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In this study a completely autonomous, zero-emission photovoltaic (PV)-based system is modeled for residential applications. Apart from the PV subsystem, an electrolyzer-hydrogen storage-fuel cell subsystem is integrated to the system to fully fulfill a varying load profile throughout the year. The fuel cell and electrolyzer components are based on proton exchange membrane technology. The model allows quantification of energy and power flows, such as power input from the PV subsystem, conversion of electricity to hydrogen, and re-production of electricity. The system components are sized to satisfy demand, which is varied through a case study conducted to investigate system performance at different capacities. The economic performance of the proposed system is assessed with a detailed cost model. The proposed system (base case) results in a unit cost of electricity at 0.216 EUR/kWh for a system capacity of 100 households, which is moderately higher than the current cost of electricity in Cyprus. A parametric study including those economic parameters with a high degree of uncertainty is conducted to investigate the sensitivity and future potential of the system. The results show that the unit cost of electricity for the proposed system can be reduced below the current cost, making the system competitive, if electrolyzer/fuel cell lifetime is increased, while the specific costs of the electrolyzer and the PV are reduced. [ABSTRACT FROM AUTHOR]

The purpose of this study is to investigate the potential of a small-scale, combined-cooling-heating-and-power system, consisting of a 1 MW e gas turbine subsystem coupled to a 0.5 MW e photovoltaic (PV) subsystem for application in Cyprus. The proposed system is completely autonomous, without any interconnections to a central power grid. To allow maximum utilization of the electricity generated by the PV subsystem, an electrolyzer unit is coupled to the system to convert excess renewable electricity to hydrogen. The generated hydrogen is injected to the natural gas supply for the gas turbine. For the generation of useful cooling and heating, the system recovers heat from the flue gas exiting the gas turbine; the recovered heat is supplied to a heat-activated absorption chiller/heater to generate cooling or heating. An electric chiller/heater is integrated to the system to supplement thermal energy when necessary. The thermal energy is supplied to nearby buildings through a district energy network. The annual average primary energy ratio of the proposed system is 0.806. For an assumed system lifetime of 20 years, the lifecycle cost of the proposed system is 11.12 million USD, resulting to a unit cost of electricity at 0.06 USD/kWh, which is a 62% reduction of the current cost in Cyprus. The results of the parametric study suggest that the economic performance of the proposed system is highly dependent on price fluctuations of the unit cost of natural gas, while the specific cost of the electrolyzer unit is also critical. The proposed system could become an important candidate for power and thermal energy generation in Cyprus as a measure to reduce the presently high cost of electricity. [ABSTRACT FROM AUTHOR]

A solar-heating-and-cooling (SHC) system, consisting of a flat-plate solar collector array, a hot water storage tank, and an absorption chiller unit is designed and modeled to satisfy thermal loads (space heating, domestic hot water, and space cooling). The system is applied for Nicosia, Cyprus, a location with prolonged summer-like conditions, where heating demand is moderate, while space cooling demand is comparatively very high. The study investigates the potential of a solar system installed and operated onsite in a detached single-family household to satisfy all necessary thermal loads. The hot water storage tank is also connected to an auxiliary heater (diesel-fired boiler) to supplement solar heating, when needed. The main purpose of the study is to model the overall system and contact a parametric study that will determine the optimum economic system performance in terms of design parameters. The system is compared, through a cost analysis, to an electric heat pump (EHP) system. It is found that the optimum system combination of solar collector area and volumetric capacity of the hot water storage tank is 70 m 2 and 2000 L, respectively. The total annualized cost (in USD) for the optimum SHC system is $3,719. The sensitivity analysis showed that the SHC system would be unfavorable to compete with EHP technology, if the solar collector cost is above $360/m 2 . [ABSTRACT FROM AUTHOR]