Performance Study On An Electricity-Heating-Cooling Cogeneration Photovoltaic Radiant Panel

With the high proportion of building energy consumption in the total energy consumption, it is of great importance to relieve the shortage of the conventional energy resource and Implementation of green energy and improve the building environment by incorporating the renewable energy such as solar energy into buildings. This paper aims at utilizing solar energy, natural energy and nocturnal radiation in a combination way. The photovoltaic thermal technology and radiative cooling technology are combined to develop a new type electricity-heating-cooling cogeneration radiant panel(PV/TC) which can be perfectly integrated with building envelops. These panels can be used as building roofs and facades or components of roofs and facades.1. Experiments were conducted to investigate the performance of PV/TC panels. The results show that PV/TC panels can effectively reduce the temperature of the solar cells with 50℃ under summer heat collecting mode. The maximum output power and conversion efficiency improved significantly with that the photoelectric conversion efficiency is 6%-7% higher than ordinary PV panels under the same condition. The heat collecting efficiency can reach 40%-50%. Under cooling mode the average cooling rate is 40-60W/m2, up to 75 W/m2. In spring under heat collecting mode, the temperature of the PV/TC panels were no higher than 40℃ with the heat collecting efficiency between 50%-70%. The photoelectric conversion efficiency can be improved by 6%-7%. The radiation heat transfer is dominant in the total heat dissipation of PV/TC panels, in proportion of 70%-90% under clear days. While under cloudy days the convection heat transfer took dominant and the total heat loss decreased significantly. The radiation heat transfer could even absorb heat form surroundings.2. The theoretical model of the PV/TC panels was established. Heat balance of the panels was studied by layer and the energy transfer process was also analyzed. Experimental formulas of clear sky temperature and emissivity were summed up and the model suitable for sky conditions with cloud was determined3. The FLUENT software was used to simulate and optimize the heat collecting and cooling performance of the panels. The results show that the temperature of the panels can be reduced and more uniformly distributed, and heat dissipation power improved by the increase of flow and decrease of pipe spacing. But heat collecting efficiency and water temperature were not ideal with reduced pipe spacing. Aluminum structure can help to make uniform transverse temperature distribution, reduce the transverse temperature fluctuations and effectively reduce the transverse temperature difference. This can ensure that the solar cells keep good power efficiency and avoid thermal stress damage caused by high temperature shorten the cells life. The optimized flow and pipe spacing were 60-180L/h and 110-130 mm respectively. In that case the temperature of the PV/TC panels were under 50℃, the heat collecting efficiency was between 40%-50% and the cooling rate was 50-63.7 W/m2.