NASA Abandons SimCIty Microwave Power Concept

TexasDex writes "Wired reports: The NASA Space Solar Power project--a method of collecting solar energy efficiently from space and beaming it down to earth--was canceled in early 2001 after enjoying intermittent attention from scientists. NASA officials cited a policy shift toward the International Space Station and the space shuttle program. But there is still hope for it yet. A conference this month in spain hopes to advance the cause, dispite the fact that there is no public funding available in the US for this project. Some even claim that microwave power is essential for farther explanation. Accordong to the folks at Maxis, Microwave power should be available around 2020, depending on which version of SimCity you play."

Comments

Re:Microwave beam misalignment

[wowbagger]

Most designs for such a system use a phased-array antenna for transmit - the beam angle can be switched in milliseconds.

They also use a very large beam with a very low power density, so that even if you were to stand in the middle of the beam you would not be cooked - you'd just feel warmth like standing in the sun.

Lastly, most designs use a retroreflector on the ground to send a small reference signal back to the bird, which uses the reference signal to steer the beam. If the beam drifts, the reference signal is lost and the system shuts down automatically.

Re:Excellent...

[orthogonal]

Now maybe a private company can develop it for 2% of the cost and we'll have cheap, environmentally benign power.

Or, now maybe we can continue to be dependent on (mostly foreign) oil, established oil companies with little incentive to develop newer and ultimately cheaper energy sources, and politicians who make sure NASA doesn't undermine those vested interests.

"NASA officials cited a policy shift toward the International Space Station and the space shuttle program."

Now, I know the Shuttle has been so tremendously successful, and the International Space Station isn't just the leftovers of the lasts gasps of the old Soviet Manned Space Flight Program, both have been so well funded since the "policy shift" three years ago in 2001 -- so, if you're going to be intellectually honest, you have to ask yourself, "what occasioned this policy shift?"

I'm not just trying to be annoyingly partisan here; I'm trying to make the point that even when it comes to science, politics takes over, and when politics takes over, you have to follow the money.

Older Idea, Asimov used it in 1950

[Anonymous Coward]

Hi there,

So many geeks and nobody read "Reason" (Supossedly 2015 AD. I, Robot; The Complete Robot; Robot Visions) ??? In that story eveything happens in a satellite around the sun that collects the energy to beam it down to Earth.

Shame on you guys... but the point is that its an OLD idea.

Read Asimov, its great!

Capital cost is a good proxy

[apsmith]

Economic energy intensity numbers mean you're using about 10 MJ for every dollar. Typical ground-side power plants cost on the order of $1000 - $3000/kW (nuclear on the high end of that, coal on the low end) which translates to 10-30 GJ/kW, or 10 - 30 million seconds - i.e. the energy payback is a few months to a year.

For a space power plant to be economically competitive, it's numbers had better be pretty close. Unfortunately right now space launch is about a factor of 10 too expensive, which puts the energy payback into the few to 10-year timeframe.

By the way, I'm the one quoted in the Wired article as saying $10 billion RD&D over 10 years would do the trick - but I don't remember saying it had to go through NASA! And yes, I will be in Spain at the meeting next week.

Asimov

[BumpyCarrot]

The earliest I've seen this power source suggested was in Asimov's I, Robot. Unfortunately, I don't have a copy on me to check the dates ;)

Re:Outstanding idea. . . and will never happen. .

[DudeG]

Well, here's a critique of the idea from someone who can't in any way be fitted into those categories: USS Clueless

[...] When it comes to power generation, the job's not done until the energy reaches the end user. The challenge of energy delivery is particularly severe for solar satellite technology.

Generally speaking, every time energy is converted from one form to another a lot of it will be lost (because of the Second Law of Thermodynamics). All technologies which generate power and deliver it to end users involve such conversions. A coal-fired electrical generation plant burns coal to produce heat, converts heat to pressure by applying a lot of that heat to a boiler to produce steam, converts pressure into mechanical motion (with a turbine), converts mechanical motion into electricity (with a dynamo), and then delivers the electricity with long distance power lines, which usually requires multiple voltage/current conversions using transformers or motor-generators. Many of those conversions are very efficient but some of them involve pretty significant losses.

The efficiencies of every step have to be multiplied together to calculate the overall system efficiency. If you have five steps and each one wastes 20%, then each step has an efficiency of 0.8, and the overall system efficiency will be 0.8*0.8*0.8*0.8*0.8 == 0.328, meaning about 33% of the original energy would be delivered to end users, with the remaining 67% being lost. But if each of those five steps wasted 30% instead of 20%, the overall system would only deliver 17% of the original energy. The more conversions required, and the worse the efficiency on those conversions, then the lower the efficiency of the overall system.

Solar satellite power generation is particularly poor in this regard. Sunlight is concentrated using mirrors (with some losses) onto a boiler (with some of the light reflecting instead of being converted to heat, and some of the heat radiating away via black-box radiation). The next few steps are the same as for a coal plant: steam drives a turbine, which drives a dynamo, which generates electricity. At that point, all you have to do is to deliver it, but that is not easy with solar satellites.

The electric power would have to be converted to microwaves (with a lot of losses). That would be beamed down to earth (with losses from atmospheric reflection, scattering and absorption). Most of the beam would strike the receiver but some would not because of beam spreading. (Also, there beam would tend to wander a bit because of atmospheric refraction, which also makes stars "twinkle".) The receiver would have to capture the microwaves that struck it and somehow convert back into electricity, and every way I know to do this has dreadfully poor yields.

Microwaves are not the only approach to the downlink, but every approach I know of for the downlink either cannot handle the power levels involved, or is terribly inefficient. Compared to terrestrial electrical power generation technologies, solar satellites inherently require more conversions, many of which have poor efficiency, and the overall system efficiency will necessarily be far worse. I would be surprised if the system had a yield as high as 5%. I would tend to think it would be even lower.

On the other hand, the energy which would have to be expended to create a solar power satellite would be huge compared to the energy needed to build a terrestrial power generation facility. Would it break even before it reached the end of its operating life? Would it actually produce more energy than it cost? I'm not so sure it would.

The capital cost to create a solar satellite would also dwarf the cost of terrestrial power plants which delivered comparable amounts of power, but the satellites and terrestrial power generators would sell their power on the same market at the same price. Could a solar satellite produce enough revenue during its o