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Recently, combining the absorption chiller and dehumidifier is a well-favored implementation for high-quality air cooling. However, the coefficient of performance of the absorption chiller is limited because of the low-grade input energy, and in most previous works, the dehumidifier’s energy requirement is independently supplied by solar energy or other high-grade energy. This paper addresses these problems by utilizing the condenser waste heat of the absorption chiller for dehumidification, which is achieved by regenerating a desiccant solution. A mathematical model of the absorption chiller and dehumidification was developed in MATLAB. Here, the energy, exergy value of the absorption chiller outputs is first analyzed with respect to the varying desiccant regeneration temperature, which shows that the condenser waste heat contains significant amounts of usable exergy. Then, an energy, exergy, and technical analysis of the dehumidifier and subsequently the coupled system reveals that utilizing the proposed integrated concept could greatly increase the air-cooling exergy efficiency from a conventional 6% to 14%. This was achieved by setting the regeneration temperature to be at least 6°C above ambient. Overall, the waste heat utilization concept enabled a more efficient building space cooling and dehumidification system than conventional multi-energy complementary systems in hot and humid climates.
Tianxiang Hu; Yongting Shen; Trevor Hocksun Kwan; Gang Pei. Absorption Chiller Waste Heat Utilization to the Desiccant Dehumidifier System for Enhanced Cooling – Energy and Exergy Analysis. Energy 2021, 121847 .
AMA StyleTianxiang Hu, Yongting Shen, Trevor Hocksun Kwan, Gang Pei. Absorption Chiller Waste Heat Utilization to the Desiccant Dehumidifier System for Enhanced Cooling – Energy and Exergy Analysis. Energy. 2021; ():121847.
Chicago/Turabian StyleTianxiang Hu; Yongting Shen; Trevor Hocksun Kwan; Gang Pei. 2021. "Absorption Chiller Waste Heat Utilization to the Desiccant Dehumidifier System for Enhanced Cooling – Energy and Exergy Analysis." Energy , no. : 121847.
Transparent envelopes account for a large amount of energy consumption of buildings, especially in hot climate regions. Glass is one of the main materials in transparent envelopes, so modifying the radiative properties of the glass is an alternative way for building energy saving. Here, a semi-transparent radiative cooling (ST/RC) glass was proposed by integrating the selective utilization of solar energy and passive radiative cooling. Comparative experiments based on two small-scale boxes were performed, which shows that the indoor air temperature of the box with the ST/RC glass is lower than that with the ordinary glass and the maximum temperature difference reached 16.4 °C, indicating that ST/RC glass can reduce the waste heat generated in the indoor environment. Besides, the daylighting level with the ST/RC glass is decreased by approximately 2/3 to support comfortable daylighting. Moreover, large-scale modeling of the building located in the Maldives was conducted and results show that the energy consumption of building could be saved by 21%–66.5% when the glass is modified to transmit visible light, reflect other solar irradiance, and emit like a blackbody, which indicates that the strategy of using light and thermal management of glass has the potential to reduce the energy consumption of buildings.
Bin Zhao; Chuyao Wang; Mingke Hu; Xianze Ao; Jie Liu; Qingdong Xuan; Gang Pei. Light and thermal management of the semi-transparent radiative cooling glass for buildings. Energy 2021, 238, 121761 .
AMA StyleBin Zhao, Chuyao Wang, Mingke Hu, Xianze Ao, Jie Liu, Qingdong Xuan, Gang Pei. Light and thermal management of the semi-transparent radiative cooling glass for buildings. Energy. 2021; 238 ():121761.
Chicago/Turabian StyleBin Zhao; Chuyao Wang; Mingke Hu; Xianze Ao; Jie Liu; Qingdong Xuan; Gang Pei. 2021. "Light and thermal management of the semi-transparent radiative cooling glass for buildings." Energy 238, no. : 121761.
Recent breakthroughs in preparing near-perfect emitters have made it possible to realize daytime radiative cooling under intensive solar radiation. However, a typical radiative cooler cannot deliver heat and may even cause an undesired cooling effect on cold days. Instead of rejecting the solar radiation back to the sky, this work proposes a new concept of capturing this “free” renewable energy while dumping waste heat through radiative cooling. The new structure features an upper solar-transparent radiative emitter and a lower solar absorber. Simulation results suggest that, to realize daytime solar heating and radiative cooling simultaneously, the emitter solar-absorptivity should be extremely low, and the absorbed solar heat should be instantly and effectively taken away by thermal carriers. With an ambient temperature of 25 °C and a maximum solar irradiance of 1000 W/m2, the emitter can always reach a sub-ambient temperature if the absorber temperature is lower than 33.9 °C in the non-vacuum case, and can exceed 70 °C if the air cavity between the emitter and absorber is vacuumized. A performance simulation in three consecutive days in Shanghai reveals that the emitter can realize daytime radiative cooling with a temperature reduction of over 9.3°C from the ambient temperature around noon.
