Naked Science Forum
Non Life Sciences => Technology => Topic started by: D. Paul F. Kuhlmann on 06/12/2010 01:30:03
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D. Paul F. Kuhlmann asked the Naked Scientists:
A Californian outfit has patented the rights to produce electricity from the Sun and transport it to Earth by high energy beams. Will this technology, if put into practice, mean that areas around the beam-down sites will be deadly? (Because of misalignment and space weather and the high microwave power?)
Also, although they have already sold futures on the market, can this system actually fly?
D. Paul F. Kuhlmann
What do you think?
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It's certainly a very seductive idea that has been going around for quite a while. I suspect if you read their patent claims in detail you will find that they are only able to patent aspects of their proposed solution, and not the overall concept.
It will certainly be challenging to make a system like this safe. Regardless of the transmission method, if it's going to be commercially viable, I would think the energy densities involved have to be enormous, although perhaps they might plan to address that by distributing lower energy levels to many distributed receivers.
Let us know the patent number (or application number) if you can, and we can take a look in more detail.
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Seems impractical and unsafe to me: Aircraft and birds flying through the beam may get cooked.
If the satellite went out of alignment it could scorch a trail across the surface of the earth.
... they have already sold futures on the market
People put a shedload of money into "cold fusion" (http://en.wikipedia.org/wiki/Cold_fusion#Further_studies): investment of money doesn't mean the project is feasible or profitable.
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I heard about this back in the 80's. It is not a new idea. With that in mind, I'd be dismayed if the US Patent office gave a patent over the "concept", although perhaps particular aspects that weren't discussed 30 years ago might be patentable.
Certainly anybody that gets a satellite up in the air would be a step ahead of the crowd.
It may or may not be a viable approach. Any time you go through a multi-step conversion process. Sunlight --> electricity --> microwaves --> electricity... you loose efficiency. And there is a HUGE cost of getting the spaceships up into the air.
I assume there is enough practice with geostationary satellites that it could be kept reasonably on track. And, if they made a bidirectional signal... download to earth, and back up. Shut down 100% immediately if they loose the uplink (because of drifting), then it would be reasonably safe.
One would still need to get a prototype up into space and make sure the laser wouldn't scatter while going through the atmosphere, clouds, and etc.
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Seems impractical and unsafe to me: Aircraft and birds flying through the beam may get cooked.
If the satellite went out of alignment it could scorch a trail across the surface of the earth.
... they have already sold futures on the market
People put a shedload of money into "cold fusion" (http://en.wikipedia.org/wiki/Cold_fusion#Further_studies): investment of money doesn't mean the project is feasible or profitable.
I think that's a pretty darn good assessment there RD.
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If such an apparatus was made...
Would it be militarized?
What could be done to prevent it from being militarized?
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The Russians have successfully launched a space mirror experiment ...
http://www.nytimes.com/1993/02/05/world/russia-s-mirror-in-space-reflects-the-light-of-the-sun-into-the-dark.html
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Interesting about the Russian mirrors.
And, yes, I think I've heard that NASA is conducting similar research, in particular relation to the solar sail concepts.
However, I've read a bit about Venus... And whether it would be practical to either colonize it (as a cloud planet), or terraform it (cool it to Earth standards, modify the atmosphere), or perhaps both as varying stages of progress.
Anyway,
That brings up the idea of whether giant (or large numbers of) mirrors could be used to significantly alter the environment on Venus.
If so, the same thing could be done on earth.
One could, in theory, make the equatorial regions on earth cooler, and the polar regions on earth warmer.
Or, perhaps there would be a way to make a Mylar solar panel... or projection system so you could shade the equatorial regions of the planet, and generate usable energy at the same time.
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One could, in theory, make the equatorial regions on earth cooler, and the polar regions on earth warmer.
Or turn winter into summer. Just think of the havoc that would cause to nature's cycle.
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I remember reading about the space solar power project some time back when PG&E (Pacific Gas and Electric) entered a contract with Solaren to beam down power by 2016. I think there is another company start up who also wish to do this. What I remember is that they chose a region outside of Fresno California to set up the antenna receiver because there is a lot of uninhabited area and there is a power substation there. The area of the antenna would be large and the energy density pretty low. I am mostly skeptical that this can be done cheaply enough to be practical. I did a quick look at saved links, but I don't know what has happened since they were published:
In this site- http://www.next100.com/2009/04/space-solar-power-the-next-fro.php
PG&E describe the project briefly.
And, this one- http://cleantechnica.com/2009/04/18/space-based-solar-power-satellite-program-from-pge-and-solaren/
is another description.
In these two sites there are further links to other information including the web site of Solaren and the company they are contracting with to provide the boosters, the actual contract, and a paper explaining the the technical details regarding safety.
