BBC: The Final Frontier for Solar Power

[j05h]

The Beeb is covering SPS, It's great seeing global media talking about space solar power. "It opens up all the other things that we are trying to do in space;"<br /><br />The graphic shows, IIRC, one of Dr. Hoyt's SPS designs. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[mavericktreethousand]

Thank you JO5H

 

[nexium]

It looks like the DoD will do this, even though the electricity from the pilot models will require large subsidies. The pilot models will, however, be able to deliver a few kilowatts intermittantly to disaster areas and war areas, where lives are presently lost getting fuel to portable generators. DOD hopes for rapid scale up to several megawatt capacity. This will insure customers for new solar panel factories, perhaps high altitude balloons and access to LEO = low Earth orbit. LEO is adaptable to a single semi polar satellite supplying most of the nations of Earth, at least occasionally, so this may inspire international cooperation. Solar synchronous orbit = about half way to GEO may be best, if the international co-operation permits a swarm of these satellites. The sun shines on solar synchronous satellites 24/7 except during rare eclipse of the Sun. www.spacesolarpower.wordpress.com Neil

 

[vulture2]

It might be tough to ensure continuous power from satellites that aren't in geosynchronous orbit, and with the beams changing position all the time, it would be difficult for aircraft to avoid them. <br /><br />Moreover, I just frankly don't believe this is a practical approach to disaster response. If the ground stations are very small, most of the power will be lost. If they are large, the power would have to be distributed by transmission lines that don't exist following a disaster. If there is any evidence that large numbers of people are killed bringing fuel to portable generators, please post it. This study sounds like another case of the DOD having more money than it knows what to do with.

 

[j05h]

<i>> It might be tough to ensure continuous power from satellites that aren't in geosynchronous orbit, and with the beams changing position all the time, it would be difficult for aircraft to avoid them.</i><br /><br />One option would be for the collectors to be separate from the transmitter stations. The transmitters would be in GEO, receiving higher-power beams from solar-collection sats. It would create some inefficiencies but provide serious redundancy.<br /><br />The power beams for proposed units are not very strong. It averages something like 2X normal insolance but mostly in microwave spectrum. It wouldn't disrupt aircraft or birds. Rectenna can be set up in crop and grazing land with no ill effect.<br /><br /><i>> Moreover, I just frankly don't believe this is a practical approach to disaster response. If the ground stations are very small, most of the power will be lost. If they are large, the power would have to be distributed by transmission lines that don't exist following a disaster. If there is any evidence that large numbers of people are killed bringing fuel to portable generators, please post it. This study sounds like another case of the DOD having more money than it knows what to do with.</i><br /><br />The ground station can be as simple as wire mesh on poles, running to a small substation. <br /><br />As far as people dieing transporting fuel for generators, I have one question. Have you paid attention to this little "war in Iraq" thing, where American soldiers routinely get ambushed in fuel convoys? <br /><br />Portable, stand-off power like SPS would be a huge boon for DoD. The infrastructure requirements are probably to much for actual disaster relief, but could speed rebuilding/recovery/development in stricken areas. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[no_way]

what i completely fail to understand, is why existing SPS research funds are not even a proper fraction of oh, fusion for instance. And how come that its not an official part of any countrys energy policy for the future.<br />What if a question about SPS was asked on a presidential candidate debate ? It would be amusing to hear the answers. Sorta like asking a teen miss about education on national television.<br />

 

[vulture2]

First, I really respect some of the authors of the recent reports, including Hugh Davis. They are visionaries. But it would be a good idea to start with the existing data (see link below) The infrastructure requirements are huge, usually over 10,000 TONS per satellite. Easy to draw on paper but the cost and risk simply make it impractical in comparison to ground-based generation, which is also advancing. And the laws of physics don't change; a smaller rectenna on the ground still requires an even larger transmitting antenna, or most of the power is lost. Any system other than a geosynchronous SPS requires a constellation of satellites before it can produce continuous power. I would invite anyone out there who believes this concept should be pursued to present at least a basic concept study that illustrates the development costs.<br /><br />link

 

[nuaetius]