Mingke Hu; Bin Zhao; Suhendri; Jingyu Cao; Qiliang Wang; Saffa Riffat; Yuehong Su; Gang Pei. Feasibility of realizing daytime solar heating and radiative cooling simultaneously with a novel structure. Sustainable Cities and Society 2021, 74, 103224 .
AMA StyleMingke Hu, Bin Zhao, Suhendri, Jingyu Cao, Qiliang Wang, Saffa Riffat, Yuehong Su, Gang Pei. Feasibility of realizing daytime solar heating and radiative cooling simultaneously with a novel structure. Sustainable Cities and Society. 2021; 74 ():103224.
Chicago/Turabian StyleMingke Hu; Bin Zhao; Suhendri; Jingyu Cao; Qiliang Wang; Saffa Riffat; Yuehong Su; Gang Pei. 2021. "Feasibility of realizing daytime solar heating and radiative cooling simultaneously with a novel structure." Sustainable Cities and Society 74, no. : 103224.
Solar heating (SH) and Radiative sky cooling (RSC) have been recognized as remarkable renewable energy technologies due to their great energy-saving potential. Recently, the combination of SH and RSC (i.e., SH-RSC) has been proposed and developed since the SH-RSC hybrid utilization can harness heat and cold from the sun and universe directly using a single system. At present, polyethylene (PE) film has been widely used in the SH-RSC system as the wind cover, but it is flimsy and easy to age. Here, we demonstrate a rigid spectral selective cover for the SH-RSC system. The cover consists of bulk zinc sulfide (ZnS) and ZnS/ytterbium fluoride (YbF3) anti-reflective multilayer coatings on both sides of the bulk ZnS. Spectral characterization shows that the fabricated ZnS-based cover has high transmissivity of 0.86 and 0.89 within the solar radiation band and the atmospheric window, respectively. Moreover, with the rigid ZnS cover, the gap between the cover and the absorber can be achieved to be vacuum condition to maximally reduce the intrinsic energy loss and improve the performance of the SH-RSC system. The thermal analysis demonstrates that the ZnS cover-based vacuum SH-RSC system shows a thermal efficiency of 43.9% at a temperature of 80 °C in SH mode and a maximum temperature reduction of 26 °C in RSC mode, which are 17.9% higher and 10.5 °C lower than that of the typical PE cover-based system, respectively. In summary, this ZnS cover provides a choice for enhancing the performance of the hybrid utilization of daytime SH and nighttime RSC processes.
Xianze Ao; Jie Liu; Mingke Hu; Bin Zhao; Gang Pei. A rigid spectral selective cover for integrated solar heating and radiative sky cooling system. Solar Energy Materials and Solar Cells 2021, 230, 111270 .
AMA StyleXianze Ao, Jie Liu, Mingke Hu, Bin Zhao, Gang Pei. A rigid spectral selective cover for integrated solar heating and radiative sky cooling system. Solar Energy Materials and Solar Cells. 2021; 230 ():111270.
Chicago/Turabian StyleXianze Ao; Jie Liu; Mingke Hu; Bin Zhao; Gang Pei. 2021. "A rigid spectral selective cover for integrated solar heating and radiative sky cooling system." Solar Energy Materials and Solar Cells 230, no. : 111270.
Aleksandar Georgiev; Gang Pei; Yuehong Su; Petia Bobadova. Editorial/ Preface of VSI:AESMT′20. Renewable Energy 2021, 179, 204 -205.
AMA StyleAleksandar Georgiev, Gang Pei, Yuehong Su, Petia Bobadova. Editorial/ Preface of VSI:AESMT′20. Renewable Energy. 2021; 179 ():204-205.
Chicago/Turabian StyleAleksandar Georgiev; Gang Pei; Yuehong Su; Petia Bobadova. 2021. "Editorial/ Preface of VSI:AESMT′20." Renewable Energy 179, no. : 204-205.
The feasibility of integrating the radiative sky cooling ability of common photovoltaic cells into the photovoltaic-thermoelectric cooler to further enhance the space cooling energy density is analyzed in this paper. Specifically, daytime cooling is obtained by the photovoltaic panel powering the thermoelectric cooler while the same photovoltaic panel provides nighttime radiative sky cooling. To achieve an optimal temporal match between the new method’s output cooling power to a cooling building’s time-varying cooling load (with 4 occupants and 24 m2 floor space), two thermoelectric cooler modes of operation are studied; The first continuously operates the thermoelectric cooler power at the time-averaged value while the second directly supplies the photovoltaic power to the thermoelectric cooler in the daytime. Furthermore, a spectral model is used to accurately estimate the radiative energy of crystalline solar cells based on their emissivity spectrum. It is found that radiative sky cooling can almost double the equivalent solar to cooling coefficient of performance over the basic photovoltaic and thermoelectric cooler system (from 0.1099 to 0.2054). The photovoltaic area only needed to be 12–17 m2, and the second operating mode can better match the supply versus cooling demand ratio while yielding a relatively consistent 10 °C difference throughout the entire day.
