Since the Feed-in Tariff is paid over a fixed term, revenue lost through reduced productivity can’t be recouped later. Depending on your FIT rate and the amount of dirt on the panels, this can amount to thousands of pounds in lost revenue.
Over time, a large amount of dirt and organic material can build up, coating the surface of the PV modules. This is especially true in agricultural settings, where the combination of airborne particles and shallow roof pitches creates conditions for the layer to build.
This layer creates a physical barrier that reduces the intensity of light reaching the semiconductor surface beneath the protective glass on each module. This causes a substantial reduction in the amount of electricity that can be generated by the system, consequently reducing income from FIT payments and electricity bill savings. How often panels need to be cleaned will depend on the site-specific circumstances, but as a general rule it is worth checking every year. In this example, the modules were cleaned at the start of spring and there is no doubt that there will be a substantial increase in generation of electricity as a result, with the resulting extra income far exceeding the cost of the cleaning process.