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• A hybrid system of PAFC, TEG, and AC is developed for the first time. • Detailed analytical model is built for a double effect AC. • Hybrid system performance is analyzed under different operating conditions. • Both power output and efficiency are higher than standalone PAFC. • Further enhancement can be obtained by using optimum values of operating conditions. In this work, a new hybrid system for combined power and cooling applications is developed and investigated. The novelty of this research originates from two major achievements. First, the use of detailed analytical model for double-effect AC with fuel cell. Second, using two heat recovery systems (TEG and AC) to utilize the waste heat from a fuel cell. The system consists of a phosphoric acid fuel cell (PAFC), ThermoElectric generator (TEG), and an absorption chiller (AC). The internal heat generation in PAFC is utilized using TEG to achieve additional electricity production, while the exhaust heat by PAFC is utilized to run an AC to produce cooling power. The results show that the maximum useful power (electricity and cooling) obtained from this hybrid system is 11% greater than the maximum electrical power generated by the standalone PAFC. The maximum efficiency of this hybrid system is 7% greater than the maximum standalone PAFC efficiency, but the improvement can reach 10% when optimizing the system operating conditions. The sensitivity analysis study demonstrates that decreasing the operating temperature, increasing the fuel pressure, and decreasing the ambient temperature could enhance the overall hybrid system performance. Additionally, we found that a better performance is achieved when the heat utilized by TEG is minimized and majority of the useful heat is used in the AC. [ABSTRACT FROM AUTHOR]

• A new solar powered electricity and cooling cogeneration system is proposed. • Various irreversible losses within the proposed system are described. • Parameters evaluating the proposed system performance are mathematically formulated. • Absorption refrigerators are effective to improve the DSSC performance. • Effects of some designing parameters and operating conditions are revealed. To improve the energy conversion efficiency of a dye-sensitized solar cell (DSSC), a novel hybrid system representatively consisting of a DSSC and an absorption refrigerator (APR) is put forward, in which the APR is used to thermally harness the part of high wavelength sunlight that not converted by the DSSC. The amount of heat from the DSSC is calculated, and mathematical formula for energy conversion efficiencies and output powers of the DSSC, APR and hybrid system are derived. Numerical calculations show that the maximum output power density and maximum energy conversion efficiency of hybrid system are enhanced by 9.93% and 9.92% in comparison with that of the single DSSC, respectively. Integration of APR to DSSC is a feasible route to effectively improve the energy conversion efficiency. Comprehensive sensitivity analyses are conducted to explore how the whole hybrid system performance depends on various working conditions and designing parameters, including porous nano-TiO 2 film thickness, photoelectron absorption coefficient, internal irreversibility factor, heat transfer coefficient and various temperatures. The research results can provide some new understandings for further enhancing the DSSC performance. [ABSTRACT FROM AUTHOR]

In this paper, the thermal performance of capillary mat cooling systems is evaluated through actual measurements under different ventilation rates. The results showed that the indoor air temperature drop rates of the ceiling, wall and floor cooling are 1.42–2.44°C/h, 0.69–1.11°C/h, 0.29–0.58°C/h, respectively, in the response phase, which can provide a reference for predictive control strategy of radiant system. Then the cooling capacity of the capillary mat is validated. The radiant heat transfer coefficient of the cooling capillary mat is about 5.80 W/m2 k. When the supply water temperature dropped from 20°C to 16°C, the total heat flux can experience an increase of 10%–30%. The heat flux for cooling ceilings is the largest, followed by cooling walls, which is 7%–17% lower; and cooling floors, which is 75%–90% lower. Orthogonal experiments illustrated that the water supply temperature and air supply volume have a significant influence on the indoor thermal environment of the hybrid systems, followed by the air supply temperature. In general, the dynamic performance of the radiant cooling system in the response phase can provide an effective reference for different control strategy considering the significant thermal inertia. [ABSTRACT FROM AUTHOR]

• A system is proposed by efficiently cascade between CO 2 and desiccant cycles. • Dissipated heat of the CO 2 cycle could be utilized to 50°C. • COP hs ′ is obviously increased, at least 15%, on an operational mode of ICTH. • Energy consumption of CO 2 cycle could be reduced over 26.3%. A novel hybrid system of liquid desiccant and CO 2 transcritical cycles is proposed, where LiCl solutions are used as desiccants. Dissipated heat of the transcritical cycle is used to regenerate LiCl solutions, and the heat could be utilized efficiently with large temperature decrease. From insight of thermodynamics, model of the hybrid system is built. Based on the calculation results, temperature of the utilized heat could range from 120°C to 50°C. In addition, temperature and humidity independence control (THIC) could be conducted by the hybrid system. Under the same dehumidification capacity, its evaporation temperature could be obviously lifted. For the hybrid system, compression work (W) of the CO 2 transcritical cycle could be reduced from 15% to 26%. Futher more, compared with cooling dehumidification at 7°C by a conventional CO 2 transcritical cycle, total power consumption of the hybrid system could be reduced by 13.7% at an evaporation temperature of 12°C. More notablely, dehumidification efficiency of the hybrid system (COP hs ′) could be increased from 15% to 30% compared with dehumidification efficiency of cooling dehumidification by CO 2 transcritical cycle (COP cs). [ABSTRACT FROM AUTHOR]

