Google Tech TalksDecember, 5 2007ABSTRACTCost-effective space solar power (SSP) -- the beaming abundant high-intensity solar power from space though atmospheric windows at laser or microwave frequencies for electric power at the surface -- could be a breakthrough technology for large-scale power generation, highly flexible power distribution and sustainable carbon-neutral base load for Earth; a goal comparable, but much closer to engineering maturity, to that of controlled thermonuclear fusion. Apart from much higher than the surface mean solar flux, continuous sunlight in space avoids otherwise cost-pacing massive storage and transmission of intermittent terrestrial solar and windpower to match electric demand curves. Access to space cost reductions will likely be driven by economies of scale from commercialization. But SSP would be markedly accelerated by experiments feasible now, some employing ISS, including orbital mirrors and microwave and and laser beaming in space.The just-released report on SSP by the National Security Space Office (available at http://... concludes that"it would be in the US Government's and the nation's interest to sponsor an immediate proof-of-concept demonstration project and a formally funded, follow-on architecture study conducted in full collaboration with industry and willing international partners." For example, I will describe our proposed demo of wireless power transmission from geosynchronous orbit (GEO) using diode laser transmitters in space and surface PV module receivers employing a self-deploying single launch one metric tonne satellite payload. Because diffractive beam spreading requires large antennas at microwave frequencies, it would be virtually impossible to launch microwave beamers large enough for efficient space-to-Earth power transfer without expensive multiple launches and in-space assembly. This limitation is overcome with the laser-based system proposed here although commercial SSP power stations might well utilize microwave beaming down the road.This experiment would demonstrate continuous electric power transfer from orbit orders of magnitude greater than anything done before, perhaps powering a remote village off the grid in the developing world. With near term and"on the shelf" components and early launch opportunities like NASA's Geo QuickRide, piggybacks on communication satellite launches, and the ISS as testbed, near term experiments could accelerate SSP from paper studies to a real alternate energy option in as little as a three to five year time frame at relatively modest cost.Speaker: Marty HoffertMartin I. Hoffert is Professor Emeritus of Physics and former Chair of the Department of Applied Science at New York University. His academic background includes a B.S. (1960) in Aeronautical Engineering from the University of Michigan, Ann Arbor; M.S. (1964) and Ph.D. (1967) from the Polytechnic Institute of Brooklyn (now the Polytechnic Institute of New York) in Astronautics; and a Master of Arts in Liberal Studies, M.A.L.S. (1969) from the New School for Social Research where he did graduate work in sociology and economics.He has been on the research staff of the Curtiss-Wright Corporation, General Applied Science Laboratories, Advanced Technology Laboratories, Riverside Research Institute and National Academy of Sciences Senior Resident Research Associate at the NASA/Goddard Institute for Space Studies. Prof. Hoffert has published broadly in fluid mechanics, plasma physics, atmospheric science, oceanography, planetary atmospheres, environmental science, solar and winds energy conversion and space solar power. His work in geophysics aimed at development of theoretical models of atmospheres and oceans to address environmental issues, including the ocean/climate model first employed by the UN Intergovernmental Panel on Climate Change (IPCC) to assess global warming from different scenarios of fossil fuel use. His early model of the evolving CO2 greenhouse in Mars' atmosphere is also of interest today -- providing both an explanation of Mars' riverbed-likechannels f...
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harrymook(March 28, 2009 at 12:23 pm)
This is not entirely true. Free electron lasers in the IR have been produced that are every bit as efficient as microwaves. Furthermore, beaming laser energy that matches the bandgap energy of a photovoltaic system is highly efficient, a 1,000 nm IR laser beam is converted to DC electricity by silicon with over 98% efficiency. Intensities of 600 W/m2 are possible. Shorter wavelengths also mean more compact optics and smaller receivers. Conjugate optics allow large numbers of receivers
SailorBarsoom(January 9, 2009 at 9:05 pm)
I think I'm glad you're not wanting to debate, because it seems you're more knowledgeable about this than I am.However, I do thank you for the contribution, since now I know these things too.
afxgrin(January 9, 2009 at 6:57 pm)
You're basically intercepting light that would be attenuated by the upper parts of the atmosphere, and have an ~50% emission into space. Now you're basically grabbing it before it hits the atmosphere, and beaming it down at a wavelength that's transparent to the atmosphere. Now all that energy gets reemitted as energy from other sources at the ground level - but at least it doesn't increase the CO2 problem - which has strong absorption smack in the middle of Earth's blackbody radiation band.
afxgrin(January 9, 2009 at 6:52 pm)
There are far IR lasers that have rather good cloud penetration. The problem however, is a lack of conversion efficiency - either to or from laser light.Microwaves are only useful up to about 6 GHz, otherwise you start getting serious RF to DC conversion losses. This is all associated to the rate of minority/majority carriers transitioning in the Schottky diodes. This is all well studied ... I'm just contributing to the conversation, not looking to debate anything with you.
bigmikeblcw(January 6, 2009 at 6:13 pm)
Yes.
Palmstream(January 6, 2009 at 2:31 pm)
No.
bigmikeblcw(January 6, 2009 at 5:55 am)
Increase global warming? Maybe. Ponder on the amount of satellites in space. We know the moon affects various aspects of earth, are we creating similar reactions from our satellites? Mars research shows that a possible degrading orbit asteroid caused catastrophic failure of the magnetic field and eventually made Mars FUBAR. Are we looking at a similar effect from satellites? True man made satellites are much smaller.
Palmstream(January 3, 2009 at 11:50 pm)
If we get space elevators, fine. If we don't, fine. 99% of the dirt for sunsat construction will come from the moon, launched in softball-sized packets every half-second by electromagnetic mass drivers. All that is necessary to launch from earth are electronics, tools, and humans, and converted Atlas and Delta rockets can do that. At last report, Obama may be coordinating missions in NASA and DOD. Look for DOE to be brought into the loop.
svobobo(December 23, 2008 at 12:10 am)
i belive that space elevators are science fiction and will be so in the future too..
christo930(December 17, 2008 at 5:21 am)
This guy is about the worst speaker I have ever heard. He wastes lots of time complaining about a lack of time. He sucks.
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