| Building energy consumption, of which space heating and space refrigerating account for the largest proportion, is now occupying for about1/3of the social total energy consumption in China. Space heating energy consumption per square meters of China is3times of that of the developed countries with similar climate condition. Demand of winter heating and summer refrigerating will improve gradually with the development of people’s living standard, which proposes a big challenge for China’s building energy saving.With the increasingly exhausted of conventional energy resources and the increasingly serious of the environmental problems, solar energy is now attracting attention for the characteristics of clean, environmental, and renewable. However, the application of solar energy needs large scale for its intermittency and low energy density. Solar energy can be well integrated with buildings in cities, which are the carrier for the solar energy application, and solar energy can significantly reduce building energy consumption. Photovoltaic technology and photo-thermal technology, which are the main application of solar energy, are rapidly developed in recent years. Photo-thermal technology is the most mature and the highest penetration of solar application, solar water heating, solar air heating, and the solar-assisted heat pump are the most common application mode. The hybrid photovoltaic/thermal (PV/T) technology integrates the PV and the photo-thermal together, and it can simultaneously generate electrical and thermal energy, increasing the comprehensive utilization efficiency of solar energy. Besides, the cooling liquid can take off PV cells heat energy; reduce the PV cells working temperature, increasing the PV cells photoelectric efficiency.Gravity assisted heat pipe, which can heat transfer depend on the phase change of its working fluid, has excellent heat transfer performance. Gravity assisted heat pipe can be well integrated with the common solar collector or the PV/T collector, and can solve the freezing problem existes in the common water based solar collector. At the same time, the indirect heat transfer through heat pipe avoids the corrosion of the absorb plate, and increases the collector’s service life. There are two combination modes; one is directly weld the heat pipe’s evaporator section with the absorb plate, while the condenser section insert to the header; the other is the remolding of the loop heat pipe, wich mean to make the whole solar collector as the loop heat pipe’s evaporator section and the coil pipe in the water tank as the condenser section, then connecte the evaporator section and the condenser section with copper pipe. Loop heat pipe can realize long distance heat transfer, can be well integrated with building; moreover, the loop heat pipe can also be well integrated with heat pump, they can employing the same working fluid, the same collector-evaporator, which can simplify the system structure remarkablely.Gravity assisted heat pipe and the loop heat pipe were integrated with the normal solar collector and the PV/T collector in this paper, proposed the gravity assisted heat pipe type PV/T system, loop heat pipe type water heating system, loop heat pipe type PV/T system. Meanwhile, integrating loop heat pipe with photovoltaic solar-assisted heat pump, proposed photovoltaic solar assisted loop heat pipe/heat pump system, the loop heat pipe can reduce the heat pump system’s energy consumption, the heat pump can overcome solar intermittency, through the switch of heat pipe working mode and heat pump working mode can improve the rate of equipment utilization and the rate of solar energy utilization.The main works of this paper are summarized as follows:(1) A gravity assisted heat pipe type PV/T system was designed and constructed, and system performance with and without glass cover were compared. The results show that system with glass cover had a higher average day photo-thermal efficiency, which was41.30%compared to37.16%, a lower average day photovoltaic efficiency, which was9.42%compared to11.51%, a lower average day exergy efficiency, which was6.87%compared to8.01%. Besides, the system’s dynamic model, and compared was constructed and compared with the experimental data, the results presented good agreement.(2) A comparison test platform between the loop heat pipe type PV/T system and the common water based PV/T system was designed and constructed, and the systems performance was compared. The results show that the loop heat pipe type PV/T system had a lower photo-thermal efficiency, but higher photovoltaic efficiency. However, the two system had almost the same exergy efficiency.(3) A loop heat pipe type solar water heating system was designed and constructed, and long term outdoor tests of the system performance under different filling ratio were carried out, and the system’s optimum filling ratio was proposed based on the cubic spline interpolation. The results show that the LHP collector and the system’s thermal efficiency presented the same fitting trend, which were increased first and then decreased; while the heat loss coefficient was always decreased. The system’s optimum filling ratio was36.6%of volume.(4) A forced loop heat pipe type water heating system was designed and constructed, and system performance under filling ratio of50%volume was experimental studied. The results show that forced LHP collector and the system’s thermal efficiency was similar with the common water based system, and the fitting day average photo-thermal efficiency was51.4%.(5) A dynamic model of PV-SAHP system was proposed, and compared with the test data. The results show that the model had a good agreement of compressor power and water temperature; Because of no consideration of the influence of two-phase, and only consideration of the influence of PV cells temperature, the simulation result of compressor inlet pressure and photovoltaic efficiency had big error with test data.(6) A PV-SALHP/HP was designed and constructed, and system performance of loop heat pipe working mode and the heat pump working mode was experimental studied. The results show that under loop heat pipe working mode, the system’s day average photo-thermal efficiency was43.6%, and the day average photovoltaic efficiency was11.3%; under heat pump working mode, the system’s day average COP was3.66, day average photovoltaic efficiency was12.1%, and the day average photo-thermal efficiency can reach57.5%. |
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