Out-of-this-world proposal for solar wind power - tech - 24 September 2010 - New Scientist
Forget wind power or conventional solar power, the world's energy needs could be met 100 billion times over using a satellite to harness the solar wind and beam the energy to Earth – though focussing the beam could be tricky.
The concept for the so-called Dyson-Harrop satellite begins with a long metal wire loop pointed at the sun. This wire is charged to generate a cylindrical magnetic field that snags the electrons that make up half the solar wind. These electrons get funnelled into a metal spherical receiver to produce a current, which generates the wire's magnetic field – making the system self-sustaining.
Any current not needed for the magnetic field powers an infrared laser trained on satellite dishes back on Earth, designed to collect the energy. Air is transparent to infrared so Earth's atmosphere won't suck up energy from the beam before it reaches the ground.
Back on the satellite, the current has been drained of its electrical energy by the laser – the electrons fall onto a ring-shaped sail, where incoming sunlight can re-energise them enough to keep the satellite in orbit around the sun.
A relatively small Dyson-Harrop satellite using a 1-centimetre-wide copper wire 300 metres long, a receiver 2 metres wide and a sail 10 metres in diameter, sitting at roughly the same distance from the sun as the Earth, could generate 1.7 megawatts of power – enough for about 1000 family homes in the US.
A satellite with the same-sized receiver at the same distance from the sun but with a 1-kilometre-long wire and a sail 8400 kilometres wide could generate roughly 1 billion billion gigawatts (1027 watts) of power, "which is actually 100 billion times the power humanity currently requires", says researcher Brooks Harrop, a physicist at Washington State University in Pullman who designed the satellite.
Since the satellites are made up mostly of copper, they would be relatively easy to construct. "This satellite is actually something that we can build, using modern technology and delivery methods," Harrop says.
Satellites laden with solar panels that can beam their energy down 24 hours a day have been discussed for decades. California agreed last December to a deal involving the sale of space-based solar power. Solar panels cost more per pound than the copper making up the Dyson-Harrop satellites, so according to Harrop, "the cost of a solar wind power satellite project should be lower than a comparative solar panel project".
So far so good, but there is one major drawback. To draw significant amounts of power Dyson-Harrop satellites rely on the constant solar wind found high above the ecliptic – the plane defined by the Earth's orbit around the sun. Consequently, the satellite would lie tens of millions of kilometres from the Earth. Over those distances, even a sharp laser beam would spread to thousands of kilometres wide by the time it reached Earth.
"Two megawatts spread across areas that large are meaningless, less than moonlight," says John Mankins, president of consultancy firm Artemis Innovation which specialises in space solar power. To beam power from a Dyson-Harrop satellite to Earth, one "would require stupendously huge optics, such as a virtually perfect lens between maybe 10 to 100 kilometres across," he says.
He also points out that the wire could burn out due to the huge current coursing through it, although he has not performed the calculations to gauge the probability of that occurring. But he does say that a smaller version of this "clever and interesting" satellite could help power some space missions. "I could imagine uses for this idea outside of the plane of the ecliptic, such as helping generate power for something like the Ulysses spacecraft, which went around the poles of the sun."
Journal reference: International Journal of Astrobiology, DOI: 10.1017/S1473550410000066
Simple Fix.Fri Sep 24 14:41:57 BST 2010 by Dave
So the beam spread out too much over the vast distances.
Easy fix.
Set up a satellite relay. Each satelite has a lens to re-focus the beam to the next satellite. The satellites can even be equiped with reflectors so you can bend the beam
Simple Fix.
Fri Sep 24 15:55:51 BST 2010 by Matt
http://rockbotics.comwell, easy to conceptualize, not easy to pull off. Remember all of those satelites have to be in a sustainable synchronis orbit, there's NO room for error when focusing beams back to an array on earth over these kinds of distances.
We would be allowing any tiny meteorite to deflect our entire power supply with a minor bump. We need to have the ability to perform microadjustments across the entire array in real time. Not what I'd call easy.
Thermal Equilibrium?
Fri Sep 24 19:46:06 BST 2010 by Rob
Lets assume for a moment we got a large chunk of energy this way. When when its done its useful work it ends up as heat.
In effect more solar energy is being received by Earth.
Does this have any appreciable effect on our thermal equilibrium?
Conversely could a large scale implementation head off some future ice age in a geo-engineering application? In this case the lack of focus wouldn't seem to be a problem.
10^27 Watts
Fri Sep 24 20:15:44 BST 2010 by Darth
Yes, if I wanted to obliterate a planet, I would aim billions of billions of gigawatts of power in a narrow beam... where is all that heat going to go? When we use energy, it doesn't go away - we just change it into another form (didn't we learn that as far back as elementary school?). More energy isn't a logical answer - more efficiency and less consumption. I'm not advocating radical-left conservation, but we need, desperately, to get rid of our addiction (requiring more and more of something to achieve the same results).
10^27 Watts
Fri Sep 24 22:30:54 BST 2010 by Mal
I doesn't matter about adding energy/heat, we are stuck with the fact that we are already converting locked up energy that is already here, coal, wind, solar, nuclear etc.. It doesn't add heat until we use it. If we need a million, or what ever the figure is, Gigawatts of energy to run the world per year, then that will be converted into the same amount of heat if it were to come from coal or beamed solar energy!
10^27 Watts
Sun Sep 26 09:47:13 BST 2010 by John Rumsey
We should be trying to avoid any energy sources that add to the total amount of heat in our atmosphere and oceans. These include: fossil fuels, nuclear (both fission and fusion), and energy beamed in from space.
We should be encouraging renewable energy sources (biofuels, solar, wind, wave, tidal, hydroelectric) that use energy that is already in the system.
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