Space-based solar power
SPS-ALPHA (Solar Power Satellite via Arbitrarily Large Phased Array) is a novel, bio-mimetic approach to the challenge of space solar power. If successful, this project will make possible the construction of huge platforms from tens of thousands of small elements that can deliver remotely and affordably 10s to 1000s of megawatts using wireless power transmission to markets on Earth and missions in space. Image: Mark Elwood, SpaceWorks Enterprises, Inc.
Continuing with the solar theme! Instead of collecting light from the sun here on earth, we look to the skies and get a (tiny) bit closer via solar power satellites.
The idea of space-based rather than terrestrial solar power systems was first mentioned in the story “Reason” written by author Isaac Asimov. Early exploration of the concept was conducted by NASA and the US Department of Energy, with the Office of Technology Assessment claiming in 1981 that “Too little is currently known…to make a sound decision whether to proceed with its development and deployment.” But NASA’s “Fresh Look” in 1997 urged “significant investments in technology to drive the costs of Earth to Orbit transportation down” in order to facilitate space solar power. More recently, interest in the idea has been stirred in the US, Russia, China, India and Japan, with China proposing a Chinese-Indian collaboration in 2012. The US asteroid mining company Deep Space Industries has also expressed interest.
The basic idea, borrowed here by the URSI White Paper on Solar Power Satellite (SPS) Systems, is that:
“…solar energy is collected in space by a satellite in a geostationary orbit. The solar energy is converted to direct current by solar cells, and the direct current is in turn used to power microwave generators…The generators feed a highly directive satellite-borne antenna, which beams the energy to the Earth. On the ground, a rectifying antenna (rectenna) converts the microwave energy from the satellite to direct current, which, after suitable processing, is fed to the terrestrial power grid.”
These systems would consist of three elements: a way of collecting the light (e.g. solar concentrators), a way of transmitting the power to earth (e.g. microwaves), and a way of receiving power from earth. Construction ideas involve building systems via lunar materials launched in orbit, constructing them on the moon, or utilising asteroid mining to gain the necessary constructing materials (The asteroid Apophis [apparently] contains enough materials to construct about 150 five-gigawatt solar power satellites).
But why in space? Several advantages are behind the recent drive to implement space-based solar systems, including
- the lack of light-filtering/distorting air, allowing for increased solar collection
- no shadows from being on earth, increasing the duration of solar collection
- no ecological interference
- quick redirection of power to where it is needed
However, as with everything, there are inherent costs to such systems, as well as technical issues:
There are further issues, such as the safety of such systems, especially concerning exposure to microwave beams at ground level, as well as cost estimates (John Mankins of Deep Space Industries claimed the SPS-ALPHA system, illustrated above, could cost $15–$20 billion). But could rising global energy demand and dwindling (conventional) fossil fuel supplies, combined with increases in solar cell efficiency and further future ventures into space provide the push for the creation of the first space-based solar systems?