Enhancement of flat-type solar photovoltaics power generation in harsh environmental conditions

Interest in solar energy has dramatically increased in recent years in the Middle East. However, despite high solar irradiance levels, harsh climatic conditions adversely affect the performance of solar photovoltaics (PVs) in the Persian Gulf. The objective of this study is to characterize the performance characteristics of PV systems utilizing either sun tracking or active cooling to increase electrical power output relative to stationary, passive cooling operation in such climatic conditions. This is achieved using dedicated experimental test facilities, that permit simultaneous PV performance characterization of sun-tracked and water-cooled configurations. Sun tracking is found to increase the daily yield of passively cooled PV modules by approximately 40% in summer months relative to stationary operation, with the largest power output gains occurring from approximately 30 minutes after sunrise to 90 minutes before solar noon, and from 90 minutes after solar noon to 30 minutes before sunset. Continuous water-cooling, with water at ambient air temperature (i.e., 35°C to 40°C), is found to increase PV module daily energy yield by approximately 15% relative to passively cooled operation in stationary conditions in summer, with the highest energy gains occurring two hours either side of solar noon. Peak electrical power output can be further increased by approximately 0.5 W for every °C reduction in water temperature below ambient air temperature, from 35°C to 2°C. Time- and temperature-relay actuated dynamic water-cooling is also investigated to reduce water consumption relative to continuous cooling. The use of a time relay-actuated five seconds-on, two-minute off cooling sequence is found to generate the same energy gain as for continuous water cooling, while requiring only 4% of continuous water consumption. This is attributed to the evaporative cooling effect caused by vaporization of a remaining thin film of water on the- module surface during the off-period of the cooling cycle.