comfortable. From Figure 7 we where S : system-installed speciﬁc fuel consumption and S : i f can see that the experiment result shows that while without system-free speciﬁc fuel consumption. the smart control system, in-car temperature was 20 C, which was too low; the temperature deviation amplitude also 3.2. Performance Veriﬁcation and Eﬃciency Comparison. was too big. However, with the smart control system, in-car From the oil consumptions at the statuses of car using and temperature sustained at the set target point (25 C) and not using the low-energy-consumption smart vehicle air- temperature deviation was very tiny. From Figure 8, we can conditioning control system, whether or not controlling see the experiment result showing that while without the compressor can reduce how many oil consumption is re- proposed smart control system and when the temperature alized. Table 3 shows the outer environmental parameters inside the cabin reaches the preset temperature, the air- and vehicle mileage on the road-test day. From Table 4, we conditioning compressor continues to work without rest. As Journal of Healthcare Engineering 9 Table 4: Actual fuel consumptions of cars at road test. Oil Compressor on/oﬀ Mileage Speciﬁc fuel Fuel Models Route Set temperature consumption frequency (km) consumption (km/L) economy (%) (L) Without proposed 0 121.4 9.5 12.78 A Highway controller 25 25 C 23 121.4 7.6 15.97 Without proposed 0 122 8.1 15.31 B Highway controller 21 25 C 19 122 6.7 18.51 Without proposed 0 120.8 9.1 12.75 C Highway controller 28 25 C 16 120.8 7.1 16.34 Table 5: Car A in-car temperature/humidity change table. Route Highway Set temperature Without proposed controller 25 C ° ° ° ° Range 16.8 C∼20.2 C 24.7 C∼25.5 C Temperature ( C) ° ° Average 18.8 C 25.2 C Range 32.3%∼38.9% 48.7%∼58.1% Humidity (%) Average 34.6% 54.4% Time Without proposed controller Set 25°C Figure 7: Car A in-car temperature change curve. a result, the oil consumption is 9.5 L, as shown in Figure 9. Compressor on/off frequency ,e speciﬁc fuel consumption is about 12.78 km/L, as shown in Figure 10. Compared with the test vehicle with the proposed smart control system, we see the temperature inside the cabin is controlled at the preset temperature and the air-conditioning compressor breaks 23 times during the evaluation period (one hour), as shown in Figure 8. As a result, the oil consumption is 7.6 L, as shown in Figure 9, saving 1.9 L of fuel consumption. In addition, the speciﬁc fuel consumption is about 15.97 km/L, as shown in Fig- ure 10, and its fuel economy is about 25%. From Table 6 we can see that, while without the smart control system, when in-car heat load approached stability, Car ° ° B (Lancer) in-car temperature ﬂuctuated within 20.4 C∼25.2 C, Car A temperature deviation reached 4.8 C, and average temperature was 22.2 C; RH ﬂuctuated within 33.3%∼36.7% and average Figure 8: Air-conditioning compressor rest times for Car A. Temperature (°C) 0:00:00 0:04:00 0:08:00 0:12:00 0:16:00 0:20:00 0:24:00 Times 0:28:00 0:32:00 0:36:00 0:40:00 0:44:00 0:48:00 0:52:00 10 Journal of Healthcare Engineering Oil consumption (L) was very tiny. From Figure 12 we can see the experiment result 9.5 10 shows that while without the proposed smart control system and when the temperature inside the cabin reaches the preset 7.6 temperature, the air-conditioning compressor continues to work without rest. As a result, the oil consumption is 8.1 L, as shown in Figure 13, and the speciﬁc fuel consumption is about 15.31 km/L, as shown in Figure 14. Compared with the test L 5 vehicle with the proposed smart control system, we see the temperature inside the cabin is controlled at the preset tem- perature and the number of air-conditioning compressor breaks is 19 times during the evaluation period (one hour), as shown in Figure 12. As a result, the oil consumption is 6.7 L, as 0 shown in Figure 13, saving 1.4 L of fuel consumption. ,e Car A speciﬁc fuel consumption is about 18.51 km/L, as shown in Figure 14, and its fuel economy is about 21%. Figure 