• Photovoltaic thermal collectors, ejector refrigeration cycle and phase change material hybrid system are introduced. • Photovoltaic thermal collectors produced heat is used as heat source of the ejector refrigeration cycle. • Total energy and total exergy efficiencies of the hybrid system are 50.84% and 60.51%. • The rate and period of investment return were obtained 29.36% and 3.405 years, respectively. In this study, an integrated system which including photovoltaic-thermal collectors, ejector refrigeration cycle and phase change material storage is developed and analyzed. The electrical power and refrigeration energy of the proposed system are about of 6666 kW and 5395 kW, respectively. The phase-change material storage sub-system consists of capric acid-lauric acid that in the absence of heat source of solar energy at night, 5395 kW refrigeration is released to cool at a temperature of 9 °C. The energy and exergy analyses are conducted and the obtained results show that overall thermal and total exergy efficiencies are about of 60.51% and 50.84%, respectively. The sensitivity analysis is performed to investigate the effect of the important operating parameters on the system performance. In this regard, Output temperature, generated heat energy and area of the photovoltaic thermal collectors; solar radiation, produced refrigeration and volume of thermal energy storage are selected. Also, the economic analysis is conducted and the obtained results indicate that the proposed system has an investment return period of 3.405 years and a prime cost of product of 20.45 US$ per ton of refrigeration. [ABSTRACT FROM AUTHOR]

Highlights • A hybrid system including high-temperature fuel cell and absorption chiller is developed. • Nanofluids are employed as absorbent for increasing of COP in the refrigeration system. • Exergy analysis has been conducted for the hybrid fuel cell refrigeration system. • Sensitivity analysis is employed for assessing of main parameters on the system performance. Abstract A hybrid system including high-temperature polymer fuel cell with capacity of 5 kW along with fuel processing unit for producing rich hydrogen from natural gas integrated by a 3 kW absorption chiller has been developed. The waste heat of flue gas from the burners is utilized in the ammonia-water absorption chiller for refrigerating purposes. The hybrid refrigeration system is simulated by Aspen HYSYS software in a steady state condition. After defining the properties of nanoparticles in HYSYS software, the water-based nanofluids are employed as absorbent liquid for increasing of COP in the refrigeration system, and their effects have been evaluated on overall system performance. The electrochemical model of the fuel cell as well as the main parameters of refrigeration system have been validated with experimental results and similar works. Electrical efficiency and overall efficiency of the hybrid system are equal to 36% and 77.3%, respectively. The overall efficiency in the presence of silver nanofluid can be increased up to 81%. Exergy analysis has been conducted for the hybrid system, and the obtained exergy efficiency of the system is equal to 29%. Sensitivity analysis has been employed for evaluating of significant parameters on the hybrid system performance. [ABSTRACT FROM AUTHOR]

A hybrid system is proposed to harvest the waste heat released in MCFC through integrating an absorption refrigerator as a bottoming cycle. A thermo-electrochemical model is used to describe the main irreversible losses in the system. The operating current density interval of the MCFC that enables the bottoming absorption refrigerator to effectively cool is determined. Numerical expressions for the equivalent power output and efficiency are derived to evaluate the performance of the hybrid system under different operating conditions. Compared to the stand-alone MCFC, the maximum power density and the corresponding efficiency of the hybrid system are found to have increased by 3.2% and 3.8%, respectively. The general performance characteristics and optimum operating regions for the hybrid system are revealed. Comprehensive parametric analyses are conducted to investigate how the hybrid system performance depends on various physical properties and working conditions such as working fluid internal irreversibility inside the absorption refrigerator, heat transfer coefficients, some thermodynamic losses related parameters, and the operating current density, temperature and pressure of the MCFC. [ABSTRACT FROM AUTHOR]

In this context, a two-stage absorption-transcritical hybrid refrigeration system is proposed. R744 is chosen as a refrigerant for the transcritical heat pump subsystem and LiBr-H 2 O working pair for the two-stage absorption refrigeration subsystem. Based on the mathematical and physical models, theoretical investigation is carried out on its performance. The main effects are discussed on COP net (the ratio of cooling capacity powered by low-grade heat to the low-grade heat consumption for the hybrid system) and COP mt (the ratio of cooling capacity powered by mechanical work to the mechanical work consumption for the hybrid system). Comparing with the normal two-stage absorption refrigeration system, theoretical results show that COP net could be improved up to about 55% when the refrigeration temperature is 7 °C. In addition, COP mt are more than 50% higher than that of the conventional transcritical refrigeration system. It is also found that both 45–55 °C low-grade heat and condensing heat could be used as actuating heat of the two-stage absorption refrigeration subsystem. [ABSTRACT FROM AUTHOR]