Photovoltaic

Photovoltaic cells convert solar radiation into electricity. The first cell was manufactured in 1954 and they have been improving in efficiency ever since.

Commercially available cells are now about 15 to 17% efficient. Like wind turbines, their output is variable and therefore they need a back-up. They are used to good effect powering remote equipment where it would be more expensive to extend the power network, in which case the back-up power comes from batteries. Alternatively they are used to reduce power consumption, as and when they can, from another continuous source such as the national grid.

They remain expensive and usually require a grant to make them commercially viable. The commercial case is enhanced further if they are used to replace another building component, such as external wall cladding.

An exciting recent development is nano photovoltaics in which photo-sensitive material is simply printed onto a wide range of suitable substrates, including rooftiles. The conversion efficiency is currently a little lower than conventional semi-conductor types but costs are reportedly only about one-tenth. The technology is already available and deployment is restricted only by the limited manufacturing capacity. This technology is attracted huge financial investment which could soon revolutionise the energy sector.