View Full Version : Solar Satellites


Godwynn
Jul 23, 2008, 05:29 PM
New York Times (http://www.nytimes.com/2008/07/23/opinion/23smith.html?_r=1&ref=opinion&oref=slogin)

AS we face $4.50 a gallon gas, we also know that alternative energy sources — coal, oil shale, ethanol, wind and ground-based solar — are either of limited potential, very expensive, require huge energy storage systems or harm the environment. There is, however, one potential future energy source that is environmentally friendly, has essentially unlimited potential and can be cost competitive with any renewable source: space solar power.

Science fiction? Actually, no — the technology already exists. A space solar power system would involve building large solar energy collectors in orbit around the Earth. These panels would collect far more energy than land-based units, which are hampered by weather, low angles of the sun in northern climes and, of course, the darkness of night.

Once collected, the solar energy would be safely beamed to Earth via wireless radio transmission, where it would be received by antennas near cities and other places where large amounts of power are used. The received energy would then be converted to electric power for distribution over the existing grid. Government scientists have projected that the cost of electric power generation from such a system could be as low as 8 to 10 cents per kilowatt-hour, which is within the range of what consumers pay now.

In terms of cost effectiveness, the two stumbling blocks for space solar power have been the expense of launching the collectors and the efficiency of their solar cells. Fortunately, the recent development of thinner, lighter and much higher efficiency solar cells promises to make sending them into space less expensive and return of energy much greater.

Much of the progress has come in the private sector. Companies like Space Exploration Technologies and Orbital Sciences, working in conjunction with NASA’s public-private Commercial Orbital Transportation Services initiative, have been developing the capacity for very low cost launchings to the International Space Station. This same technology could be adapted to sending up a solar power satellite system.

Still, because building the first operational space solar power system will be very costly, a practical first step would be to conduct a test using the International Space Station as a “construction shack” to house the astronauts and equipment. The station’s existing solar panels could be used for the demonstration project, and its robotic manipulator arms could assemble the large transmitting antenna. While the station’s location in orbit would permit only intermittent transmission of power back to Earth, a successful test would serve as what scientists call “proof of concept.”

Over the past 15 years, Americans have invested more than $100 billion, directly and indirectly, on the space station and supporting shuttle flights. With an energy crisis deepening, it’s time to begin to develop a huge return on that investment. (And for those who worry that science would lose out to economics, there’s no reason that work on space solar power couldn’t go hand in hand with work toward a manned mission to Mars, advanced propulsion systems and other priorities of the space station.)

In fact, in a time of some skepticism about the utility of our space program, NASA should realize that the American public would be inspired by our astronauts working in space to meet critical energy needs here on Earth.

O. Glenn Smith is a former manager of science and applications experiments for the International Space Station at NASA’s Johnson Space Center.

I don't understand the science of moving energy over radio transmission. Can someone smarter than me explain it, preferably not through wikipedia?

civ_king
Jul 23, 2008, 05:31 PM
what about a laser? that could work

Cutlass
Jul 23, 2008, 06:41 PM
It works like a microwave. The radio waves will probably actually be microwaves. The receiver is the part that requires more of a scientific explanation.

History_Buff
Jul 23, 2008, 07:28 PM
I don't understand the science of moving energy over radio transmission. Can someone smarter than me explain it, preferably not through wikipedia?

From a basic point of view, it's not hard. You use the power generated to create radio waves of some sort, then direct the beam at Earth. A station below will have a tailor-made antenna, and the radio waves will induce a current in the antenna, allowing you to generate power.

Microwaves would be the most likely medium, as they can be non-ionising, and therefore quite safe. Microwaves are also the most efficient at the back and forth conversion. The actual frequency you can use is limited by a number of things though. Due to physical laws, the bigger an antenna is (recieving a longer wavelength) the more efficient it tends to be. So long wavelength is good, but not to long, or the power would be absorbed by atmospheric water and CO2. This type of power transmission has been proven both safe and usable. A model helicopter was once flown using this method of power transmission on whatever news show Walter Cronkite was on.


Lasers are another alternative, but the photovoltaic cells used on the ground to collect the power are considerably less efficient than the microwave antennae.

El_Machinae
Jul 24, 2008, 11:23 AM
Most of what I know about solar satellites I gained from this website
http://www.permanent.com/p-sps.htm

§ 5.12: Energy from Space for Earth Economies -- Solar Power Satellites

§ 5.12.1 The Solar PowerSat (SPS) Concept
§ 5.12.2 PowerSats Compared to Other Energy Sources
§ 5.12.3 Environmental Effects on Biota - Non-Beam
§ 5.12.4 Environmental Effects on Biota - Beam
§ 5.12.5 Beam Effects on Communications
§ 5.12.6 Technical Issues
§ 5.12.7 Political History of the PowerSat
§ 5.12.8 The Electric Economy on Earth Concepts
§ 5.12.9 Bootstrapping to PowerSats
§ 5.12.10 Links to other Solar PowerSat (SPS) websites

The entire website is awesome.

Fugitive Sisyphus
Jul 24, 2008, 01:50 PM
Planet's Primary, Alpha Centauri A, blasts unimaginable quantities of energy into space each instant, and virtually every joule of it is wasted entirely. Incomprehensible riches can be ours if we can but stretch our arms wide enough to dip from this eternal river of wealth.

CEO Nwabudike Morgan
"The Centauri Monopoly"

uppi
Jul 24, 2008, 02:23 PM
what about a laser? that could work

A laser is a bad idea for power transmission:

The typical efficiency of a laser is very low. The power that is converted into light is usually small compared to the power that is converted into heat. And heat is very bad for a satellite, because there is no way to cool it.

And then the energy density for a decent amount of power transmitted via a beam of laser light would be way to big. This would lead to blooming and only a small amount of energy could arrive at the ground. And a high energy density would be bad for anything that crosses its path.

civ_king
Jul 24, 2008, 03:46 PM
forget i said that

History_Buff
Jul 24, 2008, 04:47 PM
Planet's Primary, Alpha Centauri A, blasts unimaginable quantities of energy into space each instant, and virtually every joule of it is wasted entirely. Incomprehensible riches can be ours if we can but stretch our arms wide enough to dip from this eternal river of wealth.

CEO Nwabudike Morgan
"The Centauri Monopoly"

Who do you think you are, Perfection?

El_Machinae
Jul 24, 2008, 07:17 PM
There's currently an entire galaxy available for each man, woman, child, and planned child on the planet.

It's not a wealth issue that we suffer from, it's a grasp issue. 'Tis why I like that Permanent site so much.

Perfection
Jul 24, 2008, 08:10 PM
Who do you think you are, Perfection?Indeed, the failure to right justify the attributation totally ruins it.

Leave the SMAC quoting to professionals. If you think one needs to be said, please contact me so I may do it properly.