Images: Supersize solar power

Concentrating photovoltaics, in which light is focused on solar cells that generate electricity, is being considered by utilities as well. The technology has been around for many years, but a number of companies are trying to improve on it with higher levels of light concentration and cheaper manufacturing.

This artist's rendering shows a concentrating photovoltaic CarouSol system from start-up GreenVolts, which has paired with PG&E to build 2 megawatts in Tracy, Calif., by the end of 2008.

Each CarouSol includes an array of power units on a platform rotating on two axes to follow the sun in the sky. Mirrors on the units concentrate the energy of 625 suns onto the solar cells, according to the company. The modular, snap-together systems sit close to the ground to keep maintenance simple. Tests have shown the CarouSol to withstand winds of 43 miles per hour. It's also supposed to provide energy at half the cost of more traditional systems.