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We discussed this question on our show
Chris - I looked up which company that was. It’s Solaren Space who are a Californian based company. Sounds intriguing. They've got permission to develop this system. They want to have a satellite array out in space at about 22,000 miles out and this would have very big photo electric cells that would harness solar energy turn that into electricity which they then convert into a microwave beam. They then beam that microwave energy down to the Earth to a very big collecting dish. Their argument is that the collecting dish would be about a 2 square mile across array, so very, very big. So the energy density of the microwave beam coming in from space would be quite low. Actually, they say if an aeroplane were to fly into that, actually the amount of heating effect the aeroplane would feel from the microwaves would be less than the heating effect of an airplane just coming out from under a cloud, and being hit by sunlight. So they say that this is not a threat to birds, planes, cars, people, or anything. And the idea there is they then sum all of their energy collected by the dish back together and this could generate – as I say, energy at the rate of 200 megawatts which is not small, but it’s also not huge either but this is just early days. The Japanese aerospace exploration industry said they're also planning something similar.
Diana - Well it’s a shame. It could at least guarantee that your in-flight meal would be warm...
Chris - I don't think we can quite stretch to that!
Click to visit the show page for the podcast in which this question is answered. (http://www.thenakedscientists.com/HTML/podcasts/show/2010.12.05-1/) Alternatively, [chapter podcast=2922 track=10.12.05/Naked_Scientists_Show_10.12.05_7614.mp3](https://www.thenakedscientists.com/forum/proxy.php?request=http%3A%2F%2Fwww.thenakedscientists.com%2FHTML%2Ftypo3conf%2Fext%2Fnaksci_podcast%2Fgnome-settings-sound.gif&hash=f2b0d108dc173aeaa367f8db2e2171bd) listen to the answer now[/chapter] or [download as MP3] (http://nakeddiscovery.com/downloads/split_individual/10.12.05/Naked_Scientists_Show_10.12.05_7614.mp3)
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The Patent file is US7612284.pdf
Patent #: US 7,612,284 B2
Date of Patent: Nov. 3, 2009
What worries me about all this is, that to be really useful, the energy density will have to increase. Even if it works perfectly, anything passing through the beam would be microwaved (and not just by the same amount as background radiation but in addition to it, and directed).
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http://www.freepatentsonline.com/7612284.html
(PDF link is on the page).
Whew..
That is just a load of crap!!! [xx(]
That is one of the problems with our patent system is that people wish to patent theory, without any practical means of implementing it, or even any practical means of verifying the validity of that theory.
So, they are wanting to patent the space deployment of parabolic mirrors for the capture of stellar light? I thought that was what the Hubble was about.
There are some good ideas such as inflatable supports, but nothing that a competent engineer couldn't come up with a single brainstorming session. And... they still would have to deal with the inevitable gas leakage if using an inflatable structure. What is the risk to an inflatable vs rigid system from micrometeorites?
The patent, of course, was a 2005 application, but I can't see that they could be close to making more than a tiny research device in the next decade... and are likely a couple of decades away from the implementation of any kind of full scale spaced based solar collector... if ever. The cost of development and implementation of such a system will be HUGE.
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So, they are wanting to patent the space deployment of parabolic mirrors for the capture of stellar light? I thought that was what the Hubble was about.
Actually, they are not. You have to look at what they claim in the patent. There are only three unique claims - 1, 14 and 25.
Without tearing it apart word by word, it seems to me that they are only able to claim an arrangement of multiple "free floating" collectors that direct light to central collector, and the associated control system.
Personally, I think they are up a gum tree. The idea of using multiple dispersed mirrors to collect light and focus it onto a single collector has been around for a very long time. The claims hinge on the term "free floating", which, of course, is baloney. They can't be free floating. Their positions have to be periodically adjusted to prevent them from drifting too far apart.
If it ever gets into a legal wrangle over the patent rights, they could easily lose.
It's not that hard to get a patent, but do the claims really protect some intellectual property, or is the patent really just a piece of marketing collateral? In this case, I think it's the latter.
(Big Honking Disclaimer: My views should not be construed as any sort of legal opinion.)
Also available here BTW.
http://www.google.com/patents/about?id=c6bJAAAAEBAJ&dq=7612284
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OK. If you understand the energies involved and the patent, can you tell the effects this would have on the atmosphere, wildlife or any safety risks (including military) this operation would have for the planet?
The podcast mentioned the heating from the test plant would be about the same as coming out from behind a cloud. If a test produces that much heat, how cooked would you get in the full scale thing? Would it heat the air? Or ionise it?
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I don't think they discussed safety protocols in the text.
As I mentioned earlier, I'd design it with a 2-way communication stream. If it drifts, send a kill command immediately.
A geosynchronous orbit is about 35,000 km.
The speed of light is about 300,000 km/s.
So, 1-way communication would be just over 1/10 seconds, and 2-way communication would require about 2/10 seconds. So, there would always be a lag of 2/10 to 3/10 of a second for a command to be followed by an action.
You could likely restrict most animals from entry into the compound, and warn aircraft. The big risk would be insects and birds... think of a mega-bug-zapper [;D]
One could deal with birds like one does for airports. Try to discourage them, and also send beam kill signals if they appear to be flying towards it.
I'm not sure of the power of a full-scale system, but I'd guess that you wouldn't want to be under it. Perhaps the power of a million microwave ovens (or more).
The actual energy density used would depend on the peak efficiency and durability of their energy transduction system.
