Tikalon Blog by Dev Gualtieri

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Orbital Solar Energy

November 21, 2011

New Jersey , where I reside, isn't the sunniest of places, but somehow it's just second to California in photovoltaic capacity. The Solar Energy Industries Association lists California's installed capacity at 94 megawatts , and New Jersey's at 75.7 megawatts.[1-2] Perhaps that thought will keep me warm when I'm shoveling snow in a few more weeks. Imagine how much more effective our photovoltaics would be if we had clearer skies; or, if daylight periods were longer.

One way to accomplish this is to put our photovoltaic arrays outside Earth's atmosphere in space. Just as the idea of geostationary communications satellite originated with science fiction author, Arthur C. Clarke , the idea of solar energy from space was the brainchild of another science fiction author, Jerry Pournelle .[3] At the time of Pournelle's writing, the economics of this didn't make sense, but it may be time to revisit the concept.

Such a reassessment has been presented in a recent report by the International Academy of Astronautics (IAA) entitled, "Space Solar Power, The First International Assessment Of Space Solar Power: Opportunities, Issues And Potential Pathways Forward."[3-6] This voluminous, 248-page study, edited by NASA veteran, John Mankins , took two years to complete.[3] For those of you who might be wondering, carbon nanotube extension cords are not required. The power would be beamed to Earth using tight microwave beams.

GEOS-13 Solar Xray Imager, first public image, July 6, 2006

GEOS-13 Solar Xray Imager, first public image, July 6, 2006,

(Via NOAA National Weather Service Space Weather Prediction Center).

Envisioned are square kilometer arrays of photovoltaic cells in Earth orbit. These would need to be assembled from individual components. To get an idea of the power that would be available, the power of the Sun incident on the Earth above the atmosphere is about 1,366 watts per square meter, as averaged over the course of a year. If our photovoltaic array efficiency , including the necessary conversion to microwave energy, is just 20%, a square kilometer would provide about 275 megawatts of power.

The Indian Point nuclear power plant , which contains three reactors that supply a substantial portion of the electricity for New York City and its suburbs, generates about 2,000 megawatts. Obviously, many square kilometers of photovoltaics would be required in space just to offset nuclear energy.

A nineteen megawatt peak power photovoltaic system

A nineteen megawatt peak power photovoltaic system near Thüngen, Bavaria, Germany.

(Photo by Oh Weh, via Wikimedia Commons).

The availability of solar power at night is a major advantage of a space-based system, but such a system has one major disadvantage. It could be used as a weapon , and space-based energy weapons have made several appearances in James Bond movies . As it is, control of the microwave beam so that it's aimed precisely at the reception station would be a major undertaking,[3] and maintenance and repair operations in space would need to be continuous.

The IAA study determined that technologies have been demonstrated in the laboratory to make this venture feasible within two decades; and that the economics of such an energy source have improved due to the need for "green" energy .[6] The report claims that orbital solar will be competitive with other energy sources within thirty years, but it didn't propose a roadmap or a specific architecture . [5-6]

Much of the system cost would be in the vehicles that lift the components into orbit. The IAA study estimated that several tens of billions of dollars would be required for the development and construction of a fleet of low-cost, reusable, vehicles.[6] Mankins, editor of the IAA study, is also president of Artemis Innovation Management Solutions LLC , a California consulting company. NASA has given Artemis a small contract to pursue space-based solar power options.[5]

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