Solar-power beaming and collecting has been a dream of sci-fi buffs and techies of various ilk for decades, with no hope in sight at all of it ever coming about.
Now there is a company, Solaren, which claims to have the ability to compete with ground-based solar energy. With a twist.
They say they have figured out how to beam energy down to collecting arrays cheaply.
All is needed they say, is way to get their equipment into orbit:
Solar panels in space can receive seven times more solar energy per unit than ones on Earth and don’t have to deal with weather or darkness. The challenge in harnessing that energy comes from the expensive costs of launching material into space, as well as figuring out how to beam energy back down to Earth.
Microwave beaming has long been the favored delivery option for space solar power advocates. Space power stations using this method would convert the electricity generated by solar panels into radio frequency (RF) waves for beaming down to an Earth receiver several kilometers wide.
A former NASA scientist demonstrated the RF concept last year by beaming 20 watts between two Hawaiian islands — barely enough energy to power a dim light bulb. That experiment cost just $1 million. A full-scale space solar power setup would require much bigger and more costly receivers.
Another more recent choice has arisen in the form of solid-state lasers. Such lasers now have enough power to deliver energy as a tightly focused optical beam that requires much less costly equipment in space and on the ground. But unlike RF, lasers can run into bigger problems with atmospheric interference and weather.
“Microwaves can beam through clouds, which lasers can’t,” Hoffert explained. “With lasers you’re going to have to have receivers in desert sites that are cloud free, and maybe backup receivers in several sites.”
Hoffert still favors lasers because of the lower costs required up front for a tech demonstration. By contrast, Solaren weighed its choices and decided to go with RF technology.
“Basically we chose RF because it is more efficient and has all-weather capability for the reliable delivery of electricity to our customers,” said Cal Boerman, Solaren’s director of energy services.
The cost of space power
Hoffert is wary of Solaren’s latest step forward and the company’s promise of delivering 200 megawatts to PG&E utility customers in California by 2016.
Hoffert estimates that Solaren could manage to get about 50 percent transmission efficiency in a best-case scenario, meaning that half of the energy collected by space solar panels would be lost in the transfer down to Earth.
Solaren would then need to launch a solar panel array capable of generating 400 megawatts. The total launch weight of all the equipment would be the equivalent of about 400 metric tons, or 20 shuttle-sized launches, according to Hoffert.
But Solaren says that it would just require four or five heavy-lift rocket launches capable of carrying 25 metric tons, or about one fourth of Hoffert’s weight estimate. The company is relying on developing more efficient photovoltaic technology for the solar panels, as well as mirrors that help focus sunlight.
“Solaren’s patented SSP [space solar power] system dramatically reduces the SSP space segment mass compared to previous concepts,” Boerman told SPACE.com.
Solaren has not provided details on just how its technology works, citing intellectual property concerns. But it expects that its space solar power can convert to RF energy with greater than 80 percent efficiency, and expects similar conversion efficiency for converting the RF energy back to DC electricity on the ground in California. The company also anticipates minimal transmission losses from the space to the ground.
Hoffert remains unconvinced without knowing the details of Solaren’s technology. He frets that “premature optimism” over unproven and perhaps scientifically implausible concepts could end up ruining the reputation of space solar power, even as advocates desperately want to see their vision come true.
“Too many space power guys have been silent, perhaps to not give comfort to opponents,” Hoffert noted in a recent e-mail to colleagues. “But scientists should not do this.”
Solaren already has signed a contract with Pacific Gas & Electric (PG&E) to deliver energy to them by 2016.
I don’t know how they’re going to do that, by their own admission the equipment is/needs “… the equivalent of about 400 metric tons, or 20 shuttle-sized launches…” in orbit to accomplish the deal.
And I don’t know if anyone has told them yet that the space-shuttle is going to be put to pasture by the end of next year.
Maybe they have a plan for that too?
They better hope so. Power companies don’t like getting stiffed on contracts.
Just ask former Enron employees.