<blockquote><font class="small">In reply to:</font><hr /><p> what i completely fail to understand, is why existing SPS research funds are not even a proper fraction of oh, fusion for instance. And how come that its not an official part of any countrys energy policy for the future. <br />What if a question about SPS was asked on a presidential candidate debate ? It would be amusing to hear the answers. Sorta like asking a teen miss about education on national television.<p><hr /></p></p></blockquote><br /><br />Space based solar is WAY out in the future. The only thing we currently have that remotely resembles it is the solar wings on the ISS, and they have been technical nightmares to operate ever since they started spinning and redeploying them. <br /><br />I don’t think any Government R&D should be allocated to this project specifically. R&D on solar efficiency, microwave transmission, and EELV/RLV I can see as long as you don’t say the application is SPS. <br /><br />When launch costs go way down, solar efficiency per pound goes way up, or we get good enough at fabrication in space to make the panels in orbit then SPS will be more than a pork barrel vanity project.<br />

 

[nexium]

Money does not solve all problems, but it helps. A firm commitment by DoD to launch a series of SSP = SPS of increasing mass will likely bring down launch costs, improve the solar panel watts per kilogram, and make terrestrial solar more practical. It may take 50 or 100 years for the technology to be competitive with fossil fuel, but it will be even longer, if we don't start soon. Neil

 

[nexium]

In some respects we can beat the laws of physics, by going to a higher frequency = shorter wave length and/or thinking closer than GEO altitude. From a balloon platform above the clouds, over a distance of 100 kilometers, ten square meters is big enough for both the transmit phased array and the rectenna. A ten kilowatt beam = 1/10 th watt per square centimeter = the allowed energy leakage from microwave ovens, we are both reasonably safe and have an effective demonstration of SSP technology. Neil

 

[nuaetius]

<blockquote><font class="small">In reply to:</font><hr /><p>Money does not solve all problems, but it helps. A firm commitment by DoD to launch a series of SSP = SPS of increasing mass will likely bring down launch costs, improve the solar panel watts per kilogram, and make terrestrial solar more practical. It may take 50 or 100 years for the technology to be competitive with fossil fuel, but it will be even longer, if we don't start soon. Neil<p><hr /></p></p></blockquote><br /><br />My only problem with this solution is that Space Solar power is not mature enough for this level of investment. It’s my money, and I don’t like to see it blown on technologies that very well might not work out. I see it like this, the Electric car predates the Internal combustion engine by about 10 years, but the tech was dropped until recently because even though it has been doable for over a hundred years now, the battery component has just caught up with the motor tech that was ready all the way back then. <br /><br />If everyone had tried to FORCE the electric car into existence before the batteries where in place then the internal combustion engine which has served us well to this point very well might not have been developed. When Space Based Solar power is ready for the market the DoD will not have to force it into existence, it will bloom on it’s own.<br />

 

[kelvinzero]

I would speculate that the reason SPS does not seem to get much direct money is that it doesnt need it. Two of it's main requirements, cheap solar power and cheaper access to space are already getting a lot of research and investment. SPS doesnt compete with ground based SP. Ground based is here now, and vital for possibly developing SPS in the future.<br /><br />Im glad there is also dabbling in beamed power.<br /><br />SPS may be a way off but you dont want to discover it is suddenly here, but you forgot to build the rockets to exploit it, leaving your country ten years behind. It is just worth keeping an eye on all the time.<br /><br />It will be very exciting when a solar power satellite can return more $ than it cost to launch. We will suddenly be in an age where millions of tons and thousands of workers in space makes perfect dollar sense.

 

[j05h]

The Suntower that is described in this paper uses ELVs. There is no need for a new rocket, just more flights to make current ones cheaper. They quote $200-400/kg to make this concepts work. This design uses minimal crew on-orbit and much of it is technologically ready. <br /><br />http://www.spacefuture.com/archive/a_fresh_look_at_space_solar_power_new_architectures_concepts_and_technologies.shtml<br /><br />SPS only needs money once someone decides it is needed and deploys the first system. <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[billslugg]

Neil<br /><font color="yellow">over a distance of 100 kilometers, ten square meters is big enough for both the transmit phased array and the rectenna. A ten kilowatt beam...</font><br /><br />The only part that I don't see is that the beam divergence would be far too high at microwave frequencies. I guess that your footprint would be at least a kilometer wide at this distance. I don't see how you could get it all squeezed down to land on just a small target. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[nexium]

We are both guessing and it is complicated though 100 kilometers of thick atmosphere. Ignoring the complications, one kilometer would become a 360 kilometers wide foot print from GEO altitude. It is directly proportional. Going to laser or millimeter waves instead of micro waves reduces the size of the transmitting antenna and/or the foot print, probably less than linear. Does any one know the spot size of a microwave beam 10 kilometers long sent from a large dish? Neil

