This giant disk floating in space isn't a UFO. It's a power generator, harvesting energy from the Sun for a variety of uses back on Earth. Such space-based solar power generators have many applications, not just on Earth, but also in space.

Solar power beamed down from space will generate electricity for California homes as soon as 2016, under a new plan by a utility company to ramp up renewable energy technology far beyond solar panels on roofs.

PG&E would buy 200 megawatts of space solar power from Solaren Corp. over 15 years under a power purchase agreement, enough to power tens of thousands of homes. The utility company has begun seeking approval for the deal from California state regulators.

Solaren would use solar panels on satellites in orbit to capture the sun's power, and then convert it into radio frequency energy that could beam down to a receiving station. The energy would then undergo a conversion to electricity and feed into PG&E's power grid.

Having solar panels in orbit could provide a clean, reliable source of solar power that avoids the interruptions of cloudy days and bad weather on Earth. That tempting prospect has led NASA and the U.S. Defense Department to investigate possibilities for space solar power, despite the hefty cost of launching solar panels into orbit.

A former NASA scientist went so far as to demonstrate the radio wave transmission technology that would carry energy from space to Earth. He and his team transmitted solar power over a distance of 92 miles between two Hawaiian islands, during a four-month experiment in 2008.

{{ video="SP080912_solar-satellite" title="Beaming Solar Power from Space" caption="Mafic Studios depicts how solar power satellites could beam energy to Earth from orbit in this animation. Credit: Mafic Studios, Inc." }}

No one has built a system with equivalent size and scale to what Solaren envisions. But the transmission technology is "very mature" and based on what communications satellites use today, said Gary Spirnak, Solaren CEO.

"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," Spirnak noted.

The pilot power satellites designed by Solaren would make use of existing launch capabilities, meaning that the plan does not require new types of rockets. The ground receiving station would also sit close to existing power transmission lines, somewhere in Fresno County, Calif.

More details about Solaren's pilot project for its power satellites are expected this summer.