Trevor Hocksun Kwan; Datong Gao; Bin Zhao; Xiao Ren; Tianxiang Hu; Yousef N. Dabwan; Gang Pei. Integration of Radiative Sky Cooling to the Photovoltaic and Thermoelectric System for Improved Space Cooling. Applied Thermal Engineering 2021, 196, 117230 .
AMA StyleTrevor Hocksun Kwan, Datong Gao, Bin Zhao, Xiao Ren, Tianxiang Hu, Yousef N. Dabwan, Gang Pei. Integration of Radiative Sky Cooling to the Photovoltaic and Thermoelectric System for Improved Space Cooling. Applied Thermal Engineering. 2021; 196 ():117230.
Chicago/Turabian StyleTrevor Hocksun Kwan; Datong Gao; Bin Zhao; Xiao Ren; Tianxiang Hu; Yousef N. Dabwan; Gang Pei. 2021. "Integration of Radiative Sky Cooling to the Photovoltaic and Thermoelectric System for Improved Space Cooling." Applied Thermal Engineering 196, no. : 117230.
Photovoltaic-thermoelectric (PV-TE) conversion is a promising method for power generation, which converts solar power into electricity using the photovoltaic (PV) effect of solar cells and simultaneously generates electricity by the Seebeck effect of the thermoelectric (TE) device based on the waste heat of solar cells. Here, the power generation of the PV-TE device at night is experimentally demonstrated using radiative cooling that harnesses the cold of the universe directly. The PV-TE device is constructed by attaching a TE device on the bottom of the glass-covered PV module, with a heat sink stuck on the opposite side of the TE device. The open-circuit voltage of the TE device integrated into the PV-TE device was measured to be approximately 9 mV, indicating that the PV-TE device can definitely generate electricity from the darkness. Moreover, a new configuration of the PV-TE device for continuous power generation in the day and night is conceptually proposed for further consideration. In summary, this work proves the possibility of the PV-TE device for nighttime power generation, which could provide an alternative pathway for a wide range of nighttime and all-day power-consumed applications, such as lower power sensors and monitors.
Bin Zhao; Mingke Hu; Xianze Ao; Qingdong Xuan; Zhiying Song; Gang Pei. Is it possible for a photovoltaic-thermoelectric device to generate electricity at night? Solar Energy Materials and Solar Cells 2021, 228, 111136 .
AMA StyleBin Zhao, Mingke Hu, Xianze Ao, Qingdong Xuan, Zhiying Song, Gang Pei. Is it possible for a photovoltaic-thermoelectric device to generate electricity at night? Solar Energy Materials and Solar Cells. 2021; 228 ():111136.
Chicago/Turabian StyleBin Zhao; Mingke Hu; Xianze Ao; Qingdong Xuan; Zhiying Song; Gang Pei. 2021. "Is it possible for a photovoltaic-thermoelectric device to generate electricity at night?" Solar Energy Materials and Solar Cells 228, no. : 111136.
Cool storage has been considering an efficient and cost-effective means to enhance the behavior of a refrigerator. However, its drawback in temperature control of the refrigerator compartment has not received enough attention. The controllable two-phase loop thermosyphon has the prospect of solving this problem. In this study, a novel cool-storage refrigerator integrated with a controllable two-phase loop thermosyphon is built to investigate its precise temperature control capacity. The phase change material is optimized by the orthogonal experiment method. The controllable two-phase loop thermosyphon presents the optimal cooling performance for the fresh food compartment when the filling ratio is 27.0%. As the average temperature of the fresh food compartment increases, the one on-off cycle of the controllable two-phase loop thermosyphon maintains at 32 min, and the operation ratio varies from 86.3% to 13.6%. The temperature control accuracy can be improved from 2.1°C to 0.6°C and the overall time of one on-off cycle decreases from 49.8 min to 22.4 min. The operation ratio gradually increases from 7.2% to 38.56% as the ambient temperatures increase. The results demonstrate that the controllable two-phase loop thermosyphon is a feasible and effective way to improve the temperature control performance of the cool-storage refrigerator.
Weixin Liu; Chuxiong Chen; Jingyu Cao; Lijun Wu; Wei Ren; Dongsheng Jiao; Gang Pei. Experimental study of a novel cool-storage refrigerator with controllable two-phase loop thermosyphon. International Journal of Refrigeration 2021, 129, 32 -42.
AMA StyleWeixin Liu, Chuxiong Chen, Jingyu Cao, Lijun Wu, Wei Ren, Dongsheng Jiao, Gang Pei. Experimental study of a novel cool-storage refrigerator with controllable two-phase loop thermosyphon. International Journal of Refrigeration. 2021; 129 ():32-42.
