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Orbiting Solar Panels Beam Energy From Space

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Elizabeth M
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Re: Sci Fi to Reality
Elizabeth M   4/8/2014 4:59:04 AM
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Thank you for that thorough evaluation of this system, fm. According to your calculations it seems that the economics don't add up, but I suppose that's up to the Navy to find out and decide, and perhaps they have a workable solution to solve this problem.

PV_Aficionado
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Iron
Re: Sci Fi to Reality
PV_Aficionado   5/1/2014 3:17:39 PM
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Credentials: I have been working space solar arrays for over 35 years.  My college project was Space Solar Power Systems (SSPS) later called SBSP originally suggested by 1941 Asimov SF and later made credible by Peter Glaser in a US patent for "practical" application. (See Wiki for more in depth).  SiliconGreybeard is right, low power microwave beamed to earth surface receiver/converters (rectenna size:square miles) was the generally agreed upon technique for safe delivery and conversion. Jaffe of NRL is correct in a key need was a distributed beaming capability which will subsequently need to be synchronized to avoid nulling of the beamed power at the receiver. I have designed and built solar arrays (S/A) which have lasted on orbit for over thirty years with graceful (predictable) degradation in Geosynch orbit where these should be parked.  That's not an issue.  But fm and Daniyal_Ali are also right.  Here is the challenge: at 0.10/ kWhr, and 30 years of perfect operation, it leaves only $26.2/watt to build and deliver the complete system (not including amortized nonrecurring costs). The industry shows space rated arrays typically cost between $600 to $5000/watt.  Current terrestrial solar panel technology which might be capable for space use may get to $4/watt, though the terrestrial ones are looking to eventually <$1/watt wholesale, but space is tough!    To go from $600/W to $4/watt for space S/A is beyond current technology.  Next,  the cheapest cost to space at Geo is ~10000/lb, though SpaceX hopes to get that in the realm of $1000/lb.  Space S/A weigh 14 to 36 W/lb, though there is some hope to get to 180 W/lb eventually.  That is $.05lb/watt or $50/watt for launch.  Launch cost would need to get below $200/lb ($10/W) to make the system feasible.  Then you need to pay for the ground based rectennas and all the balance of system with the $26-$4-$10=$12/W left over.  Possible? Yes.  Near term (next 30 years)? No.  Should we do it? Ultimately for the species, yes.  More cost effective than terrestrial solar?  In 50 years?  That's TBD.

notfred
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Iron
solar energy from space
notfred   5/27/2014 11:58:33 PM
I don't understand why people keep thinking this is a viable thing.  In order to be useable you'd need to construct a system capable of delivering 500GW to 1000GW of electricity on Earth, comparable to a standard power station, otherwise, what's the point.  First off the space based panels would have to be made of galium arsenide to withstand the radiation in space.  Ordinary silicon panels would die after 6 months to a year.  Galium Arsenide panels are 50X more expensive, even if they are 40% efficient.  At an overall system efficiency of about 7% (panel efficiency = 40%, convert to microwave = 75%, atmospheric losses 50%, receiving antenna losses = 75%, convert to 60 Hz AC = 60%) .4 x .75 x .5 x .75 x .6 = .67) we'd need a huge solar array.  At 100% efficiency we'd need the total panel size to be 1000GW/1400watt per foot = 714,000 sq ft.  At 7% overall efficiency the panel size would be over 10 million sq feet.  That's 2/3 of a mile on a side.  And what keeps the panels all in the same plane?  A giant truss of some kind.  Currently the solar panels on the ISS are the largest we have in space.  Do any readers recall the frequent problems they've had?  These are microscopic compared to our sci-fi panels!  And how will you keep something this large pointed at the sun?  It becomes a giant solar sail.. constantly being pushed away by the sun.  It would have to be in geo-synchronous orbit and sending it's 1000GW microwave beam through the path of thousands of satelites in lower orbit.  And how do you maintain it?  What about space debris.. this thing will make a nice target!  And how do you even get it up there in the first place?  We'd be talking about 1000's of launches!!  And you want robots to assemble it?  What robots?  This thing would probably cost more than the GNP of the entire world!!  I could go on and on.  This whole idea is ridiculous!

Next thing we know, someone will propose putting solar panels on roads!  Yes, I know, they already have, and if you believe that will work, I guess you might as well believe this too.

Sorry for being so sarcastic and perhaps exagerating a tad.. but I just get tired of these crazy schemes!  I run an engineering company and it seems half of my time is spent explaining to clients why some things are just not practical!!

If you don't believe me, perhaps you'll believe Elon Musk!  http://www.popularmechanics.com/how-to/blog/elon-musk-on-spacex-tesla-and-why-space-solar-power-must-die-13386162

Elizabeth M
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Re: solar energy from space
Elizabeth M   5/28/2014 5:24:36 AM
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notfred, your points are well taken and yes this seems a bit far fetched. But I think people thought that about putting somone on the moon way back when. Maybe it is a bit out there but with one of the top scientists in the world on it, I think maybe someday it could be viable. Of course, you are an engineer and I'm just a writer, so I could be wrong! This is why it's great when our readers weigh in on stories to provide real-world perspective.

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