Space-Based Solar Cells Could Power Entire Earth

Gigantic satellites orbiting the Earth, equipped with solar cells, could collect enough energy from the sun every year to power the world seven times over. Beaming the energy down to Earth in the form of microwaves or a laser, the satellites would provide energy which would be gathered in antennas on the ground and then converted to electricity.


It may sound like a far-fetched idea, but researchers from the National Security Space Office (NSSO) say that the plan is technologically feasible, and could provide more energy than could fossil fuels, wind and nuclear power combined. They have recently presented their findings to the US government, recommending that the government spend $10 billion over the next 10 years to build a test satellite capable of electromagnetically beaming 10 megawatts of electric energy down to Earth.

"A single kilometer-wide band of geosynchronous earth orbit experiences enough solar flux in one year (approximately 212 terawatt-years) to nearly equal the amount of energy contained within all known recoverable conventional oil reserves on Earth today (approximately 250 TW-yrs)," according the report. "This far exceeds the projected 30TW of annual demand in mid-century."

The "space-based space power" (SBSP) construction would consist of kilometer-sized solar panel arrays, which could operate at night and during cloudy conditions.

The report explains that there are a couple ways the apparatus could work. The solar collectors could be places in one of three Earth orbits (geostationary, medium-Earth, or low-Earth) or could even be placed on the moon. These collectors could capture solar energy either by photovoltaic or solar dynamic methods. Finally, the collected energy could be beamed down to Earth by either coherent visible or infrared light.

"In the vicinity of Earth, every square meter of space receives 1.366 kilowatts of solar radiation, but by the time it reaches the ground, it has been reduced by atmospheric absorption and scattering; weather; and summer, winter and day-night cycles to less than an average of 250 watts per square meter. Space-Based Solar Power offers a way to break the tyranny of these day-night, summer-winter and weather cycles, and provide continuous and predictable power to any location on Earth."

The report explains that an area in space receives 8-10 times the energy flux for the annual average compared with an equivalent area on the surface of the Earth, and as much as 30-40 times the energy flux in a given week than the same area located in a favorable place on the ground after considering day/night, summer/winter, and dust/weather cycles.

Even after losses in wireless power transmission, the reduced need for overcapacity and storage to make up for periods of low illumination translates into a much lower land usage vs. terrestrial solar for an equivalent amount of delivered energy.

One of the biggest technical challenges of the plan is in launching the satellite, which would have a mass of about 3,000 tons-more than 10 times that of the International Space Station. Such a feat would require the development of lower-cost space launches. Today the United States initiates less than 15 launches per year. Construction of a single SBSP satellite alone would require in excess of 120 such launches.

"SBSP cannot be constructed without safe, frequent (daily/weekly), cheap, and reliable access to space and ubiquitous in-space operations," the report states. "By lowering the cost to orbit so substantially, and by providing safe and routine access, entirely new industries and possibilities open up." These possibilities may include space tourism, manufacturing, lunar or asteroid resource utilization, and eventually settlement to extend the human race, the report suggests.

The concept of SBSP was actually suggested as early as 1968 by Peter Glaser of a company called Arthur D. Little. However, his design was estimated to cost about $1 trillion to build, and required hundreds of astronauts to construct the solar panels while in space. With advances in photovoltaics, electronics and robotics, which would reduce the cost and eliminate the need for humans to assemble the equipment in space, the idea emerged again about a decade ago.

In 1995, NASA researchers found that, though feasible, SBSP was still not competitive when measured against the $0.05/kWh price of electricity and $15/barrel price of oil prevalent at that time. But in the past few years, especially since 9/11, much as changed, from increased oil costs to wide concern over oil resources and politics, to rising demand and competition from Chinese and Japanese economies.

Illustration of NASA's Suntower in late '90sIllustration of NASA's Suntower in late '90s

Over the past three decades, the report details, NASA and the DOE have collectively spent $80 million in sporadic efforts studying this concept (by comparison, they note that the U.S. government has spent approximately $21 billion over the last 50 years continuously pursuing nuclear fusion). In this latest analysis, which took place over the past six months, more than 170 academic, scientific, technical, legal, and business experts around the world contributed, largely through e-mail and online communication.

