Prospective Photovoltaic-Thermoelectric Hybrid System

Photovoltaic-thermoelectric (PV-TE) hybrid system is an appealing idea due to its potential to harvest thermal energy produced in photovoltaic conversion process or mitigate the temperature effect through cooling. The rationale for developing PV-TE hybrid system is illustrated in Fig. 1, which depicts three possible strategies that might lead to a higher overall efficiency of the hybrid system than that of photovoltaic system alone. In strategy (a), thermoelectric device is used as a cooler that is in direct contact with the solar cells. Since the solar cells exhibit negative temperature coefficient, reducing the operating temperature of the solar cells could lead to an increase in the power output of the solar cell. In strategy (b), thermoelectric device is arranged in similar manner as strategy (a) but used as a thermoelectric generator. Thermalisation loss inside solar cells will lead to an increase in the temperature of the solar cells, which in turn establishes a temperature difference across the thermoelectric generator. As a result, the waste thermal energy from the solar cell can be utilised by thermoelectric generator to convert into useful electric power. In strategy (c), the solar energy in infrared spectrum, which has no use to solar cells, is separated from the visible spectrum and directed to a thermoelectric generator for power generation. Clearly, these strategies are built on the sound scientific rationales. The key question is if they will lead to a realistic improvement when other influences are taken into consideration. This paper aims to offer critical assessments on the prospect in these research directions.