Space as the Source of Our Future Energy
May 22, 2009
The idea is to launch giant orbiting solar collectors into space, where there is no night, and beam the power to receivers on the ground, where it is fed as electricity to the grid. Long championed by former President Dr. Abdul Kalam, and the Aerospace Society of India (AeSI), the idea is seen as a long-term solution for energy security and climate change, and the most environmentally benign and scalable renewable energy option, which deserves its own focused development programme.
Such satellites would be the largest, most ambitious space projects ever contemplated. A single solar power satellite would be several kilometres long, with a transmitting antenna about a kilometre across, and generate between one and ten Gigawatts (as much power as 10 nuclear power plants). It might weigh tens of thousands of metric tons and would require a fleet of reusable space vehicles to construct. Follow-on designs might use materials from the Moon.
Existing communications satellites use a similar process, using the power of the Sun on their solar arrays to power a radio transmitter for sending radio and television signals. But the small antenna on communications satellites prevents them from being able to focus a beam for power-beaming. To beam power, the transmitter must be increased to almost a kilometre long, and a special receiver, a rectifying antenna, or rectenna is required. The rectenna would be several kilometres across, about the size of a municipal airport, made of a thin metal mesh, and would be 80 per cent transparent to sunlight, allowing the land underneath it to be used for pastoral, agricultural use or production of algae biodiesel. Far from some scary space-ray, the large transmitting and receiving antenna, the high conversion efficiency, and the constant availability allow the beam to be very low power—about a sixth the strength of sunlight on a warm sun tan beach day. Except that sunlight contains high frequency ultraviolet rays which can strip off electrons in our cells and cause cancer. The beam from a Solar Power Satellite would be of low frequency, very similar to current wi-fi devices, and is non-ionizing and not dangerous like UV.
Proponents feel it is an attractive option for several reasons. One, by 2025 the world will have added another two billion people, its energy needs will have doubled, the combustion of fossil fuels will continue to alter the composition of the atmosphere with concerns about climate change, and by mid-century we would have exhausted most of our fossil fuels. By mid-century India alone would have added 300,000,000 people, expanded its electrical generating capacity eleven-fold, from 121 GWe to 1350 GWe, moved upwards of 60 per cent of its population to cities, and exhausted all or almost all of its fossil resources. How are we to maintain a sustainable civilization if we remain a closed system and never access the vast wealth of all the rest of the universe?
In space faring advocate Mike Snead’s excellent paper, “The End of Easy Energy and What to Do About It,” he lays out the need and opportunity for Space Solar Power. Today the total world needs about 81 Billion Barrel of Oil Equivalent (BOE) thermal or about 15 TWe. And by 2100, to complete development to the “gold standard” of 30 BOE per capita, will require an expansion to probably 300 billion BOE, or roughly 55 TWe. By 2100 we will probably be about 50 years beyond the age of oil, and will have had to increase our renewable/sustainable energy 26 times. Even with a massive up-scaling of terrestrial renewable energy in the most optimistic estimates, the deficit is still close to 60 per cent. 55TWe is just very hard to come by on Earth. But what if we go to space, where energy is abundant, where the Sun never sets and delivers up to 9 times as much energy per unit area as on Earth, and 24 hours a day? There, in the Geostationary belt alone, is thought to be in excess of 177TWe of exploitable green solar energy—and it will be there for at least a billion years. If we could provide 55 GWe of green energy we fix our climate and energy problems in the long run, and we would grow the Gross World Product (GWP) over ten-fold. Imagine a world greater than an order of magnitude wealthier, a world fully developed with the security that a high standard of living brings. Can we afford to ignore a resource that vast? Does not extraordinary reward justify extraordinary effort? Those in the space movement think it cannot be ignored and that we need not only have to look beneath our feet for our energy, but can look to the stars for renewable, sustainable, scalable energy, and for a cleaner, brighter tomorrow.