The NSSO report emphasizes that the scheme would be economically viable, with paybacks as early as one year after implementation (not considering preliminary R&D).

"SBSP could be utilized to split hydrogen from water and the carbon monoxide (syngas) from carbon dioxide which can then be combined to manufacture any desired hydrocarbon fuel, including gasoline, diesel, kerosene and jet fuel," the report said.

"When all indirect and support costs are included, it is estimated that the DoD [Department of Defense] currently spends over $1 per kilowatt hour for electrical power delivered to troops in forward military bases in war regions. The fully burdened average price of fuel for the Army exceeds $5 a gallon. For Operation Iraqi Freedom, the estimated delivered price of fuel in certain areas may approach $20 a gallon."

The report also addresses the impact on Earth of beaming all that energy down. The researchers explain that microwave-receiving rectennas allow more than 90% of ambient light to pass through, but absorb almost all of the beamed energy. This means that the method generates less waste heat than terrestrial solar systems because of greater coupling efficiency, and also that the area underneath the rectenna can continue to be used for agricultural or pastoral purposes. In some cases, if desired, land in colder regions could even use some of the extra energy to maintain crops year-round.

Rectenna on EarthRectenna on Earth

And if you remember that just a year ago, a scientist named Roger Angel had a multi-billion-dollar idea to launch a "solar shade" to protect the Earth from additional sunlight, the NSSO report assures that its design won't have negative effects on global warming.

"While it may seem intuitively obvious that SBSP introduces heat into the biosphere by beaming more energy in, the net effect is quite the opposite," the report says. "Fossil fuel burning emits large amounts of waste heat and greenhouse gases, while terrestrial solar and wind power also emit significant amounts of waste heat via inefficient conversion. Likewise, SBSP also has solar conversion inefficiencies that produce waste heat, but the key difference is that the most of this waste heat creation occurs outside the biosphere to be radiated into space.

"The losses in the atmosphere are very small, on the order of a couple percent for the wavelengths considered. Because SBSP is not a greenhouse gas emitter (with the exception of initial manufacturing and launch fuel emissions), it does not contribute to trapping action and retention of heat in the biosphere."

For now, it seems the two biggest players in the alt-energy "race" would be--as the NSSO report puts it--Manhattan and Apollo.

More info:

Space-Based Solar Power As an Opportunity for Strategic Security
New Scientist

Lisa Zyga
Science Blogger

Oct 14, 2007
by Phantasmagoria (not verified)

Right, I recommended this

Right, I recommended this idea to people I knew right after I heard about it in class.  Then someone intelligently quipped to me, "What happens if the source beam misses?  That laser would be catastrophic."

It would be imperative to have complete control over the energy beam, whatever form it is, lest it should slightly miss.  Such a thin beam, at such a long distance, needs an unimaginably stable source position.  If the collecting stations, and the projecting source, move just a centimeter, this translates into a huge movement of the endpoint of the beam on the Earth.

Oct 14, 2007
by Anonymous (not verified)


The power density of the beam is very low. If it missed, it wouldn't be a major danger to anyone. If it were dangerous, it would never get past environmental impact statements, since you can't keep birds from flying into the beam. This is not some Michael Crichton novel where the birds might burst into flame. This technology has been discussed and researched for decades. Go back to the 70s when the country was going through an energy crunch and you'll find tons of articles about SPSS (solar power satellite systems, as they were called then). And the problems were the same even back then. Too damned expensive to put tens of thousands of tons of satellites into orbit.

Oct 15, 2007
by Anonymous (not verified)

additional reason for moon base?

The moon is loaded with the raw material to make solar arrays.  USA could lead a colaborated effort with other contries and manufacture these arrays using a moon base.  The arrays could either be on the surface or in orbit  of the moon. 

Oct 15, 2007
by Anonymous (not verified)

what did you mean by : "For

what did you mean by : "For now, it seems the two biggest players in the alt-energy "race" would be--as the NSSO report puts it--Manhattan and Apollo."

 can you detail a bit more what apollo and manhatan projects are ?

