# Space‐Based Solar Power

Not sure where to put this, but the main scope is energy and that's physics.

http://spacesolarpower.files.wordpress.com/2007/10/final-sbsp-interim-assessment-release-01.pdf [Broken]

Looks like we may have solutions here.

The SBSP Study Group concluded that space-based solar power does present a strategic opportunity that could significantly advance US and partner security, capability, and freedom of action and merits significant further attention on the part of both the US Government and the private sector.

The SBSP Study Group concluded that while significant technical challenges remain, Space-Based Solar Power is more technically executable than ever before and current technological vectors promise to further improve its viability. A government-led proof-of-concept demonstration could serve to catalyze commercial sector development.

The SBSP Study Group concluded that SBSP requires a coordinated national program with high-level leadership and resourcing commensurate with its promise, but at least on the level of fusion energy research or International Space Station construction and operations.

The SBSP Study Group concluded that should the U.S. begin a coordinated national program to develop SBSP, it should expect to find that broad interest in SBSP exists outside of the US Government, ranging from aerospace and energy industries; to foreign governments such as Japan, the EU, Canada, India, China, Russia, and others; to many individual citizens who are increasingly concerned about the preservation of energy security and environmental quality While the best chances for development are likely to occur with US Government support, it is entirely possible that SBSP development may be independently pursued elsewhere without U.S. leadership.

Certain key questions about Space-Based Solar Power were not answerable with adequate precision within the time and resource limitations of this interim study, and form the agenda for future action (a complete description of these questions can be found in Appendix A – Space Based Solar Power Design Considerations and Tradeoffs). The fundamental tasks/questions are:

-Identification of clear targets for economic viability in markets of interest
-Identification of technical development goals and a roadmap for retiring risk
-Selection of the best design trades
-Full design and deployment of a meaningful demonstrator

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russ_watters
Mentor
At their estimate of $1-$2/kWh, it's a long way from feasible.

HallsofIvy
Homework Helper
Have they suggested how to get the energy generated back to earth?

mheslep
Gold Member
I had never consider SBS anywhere close to feasible, but with the publication of an article in the Economist special report I'm bringing this thread back to life.

The Economist
Space solar power
Let the sun shine in

Essentially, the renewed interest is due to possible reductions in lift cost brought on by private enterprise, and a recent long distance microwave power transmission test.

-History: First scientific footing by Peter Glaser (Authur D Little) 1968, building on the work of William Brown, Raytheon. Idea updated from time to time by NASA, Boeing, Lockheed, and the US DoD.
-'No technical show stoppers' (?). Estimated cost now 50 cents/ kWh.
-May 2008 Hawaiin Microwave test. A stunt. http://blog.wired.com/wiredscience/2008/09/visionary-beams.html".
-Most likely design: Large space based geosynch. reflectors concentrate light on space based highly efficient PV (40%) which produce electricity, beamed to earth as microwave using solid state amplifiers. Large receiver on the ground - ~ sq kms. Power density on earth is not lethal.
-Lift cost. Currently $6-10k per kg. Private launch people like Elon Musk believe they can do$3K. The NSSO (Andre's DoD link 1st post) report says $440/kg would enable 8-10 cent /kWh energy. Other PF threads: https://www.physicsforums.com/showthread.php?t=246498" '08 https://www.physicsforums.com/showthread.php?t=104129" '05 At their estimate of$1-$2/kWh, it's a long way from feasible. Hence the military interest, as per the linked DoD report they estimate they pay$1/kWh now in forward deployed areas (mobile diesel generators), and shipping fuel to these areas is 70% of the total military mass lift.

Have they suggested how to get the energy generated back to earth?
Microwave preferred. Very large receiver, couple square km

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Have they suggested how to get the energy generated back to earth?

The initial approach the Japanese are taking is to collect the light in space from a satellite, and beam it to a collection site in the middle of the ocean. I am not sure how they plan to compensate for losses as the beam penetrates the atmosphere. (thread dig from 07'? Aw, not much to talk about lately anyways...)

The initial approach the Japanese are taking is to collect the light in space from a satellite, and beam it to a collection site in the middle of the ocean. I am not sure how they plan to compensate for losses as the beam penetrates the atmosphere. (thread dig from 07'? Aw, not much to talk about lately anyways...)

Even when you get the energy into the middle of the ocean (i assume you're doing that for safety?)...you're going to have a lot of line loss trying to get the power to any usable region...unless you're talking about this being a large enough operation that you would build a superconducting transmission line to the mainland, which will also be quite expensive.

~Lyuokdea

At their estimate of $1-$2/kWh, it's a long way from feasible.

Power satellites are not going to contribute to solving the energy crisis at that price, you need more like 1-2 cents per kWh.

So what would it take? Two cent power is a revenue stream of $160 per kW per year. Could pay back$1600 per kW in ten years. The main cost element, lift to GEO, has to be reduced by about 200 to one for power satellite to be worth doing. At 5kg/kW, and $100 per kg, that's about 1/3 of the allowable cost. So the problem has now been reduced to shipping a million tons per year to GEO at a cost of$100/kg. I don't think that can be done at all with chemical rockets all the way (the mass ratio kills you) but chemical to 5 or perhaps 8 km/sec and using ablation lasers for the rest of the delta V to GEO looks like it might do it. Google henson oil drum or ask me for a copy of Beamed Energy and the Economics of Space Based Solar Power.

Keith Henson
hkeithhenson at gmail dot com