FYI,

"Whatever Happened to Solar Power Satellites?"
The Space Review
http://www.thespacereview.com/article/214/1

: At the end of June, a conference about space based solar power
: generation was held in Granada, Spain. The conference provided
: progress reports from groups in Europe, the US, and Japan who are
: working on concepts and plans for building solar power plants in
: orbit that would beam electricity down for use on Earth.

: It sounds like the perfect solution for our future energy needs.
: The Sun is constantly sending energy to the Earth and all we need
: to do is catch it and then use it. Unlike current energy sources,
: we are not going to run out of sunlight anytime soon, it wouldn't
: contribute to global warming, and it is available everywhere (or to
: put it another way, we don't need to get most of our sunlight from
: a politically unstable region).

: The idea of generating power in space has been around for a while,
: but has never really gotten off the ground. Concepts for solar
: power satellites were being discussed in the 1960s and they have
: received varying amounts of interest since then. If solar power
: satellites are such a great thing, why haven't more people been
: more excited about them? The theory of the concept is sound, but
: there are a number of hurdles that are holding development back.

: In orbit, a solar power satellite would be above the atmosphere and
: could be positioned so that it received constant direct sunlight.
: Some energy would be lost in the process of transmitting power to
: stations on the Earth, but this would not offset the advantage that
: an orbiting solar power station would have over ground based solar
: collectors.

: There are also opportunity costs associated with both options. On
: Earth, land used for generating solar power is not being used for
: other things. Rooftop space may not be valuable, but acres of
: farmland are. There is also only a limited number of available
: slots in geosynchronous orbit where a satellite could be placed to
: continuously beam power to a specific receiver. Where land is at a
: premium, a satellite would have an advantage over a ground-based
: system.

: Another barrier is that launching anything into space costs a lot
: of money. A substantial investment would be needed to get a solar
: power satellite into orbit; then the launch costs would make the
: electricity that was produced more expensive than other
: alternatives. In the long term, launch costs will need to come down
: before generating solar power in space makes economic sense. But is
: the expense of launching enough to explain why so little progress
: has been made?

: Is there enough money available for these purposes, but not enough
: to launch even one solar power satellite that would help the world
: develop a new source of energy?

: In the 2004 budget the Department of Energy has over $260 million
: allocated for fusion research. Obviously the government has some
: interest in funding renewable energy research and they realize that
: private companies would not be able to fund the development of a
: sustainable fusion industry on their own. From this perspective,
: the barrier holding back solar power satellites is not purely
: financial, but rather the problem is that there is not enough
: political will to make the money available for further development.

: There is a very interesting discussion on the economics of large
: space projects that makes the point that "the fundamental problem
: in opening any contemporary frontier, whether geographic or
: technological, is not lack of imagination or will, but lack of
: capital to finance initial construction which makes the subsequent
: and typically more profitable economic development possible.
: Solving this fundamental problem involves using one or more forms
: of direct or indirect government intervention in the capital
: market."

: Even if a solar power system was built and launched there would
: still be the economic problem of producing electricity at a cost
: that is comparable to other options. Government subsidies can help
: get this new industry on its feet but it will need to compete in
: the market in order to survive. This is a challenge for all
: emerging renewable energy solutions.

: Current non-renewable energy supplies are cheap. Even with the
: recent increases in the price of oil, it is still historically low.
: Adjusted for inflation, gas prices are still much lower than they
: were during the oil crisis in the 1970s. With current prices there
: is little incentive for customers or producers to pursue
: alternatives. Even if oil prices continue to increase, it is not
: likely that this will be enough to drive demand for alternatives.
: Although we will eventually run out of oil, coal, and other non-
: renewable energy sources, in the short term rising oil prices will
: simply generate more oil.

: There are large amounts of known reserves that are too expensive to
: profitably develop when oil is below a certain price. As soon as
: the price increases past a certain threshold, a given field can be
: developed at a profit. From an economic standpoint, energy
: producers will take advantage of this and will make use of their
: existing infrastructure to extract, refine, and distribute as much
: oil as possible regardless of how high the price of a barrel of oil
: goes.

: Again the problem is more of a political one than an economic one.
: There will not be a financial reason to start creating a solar
: power system in space unless we reach a decision to include the
: hidden environmental costs of our current non-renewable sources of
: energy into the equation. In the near term we certainly can afford
: to keep burning more oil, but are we willing to start investing in
: alternatives so we don't have to?

: A fully-operational solar power satellite system could end up
: needing to be enormous. Some designs suggest creating rectangular
: solar arrays that are several kilometers long on each side. If we
: assume that enough money could be found to build something like
: this and that it could be run competitively against other energy
: options, there is the very real problem of figuring out how to get
: it into orbit or how to build it in orbit from separate smaller
: pieces.

: The largest solar panels ever deployed in space are currently being
: used on the International Space Station. They cover more than
: 830 square meters and are 73 meters long and 11 meters wide. These
: large panels make the ISS one of the brightest objects in the night
: sky. Scaling up from there to something much larger would be
: challenging, but the good news is that we can take one thing at a
: time.

: For a proof of concept satellite it makes sense to use the
: station's solar panels as a baseline. By taking advantage of
: improvements in solar cell technology we could launch a
: demonstration satellite of the same size that generates up to
: 3 times as much power. The station's solar panels are
: 14% efficient, but recent advances with solar cells and solar
: concentrators could allow us to build panels that are up to
: 50% efficient.

: If this demonstration system validated the theory behind generating
: power in space and beaming it down to Earth, the next step would be
: figuring out how to put even bigger solar panels in space. It may
: be that with our current launch options it simply isn't possible to
: launch an operational solar power system into orbit.

: There are a number of reasons why we won't be seeing huge orbiting
: solar collectors beaming us lots of energy anytime soon. Starting
: the development of such a system by building small proof of concept
: satellites is completely within our reach, though. There are
: economic, political, and engineering hurdles in the way, but none
: of these should be enough to stop the idea if we choose to pursue
: it. Once a successful demonstration has been achieved, there may be
: enough interest in government or in private industry to continue
: working toward fully-operational solar power satellites.

Mark Reiff