Extra-Planetary Solar Arrays

“The dots to which our energy beams are directed…are cold and hard and human beings like myself live upon their surfaces — many billions of them. Our beams feed these worlds energy drawn from one of those huge incandescent globes that happens to be near us. We call that globe the Sun and it is on the other side of the station where you can’t see it.”

Speaking to his incredulous robot, the protagonist in the Isaac Asimov story “Reason” explains the basic functioning of Solar Station #5, a space-based solar power station in geosynchronous orbit with the Earth. First described by Asimov in 1941, space-based solar power (SBSP) may have moved from the realm of science fiction to reality, receiving interest from government and industry as an emissions-free, renewable energy source with no issues of intermittency or battery storage.

SBSP relies on solar power collection by panels attached to satellites in orbit, from which the energy is wirelessly beamed to the Earth’s surface. Since these satellites are stationed outside the atmosphere, virtually uninterrupted collection is possible of a light much more intense than that absorbed on Earth. In the most likely configuration, the host satellite would convert photons into electricity, powering a microwave emitter focused on a collector on the Earth’s surface.

Source: NASA

While extra-planetary solar arrays and wireless energy transmission have been investigated on an experimental scale, several recent high-profile commitments to SBSP may signal its growing feasibility. In April of 2009, the utility Pacific Gas & Electric contracted with an SBSP provider to buy 200 MW of solar power by 2016. If completed, this project would be the first application of the technology. Last year Japan announced a plan to launch a solar power satellite by 2030, which would transmit power via laser beam. Additionally, in 2007 the US National Security Space Office released a report proclaiming their intention to implement SBSP, referring to it “as a potential grand opportunity to address not only energy security, but environmental, economic, intellectual, and space security as well.”

Yet since wireless energy transmission from space has never actually been implemented, its viability by 2016 is questionable, hinging on technology constraints and the high cost of rocket launch. High-intensity transmission and terrestrial collection would have to be perfected, and concerns remain about environmental disturbance and safety issues created during transmission, as well as the effects of excessive heat on the solar cells.

In the prevailing theory, large disassembled solar panel arrays would be launched by heavy-lift rocket to low earth orbit, where they would then be assembled and brought to geostationary orbit by smaller rockets. Even assuming a solar panel mass of 1kg/kW, the minimum cost for a heavy-lift rocket is $11,538/kg, bring the total cost for a 2GW power station upwards of $11.5 billion. Another unlikely option suggested by NASA is to establish a construction site on the moon, where less gravity means cheaper rocket launches (yet initial investment in lunar infrastructure would reached untold billions).

Although the near constant stream of high-energy photons available outside the atmosphere is a tantalizing source of energy, the technological impediments and astronomical costs make implementation unlikely, considering the massive risk taken on by any investor. While government and private sector research and funding continues for the technology, SBSP may remain a well-intentioned fantasy.

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1 Comment

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One response to “Extra-Planetary Solar Arrays

  1. bhgully

    Wow, impressive that there is enough of a power generation benefit to make it worth it to a) send the system into orbit given the extreme costs you pointed out and b) transmit back to Earth’s surface given what I can only assume to be an extremely lossy wireless transmission …or at least enough to get companies to announce solid plans. Very interesting.

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