Space-based solar power... again

[radarredux]

Who has substantial electrical needs at a moments notice in remote and potentially non-friendly locations? The military.<br /><br />One potential solution to addressing this problem is space-based solar power. MSNBC has an article on this topic, including links to additional information. The gist is that while the economics of the equation is improving (e.g., solar power efficiency has tripled in the last 10 years, while fuel prices have also tripled in the same period), the case still can't be made for private companies to invest the money for a risky venture for a much wider audience.<br /><br />However, the military could fund the early work and become an initial customer, thus lowering investment risk. Then, ongoing trends in solar panel efficiency and energy cost as well as a need to reduce global greenhouse gasses could make space-based power a reasonable solution for a wider audience.<br /><br /><b><font color="yellow">Power from space? Pentagon likes the idea</font>/b><br />http://www.msnbc.msn.com/id/21253268/<br /></b>

 

[webtaz99]

Like many other things, it is waiting for a cheap, big launcher. <div class="Discussion_UserSignature"> </div>

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>Like many other things, it is waiting for a cheap, big launcher. <p><hr /></p></p></blockquote><br />Actually, no.<br /><br />It is waiting for the big technological risks to be grounded, i.e. it needs a smallscale concept qualification prototype.<br /><br />From then on, economics enters the picture, and we can start saying at what point in launch prices it becomes economical. <br />It may already be now, we dont know, because we dont know certain basic important operating variables, like how much mass you actually have to launch to get a megawatt of useful energy back down to earth.<br />We have plans and calculations, but without validating any of them, we just dont know, the unknowns in the entire architecture are too big.<br /><br />Or, as NASA managers would say, the Technological Readyness Level is too low. Managing and resolving these unknowns is the perfect task for government research dollars.<br />

 

[docm]

The PV tech isn't near good enough plus if you use a high-temp thermal collector who's going to maintain the Brayton cycle hardware in orbit?<br /><br />You see that's the whole rub: maintenance. Down here you can maintain almost anything, and your odds of having the hardware perforated by pieces of some Chinese weather satellite are much reduced <img src="/images/icons/tongue.gif" /><br /><br />Those are high risks when you're talking about putting a lot of economic eggs in a very few hard to get to baskets. <div class="Discussion_UserSignature"> </div>

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>You see that's the whole rub: maintenance.<p><hr /></p></p></blockquote><br /><br />Designing your square kilomters worth of solar arrays on geostationary to require maintenance in the first place is the definition of insanity.<br /><br />News: nowadays, thin-film solar cells are manufactured by roll-to-roll manufcaturing mehtods. The only form of maintenane you would want for the arrays is robots running around on rails and unrolling new sheets where cells have degraded.<br /><br />Anyway, thats all speculations. Without couple of trial projects we dont know jack about the maintenance requirements, required lift masses and so on. You dont design a completely new type of power plant on paper for commercial operations.<br />Thats like planning to run country on nuclear power BEFORE the Manhattan project.<br /><br />Once again, we are SORELY missing pilot projects.

 

[cuddlyrocket]

<blockquote><font class="small">In reply to:</font><hr /><p>Then, ongoing trends in solar panel efficiency and energy cost as well as a need to reduce global greenhouse gasses could make space-based power a reasonable solution for a wider audience.<p><hr /></p></p></blockquote><br />All these trends apply to ground-based solar power as well, and the latter is much cheaper for any specified level of power and reliability (and this is before considering other, even cheaper, sources of power).<br /><br />The military have a specific use where economics is not a high priority. So it may make sense for them, but that doesn't mean it will make sense for a power company. If the military build one, it will only serve to demonstrate this in practice (though the calculations speak for themselves).

 

[nexium]

We have been transmitting power from space for 50 years. Perhaps we need to build a one square kilometer rectenna and see if we can get more or less than one milliwatt? Perhaps it is already built. Does Aricibo radio telescope pick up a milliwatt, if tuned for very broadband?<br />Assuming we can get a milliwatt, of the megawatt being presently broadcast at Earth = one part per billion; we can aim a satellite or two at the Arecibo antenna to be sure the output increases measurably. We should likely repeat the experiment at several other radiotelescopes around the world. Next we build a 100 meter antenna array in low Earth orbit to send two kilowatts in a very narrow beam to Arecibo and other radio telescopes. If less than one kilowatt is received, we need to find a better way, as we need to lose less than half the signal to make SBSP = spacebased solar power practical.<br />In theory using millimeter waves, instead of microwaves will provide a tighter = narrower beam, so nearly all the energy falls on the radio telescope.<br />We can repeat the experiment with a two kilowatt transmitter, a large antenna kept aloft by a high altitude balloon, which tests part of Earth's atmosphere. I'm sure these expariments have been done in the past for other reasons, but sometimes we are surprised when we do an experiment with a single result in mind, such as SBSP.<br />I think we will decide that even millimeter waves cannot deliver ten kilowatts to one square meter, with a reasonable size antenna array, 36,000 kilometers away at GEO altitude. We may need to think ultraviolet laser diodes to get that tight a beam for military portable power reception from GEO altitude.<br />We do not need, nor want that tight a beam for civilian very large fixed rectennas, so the millimeter waves may be the best option for large scale.<br />My guess is we should forget millimeter waves and microwaves for the millitary application and go directly to laser diodes of the color presenty best. These can be

