The immense global energy flux from the Sun makes it the prime candidate for future sustainable energy production. Solar energy can be deployed at personal, community or regional scales, using both simple and advanced technologies. You have probably already seen solar PV panels that power automatic roadside weather stations and other low-drain communications systems. The panels require low maintenance and usually charge batteries to allow them to remain operational during the night. In poor countries where the energy infrastructure is rudimentary or absent, PV systems hold out great potential. An important use is for daytime pumping of water from wells

The main hindrance to greater deployment is simply that of cost; at between US$ 0.2 to 0.5 per kWh, solar PV electricity was almost ten times as expensive in 2005 as that from the cheapest fossil-fuel source, natural gas. To progress, the technology requires continued reduction in the cost of the solar cells themselves – but the enormous reduction in cost of silicon-based computer hardware since the 1970s is cause for optimism

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