Comparative Experimental Study on Cooling and Power Generation of Cavity Water-Cooled Photovoltaic Windows Under Different Orientations
This study addresses the absence of empirical data on how orientation affects cavity water cooling and power generation in hollow photovoltaic (PV) windows. Two identical experimental chambers were constructed on a rooftop in Xiamen, China, and tested under summer conditions. One chamber's window (Window A) received no water supply, while the other (Window B) was supplied with water at a constant flow rate via a bottom-inlet/top-outlet diagonal configuration. The hollow PV window comprised 6 mm ultra-clear tempered glass, a 12 mm air cavity, a 3.2 mm CdTe photovoltaic layer, and 6 mm ultra-clear tempered glass (total thickness 28.34 mm). Key parameters included a CdTe standard efficiency of 16.5%, temperature coefficient of -0.189%/°C, transmittance of 0.47, and coverage ratio of 0.6. Results show that cooling and power enhancement depend primarily on solar irradiance intensity, duration, and water supply temperature. The inner surface cooling effect ranked as southeast (44.1%) ≈ east (44.0%) > west (41.7%) > southwest (38.3%) > south (36.9%). Daily power enhancement efficiency ranked as south (34.6%) > southwest (23.1%) > west (16.7%) > southeast (11.9%) > east (6.7%). The ratio of heat change in inlet/outlet water to cumulative solar radiation ranked as south > southeast > west ≈ southwest ≈ east. The optimal orientation for cavity water-cooled PV windows in Xiamen is south-facing. These findings provide empirical benchmarks for integrating water-cooled PV windows into building envelopes.