Space Solar is working on a satellite project called CASSIOPeiA, which Physics World describes looking like a “spiral staircase in which the photovoltaic panels are the ‘steps’ and the microwave transmitters — rod-shaped dipoles — are the ‘landings.'” It is helical in shape and contains no moving parts.
“Our system is made up of hundreds of thousands of identical dinner-plate-sized power modules. Each module has a photovoltaic cell that converts solar energy into direct current,” said Sam Adlen, CEO of Space Solar.
“This DC power then drives the electronics to transmit power…down toward Earth from the dipole antennas. This power up in space is converted to [microwaves] and transmitted in a coherent beam to Earth, where it is received by a rectifying antenna, converted back to electrical energy and fed into the grid.”
Adlen said robotics technologies for space applications, such as in-orbit assembly, are developing at a rapid pace.
Ceriotti wrote that SPS-ALPHA, another project, has a enormous solar collector structure that includes multiple heliostats, which are modular miniature reflectors that can be moved individually. These concentrate sunlight into separate power-generating modules, from where it is transmitted back to Earth by another module.
Safety in space
Those plans involve enormous beams of microwave or radio waves. But solar energy from space is relatively sheltered. In the case of microwave radiation from a solar facility in space, “the only known effect of those frequencies on humans or living things is tissue heating,” Vijendran said. “If you were to stand in that beam at that level of power, it would be like standing in … the evening sun.” Still, Caplin said, more research is needed to examine the effects of those microwaves on humans, animals, plants, satellites, infrastructure and the ionosphere.
Getting that across to the public could remain a challenge, though. “There’s still a perception issue that needs to be addressed, and it’s going to take a lot of commitment to get it to market,” Adlen said.
Military attacks using solar energy from space could also be a concern. But even if a space solar plant were hijacked for military reasons, equipment would limit the beam to a sheltered intensity so it couldn’t be used to harm people or ecosystems on Earth, Ceriotti said.
In addition to environmental concerns, there are additional concerns that need to be addressed before deployment. Another potential risk is interference with communications signals, although Gibney wrote that the beam frequency would not interfere with aircraft communications. It is essential to consider some other physical hazards.
Orbiting debris, such as meteorites or space junk, could hit the station and damage it, Vijendran said. If impacts on the solar plant generate debris, that could also cause problems. In addition, the equipment itself would have to be deorbited when it reaches the end of its life cycle. “ESA has the Clean Space Initiative. Whatever we send into space, we have to think about the entire life cycle, from cradle to grave,” Caplin said.
Finally, the project will still have an environmental impact. Putting the solar plant hardware into orbit, building it and controlling it will generate pollution and apply a significant amount of fuel, Ceriotti wrote. Hundreds of launches could be required.
Start the economy
In addition to the environmental impact, these launches will cost money. Cost has been the main barrier to building a space solar plant, Caplin said. “As the landscape changes and it becomes cheaper to send to space overall, we can put that back on the table. The money speaks for itself. We have two independent cost-benefit studies on the table, and both have shown that it could be feasible.”
Ceriotti said the costs of solar power in space will include production costs, maintenance costs and launch costs.