Chicago/Turabian StyleWeixin Liu; Chuxiong Chen; Jingyu Cao; Lijun Wu; Wei Ren; Dongsheng Jiao; Gang Pei. 2021. "Experimental study of a novel cool-storage refrigerator with controllable two-phase loop thermosyphon." International Journal of Refrigeration 129, no. : 32-42.
Solar energy and universe coldness are two renewable and clean energy constantly sent from outer space to the earth. Solar thermal collectors and radiative coolers respectively harvest heat and cooling energy in this context. However, their static and monofunctional spectral properties mismatch energy demands in regions with large air temperature fluctuations throughout the whole year. In this work, a rotatable bifacial solar photothermic and radiative cooling (PT-RC) module capable of flexibly switch between solar heating and radiative cooling modes is proposed to realize smart thermal management. In the solar heating mode with solar irradiance of 1000 W/m2, the PT-RC module shows 83.3% solar thermal efficiency, which is even slightly higher than that of a typical solar thermal module. In the radiative cooling mode, the PT-RC module reaches up to 69.9 W/m2 net radiative cooling power and 11.7 °C temperature reduction. The heat and cooling energy of the PT-RC module throughout a typical day in Hefei city totals 17.7 MJ. This bifacial PT-RC module provides an alternative solution for integrating solar energy and universe coldness and shows potential in flexibly providing heat and cooling energy in different seasons.
Mingke Hu; Bin Zhao; Xianze Ao; Suhendri; Jingyu Cao; Qiliang Wang; Saffa Riffat; Yuehong Su; Gang Pei. Performance analysis of a novel bifacial solar photothermic and radiative cooling module. Energy Conversion and Management 2021, 236, 114057 .
AMA StyleMingke Hu, Bin Zhao, Xianze Ao, Suhendri, Jingyu Cao, Qiliang Wang, Saffa Riffat, Yuehong Su, Gang Pei. Performance analysis of a novel bifacial solar photothermic and radiative cooling module. Energy Conversion and Management. 2021; 236 ():114057.
Chicago/Turabian StyleMingke Hu; Bin Zhao; Xianze Ao; Suhendri; Jingyu Cao; Qiliang Wang; Saffa Riffat; Yuehong Su; Gang Pei. 2021. "Performance analysis of a novel bifacial solar photothermic and radiative cooling module." Energy Conversion and Management 236, no. : 114057.
Although a thermoelectric device (TED) sub-cooler can improve the trans-critical carbon dioxide (TCO2) cycle, the maximum heating capacity by a single TED is limited by its internal properties. This paper integrates two serially connected and independently powered TED sub-cooler devices into the trans-critical carbon dioxide (TCO2) cycle to achieve a better share of the total heating capacity amongst the TED sub-coolers. A multi-objective optimization approach is used to further optimize this new TCO2+2-TED cycle in terms of coefficient of performance (COP) and system size. A capital cost analysis is also conducted to prove that this implementation is economically feasible. In the analysis, the effect of the number of thermoelectric modules, the heating capacity ratio between the two TED sub-coolers, and the type of thermoelectric module have been studied. Furthermore, both the water heating and refrigeration case studies have been separately studied by using the NSGA-II algorithm. Results show that, in both cases, only one unique solution out of 50 in the Pareto front registered the TCO2+2-TED cycle, which offered a further 6.24% COP improvement for water heating over the common TCO2+TED cycle solutions. The TED sub-cooler costs 20% of the compressor, so the solution is reasonably economical.
Trevor Hocksun Kwan; Yongting Shen; Gang Pei. Multi-objective approach for the performance and economic optimization of the two TED sub-cooled trans-critical carbon dioxide cycle. International Journal of Refrigeration 2021, 127, 89 -100.
AMA StyleTrevor Hocksun Kwan, Yongting Shen, Gang Pei. Multi-objective approach for the performance and economic optimization of the two TED sub-cooled trans-critical carbon dioxide cycle. International Journal of Refrigeration. 2021; 127 ():89-100.
Chicago/Turabian StyleTrevor Hocksun Kwan; Yongting Shen; Gang Pei. 2021. "Multi-objective approach for the performance and economic optimization of the two TED sub-cooled trans-critical carbon dioxide cycle." International Journal of Refrigeration 127, no. : 89-100.
