Solar power!

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pioneer0333

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I'm just pokin-around in my head, but would it be possible to create a kind of or sort of "solar power station" in space? Bare with me now, but with this, would it be possible to collect HUGE amounts of solar-energy on some kind of gigantic solar panel arrangement, and then direct the energy that is collected and direct it to a certain point on Earth? And I'm guessing the point on Earth that recieves this energy would be some kind of super-senstive and super-absorbent solar cell, which then coverts it into electrical energy? Just asking!!! <div class="Discussion_UserSignature"> </div>
 
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doubletruncation

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This idea has been floating around for a long time - it was especially big back in the energy crisis of the 70s. The biggest challenge for the solar power satellites has always been the cost of getting things into orbit. To really collect a significant amount of energy you need huge arrays - square kilometers at least. When people talk about building space elevators or other schemes for reducing the cost of putting large amounts of materials into space solar powered satellites are usually listed as one of the "short-term" gains. The other challenge for solar powered satellites is getting the energy down to Earth where we can use it. In principle you could do it with a microwave, I don't know how big of a technical challenge it would be to do it though (IIRC a prototype has been demonstrated over short distances). Also there are some environmental concerns of shooting continuous very intense microwave beams from space to the ground. <div class="Discussion_UserSignature"> </div>
 
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siarad

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This was going around in the late 1950's where MASER were to be used to return the power. I seem to recall that safety was a factor with such huge no-go zones.<br />
 
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agnau

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For some reason I always thought of a Orbiting Solar Power Station receiving microwave beams from other stations closer to the sun (say Venus orbital distance) although significantly enough out of the orbital plane to keep our current solar radation levels.<br /><br />This earth-orbit station would then in theory transmit power down like a cable-satallite transmits signals. I never thought of what wave length or amplitude it would send in.<br /><br />*** Although, here's a curious thought -- can any energy be recovered from radio signals?
 
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Saiph

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the latest incarnation of power transmission is a more dispersed microwave beam, so it doesn't fry anybody. To recieve it a large antena array on the ground would be constructed, a square mile or so of conducting cables and such to pick up the microwave beam. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>
 
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siarad

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Thanks.<br />I think the MASER was suggested as it wasn't affected by ionisation or clouds etc or at least little affected whereas incoherent waves would, being toffee hammers instead of a sledgehammer <img src="/images/icons/smile.gif" />
 
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nexium

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One idea is a 1000 kilometer mirror in a solar stationary, semi polar orbit which could send a wide beam of sunlight to solar receiving sites around the world. Each site receiving the sun beam a few hours per day, preferably near sunset which is the peak demand period in most locals. If a typical receving site had a diameter of 100 kilometers, the energy level would be ten times that of sun light assuming 10% of the energy hit the receiving site. Photo voltaic panels and/or solar power towers would convert the solar energy to electricity. While a single mirror this large would provide several percent of Earth's energy needs, the huge receving sites would be extremely costly; hot spots in the beam would likely be fatal to man and beast, and the average temperature of Earth would likely increase by 0.5 degrees c = 0.9 degrees f. The efficiency drops if we try to do this smaller scale except a billion free flying balloon suported mirrors might achieve 10% efficiency to 100 meter solar sites, with miminal hazard to man and beast. The cost per KWH = kilowatt hour might also be lower. Earth would not be warmed if the top 1/3 of each balloon was white or a mirror finish, but it is not very high tech. Neil
 
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nexium

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Present solar cells produce about 300 watts per square meter in space if aimed at the sun = 300 megawatts per square kilometer. So ten square kilometers would produce 3 gigawatts. Perhaps 1/2 gigawatt could be put on the grid, by a rectenna several kilometers in diameter. The entire system would need a massive retrofit in 30 years or less, so it may be more costly than making electricity from coal, even if we can deliver materials from Earth at $100 per pound = $220 per kilogram. SIG = Space Island Group is pretending they can do this, but most of us are skeptical. Neil
 
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pizzaguy

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<font color="yellow">Present solar cells produce about 300 watts per square meter in space if aimed at the sun = 300 megawatts per square kilometer. So ten square kilometers would produce 3 gigawatts.</font><br /><br />Whoa, slow down! I have a major problem with your math! Where are you finding solar cells that produce 300 watts/sq meter??<br /><br />AND EVEN IF YOU CAN FIND THEM:<br />The available energy at ground level is around 300 to 700 watts/square meter. You can't get 100% of that energy as electricity - because solar cells are not 100% effiecent. But I'll give you the "300 watts / square meter" figure. Ok....<br /><br />300 watts a square meter, fine. A square kilometer is 1,000 square meters, right? So would that not provide 300,000 watts in a square kilometer? (.3 Megawatts/sq km)<br /><br />Ok so far?<br /><br />Now, remember, the atmosphere steals more than half the available energy. In space (near earth, that is,) I believe the actual sun's energy level is around 1400 watts/square meter. <br /><br />Now, the cells are not 100% effiecent - currrent sales literature claims 15% or so. Let's be generous and say 50%!<br /><br />So, 1400 watts per sqare meter minus 50% loss in the solar cells (and no one has a 50% effeicent solar cell) in a 1 square kilometer array would yeild .7 megawatts. <br /><br />But again, that's .7 megawatts per sq/km <font color="yellow">IF</font>you can find a 50% effiecent solar cell and <font color="yellow">MINUS</font>the loss in the medium used to transport the energy to ground level.<br /><br />So a square kilometer solar panel array in space cannot possibly yeild even .7 Megawatts!<br />And a 10 square kilometer array couldn't produce 7 megawatts. <br /><br /><br /><br /><br />Now, someone check MY math! <div class="Discussion_UserSignature"> <font size="1"><em>Note to Dr. Henry:  The testosterone shots are working!</em></font> </div>
 
