Design and performance test of CPC-PV/TE hybrid power generation system in greenhouse

With the rapid development of agricultural science and technology, various types of environmental testing equipments and production facilities consume a lot of energy in greenhouse. Therefore, it is important to design a high-efficiency greenhouse power supply device. At the same time, the energy crisis in the 21st century and the air pollution caused by burning of fossil fuels become serious. It can not wait to solve the environmental pollution. Therefore, increasing the development and utilization of solar energy is imminent. Solar energy is a kind of clean and renewable energy, and the study of solar energy development and utilization has become a hot issue nowadays, but in general, its efficiency is low. In order to solve the problem of large fossil energy consumption in the greenhouse and the current inefficient use of solar energy, compound parabolic concentrator-photovoltaic/thermoelectric hybrid power generation system (CPC-PV/TE) based on the characteristics of greenhouse in Northeast China is proposed in the present paper. A system contains CPC, PV/TE hybrid system and flat heat pipe. CPC converges light to the surface of photovoltaic cells. It enhances light irradiation intensity. Photovoltaic cells use the photovoltaic effect principle to generate electricity. Attached to photovoltaic cells, thermoelectric power generator modules convert the excess heat generated by photovoltaic cells power generation to electricity power simultaneously. Flat heat pipe is used as heat transfer element, and then a certain amount of water is used to effectively transfer the rest of the heat. In order to express the performance of CPC-PV/TE hybrid power generation system accurately, a comprehensive energy transfer model has been established, and the efficiency of CPC-PV/TE hybrid system and PV or TE module alone under different levels of irradiation and various water flows has been discussed. The results show that the faster the cooling water flows, the higher the generated power by CPC-PV/TE hybrid system is, but there is a limit. The efficiency of CPC-PV/TE hybrid system is greater than the PV or TE module alone. Moreover, experimental test system has been built, and a series of experimental researches have been done on CPC-PV/TE hybrid system with water-cooled flat heat pipe in greenhouse of Northeast Agricultural University. As a result, in transient experimental research, photovoltaic power generation accounts for a large proportion, so variation tendency of generated power by CPC-PV/TE system is similar to photovoltaic. For thermoelectric power generation modules join in the CPC-PV/TE hybrid system, the generated power and the efficiency of CPC-PV/TE hybrid system increase; it gains the maximum power output of 125.98 W, and the efficiency gets to 20.06%. A cascade utilization of solar energy is achieved, and then its utilization is improved. From April 7, 2015 to April 11, 2015, the daily performance of CPC-PV/TE hybrid system has been evaluated, and the generated power of CPC-PV/TE hybrid system varies from 2.35 to 3.24 MJ. The efficiency of CPC-PV/TE hybrid system in these days is more than 18.57%, and the highest value is 19.15%. CPC-PV/TE hybrid system is superior to existing PV/TE system. More importantly, CPC-PV/TE hybrid system basically meets the power requirements of the greenhouse environment monitoring systems and lighting equipments. It has a greater advantage in the field of solar energy comprehensive utilization. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.