Cheap balloon approach to focus solar energy

Cool Earth Solar of California has come up with a cheap and novel idea for focussing the sun's rays on small solar cells that might tackle the cost efficiency ratio issue for solar cells in quite a different way - metalised balloons.

"Anyone who has children will be familiar with aluminised party balloons. Such balloons are made from metal-coated plastic. Cool Earth’s insight was that if you coat only one half of a balloon, leaving the other transparent, the inner surface of the coated half will act as a concave mirror. Put a solar cell at the focus of that mirror and you have an inexpensive solar-energy collector."

See Economist Technology Quarterly.