 

[josh_simonson]

Indeed, if it's cheap in space, it's cheaper on earth. Anyone flying over the western US during the day is quickly struck at how much absolutely empty space there is out there. Just a couple of those salt flats rigged with solar collectors could power the entire country. Frankly I'd feel better about my energy security if it were maintained by hispanic laborers than aerospace companies.<br /><br />In Scandinavia they're using off-peak surplus power to pump water backwards through hydro-dams to store the power for peak daytime demand, the reverse could work as well with surplus solar power providing regenerative hydro power at night. Yeah solar works best in the tropics, but transporting power from the tropics to northern cities is a much shorter commute than from GEO.<br /><br />It's kind of funny that this article says SBSP may be possible someday soon, when in many places you can put solar panels on your house and they'll pay for themselves in 5-10 years - that's a 10-20% rate of return.

 

[holmec]

WOW!<br /><br />I suppose the project would only make sense if it was really, really big and made a lot of power all the time.<br /><br />With silicone at a premium, and with other countries wanting to send probes and people to the moon, it doesn't make sense that such a project would be strictly military or even of one country. Such a project would be expensive and susceptible to attacks.<br /><br />It would seem to me that a geo-thermal power plant would be better off. <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[no_way]

<blockquote><font class="small">In reply to:</font><hr /><p>It would seem to me that a geo-thermal power plant would be better off. <p><hr /></p></p></blockquote><br />There are a few options for our energetic future, like fusion, new generation of clean fission powerplants, geothermal which is in wide use already and so on.<br />However, totally NOT exploring one of the potentially cleanest and most abundant in the long run is horribly irresponsible.<br /><br />Compare the funding that has been spent on SPS prototypes with the fusion research ...

 

[comga]

"In Scandinavia they're using off-peak surplus power to pump water backwards through hydro-dams to store the power for peak daytime demand,.."<br /><br />Very apro pos. In the fifties there was widespread and successful opposition to pumped storage in upstate New York. IIRC, even the Sierra Club weighed in supporting a new clean alternative source of power: nuclear energy. <br /><br />The lesson? Let's test this on a small scale before betting the farm on it. Like fusion that has been just around the corner for thirty years, it cannot yet be relied on.

 

[holmec]

<blockquote><font class="small">In reply to:</font><hr /><p>However, totally NOT exploring one of the potentially cleanest and most abundant in the long run is horribly irresponsible.<br /><p><hr /></p></p></blockquote><br /><br />Not exploring? Solar Cells have been in use for decades. This is nothing new. Lasers have been around since the 50's. Space based solar energy is a matter of economics and engineering but no new science is there.<br /><br />I would think you need it to be large to get more bang for the buck.<br /><br />The technique of transferring power via laser to a solar cell is fairly new. Saw it demoed with a RC aircraft. <br /><br />But is your going to make large solar panels out of silicone and place them in solar orbit, or some type of geosync earth orbit, and then transfer the power by electrically shooting a laser to another silicone solar panel on the ground to make electricity and thereby making hydrogen to run your vehicles, how much power to you loose in the transfer?<br /><br />Or should the scheme be to place a reflector that you can focus and control and transfer the solar light directly to the ground based solar panels?<br /><br />I would assume that the latter would be easier on the pocket book on the material side.<br /><br />I suppose that they need to come up with as scheme as of yet, or someone is keeping that under their hat.<br /><br /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#0000ff"><em>"SCE to AUX" - John Aaron, curiosity pays off</em></font></p> </div>

 

[cuddlyrocket]

<blockquote><font class="small">In reply to:</font><hr /><p>However, totally NOT exploring one of the potentially cleanest and most abundant in the long run is horribly irresponsible.<p><hr /></p></p></blockquote><br /><i>Solar power</i> is explored all the time. <i>Satellite</i> Solar Power is not explored at all because simple calculations show you're better off building a solar power plant on Earth. The only reason we haven't got one yet is that solar power on Earth is still more expensive than other Earth-based alternatives, though the cost is coming down rapidly and will probably be competitive in the near future. Then they'll spring up all over the place, <i>except</i> in orbit!<br /><br /><i>Silicon</i> - an element used to make microchips and solar cells, amongst other things.<br /><i>Silicone</i> - a polymer used to make breast implants, amongst other things.<br />- It's best not to get the two confused! <img src="/images/icons/smile.gif" />