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As I mentioned earlier, I'd design it with a 2-way communication stream. If it drifts, send a kill command immediately.
Probably don't so much need a "kill command" as a "keep alive" command, so that if there's an interuption in the 2-way communication the beam's stopped immediately even if the 2-way is down.
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I am not going to go back and read the safety protocol, but what my very rusty steel trap memory tells me is that the energy density was only a few percent of that in a standard microwave. This suggests that safety backups could run on a timetable of minutes without any real concern. There is also my tinfoil hat that I try not to wear in public.
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If a bird flies at about 20 miles per hour, then it would cross the centre of the beam in about 6 minutes. If the standard microwave is 1000W, then it would get a few percent of that - say 30W, divided by 10 as it's only 6 minutes. 3 Watts.
Can I cook an eye?
If the big brother of the test plant was intentionally used as a weapon against people. How long could you stay in it?
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I'm lost on your calculations. How big is the beam? Is that something i skipped when looking at the patent calculations?
If a bird is flying 20 MPH... that is a mile every 3 minutes... 6 minutes would be 2 miles. That only gets you to the center of the beam??
Ahh.. I see some details on Wikipedia.
http://en.wikipedia.org/wiki/Solar_power_satellite
It has been suggested that, for best efficiency, the satellite antenna should be circular and about 1 kilometer in diameter or larger; the ground antenna (rectenna) should be elliptical, 10 km wide, and a length that makes the rectenna appear circular from GEO (Geostationary Orbit). (Typically, 14 km at some North American latitudes.) Smaller antennas would result in increased losses to diffraction/sidelobes. For the desired (23 mW/cm²) microwave intensity [55] these antennas could transfer between 5 and 10 gigawatts of power.
According to some research, to collect and convert the target volume of power, the satellite would require between 50 and 100 square kilometers of collector area (if readily available ~14% efficient monocrystalline silicon solar cells were deployed). State of the art multi-junction solar cells with a maximum efficiency of 43% [56] could reduce the necessary collector area by two thirds. In any case, an SPS's structure will necessarily be large (perhaps kilometers across), making it larger than most man-made structures on Earth, and building structures of such size in orbit has never been attempted.
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Safety
The use of microwave transmission of power has been the most controversial issue in considering any SPS design.
At the Earth's surface, a suggested microwave beam would have a maximum intensity at its center, of 23 mW/cm2 (less than 1/4 the solar irradiation constant), and an intensity of less than 1 mW/cm2 outside of the rectenna fenceline (the receiver's perimeter).[55] These compare with current United States Occupational Safety and Health Act (OSHA) workplace exposure limits for microwaves, which are 10 mW/cm2,[69] - the limit itself being expressed in voluntary terms and ruled unenforceable for Federal OSHA enforcement purposes.[citation needed] A beam of this intensity is therefore at its center, of a similar magnitude to current safe workplace levels, even for long term or indefinite exposure. Outside the receiver, it is far less than the OSHA long-term levels[70] Over 95% of the beam energy will fall on the rectenna. The remaining microwave energy will be absorbed and dispersed well within standards currently imposed upon microwave emissions around the world.[71] It is important for system efficiency that as much of the microwave radiation as possible be focused on the rectenna. Outside of the rectenna, microwave intensities rapidly decrease, so nearby towns or other human activity should be completely unaffected.[72]
So this plan would be a HUGE receiver, but at relatively low power. They even talk about allowing airplanes to fly through it (why not go around?) But, not allowing balloons to fly through it (which have less directional control than the airplanes that are permitted to fly through it).
If your microwave is about 2000 cm2 at the base, and 1000 W, that is 500mw/cm2, or about 20x as powerful... very rough estimate....
I guess I was envisioning a small, high power beam.
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It is interesting to note that the patent did not state the ground area of the beam or the potential energy projected. The old Geezer is probably right - a patent suit could fail. The information we put together came from reports of best engineering scenario physics. The reality may be a beam a few sqaure miles across or a single bright spot. The potential risks of flying this program, in my mind, still outweigh the benefits of collecting the solar radiation on the ground.
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The old Geezer is probably right -
That's Mr Old Geezer to you, sonny! [:D]
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I was just listening to the related podcast at the top of this page.
The total energy from the sun, across the spectrum, that lands on one square metre of the ground is about 1000W.
This proposed enregy beam would be equal to the suns intensity but tuned to the receiver in a narrow band of the spectrum.
An area of 2 sq. miles is 5179976 sq metres. Or 5.18 billion Watts!
Imagine what could be done with that.
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D. Paul F. Kuhlmann:
You have identified the silliness of the whole satellite power idea. There is more than enough energy right here on the surface of the earth and it is much less expensive to set up. I think that ground based photovoltaic systems are much more economical than satellite, even given the fact that stationary earth based panels get only six hours of charging/day when looking at a clear sky. Moving power from arid regions where the sky is always clear to other time zones should be much more efficient than moving power the much larger distance, from synchronous earth orbit, of 24K miles. Solar thermal is quite a bet more efficient, but the photovoltaic story seems to be a big secret from the general public.
Steve