Pin fin two-phase micro gap coolers for concentrating photovoltaic arrays

Abstract

Paper presented to the 3rd Southern African Solar Energy Conference, South Africa, 11-13 May, 2015.

Concentrating photovoltaic (CPV) systems are among the most promising renewable power generation options but will require aggressive thermal management to prevent elevated solar cell temperatures and to achieve the conversion efficiency, reliability, and cost needed to compete with alternative techniques. Two-phase, evaporative cooling of CPV modules has been shown to provide significant advantages relative to single-phase cooling but, to date, the available two-phase data has been insufficient for the design and optimization of such CPV systems. This Keynote lecture will begin with a brief review of CPV technology and the solar cell cooling techniques described in the literature. Energy modeling, relating the harvested solar energy to the “parasitic” work expended to provide the requisite cooling, will be used to support the efficacy of twophase cooling for CPV applications. Attention will then turn to the available correlations for pin-finned microgap coolers and the gaps which must be addressed to enable such thermal management for CPV arrays. This will be followed by a detailed description of an experimental study of 3 pin-finned microgap coolers for CPV systems and the derived heat transfer and pressure drop correlations. The data spans a large parametric range, with heat fluxes of 1 - 170 W/cm2, mass fluxes of 10.7 - 1300 kg/m2-s, subcooled (single phase) flow as well as exit qualities up to 90%, and 3 heat transfer fluids (water, HFC-134a, HFE-7200). The lecture will close with a brief case study of two-phase CPV cooling, demonstrating that the application of this thermal management mode can lead to a highly energy efficient CPV system.