Experimental investigation on effects of thermal resistances on a photovoltaic-thermoelectric system integrated with phase change materials

Phase change materials have been introduced into the concentrated photovoltaic-thermoelectric hybrid system to control its operating temperature. As the poor thermal conductivity of phase change materials (paraffin in this paper), the expanded graphite and copper foam are respectively added into the paraffin to decrease its thermal resistance. An experimental platform containing three concentrated photovoltaic-phase change material-thermoelectric hybrid subsystems is established. Experimental comparisons of performances among the concentrated photovoltaic system, the conventional concentrated photovoltaic-thermoelectric hybrid system, and the concentrated photovoltaic-phase change material-thermoelectric hybrid system are firstly carried out. Then, a series of comparative experiments are conducted to reveal the effects of thermal resistances on the hybrid system performance. The results demonstrate that the improved phase change material can well maintain the photovoltaic-thermoelectric hybrid system at the desired temperature and generate more electricity. The temperature of the photovoltaic cell in the concentrated photovoltaic-phase change material-thermoelectric hybrid system is nearly 50 °C while the one in the concentrated photovoltaic-thermoelectric hybrid system reaches about 80 °C. The average output power of the concentrated photovoltaic-phase change material-thermoelectric hybrid system increases by 23.52% compared with the concentrated photovoltaic-thermoelectric coupling system. The expanded graphite and copper foam both can decrease the thermal resistance of paraffin, and the expanded graphite has a better effect. The thermal resistance of the cooling system has little effect on the operating conditions of the photovoltaic cell and phase change material but greatly affects the performance of the thermoelectric generator.