Efficiency Analysis of Minichannel Heat Exchangers for High-Concentration Photovoltaic Systems

High-Concentration Photovoltaic (HCPV) systems operate under high heat fluxes, onthe order of MW/m2 , requiring effective thermal management. Experimental studies ofminichannel cooling for HCPV seldom extend from the laboratory to complete modulesoperating outdoors. This study experimentally evaluates seven water-cooled minichannelheat exchangers at three scales: a laboratory setup with electrical cartridge heating, outdoorsingle-cell monomodules, and complete 25-cell modules. Six were micromachined inaluminum, and one was manufactured in a cobalt–chromium–tungsten (CoCrW) alloyby Direct Metal Laser Sintering (DMLS). The total thermal resistance ranged from 0.24 to0.84 °C/W, while pressure drops remained below 2 kPa at 60 mL/min. An empiricalNusselt number correlation for the tested straight-channel heat exchangers (22 ≤ Re ≤ 107)predicted 96% of the experimental data within ±30%. Under outdoor operation, thetwo modules, one equipped with the aluminum heat exchangers and the other with theCoCrW heat exchangers, achieved electrical efficiencies of 23.02% and 22.01% and combinedefficiencies of 43.62% and 42.33%, respectively, with cell temperatures between 40 and50 °C. The exergy content of the recovered thermal energy was 2–3%, so the module exergyefficiency of approximately 25% was determined mainly by the electrical output. Overall,the results demonstrate the potential of minichannel heat exchangers for simultaneousthermal and electrical energy recovery in HCPV modules.