The impact of cooling on cell temperature and the practical solar concentration limits for photovoltaics

Abstract

SUMMARYThe solar concentration limit for densely packed, high-concentrated photovoltaic (HCPV) cells was analyzed for a novel two-phase cooling design. Eight working fluids were examined in the two-phase cooling analysis: R134a, R11, R113, R114, R123, R141b, water, and ammonia. In addition, the study investigated the concentration limit for mass flow rates ranging from 10 À3 to 1 kg s À1 . Results from this analysis showed that the limits neared 2000 suns for the six organic fluids examined, whereas for water and ammonia, the practical concentration limit reached about 4000 and 6000 suns, respectively. It was concluded that water and ammonia exhibited greater limits of concentration because they possess greater values of sensible and latent heats compared with the organic fluids examined. The results using this two-phase cooling design were then compared with computational and experimental reference data from other HCPV studies conducted that used cooling mechanisms, such as impinging jets, liquid immersion, and microchannel cooling. Together, the data was compiled and compared with a simplified, one-dimensional, theoretical model using a generic, hypothetical cooling mechanism for densely packed HCPV cells. The general, practical solar concentration limit was predicted to be approximately 10 000 effective suns for a cooling device with a heat transfer coefficient on the order of 10 6 W m À2 K À1 . At this limit, it was determined that the cells' conductive resistance, rather than the external cooling mechanism, becomes the controlling factor for heat removal.

A holistic approach to thermodynamic analysis of photo-thermo-electrical processes in a photovoltaic cell

“…Much of the energy of the absorbed photons is dissipated as heat (5) due to vibronic interaction. The generated photovoltaic power is transferred to the shunt resistance (6), to the p-n junction for its polarization (8), to the load (14) and to the internal series resistance (11).…”

“…Saloux et al [7] developed electrical and thermal models of PV/T system operating under different environmental conditions such as solar intensity and ambient temperature considering the irreversibilities. Ho et al [8] analyzed the solar concentration limits for high concentrated photovoltaic cells by using a two-phase cooling design. The results from their analysis emphasized that the limits are close to 2000 suns for the six organic fluids investigated, but for water and ammonia, the practical concentration limit could rise until about 4000 and 6000 suns, respectively.…”

Design and Fabrication of a Novel Hybrid-Structure Heat Pipe for a Concentrator Photovoltaic

“…Numerous methods have been used to increase the conversion efficiency of HCPV [1][2][3]. Despite its high efficiency in all types of solar cells, 60%-64% of collected solar energy is transformed into heat rather than electricity.…”

New insights for phase-change immersion cooling enhancement of solar cells under high concentration ratios

“…Much attention has been attracted in the advanced cooling methods of solar cells operated under high illuminations, such as jet impingement cooling, microchannel cooling, nanofluid cooling, and two‐phase flow cooling . The detailed review of the cooling technologies for HCPV systems can be seen in Table .…”