Increased electrical yield via water flow over the front of photovoltaic panels

Reflection of the sun's irradiance typically reduces the electrical yield of PV modules by 8-15%. Facade applications located in the tropics may even experience a 42% drop in yield, due to flat incidence angles. Additionally, when a module's cell temperature is elevated there is 0.4%/K decrease in voltage and power for single- and multi-crystalline silicon solar cells: in reference to STC, that number may reach 20%. Numerous ideas to reduce reflection have been proposed, but most have drawbacks: antireflective-coatings are not durable and structured surfaces are expensive, accumulate dust and are difficult to clean. Yet water, with a refractive index of 1.3, is a viable intermediary between (n(glass) =1.5) and air (n(air) = 1.0). In addition to help keeping the surface clean, water reduces reflection by 2-3.6%, decreases cell temperatures up to 22degreesC and the electrical yield can return a surplus of 10.3%; a net-gain of 8-9% can be achieved even when accounting for power needed to run the pump. (C) 2004 Elsevier B.V. All rights reserved.