Oct 15, 2007
by Lisa Zyga

Manhattan and Apollo

Manhattan=Nuclear Power

Apollo=Sun-Based Solar Panels

(Nicknames based on historical uses of similar technology) 

Oct 16, 2007
by Jim (not verified)

SBSP construction

An idea that has been bandied about for some time may finally come to fruition! This may be an oppportune time to question, again, the possibility of space based construction.

Moon based facilities could cut costs dramatically. After initial setup - which would benefit many areas of research/science - this could become our biggest step in the exploration of space. With space based power generation available to beam power wherever we choose, a large obstacle is overcome.

Dreams can come true when the sky's the universe is the limit.

Oct 16, 2007
by tinfoil (not verified)


I find it quite interesting that "SBSP" also happens to stand for "Spongebob Squarepants." Just a coincidence? Perhaps; but perhaps NOT...

Oct 16, 2007
by Anonymous (not verified)

A Moon base would not be a

A Moon base would not be a feasible way to build these.

1-Ship all materials there (or mine them from the moon if you like, you still need the equipment and machinery to mine and refine ore).

2-Oxygen and various ways of keeping humans alive on the moon where there is little gravity, no oxygen, etc...

 Or we can build various pieces and parts here and assemble them in space where we just need some nuts and bolts and a fancy ratchet gun to tighten the nuts/bolts.

Oct 16, 2007
by Anonymous (not verified)

Regarding assumed dangers

Read the .... article!

Oct 16, 2007
by Darnell Clayton (not verified)

This will not happen unless...

This is a great idea, but I have serious doubts about this happening without a space elevator.

 Even if rocket launches dropped down to reasonable prices, by the time you launch all of those rockets you would have already added a significant amount of pollution to our world, defeating the whole purpose, at least environmentally.

 To my knowledge, only a space elevator has the ability to meet the frequent (and safe) requirements to get something like this built.

Yeah, its the "hole in the bucket" scenario, but unless we can develop an alternative to rockets, I don't see this idea going anywhere fast.

Oct 19, 2007
by Orion (not verified)

This is old "High Frontier"

This is old "High Frontier" stuff.  Gerard O'Neill's L5 Society mapped it all out 20 years ago.  You mine the regolith on the Moon, process it into useful metals, then shoot it into orbit where you assemble it into solar power satellites and beam the power down to Earth.

 We had all the technology we needed back then except the cheap heavy-lift launch rocket.  NASA had alected to go with the Space Shuttle instead and that turkey could never have provided the reliable lift for all the parts that had to go into space from Earth first.  It actually doesn't cost all that much to launch 1-way supply rockets into space; the real cost is in building and maintaining the launch facility.  The more rockets you launch, the lower the cost per launch. 

Nov 15, 2007
by Roger Plafkin (not verified)

Beaming Down Energy From Sattelites

Is it too much to hope for that energy, whether it be solar or any other type of energy created by motion, such as a generator on a bicycle, which produces a light beam, could be produced just by the shuttle orbiting the earth. If you peddle a bicycle at a higher rate of speed, and you have a generator on the wheel, the light beam becomes more intense. In other words, whatever we place in space will create energy because of the speed which the object is going. Solar panels are fine, and certainly could produce all of the energy that the earth would need, but an immediate help would be to be able to bring down to earth all of the energy that is being created by moving objects.

Roger Plafkin
Plafkin Farms(View on and

Apr 28, 2008
by Anonymous


thata amazzzinng

Jul 18, 2008
by Anonymous

Robotic construction of

Robotic construction of solar collectors out of the regolith on the moon at the south pole

There are already conceptual NASA plans for this. There is the trouble of waiting for the next rocket system to come online. If we could use liquid hydrogen alone as rocket propellant, rocket pollution would go away as a problem. Another option that should be revisited is nuclear powered rockets.
Everyone is afraid of nuclear, but space is a big place and the radiation from a
small nuclear power plant is insignificant compared to the radiation in outer space.