Thermo-economic optimization of a hybrid photovoltaic and thermoelectric power generator using overall performance index

A thermo-economic assessment of a hybrid concentrated photovoltaic–thermoelectric power generator (CPV–TEG) is performed based on the first law of thermodynamics and principles of costing. This study aims at estimating the optimum water-cooled CPV–TEG design parameters that yield the maximum overall performance. The influence of key parameters (such as direct normal irradiance (DNI), geometric concentration, thermoelectric figure of merit, temperature ratio of thermoelectric junction and heat sink thermal resistance) and their significance on the performance and cost of the system is examined. A performance measure known as the overall performance index (OPI) is used to evaluate the optimum design of the CPV–TEG system operating within the limits of allowable cell temperatures. OPI can incorporate several performance indicators that are crucial for performance estimation of a hybrid system by using a mass coefficient for each indicator based on its priority in the overall system performance. OPI accounts for three performance indicators of the CPV–TEG system, namely: energy efficiency, cost of the solar receiver (COSR) and levelized cost of energy (LCOE). The variation of the OPI provides an indication of the performance of the hybrid system under different design parameters and the selection of the appropriate design of the system to be at a point where the OPI is a maximum. Two scenarios are considered such that different mass coefficients are assigned to the performance indicators when evaluating the system performance. In the first scenario (performance case), energy efficiency is given the highest priority while for the second scenario (economic case), the cost of the solar receiver (CPV–TEG system) is given more emphasis. Optimization is performed for the water-cooled CPV–TEG design such that the PV temperature is kept below the maximum allowable cell temperature of 100 °C. LCOE of 0.0392 $ kWh⁻¹ was obtained with an optimum OPI of 94.7% for the economic case.