Every year, the Earth absorbs a staggering 3.85 x 1024 joules of energy. Put another way, it means that in one hour the sun gives us more energy than humanity used in the whole of 2002. Clearly, the sun can provide more energy than we need - if only we could harvest it at a competitive cost.
One way to reduce the cost of solar power is to focus the light onto a collector. But this can be expensive. The solution? Fresnel lenses. These consist of patterns of saw-tooth ridges or prisms on a transparent sheet, with each ridge bending the light towards a focal point or line. They are cheap because they can be printed on a flat sheet.
Read more in the New Scientist