Q: Research seems to suggest that solar PV panels are not especially durable and suffer from failure. Even if they lasted 25 years of time (and I have not seen one company offering the domestic user anything like that length of guarantee), I have read that they deteriorate in efficiency and need constant cleaning otherwise the output declines significantly. Is this correct? If so, how practical is it for a householder to access the roof to actually clean these panels?

A: Durability and quality, plus of course consistant output of any PV module depends on build quality. On the whole though, unless buying cheap far eastern products with strange brand names, solar PV modules will degrade in output by circa 1% a year. This is the case with most crystalline technology (different with thin film though, which is largely unused in the UK).

The key in choosing PV modules will be check out the data sheet and search online for reports on the product. Good installers will only provide products they know will last the distance, as they are ones to be called back at times of failure.

Regarding cleaning, this is indeed an issue in Southern Europe, North Africa, etc, where the rainfall is quite low and airborne dust high. A layer of dust will build up on the modules causing a drop off in generation. Luckily for us in the UK, we have a good supply of rainfall, just about all year round  at regular intervals. The rain will bring the modules' self-cleaning properties into play, and a good shower will even remove bird droppings. A layer of light dust deposited in most dry periods in the summer will have a negligable effect on generation.

A few of our customers have felt the need to wash their modules this summer, and have reported hardly any change at all in generation after the process.

Picture by Patrick Feller

About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.

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