India and Space Solar Power

from: http://epaper.sakaaltimes.com/ST/ST/2009/05/22/index.shtml (page 6)
Power-The Final Frontier
Could satellites in orbit be a source of future energy? Its possible.
Somewhere around 2015, more Indians will live in cities than rural areas, and the trend will continue until by 2030, more than 60% of Indians will live in cities. Cities need reliable power. By 2050, India will have gone from 1.2 Billion to 1.5 billion people, adding almost as many additional citizens as it had at Independence. To meet developmental goals by 2050, GOI plans require installed electrical capacity to grow by 11-fold, from 121 GW to 1350 GW, a 5.5% rate of growth (actual growth in 2006 was 7%). Fully 50% of current and future electrical supply is projected to come from coal. At 5.5% annual growth, India will completely exhaust its domestic coal supplies by 2063.
The global situation is equally challenging. By 2030 the world will have added another 2 billion people and total energy demand will have doubled (15TW to 30TW). Demand is likely to go as high as 55TW between 2050 and 2100. An energy system based on combustion of fossil fuels creates huge amounts of greenhouse gasses, particularly carbon dioxide. Leaders committed to stemming climate change would have to add 16 terrawatts of carbon-neutral energy to stabilize CO2 at four times pre-industrial levels, and 40 terrawatts to stabilize at twice pre-industrial levels. That is a lot of green energy! Also, and more worrying to some, sometime before mid-century, first oil, then gas, then coal will all peak in production. Unable to keep up with demand, traditional sources will first plateau, and then begin a steady decrease in global production. What will fill the gap?
Many look to terrestrial solar to fill the gap, and it will have a huge role to play. But although the amount of solar energy falling on the Earth far exceeding the needs of humanity, for the particular application of reliable, dispatchable, 24-hr electrical power, terrestrial solar faces many challenges, not the least of which is that any ground based power plant will spend half the time in night, producing nothing. In fact, terrestrial solar systems produce useful power less than 25% of the day.
A bold and different solution to tapping the suns energy, and one posed by former President Dr. APJ Kalam, and the Aeronautical Society of India (AeSI), and seconded by other private organizations in the United States, is the Space-Based Solar Power (SBSP).
In this concept, very large satellites, the largest every constructed, made up of kilometers of solar cells would collect the Sun’s energy where there is no night, and convert it to radio-waves to be beamed to special receiving antenna farms on the ground (called rectennas) about the size of a municipal airport. The energy is sent in the form of a low energy beam at about 1/6th the intensity of sunlight you would experience if you went for a sun-tan at the beach. But because it is a low-energy, non-ionizing wavelength, it is not as dangerous as sunlight with its high energy ultraviolet rays. At the rectenna, the energy is reconverted and sent via the existing electrical grid. Such satellites would necessitate a fleet of re-useable space planes, and as a consequence of economies of scale, reduce the cost of space access a hundred fold, enabling many other applications.
Space Solar Power is one of the very few renewable energy options that is both scalable to the levels we need (the Geostationary Belt is thought to be able to support enough satellites to produce 177 TW), and be able to provide 24-hr power (not just when the Sun shines or wind blows). It also appears to be the most benign of any of the major energy options. It produces no radioactive waste. Despite minor emissions and significant energy expenditure during manufacture and launch, the lifecycle CO2 emission of a Powersat is 60x less than coal, and has an energy payback period of a mere two years. Extensive Environmental Protection Agency (EPA) tests failed to show any significant biohazard for such a low energy beam. A rectenna is over 80% efficient at converting the beam to electricity. That means less than 20% of the incident energy is rejected to the biosphere as waste heat compared to greater than 50% for all other power sources. The rectenna also operates without the need for scarce water for cooling. High energy conversion efficiency means land used for the rectenna is much more productive than either ground solar or wind, conserving scarce land. Additionally, the rectenna is >80% transparent to sunlight, and stop 99% of the beam, meaning land underneath it can be used for agricultural and pastoral uses. Proponents feel that given these merits, Space Solar Power deserves its own development program.
Here is an interview as well from the Pune Mirror: http://www.punemirror.in/index.aspx?page=article&sectid=2&contentid=20090413200904130234463648ecfff86&sectxslt=&pageno=2
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