Research On A Stand-alone Photovoltaic Air Conditioning System

Due to the rising prices of conventional energy and increasing tense of energy situation, promoting renewable energy becomes an effective way to relieve the energy crisis. Photovoltaic power generation technology has been developing rapidly since the 90s. The annual output and installed capacity increased year by year, with an improving photoelectric conversion efficiency but a declining price. At the same time, with the improvement of people's living standards, the proportion of air conditioning energy consumption in the building energy consumption is increasing too. So energy saving in the air conditioning system attracts more people's attention. The photovoltaic powered air conditioning system appeared since the rapid development of PV industry and the need to save energy and reduce emission. In this paper, a kind of AC stand-alone photovoltaic powered air conditioning system is studied.A development overview of PV technology, PV powered air conditioning technology and other PV refrigeration technologies are illustrated. And the advantage and compose of PV powered air conditioning system is also introduced. A simple description of every part is introduced, including its classification, key parameters and operating characteristics in the system. The factors that influence solar array and battery performance are focused.The design of a stand-alone PV powered air conditioning system is described. The rating voltage of this system is 48V, and it's made up by a 1.92kWp solar array, 200Ah battery bank, 3kVA inverter, the corresponding solar power controller and a 1.2HP frequency conversion air conditioning, providing cooling and heating for a 23.5 m2 room. And special attention on the installation of solar array is paid.Experimental studies on operating characteristics of cooling and heating for an AC photovoltaic powered air conditioning system are conducted. The PV array can supply 77.7 percent and 84.4 percent energy that consumed by air conditioner in the winter day and summer day respectively. The COPsol of system reaches 0.37 in winter. All of the energy consumed at night both in winter and summer can be fulfilled by battery bank. Detailed analysis of the performances and efficiencies of main parts in the system is illustrated. The output performance of PV array is affected by surface temperature and the irradiance. Start-up performance of the air conditioner is studied and its soft-start feature reduces the investment cost of inverter. The relationship between the inverter efficiency and the air conditioning power is also studied, finding that the lower actual inverter efficiency is caused by the mismatch between the air conditioning power and inverter's rating capacity, and its efficiency decreases with decreasing load power. Performance tests and comparison between old batteries and new ones were done. The capacity efficiency, power efficiency and voltage efficiency of the old battery bank decreased due to unbalanced battery voltage, poor maintenance and untimely charging other reasons.A model of the stand-alone PV air conditioning is built using TRNSYS. This model is modified and verified by comparison between test values and simulation values. Then a whole year simulation on the performance of the system is conducted.