The energy efficiency of fuel cell-based cogeneration systems is limited by the stack’s natural characteristics, and fuel cell water recovery is an energy-consuming process. Here, an alternative system concept is proposed, which recycles the fuel cell’s waste heat to the thermoelectric heater’s cold side to increase its temperature. Hence, the temperature difference across the thermoelectric cooler drops to increases the coefficient of performance for water heating. Furthermore, by cooling the fuel cell’s flue gas, by-product liquid water recovery is achieved. A system-level mathematical model is developed to combine the 1 kW fuel cell stack and thermoelectric cooler/heater model, which analyzes the hybrid system’s performance for efficiently generating power, heat, and drinking water. During the analysis, the hot side temperature, thermoelectric cooler size, and humification rate have been parametrically swept. Results show that adopting thermoelectric modules of 12 or more and lowering the airflow rate to 0.02 kg/s enabled energy efficiencies of up to 1.1 under an ambient 283.15 K and reference 323.15 K temperature heat transfer conditions. Also, up to 1.5 kg/h of liquid water could be recovered if the water-heating temperature is changed to 308.15 K.
T.H. Kwan; Y. Shen; G. Pei. Recycling fuel cell waste heat to the thermoelectric cooler for enhanced combined heat, power and water production. Energy 2021, 223, 119922 .
AMA StyleT.H. Kwan, Y. Shen, G. Pei. Recycling fuel cell waste heat to the thermoelectric cooler for enhanced combined heat, power and water production. Energy. 2021; 223 ():119922.
Chicago/Turabian StyleT.H. Kwan; Y. Shen; G. Pei. 2021. "Recycling fuel cell waste heat to the thermoelectric cooler for enhanced combined heat, power and water production." Energy 223, no. : 119922.
The solar cells commonly adopted in the photovoltaic/thermal (PV/T) have negative temperature coefficients, leading to a significant decrement in electrical efficiency as cell’s temperature exceeds 80 °C, and thus the PV/T systems are mainly used at low-temperature applications. A new type of InGaN/GaN multiple quantum wells (InGaN/GaN MQWs) cells have attracted increasing interest in past few years. The cells have positive or near-zero temperature coefficients and are a promising option in medium-high temperature applications. It is the first time that InGaN/GaN MQWs cells are proposed in a PV/T system, and evacuated flat plate PV/T (EFP-PV/T) collectors are employed. A mathematical model is established to investigate the performance of EFP-PV/T collectors using two kinds of InGaN/GaN MQWs cells at high temperatures. Performance comparison with PV/T systems using conventional solar cells is also conducted. As the operating temperature increases to 150 °C, the efficiency of traditional cell-based PV/T collector decreases to 5.21%, while the efficiency of Type-1 InGaN/GaN MQWs has a minor drop from 4.34% to 4.16% and it increases to 2.07% for Type-2 InGaN/GaN MQWs. The characteristics of large absorption coefficient, radiation-hard, and superior thermal stability, and positive or near-zero temperature coefficients make InGaN/GaN MQWs cells suitable for use in high-temperature PV/T systems.
Xiao Ren; Jing Li; Datong Gao; Lijun Wu; Gang Pei. Analysis of a novel photovoltaic/thermal system using InGaN/GaN MQWs cells in high temperature applications. Renewable Energy 2020, 168, 11 -20.
AMA StyleXiao Ren, Jing Li, Datong Gao, Lijun Wu, Gang Pei. Analysis of a novel photovoltaic/thermal system using InGaN/GaN MQWs cells in high temperature applications. Renewable Energy. 2020; 168 ():11-20.
Chicago/Turabian StyleXiao Ren; Jing Li; Datong Gao; Lijun Wu; Gang Pei. 2020. "Analysis of a novel photovoltaic/thermal system using InGaN/GaN MQWs cells in high temperature applications." Renewable Energy 168, no. : 11-20.
An evacuated flat-plate photovoltaic/thermal (E-PV/T) collector was proposed. The inner space of the E-PV/T collector is vacuumed to suppress non-radiative heat losses, thus increasing thermal efficiency of the collector. Therefore, the E-PV/T collector has the potential to simultaneously deliver electricity and heat at high temperatures. A mathematic model was developed to evaluate the performance of the E-PV/T collector. The effect of some key parameters (e.g., initial water temperature in the water tank, vacuum degree, long-wave panel emissivity, and temperature coefficient of solar cells) on the performance of the E-PV/T system was investigated and the results were compared with a normal flat-plate PV/T (N-PV/T) system. Results suggest that the vacuum helps to enhance the total efficiency by nearly 10 percentage points in high-temperature conditions (>80 °C). The vacuum degree of the upper space exerts a greater effect on system efficiencies compared to that of the lower space. Lower long-wave panel emissivity and greater temperature coefficient of the solar cell promote the performance of the collector. By lowering the long-wave panel emissivity from 0.95 to 0.05, the total efficiency soars from 26.82% to 61.20%. This study may help to guide parametric optimization and operation strategy of flat-plate PV/T collectors for high-temperature applications.
Mingke Hu; Chao Guo; Bin Zhao; Xianze Ao; Suhendri; Jingyu Cao; Qiliang Wang; Saffa Riffat; Yuehong Su; Gang Pei. A parametric study on the performance characteristics of an evacuated flat-plate photovoltaic/thermal (PV/T) collector. Renewable Energy 2020, 167, 884 -898.
