• Energy Research

Abstract Concentrated photovoltaic is a promising route to achieve high efficiency solar conversion. Concentration of sunlight increases the irradiation on panel along with its temperature. At higher temperature, the efficiency of the cells drops necessitating active cooling. However, flow of a coolant consumes pumping-power leading to reduction in net power output. These two counter-acting factors lead to a two-stage optimization for designing an advection cooled concentrated photovoltaic (ACCPV) system. Here, we attempt developing a design methodology where standard numerical scheme for solving a multi-level conjugate heat problem is utilized to obtain optimal operating conditions in terms of the coolant flow rate, and the sunlight concentration ratio for a series of widely used photovoltaic materials: a-Si, m-Si, p-Si, CIGS, CdTe. For the chosen ACCPV geometry, the estimated concentration ratios are computed to be 7, 9, 9, 16 and 20 for m-Si, p-Si, CIGS, p-Si and CdTe cells, respectively. Even though the estimated values of optimal parameters depend on the choice of PV material, coolant and the geometry of the system, the methodology presented here is universally applicable for any such ACCPV system. The general intuition - higher the irradiation, better the performance - is demonstrated to be false through the present analysis.

Abstract Solar-PV is the most mature technology for the solar energy utilization. The design of such PV-based systems are done in terms of the rated power of the panels while the rating is determined at the standard test condition of a specified temperature, irradiance level and for the standard AM1.5G solar spectrum. However, such rated output is never achieved as the actual operating conditions vary widely from the standard one. Hence, it is critical to estimate the actual power output under certain operating conditions in a given location for a proper design. Here, we provide a comprehensive method for estimating the actual power output which is applied to a particular location (Kanpur, India). Three major factors are computed which cause deviation of the power output from the rated value: spectral factor, temperature factor and irradiance factor. The combined effect is expressed through power factor which is observed to be dominated by the irradiance factor. It is observed that the actual power is significantly less - from 40% to 75% of the rated value - for the whole year which needs to be accounted for during the sizing-decision. The current study applies the estimation method on five commonly used PV materials and identifies amorphous silicon panel to be best suited for Kanpur for the prevailing condition in spring and summer seasons because it provides the highest output for the same rated power. The case study of Kanpur clearly demonstrates the effectiveness of the present method and its usefulness in the design process.