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bdewoody

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A square kilometer is 1,000,000 square meters <div class="Discussion_UserSignature"> <em><font size="2">Bob DeWoody</font></em> </div>
 
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MeteorWayne

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"300 watts a square meter, fine. A square kilometer is 1,000 square meters, right?"<br /><br />Actually a sq km is 1000m X 1000 m = 1 million sq meters. Have to be careful with area <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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pizzaguy

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I only asked 'cause I KNEW deep down inside I was missing something!<br />Thanks guys!<br /><br />Ok, so a million square meters = 1 sq/km.<br /><br />So if we get 300 watts per sqaure meter, then then we have 300 megawatts per sq/km. <br /><br />Oh, DAMN - is that what Neil said in the first place?<br /><br />Like I said, the cells aren't that efficient BUT in space they'd start out with 2-3 times more energy, so THERE I think 300 watts/sq meter is reasonable.<br /><br />But how do you get the energy back to earth? <div class="Discussion_UserSignature"> <font size="1"><em>Note to Dr. Henry:  The testosterone shots are working!</em></font> </div>
 
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MeteorWayne

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BTW, I agree that the 300 W/sq meter is way out of the ballpark. <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>
 
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ldyaidan

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Here's an article that suggests with new discoveries, we may be able to push that to 65% efficiency. Very nice improvement!<br /><br />http://www.futurepundit.com/archives/002789.html<br /><br />There are also several other new technologies out there that are showing promise for great improvements. <br /><br />Since one of the major expenses would be getting these cells into orbit, perhaps the theory that the lunar regolith can be used to create solar cells would be a worthy investigation. Either way, we have to have cheap, reliable transport to and from space. Once we get that, the possibilities are nearly endless.<br /><br />Rae<br /><br /><br />
 
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nexium

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You will notice that I assumed 5/6 of the output of the solar cells would be lost, by the time the energy is on the grid. 1 Collection losses may be sizable due to the ten square kilometers of solar panel. I suggest enough solar cells in series to produce a million volts dc, so the current for 2800 megawatts is 2800 amps passing though a 10 kilometer embilical cord to the transmitter modual. After the IR loss the voltage is about 900,000 volts which can be applied to about ten kysitrons in series. Perhaps ten such strings in parallel are needed to use the 2800 amps. 2520 megawatts input. Output is 1260 megawatts of microwaves out into 100 wave guides. Wave guides are very efficient, but 100 driven elements may convert only 1100 megawatts to microwaves in the very narrow beam to Earth. Some energy is scattered from the beam especially in Earth's atmosphere so 1000 megawatts falls on the rectenna, which produces 800 megawatts of low voltage dc. Elements in series parallel apply about 800 volts dc to about 100,000 inverters (input 8 kilowatts each) which produce about 300 volts RMS 60 hertz ac at 7 kilowatts each for a total of 700 megawatts which can be put on the grid at 300,000 volts if we have the inverter outputs in series strings of 1000 inverters each, so that they produce 3 phase ac. If this is not practical, then we need transfromers with about 1000 primaries, which are not very efficient resulting in about 500 megawatts being put on the grid. Worse, some of my numbers are optimistic, so we could have less than 1/2 gigawatt put on the grid on the average.<br /> The purpose of the embillical cord is: The solar cell array needs to point at the Sun and the antenna array (about one square kilometer) needs to point at Earth. Perhaps once per year it will be necessary to shut down the system to untangle the embilical cord.<br />I suggested klysitrons as they produce much less interferance than magnetrons and can carry high speed data. The leakage from the system will
 
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pizzaguy

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Transporting energy via RF seems silly to me - not just in YOUR example but in general.<br /><br />Say, at 2 gHz, you want to go 300 miles - that's 152 dB path loss, and that assumes NO additional loss when passing thru the atmosphere.<br /><br />I think your assumption of how much energy would make it to the grid is way too generous.<br /><br />Transporting engery via RF - sounds like somethink Tesla would suggest. <img src="/images/icons/crazy.gif" /> <div class="Discussion_UserSignature"> <font size="1"><em>Note to Dr. Henry:  The testosterone shots are working!</em></font> </div>
 
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nexium

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So if the path loss is 400 db for 36,000 kilometers; can we get a transmitting antenna gain of 200 db and a retenna gain of 200 db, so that nearly all the power is delivered to the rectenna? Apparently the analysts in the 1985 study (which cost $25 million) thought that most of the energy would be delivered, if the antennas were big enough?<br />I agree the atmospheric and ionized layer losses are large on some frequencies. Some laser wave lengths have low path loss at one watt per square inch or less of beam cross sectional area, but apparently the best lasers only convert about 1% of the input energy to photons, making disposal of the 99% heat dfificult in a vacuum. Neil
 
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