AMA StyleMingke Hu, Chao Guo, Bin Zhao, Xianze Ao, Suhendri, Jingyu Cao, Qiliang Wang, Saffa Riffat, Yuehong Su, Gang Pei. A parametric study on the performance characteristics of an evacuated flat-plate photovoltaic/thermal (PV/T) collector. Renewable Energy. 2020; 167 ():884-898.
Chicago/Turabian StyleMingke Hu; Chao Guo; Bin Zhao; Xianze Ao; Suhendri; Jingyu Cao; Qiliang Wang; Saffa Riffat; Yuehong Su; Gang Pei. 2020. "A parametric study on the performance characteristics of an evacuated flat-plate photovoltaic/thermal (PV/T) collector." Renewable Energy 167, no. : 884-898.
This paper proposes a comprehensive thermodynamic and economic model to predict and compare the performance of concentrated solar power plants with traditional and novel receivers with different configurations involving operating temperatures and locations. The simulation results reveal that power plants with novel receivers exhibit a superior thermodynamic and economic performance compared with traditional receivers. The annual electricity productions of power plants with novel receivers in Phoenix, Sevilla, and Tuotuohe are 8.5%, 10.5%, and 14.4% higher than those with traditional receivers at the outlet temperature of 550°C. The levelized cost of electricity of power plants with double-selective-coated receivers can be decreased by 6.9%, 8.5%, and 11.6%. In Phoenix, the optimal operating temperature of the power plants is improved from 500°C to 560°C by employing a novel receiver. Furthermore, the sensitivity analysis of the receiver heat loss, solar absorption, and freeze protection temperature is also conducted to analyze the general rule of influence of the receiver performance on power plants performance. Solar absorption has a positive contribution to annual electricity productions, whereas heat loss and freeze protection temperature have a negative effect on electricity outputs. The results indicate that the novel receiver coupled with low melting temperature molten salt is the best configuration for improving the overall performance of the power plants.
Honglun Yang; Qiliang Wang; Jingyu Cao; Gang Pei; Jing Li. Potential of performance improvement of concentrated solar power plants by optimizing the parabolic trough receiver. Frontiers in Energy 2020, 14, 867 -881.
AMA StyleHonglun Yang, Qiliang Wang, Jingyu Cao, Gang Pei, Jing Li. Potential of performance improvement of concentrated solar power plants by optimizing the parabolic trough receiver. Frontiers in Energy. 2020; 14 (4):867-881.
Chicago/Turabian StyleHonglun Yang; Qiliang Wang; Jingyu Cao; Gang Pei; Jing Li. 2020. "Potential of performance improvement of concentrated solar power plants by optimizing the parabolic trough receiver." Frontiers in Energy 14, no. 4: 867-881.
Solar energy is a potential source for a thermal power generation system. A direct vapor generation solar organic Rankine cycle system using phase change material storage was analyzed in the present study. The overall system consisted of an arrangement of evacuated flat plate collectors, a phase-change-material-based thermal storage tank, a turbine, a water-cooled condenser, and an organic fluid pump. The MATLAB programming environment was used to develop the thermodynamic model of the whole system. The thermal storage tank was modeled using the finite difference method and the results were validated against experimental work carried out in the past. The hourly weather data of Karachi, Pakistan, was used to carry out the dynamic simulation of the system on a weekly, monthly, and annual basis. The impact of phase change material storage on the enhancement of the overall system performance during the charging and discharging modes was also evaluated. The annual organic Rankine cycle efficiency, system efficiency, and net power output were observed to be 12.16%, 9.38%, and 26.8 kW, respectively. The spring and autumn seasons showed better performance of the phase change material storage system compared to the summer and winter seasons. The rise in working fluid temperature, the fall in phase change material temperature, and the amount of heat stored by the thermal storage were found to be at a maximum in September, while their values became a minimum in February.
Jahan Zeb Alvi; Yongqiang Feng; Qian Wang; Muhammad Imran; Lehar Asip Khan; Gang Pei. Effect of Phase Change Material Storage on the Dynamic Performance of a Direct Vapor Generation Solar Organic Rankine Cycle System. Energies 2020, 13, 5904 .
AMA StyleJahan Zeb Alvi, Yongqiang Feng, Qian Wang, Muhammad Imran, Lehar Asip Khan, Gang Pei. Effect of Phase Change Material Storage on the Dynamic Performance of a Direct Vapor Generation Solar Organic Rankine Cycle System. Energies. 2020; 13 (22):5904.
Chicago/Turabian StyleJahan Zeb Alvi; Yongqiang Feng; Qian Wang; Muhammad Imran; Lehar Asip Khan; Gang Pei. 2020. "Effect of Phase Change Material Storage on the Dynamic Performance of a Direct Vapor Generation Solar Organic Rankine Cycle System." Energies 13, no. 22: 5904.
