Images: Supersize solar power

Newer solar thermal plant designs incorporate several hours of storage, either by storing hot water or molten salt. This allows them to operate during the entire day, rather than only when the sun is out. Economically, the storage makes a very big difference because it allows utilities to meet peak demand hours, which is the most expensive time to supply electricity.

Solar thermal start-up SkyFuel uses reflective troughs or Fresnel lenses to focus light onto a pipe that carries a heat transfer liquid. Typically, that liquid is either oil or water, which is converted to steam to turn a power generator. Instead, SkyFuel's design calls for circulating molten salt that is transferred to storage tanks. This allows a utility to make electricity (from the heated salt) on demand and charge more for the product.