CALIFORNIA, USA - As a prototype prepares for tests in orbit, Nature looks at five of the biggest challenges for space-based solar power
The European Space Agency is investigating whether orbiting solar arrays could beam renewable energy to Earth, as shown in this artist’s illustration. For 100 years, people have dreamed of sending vast arrays of solar panels into space and beaming their energy down to Earth. Unlike intermittent renewable-energy sources on the ground, these orbiting panels would always bask in bright sunlight and would potentially offer a continuous supply of power.
Now such schemes are beginning to look possible, thanks to cheaper hardware and the falling cost of space launches. Teams around the world are working on key parts of space-based solar-power systems, and a prototype built by researchers at the California Institute of Technology (Caltech) should begin experiments in orbit this month.
“There’s nothing outlandish in this that would require new physics,” says James Carpenter, who co-leads the Solaris initiative, a feasibility study undertaken by the European Space Agency (ESA) that could lead to full development of the technology from 2025. “Economically, it’s comparable, for example, with nuclear power,” says Carpenter, who is based at ESA’s European Space Research and Technology Centre in Noordwijk, the Netherlands.
According to the comapany, Space-based solar power would be viable only if it were implemented on a massive scale. Scientists anticipate building kilometres-wide arrays of solar panels that would orbit Earth at a distance of around 36,000 kilometres. The energy that they harvest would be converted to microwaves and beamed down to surface-based receivers with even larger physical footprints.
Beaming microwave energy from space is surprisingly safe. The beam’s frequency will be chosen so that it does not disrupt aircraft communication. And because its power would be spread over such a wide area, the average energy density received by ground stations would be around 50 watts per square metre, says Carpenter, equivalent to the harmless level of microwaves that can leak from a microwave oven. “It’s within what would be considered a normal safety recommendation for human exposure,” he says.
But researchers will need to prove that there are no adverse effects on humans, animals or the wider environment. “I think they need to take the lead from the mobile-wireless industry that went through the same concerns, and to not trivialize these concerns, but prove it with studies,” says Jones.
Source: Nature