Pacific Gas and Electric, which serves San Francisco and northern California, has announced it will seek approval from US regulators to purchase 200 megawatts worth of solar energy delivered from solar panels located in space.

The panels will be built and put in place by space solar power company Solaren over 15 years. Once completed, it is hoped they could produce enough clean energy to fuel half a million homes.

Solaren plan to fire a satelitte into space by a rocket. The device will be able to convert solar energy into a usable form and send it wirelessly to Earth.

Capturing solar energy from space has never been done commercially, mostly because the cost was considered too high.

But Solaren claims it has developed a technology that would make it commercially viable within the next seven years.

The project was announced on a question and answer session on Pacific Gas and Electric's blog: "While a system of this scale and exact configuration has not been built, the underlying technology is very mature and is based on communications satellite technology. For over 45 years, satellites have collected solar energy in earth orbit via solar cells, and converted it to radio frequency energy for transmissions to earth receive stations. This is the same energy conversion process Solaren uses for its (space solar power) plant," it said.

The advantage of space solar power is that energy can be harnessed at all times, even at night or when it's cloudy. Solaren's contract calls for it to deliver baseload power, the electricity needed to meet customer demand.

Another company called Space Energy has been formed to also tap solar energy from space using a similar technique as Solaren.

Daniel Kammen, professor in energy and resources at the University of California, Berkeley, told the Guardian: "The ground rules are looking kind of promising ... it is doable. Whether it is doable at a reasonable cost, we just don't know."