 

[webtaz99]

Several comments:<br /><br />Even though the basic tech for SSP is proven, yes, improvements still need to be made and demonstrated.<br /><br />It is currently more efficient to go with microwaves than a laser for transmission. That may change, may not.<br /><br />Yes, a ground based solar plant is less costly, but one in geo gets stronger sunlight and gets it for a MUCH higher percentage of the time. Also, microwaves can transmit despite clouds which would lower ground based output. <div class="Discussion_UserSignature"> </div>

 

[spacester]

<p>spaceref gives a different spin: spaceref<br /><br />The Cosmic Log piece is very nice, lotsa good links. Here are a couple more.<br /><br /> space future archives<br /><br />Then there's the Motherlode at spacefuture<br /><br />I have a nice AIAA paper in my archives, but the copyright thing is unclear to me. I don't see it elsewhere on the web.<br /><br />***<br />Also from my archives:<br /><br />The FRIIS EQUATION give an estimate of efficiency of power transfer;<br /> Pr = Pt * Ar * At / [ L^2 * R^2 ] * Eabs<br /><br />Where - <br /><br />Pr = power received<br />Pt = power transmitted<br />Ar = area of receiver (sq m)<br />At = area of transmitter (sq m)<br />L = lambda - wavelength (m)<br />R = range - (m)<br />Eabs= eta -absorptance (between 0 and 1)<br /><br />WPT (wireless power transfer) occurs most efficiently where Eabs is<br />close to one. This is true for visible parts of the spectrum, near<br />the CO2 line, and below 10 GHz (3 cm).<br /><br />Clouds cause problems at shorter wavelengths. Longer wavelengths<br />imply very large collector and transmitter areas. Large areas mean<br />large costs.<br /><br /><br /><br /><br /><br />From: ()<br />Subject: Re: Solar PowerSats. <br />Newsgroups: <br /><br />Date: 2001-06-29 09:27:04 PST <br /><br />Luke Campbell wrote in message ...<br /> /> William Mook wrote:<br /> /> <br /> /> > The FRIIS EQUATION give an estimate of efficiency of power transfer;<br /> /> > Ar * At<br /> /> > Pr = Pt * -------------- Eabs<br /> /> > L^2 * R^2<br /> /> <br /> /> This can't be right. For 1 square km reciever stations, a 1 square meter<br /> /> emitter, 10 micron radiation, a distance of 36000 km (</p> <div class="Discussion_UserSignature"> </div>

 

[comga]

CuddlyRocket "...you're better off building a solar power plant on Earth. The only reason we haven't got one yet is that solar power on Earth .."<br /><br />Well, we are getting at least one on Earth. I just drove by the site in southern Colorado, just south of Alamosa. 8.2 MW according to http://www.renewableenergyaccess.com/rea/partner/story?id=48314<br /><br />There is no mention here of cost. However, at about 8.7 cents per killwatt hour in the Denver area (Actually, the per kwh rate is about half of this.) and assuming the equivalent of six hours a day of operation for 300 sunny days a year, the value of the power generated is $1.2M per year. Assuming further that this is used to pay just the carrying cost at an artifically low interest rate, the plant may cost $25-$50M. We can't build, launch and operate anything bigger than a basketball for that much, never mind something covering tens of acres. <br /><br />Furthermore, just building this facility will lower the cost of the next one. Despite many promises, the cost of launch has shown no comparable progress. <br /><br />I wish it wasn't so.

 

[j05h]

You're all missing the point. This is about deployable, use-as-needed solar power for military applications. The rectennae on the ground will be a wire mesh spread between towers, collecting microwaves from the SPS above. The rectennae can be deployed relatively rapidly. The impetus is how much fuel the US military needs to run generators, not the ideal green-power solution. The Army doesn't have time to set up solar farms or dig geothermal taps. They need something they can roll out in days or weeks.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[cuddlyrocket]

<blockquote><font class="small">In reply to:</font><hr /><p>Yes, a ground based solar plant is less costly, but one in geo gets stronger sunlight and gets it for a MUCH higher percentage of the time. Also, microwaves can transmit despite clouds which would lower ground based output.<p><hr /></p></p></blockquote><br />A ground-based plant is still much less costly even when you make it larger (to compensate for the less strong sunlight) and include storage (to compensate for the longer night and clouds etc). See Comga's post above for an indication of just how big is the difference in cost.

 

[webtaz99]

<img src="/images/icons/rolleyes.gif" /> I have never heard someone say "no ground based solar" or "only space solar". <div class="Discussion_UserSignature"> </div>

 

[cuddlyrocket]

Well no, but I don't see what that has to do with anything!