Letters
Life of PV Systems
The IAEEL Newsletter 4/96 contained very interesting material on the use of photovoltaics and lighting. One of the characteristics most people will require to know relates to the average achieved life of individual PV cells.I F Davies, Surrey, UK
Reply: The photovoltaic modules have a demonstrated life of at least 20 years under very harsh conditions. This is true for modules with monocrystalline silicon cells, and should also apply to other cell technologies which have not been in use that long, such as copper CIGS (copper-indium-gallium-diselenide) thin film cells, according to lab results.
There is some confusion with regard to the degradation of amorphous silicon cells, which actually degrade substantially during the first few months. Thereafter, however, they remain very stable, and it is the stabilized capacity that the customer pays for.
It is quite possible that well-laminated modules can last longer than 20-30 years. However, all other parts of the system would have to be replaced much earlier, with the possible exception of the module support structure which should last several decades. The other parts of the system are: charge and load controller, batteries, lamps and ballasts, luminaires, wiring, switches and outlets, (possibly) DC/AC inverters, and finally, for concentrator-type modules, tracking devices and bearings, and lenses or mirrors.
The expected life of any such component will vary depending largely on where and how often it is used. The battery is often the weak link and can hardly be expected to last more than five years.
Editors