9: Oil consumption for Car A. From Table 7 we can see that, while without the smart control system, when in-car heat load approached stability, Specific fuel consumption (km/L) Car C (Solio) in-car temperature ﬂuctuated within ° ° ° 21.8 C∼25.3 C, temperature deviation reached 3.5 C, av- 15.97 erage temperature was 23.4 C, RH ﬂuctuated within 30.6%∼37.8%, and average humidity was 33.4% and in-car 12.78 environment presented a low temperature/humidity status, lower than the suggested comfortable range. However, with the smart control system, when in-car heat load approached stability, the in-car temperature ﬂuctuated ° ° within 24.1 C∼27.4 C; temperature deviation was only ° ° 3.3 C, average temperature sustained at 25.5 C; RH ﬂuc- tuated within 43%∼52.8%, average humidity was 46.6%; in- car average temperature was slightly higher than the set one but still was within the allowable range, making in-car Car A driver and passengers feel comfortable. From Figure 15 we Figure 10: Speciﬁc fuel consumption for Car A. can see, the experiment result shows that while without the smart control system, in-car temperature continued to go ° ° Table 6: Car B in-car temperature/humidity change table. down from approx. 26 C to close to 20 C, making the in-car environment be in too-low temperature state. While with Route Highway the smart control system, after certain time, in-car tem- Without proposed ° ° Set temperature 25 C perature became stable, at the set target point (25 C) is controller sustained. Since Car C emission capacity is lower than Car ° ° ° ° Temperature Range 20.4 C∼25.3 C 25.5 C∼27.6 C A and Car B, the temperature deviation amplitude was ° ° ° ( C) Average 22.2 C 26.2 C bigger than Car A and Car B. From Figure 16, we can see Range 33.3%∼36.7% 41.5%∼56.2% Humidity (%) the experiment result shows that while without the pro- Average 35.3% 50.1% posed smart control system and when the temperature inside the cabin reaches the set temperature, the air-con- humidity was 35.3%; in-car environment presented a low ditioning compressor continues to work without rest. As a temperature/humidity status, lower than the suggested com- result, the oil consumption is 9.1 L, as shown in Figure 17, fortable range. While with the smart control system, when in- and the speciﬁc fuel consumption is about 12.75 km/L, as car heat load approached stability, the in-car temperature shown in Figure 18. Compared with the test vehicle with ° ° ﬂuctuated within 25.5 C∼27.6 C, temperature deviation was the proposed smart control system, we see the temperature ° ° only 2.1 C, average temperature sustained at 26.2 C; RH inside the cabin is controlled at the preset temperature, the ﬂuctuated within 41.5%∼56.2%, and average humidity was number of air-conditioning compressor breaks is 23 times during the evaluation period (one hour), as shown in 50.1%; in-car average temperature was slightly higher than the set one, but still was within the allowable range, making in-car Figure 16. As a result, the oil consumption is 7.1 L, as driver and passengers feel comfortable. From Figure 11 we can shown in Figure 17, saving 2 L of fuel consumption. ,e see, the experiment result shows that while without the smart speciﬁc fuel consumption is about 16.34 km/L, as shown in control system, in-car temperature sustained within Figure 18, and its fuel economy is about 28%. ° ° 20 C∼22 C, which was too low; the temperature deviation From the experiment, we can see that the low-energy- amplitude also was too big. While with the smart control consumption smart vehicle air-conditioning control system system, after certain time, in-car temperature became stable, revealed from this study can solve the problems of low in-car sustained at the set target point (25 C), temperature deviation air humidity and signiﬁcant oil consumption rate consumed km/L Journal of Healthcare Engineering 11 Time Without proposed controller Set 25°C Figure 11: Car B in-car temperature change curve. Compressor on/off frequency Specific fuel consumption (km/L) 19 20 18.51 15.31 