 

[billslugg]

neil<br />I found this pdf of a paper from Caltech. It is an article that lays out two systems, microwave and laser, for delivering power to place small payloads into orbit. On pg. 393 they show that they use 16 μrad as their beam divergence in both cases.<br /><br />A ten meter diameter beam would diverge to only 16 meters at 100 km with this kind of divergence. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[webtaz99]

I guess it's worth noting that the first lasers were masers.... <img src="/images/icons/wink.gif" /> <div class="Discussion_UserSignature"> </div>

 

[vulture2]

>>A ten meter diameter beam would diverge to only 16 meters at 100 km with this kind of divergence.<br /><br />Beam divergence varies inversely with aperture. The article you reference by Kare and Parkin states that achieving 16urad beam divergence at 140GHz would require an array with a diameter of 462 meters and an area of 168,000 square meters. The authors describe this as "uncomfortably large", even for a ground-based transmitter. For a 10-meter antenna the beam divergence would unfortunately be many times greater than 16 urad.

 

[billslugg]

Thanks Vulture2<br />Would the increase in divergence be linear? Would a ten meter dish thus have 46 times the divergence?<br />Thus the 16 meter wide spot would actually be 736 meters? A ten meter receiving dish would then absorb only (16/736)^2 or .04% of the input energy? Does not sound good in any event. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[vulture2]

The paper indicates that:<br /><br />beam divergence =2.44 * wavelength / antenna diameter<br /><br />i.e. a simple inverse relationship. The diameter given was for the highest feasible microwave frequency, and is similar to the diameter of proposed antennas for solar power satellites. <br /><br />The SPS 2000 study assumed a 1000km equatorial orbit (over equatorial countries only, but fewer satellites needed), a 100m transmitting antenna and a 3 km diameter (7 sq. km) receiving antenna. Even in a poor country, that's a big antenna. <br /><br />If this much money was available to some of the poorer countries of the world, they would very likely benefit a lot more from investing it in clean water, education, medical care, and industrial development. The equatorial countries also for the most part have excellent power factors for ground-based solar and would benefit more from 7 square kilometers of solar panels (which could be placed near the locations where power is needed) than from the rectennas.<br /><br />I love space. I simply think we should be realistic. The one part of the original SPS program I believe is feasible is the two-stage-to-orbit fully-reusable shuttle with the methane-LOX fueled flyback first stage that most of the contractors proposed using.

 

[richalex]

You might find this 54-minute video on YouTube interesting. <br /><br />Electricity from Orbit: The case for R & D<br /><br />"The just-released report on SSP by the National Security Space Office (available at http://www.nss.org/settlement/ssp/library/nsso.htm ) concludes that 'it would be in the US Government's and the nation's interest to sponsor an immediate proof-of-concept demonstration project and a formally funded, follow-on architecture study conducted in full collaboration with industry and willing international partners.'"

 

[vulture2]

Some points from the DOD study might be of interest:<br /><br />FINDING: The SBSP Study Group found that even with the DoD as an anchor tenant customer at a price of $1â€2 per kilowatt hour for 5â€50 megawatts continuous power for the warfighter, when considering the risks of implementing a new unproven space technology and other major business risks, the business case for SBSP still does not appear to close in 2007 with current capabilities (primarily launch costs). <br /> <br />FINDING: The SBSP Study Group found that in order to costâ€effectively build much larger SBSP systems, the U.S. needs Lowâ€Cost and Reliable Access to Space (LCRATS). <br /><br /> • Reusable spaceplanes — which deliver aircraftâ€like safety, reliability, operability, maintainability, rapid turn around, high flight rates, and very low cost per flight — are the most likely nearâ€term approach to achieving LCRATS. <br /> • At this time, private industry is unable to justify the very large and financially risky investments necessary to develop LCRATS, or commercial ubiquitous onâ€orbit space operations, without significantly increased assistance of the federal government. <br /><br />Personally I would be surprised if a DOD that is so short of soldiers it has extended tours in Iraq to 15 months really has the spare money to build a reusable spaceplane, but if they do I'd be the last to stand in their way. I agree that a fully reusable spaceplane is exactly what is needed, not just for this project but for human spaceflight in general to ever become practical. My great disappointment is that NASA is more interested in replaying Apollo than in developing an enabling technology.<br />