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In the enthalpy difference lab with a solar simulator, the performance of the indirect expansion solar-assisted multi-functional heat pump (IX-SAMHP) can be tested in stable external environment quantificationally. In this paper, the performances of the IX-SAMHP working in the solar water heating mode and solar space heating mode were compared under different conditions. The experimental results indicate that the evaporating heat exchange rate and condensing heat exchange rate were synthetically effected by the evaporating and condensing temperature in the solar water heating mode. Moreover, compared with the situation without irradiation, when the irradiation was 500 W/m2, the evaporating heat exchange rate and condensing heat exchange rate increased by 37.4% and 32.3%, respectively. In the solar space heating mode, when the irradiation increased from 0 W/m2 to 500 W/m2, the heating capacity increased by 20.4%. In the second-law analysis, the calculating results demonstrate that the exergy efficiency of the IX-SAMHP would be enhanced by inputting solar energy to the evaporator.

The proposed low-temperature solar thermal electric generation is based on the compound parabolic concentrator (CPC) of small concentration ratio and Organic Rankine Cycle (ORC). The technologies of CPC and ORC are analyzed, and feasibility of the system is demonstrated. In particular, two-stage collectors and heat storage units are adopted to improve heat collection efficiency. Organic fluid is preheated by flat plate collectors (FPCs) prior to entering a higher temperature heat exchanger connected with the CPC. The two-stage heat storage units are composed of two types of phase change material (PCM) with diverse melting temperatures. The novel configuration is carefully designed to react to different operating conditions. The fundamentals are illustrated for both simultaneous and separate processes of heat collection and power conversion. Mathematic models are built for heat transfer and thermodynamics of the innovative system. Coupling relationship among the proportion of FPC to CPC, the melting temperature of the first-stage PCM and the overall collector efficiency is established. The benefits of the preheating concept and cascaded heat storages are investigated in detail in comparison with the single-stage system. The results indicate that the increase in collector efficiency of the two-stage system is appreciable.

The performance of a photovoltaic solar assisted heat pump (PV-SAHP) with variable-frequency compressor is reported in this paper. The system is a direct integration of photovoltaic/thermal solar collectors and heat pump. The solar collectors extract the required thermal energy from the heat pump and at the same time, the cooling effect of the refrigerant lowers the working temperature of the solar cells. So this combined system has a relatively high thermal performance with an improved photovoltaic efficiency. To adapt to the continuously changing solar radiation and ambient temperature conditions, the refrigerant mass flow rate should match the heat gain at the evaporator accordingly. A variable-frequency compressor and an electricity-operated expansion valve were used in the proposed system. Mathematical models were developed to evaluate the energy performance of the combined system based on the weather conditions of Tibet. The simulation results indicated that on a typical sunny winter day with light breeze, the average COP could reach 6.01, and the average electricity efficiency, thermal efficiency and overall efficiency were 0.135, 0.479 and 0.625 respectively.