Although interfacial atmospheric water generation is a new concept that can generate freshwater from renewable energy, its water generation rate is too low for widespread use. This paper proposes to integrate the fuel cell to a similar device but instead uses the electrochemically generated waste heat to drive the regeneration process of the liquid sorbent material. Furthermore, the electrochemically generated water is used to increase the relative humidity of the incoming air. Thus, by solely relying on the fuel cell waste products, water recovery rates that are theoretically higher than direct atmospheric water generation are achieved. A steady-state physics model based on the difference in water partial pressure to achieve water absorption and desorption is used to analyze the liquid sorbent device’s performance. Furthermore, the effect of various design parameters such as the salt mass fraction, the fuel cell operating power, the ambient relative humidity, etc. have been studied. Results demonstrate that up to 1.8 kg/h and 0.82 kg/(m2 h) of liquid water can be obtained by fuel cells with an operating temperature range that is consistent with the high-temperature proton exchange membrane fuel cell. This implementation would allow an FC waste heat utilization ratio of up to 0.8.
Trevor Hocksun Kwan; Yongting Shen; Tianxiang Hu; Gang Pei. Passively improving liquid sorbent based atmospheric water generation by integration of fuel cell waste products. Journal of Cleaner Production 2020, 287, 125007 .
AMA StyleTrevor Hocksun Kwan, Yongting Shen, Tianxiang Hu, Gang Pei. Passively improving liquid sorbent based atmospheric water generation by integration of fuel cell waste products. Journal of Cleaner Production. 2020; 287 ():125007.
Chicago/Turabian StyleTrevor Hocksun Kwan; Yongting Shen; Tianxiang Hu; Gang Pei. 2020. "Passively improving liquid sorbent based atmospheric water generation by integration of fuel cell waste products." Journal of Cleaner Production 287, no. : 125007.
This paper aims to present a novel concentrator-photovoltaic window (CPVW) for the building application, which is able to provide a uniform daylighting environment. In order to study the daylighting performance of the CPVW, the ray-tracing simulation model for the complex window systems are built and validated by the outdoor experimental results. The daylighting uniformity of the proposed window system is analyzed and compared with the state-of-the-art semi-transparent photovoltaic window system (STPVW). The coefficient of variation (CV) is developed to evaluate the daylighting uniformity of photovoltaic windows. It was found that with the use of the CPVW, the daylighting uniformity can be significantly enhanced, while enlarging the active daylighting area at the same time: the CV values are decreased from 0.647, 0.642, 0.606, 0.595, 0.639, 0.624, 0.764 (for the STPVW) to 0.011, 0.044, 0.054, 0.054, 0.113, 0.171, 0.220 (for the CPVW) at various incidence angles. Due to the sun rays reallocation of the concentrator, the active daylighting area can also be enlarged: the ratio of the active illumination area offered by the CPVW to that by the STPVW can be up to 6.69×. Thus, with the use of the concentrator-photovoltaic window system on the building, not only can the solar energy utilization be greatly enhanced and does suit the building energy demands well, but also it improves the daylighting uniformity and active natural daylighting area significantly.
Qingdong Xuan; Guiqiang Li; Yashun Lu; Bin Zhao; Fuqiang Wang; Gang Pei. Daylighting utilization and uniformity comparison for a concentrator-photovoltaic window in energy saving application on the building. Energy 2020, 214, 118932 .
AMA StyleQingdong Xuan, Guiqiang Li, Yashun Lu, Bin Zhao, Fuqiang Wang, Gang Pei. Daylighting utilization and uniformity comparison for a concentrator-photovoltaic window in energy saving application on the building. Energy. 2020; 214 ():118932.
Chicago/Turabian StyleQingdong Xuan; Guiqiang Li; Yashun Lu; Bin Zhao; Fuqiang Wang; Gang Pei. 2020. "Daylighting utilization and uniformity comparison for a concentrator-photovoltaic window in energy saving application on the building." Energy 214, no. : 118932.
A novel solar power tower system that integrates with the cascade supercritical carbon dioxide Brayton-steam Rankine cycle is proposed to tackle the challenges of a simple supercritical carbon dioxide system in solar power systems. It provides a large storage capacity and can react to the fluctuation of solar radiation by adjusting the mass flow rate of molten salts in the receiver and heat exchanger. The fundamental is illustrated and comprehensive mathematical models are built. Energy and exergy analysis in the heat collection and power conversion processes is conducted. A comparison between the novel system and simple supercritical carbon dioxide system is made at a design plant output of 10 MW. Results indicated that: (1) the cascade system has a lower receiver inlet temperature, wider temperature difference across the receiver, higher specific work of the thermal energy storage system and lower mass flow rate of the working fluids. The solar-thermal conversion efficiency of the receiver is improved significantly. The heat gain of the tower receiver of the novel system is 53.4 MWh, which is about 7.1 MWh more than that of the simple system. The electricity production of the cascade system is improved by 9.5% at design point; (2) The novel system can generate constant electricity in a wide range of solar radiation and offer flexible control strategy for heat collection and storage. It is a promising option for central solar tower technology with a high efficiency, large storage capacity and short payback period.
