Will SpaceX Enable Space-Based Solar Power?

11 January 2013 by Troy McConaghy, posted in Spaceflight

NASA Suntower concept

NASA Suntower concept

 

Will we ever gather solar power in space and beam it to Earth (e.g. using microwaves) for capture and distribution by our electrical grids?

This idea is known as Space Solar Power (SSP) or Space-Based Solar Power (SBSP), and has been around for over 40 years. It has several advantages. Most notably, ground-based solar power collectors only work when the sun is shining (i.e. less than half the time), whereas space-based collectors could work most of the time, depending on where they are. Space-based solar collectors would also be outside the Earth's atmosphere, which reflects or absorbs a lot of light before it ever gets to the ground.

The solar collectors are usually thought of as being on Earth-orbiting satellites, but they could also be on the surface of the Moon, or pretty much anywhere in the solar system. In fact, one of the first suggestions was to have the solar collectors on the planet Mercury. (This was the setup in Clifford Simak's 1941 science fiction story Masquerade.)

A NASA lunar base concept drawing

A NASA lunar base concept drawing

 

It's usually assumed that the solar collectors are manufactured on Earth using materials mined on Earth and then launched into space. Several people (e.g. Gerard K. O'Neill and David Criswell) have suggested mining the materials on the Moon or an asteroid. Materials processing and equipment manufacturing could also be done on the Moon or in space.

The gathered energy could be sent to Earth in a variety of ways, but the most common suggestion is to use a tight beam of microwaves. The microwaves could be picked up by a rectenna, a special kind of antenna that converts microwaves into direct current electricity. This idea is known as Wireless Power Transmission (WPT).

microwave beam

One objection to WPT has been that the microwave beam would be unsafe. What if the satellite accidentally pointed its microwave beam at a city? As it happens, the beam can be designed so that its intensity would be safe. You just need a really big rectenna array to pick it up.

So why isn't my electric tea kettle powered by energy that was gathered by a space-based solar power collector?

The main obstacle for SBSP has been the cost of launching the required materials from Earth's surface. It has been too expensive: the money you'd make from selling the electrical power wouldn't be enough to cover the costs of deploying the system.

Will SpaceX Make SBSP Feasible?

SpaceX is reducing launch costs. Also, there have been improvements in solar cells and wireless power transmission. Maybe space-based solar power will soon become economically feasible?

Solar power satellite sandwich or abascus concept

Other NASA concepts

 

Lots of Studies

The idea of space-based solar power is cool and potentially revolutionary, so many studies have been done to figure out if, or when, it might become economically feasible. A great list of all the latest studies can be found in the National Space Society's online Space Solar Power Library. Most of the studies listed are free to download.

One of the most recent big studies was conducted by the International Academy of Astronautics (IAA). It came out in 2011 and was edited by John C. Mankins. The authors looked at three possible systems, all involving satellites in geostationary orbit around the Earth. What were some of their main conclusions?

"Solar Power Satellites are technically feasible. There are no fundamental technical barriers that would prevent the realization of large-scale SPS platforms during the coming decades."

"…there are key challenges in achieving the very low cost operations needed to achieve economically viable SPS. The most critical of these was the essential requirement for very low cost ETO [Earth Transfer Orbit] transport."

"Solar Power Satellites appear to be technically feasible as soon as the coming 10–20 years…"

"The mature (high-TRL [Technology Readiness Level]) technologies and systems required to deploy economically viable SPS immediately do not currently exist; however, no fundamental breakthroughs appear necessary and the degree of difficulty in projected R&D appears tractable."

It's going to take decades to research, develop, test and deploy the systems needed to realize an economically viable space-based solar power system. Some of that work could be funded by various governments, and some could be funded by private companies.

SBSP Companies?

Amazingly (to me), there are some companies actively pursuing SBSP. These include Solaren, Space Energy, and PowerSat Corporation. Solaren even has a contract with a California power company to provide power to their grid starting in 2016. Will they be able to deliver? I don't know. I doubt it. 2016 is only three years from now.

Bottom Line

The bottom line with space-based solar power is that it's a cool idea that would work, but there's a lot to be done first.

Suggested Further Reading

Ad Astra, the Magazine of the National Space Society (NSS), featured a special report on space-based solar power in Volume 20, Number 1, Spring 2008. It's available from the NSS website.

The NSS Space Solar Power Library (online).

Glaser, Peter E., Davidson, Frank P. and Katinka I. Csigi. Solar Power Satellites: A Space Energy System for Earth. Wiley-Praxis Series in Space Science and Technology, 1997. Peter Glaser is regarded as the inventor of the solar power satellite.

Flournoy, Don M. Solar Power Satellites. Springer, 2011.

Image Sources

All images are courtesy of NASA (so public domain).

About this Blog

Outer Spacing is a blog about space exploration and development. It's written by Troy McConaghy (@TroyMc on Twitter).


2 Responses to “Will SpaceX Enable Space-Based Solar Power?”

  1. Khalil A. Cassimally | Permalink

    Interesting. While microwaves may be designed/emitted so as not to be harmful, I wonder about the possibility that they create interferences. If I'm not mistaken most signals here are through radio waves (is that correct?) so I'm not sure if interference is actually an issue though...

    • Troy McConaghy | Permalink

      The broadcast antenna used by a radio station sends its radio waves in all directions pretty much equally, something like a light bulb. A solar power satellite would emit a very narrow microwave beam in one direction (the direction of the rectenna on the ground), more like a spotlight. So even if interference is an issue, it's only an issue in the area of the rectenna, which could be out in the middle of nowhere.

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