Optical, electrical, and thermal performance enhancement for a concentrating photovoltaic/thermal system using optimized polynomial compound parabolic concentrators

Performance of a concentrating photovoltaic/thermal system directly depends on the solar irradiation gathered by concentrators. Few studies tackled the systemic and general optimizations of optical efficiency and uniformity of energy distribution for two-dimensional compound parabolic concentrators (CPCs). In this paper, a polynomial CPC is proposed. To evaluate the optical efficiency and uniformity of the concentrated irradiation, an interpolation method is also proposed. Using genetic algorithm, the optimized polynomial CPCs with different polynomial orders are determined. With fourth order, the concentrating efficiency reaches the theoretic limit, and the concentrated irradiation is relatively uniform. Accordingly, the optimized polynomial CPCs for concentration ratios not larger than 10 are determined. Using a double-pass spectral beam splitting photovoltaic/thermal system model, the electrical and thermal performance using the determined optimized polynomial CPCs is calculated. For concentration ratios not larger than 10, the optimized polynomial CPC is able to provide high concentrating efficiencies with good uniformity. Moreover, the maximum temperature of the photovoltaic cell is smaller than 325 K. And then, the optimized polynomial CPCs for multiple incident angles are presented, along with the system performance. For multiple incident angles, the optimized polynomial CPC also shows good performance, but the size increases.