Honglun Yang; Jing Li; Qiliang Wang; Lijun Wu; María Reyes Rodríguez-Sanchez; Domingo Santana; Gang Pei. Performance investigation of solar tower system using cascade supercritical carbon dioxide Brayton-steam Rankine cycle. Energy Conversion and Management 2020, 225, 113430 .
AMA StyleHonglun Yang, Jing Li, Qiliang Wang, Lijun Wu, María Reyes Rodríguez-Sanchez, Domingo Santana, Gang Pei. Performance investigation of solar tower system using cascade supercritical carbon dioxide Brayton-steam Rankine cycle. Energy Conversion and Management. 2020; 225 ():113430.
Chicago/Turabian StyleHonglun Yang; Jing Li; Qiliang Wang; Lijun Wu; María Reyes Rodríguez-Sanchez; Domingo Santana; Gang Pei. 2020. "Performance investigation of solar tower system using cascade supercritical carbon dioxide Brayton-steam Rankine cycle." Energy Conversion and Management 225, no. : 113430.
The sun and outer space are the ultimate heat and cold sources for the earth, respectively. They have significant potential for renewable energy harvesting. In this paper, a spectrally selective surface structure that has a planar polydimethylsiloxane layer covering a solar absorber is conceptually proposed and optically designed for the combination of photothermic conversion (PT) and nighttime radiative sky cooling (RC). An optical simulation is conducted whose result shows that the designed surface structure (i.e., PT-RC surface structure) has a strong solar absorption coefficient of 0.92 and simultaneously emits as a mid-infrared spectral-selective emitter with an average emissivity of 0.84 within the atmospheric window. A thermal analysis prediction reveals that the designed PT-RC surface structure can be heated to 79.1°C higher than the ambient temperature in the daytime and passively cooled below the ambient temperature of approximately 10°C in the nighttime, indicating that the designed PT-RC surface structure has the potential for integrated PT conversion and nighttime RC utilization.
Bin Zhao; Xianze Ao; Nuo Chen; Qingdong Xuan; Mingke Hu; Gang Pei. A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling. Frontiers in Energy 2020, 14, 882 -888.
AMA StyleBin Zhao, Xianze Ao, Nuo Chen, Qingdong Xuan, Mingke Hu, Gang Pei. A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling. Frontiers in Energy. 2020; 14 (4):882-888.
Chicago/Turabian StyleBin Zhao; Xianze Ao; Nuo Chen; Qingdong Xuan; Mingke Hu; Gang Pei. 2020. "A spectrally selective surface structure for combined photothermic conversion and radiative sky cooling." Frontiers in Energy 14, no. 4: 882-888.
Despite the success of atmospheric water generators for providing drinking water to remote regions, this technology has a high specific energy consumption. This paper proposes to reuse the electrochemical water of the fuel cell for the vapor compression cycle based atmospheric water generator (VCC-AWG); After passing through an ambient heat exchanger to remove the electrochemical waste heat, the fuel cell flue gas that enters the VCC-AWG is at a higher relative humidity than natural atmospheric air, thus the freshwater yield per energy input can be significantly increased. Hence, the FC-VCC-AWG hybrid system is proposed to be a power and freshwater supply of a grid-independent home. The fuel cell model, the vapor compression cycle’s thermodynamic model, and humid air physics are coupled to analyze the overall system in terms of the fuel cell’s working condition, incoming airflow rate, compressor power consumption, and the ambient relative humidity. When RH = 0.75, adding a 2 kW fuel cell generated up to 3 kg/hr of freshwater, which is 50% higher than excluding the FC. The specific energy consumption can be 200 Wh/kg, so the VCC-AWG can be integrated with small sacrifices to the FC power output.
Trevor Hocksun Kwan; Yongting Shen; Tianxiang Hu; Gang Pei. The fuel cell and atmospheric water generator hybrid system for supplying grid-independent power and freshwater. Applied Energy 2020, 279, 115780 .
AMA StyleTrevor Hocksun Kwan, Yongting Shen, Tianxiang Hu, Gang Pei. The fuel cell and atmospheric water generator hybrid system for supplying grid-independent power and freshwater. Applied Energy. 2020; 279 ():115780.
Chicago/Turabian StyleTrevor Hocksun Kwan; Yongting Shen; Tianxiang Hu; Gang Pei. 2020. "The fuel cell and atmospheric water generator hybrid system for supplying grid-independent power and freshwater." Applied Energy 279, no. : 115780.