Car B Car B Figure 14: Speciﬁc fuel consumption for car B. Figure 12: Air-conditioning compressor rest times for car B. Table 7: Car C in-car temperature/humidity change table. Oil consumption (L) 9 Route Highway 8.1 Without proposed Set temperature 25 C 6.7 controller ° ° ° ° Temperature Range 21.8 C∼25.3 C 24.1 C∼27.4 C ° ° ° ( C) Average 23.4 C 25.5 C Range 30.6%∼37.8% 43%∼52.8% Humidity (%) 4 Average 33.4% 46.6% load, change the air-conditioning capacity mode of air- conditioning system according to the heat load detected, sustain in-car environment comfortable, and implement the idea of supplying refrigerating capacity to balance heat load Car B accurately. When in-car environment reaches the target Figure 13: Oil consumption for car B. temperature, the system will properly halt compressor to have in-car space maintain in a comfortable temperature by the air-conditioning system, occurred in conventional range; and be able to reduce vehicle’s oil consumption. vehicle air-conditioning system that uses mixing of warm Comparison of the features of studied speciﬁc low-energy- and cold air to regulate in-car environmental temperature. consumption smart vehicle air-conditioning control system ,e control system introduced in this study does not need to against the conventional air-conditioning system is shown in modify vehicle air-conditioning system devices; what it Table 8. needs to do is merely add the study-introduced new low- ,is study is limited to the fact that the vehicles under energy-consumption smart vehicle air-conditioning control test are mainly based on traditional fuel engine. From the system. ,e system thus becomes able to detect the total heat above experiments, we can conclude that we can obtain Times Temperature (°C) 0:00:00 0:05:00 0:10:00 0:15:00 0:20:00 km/L 0:25:00 0:30:00 0:35:00 0:40:00 0:45:00 12 Journal of Healthcare Engineering Time Without proposed controller Set 25°C Figure 15: Car C in-car temperature change curve. Compressor on/off frequency Specific fuel consumption (km/L) 16.34 12.75 Car C Car C Figure 18: Speciﬁc fuel consumption for Car C. Figure 16: Air-conditioning compressor rest times for Car C. control mode of the proposed system to improve the en- vironmental comfort level and endurance of vehicle while Oil consumption (L) achieving energy saving. 9.1 4. Conclusion 7.1 From the experimental result, we can see that the planned system can get signiﬁcant beneﬁt from vehicle air-conditioning L 5 thermostatic control; in-car average temperature can be ° ° maintained within 25.2 C∼26.2 C; when in-car heat load is stable, temperature ﬂuctuating range is tiny; in-car average 2 humidity can be maintained within 46.6%∼54.4%; both pa- 1 rameters are within the suggested range, enabling in-car passengers to enjoy the comfortable environment. When Car C maintaining in-car environment at a comfortable temperature range, the halting of compressor can reach 16∼23 times and can Figure 17: Oil consumption for Car C. save fuel; fuel-saving percentage reaches 21%∼28%. From the experimental result, we get the conclusion: low emission-ca- eﬀective control for the comfort level inside the cabin and pacity vehicles can get better fuel-saving eﬀect. ,e reason why achieve energy-saving beneﬁts for traditional vehicles by we bring up the low-energy-consumption smart vehicle air- using the proposed air-conditioning system. In the future, conditioning control system in this study is to oﬀer a ther- the air-conditioning system of the hybrid electric vehicle and mostatic in-car environment to the driver and passengers. the electric vehicle can also be combined with the intelligent While the low-energy-consumption air-conditioning control Times Temperature (°C) 0:00:00 0:04:00 0:08:00 0:12:00 0:16:00 0:20:00 km/L 0:24:00 0:28:00 0:32:00 0:36:00 0:40:00 0:44:00 Journal of Healthcare Engineering 13 Table 8: Comparison table of low-energy-consumption smart vehicle air-conditioning control system vs. conventional air-conditioning system. 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