...100 MW of Space Solar Power ...per single launch!
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From: Sylvia Else on 18 Dec 2009 23:32 Androcles wrote: > "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message > news:00a4c352$0$1494$c3e8da3(a)news.astraweb.com... >> Androcles wrote: >>> "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message >>> news:00a7e786$0$23359$c3e8da3(a)news.astraweb.com... >>>> Peter Fairbrother wrote: >>>>> Greg D. Moore (Strider) wrote: >>>>>> "Sylvia Else" <sylvia(a)not.at.this.address> wrote in message >>>>>> news:00185a93$0$2120$c3e8da3(a)news.astraweb.com... >>>>>>> An obvious solution would be battery storage to balance supply >>>>>>> against demand. Pity we don't have anything that approaches being >>>>>>> usable that way. >>>>>>> >>>>>> The one I'm hearing more and more about is compressed air. Not a >>>>>> panacea, but apparently may be quite workable in many cases for peak >>>>>> power loads. >>>>> There is also pumped storage, eg Ffestiniog in Wales. >>>>> >>>>> http://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity >>>>> >>>>> -- Peter Fairbrother >>>> Pumped storage works - but like hydro, you can't just decide to build >>>> one. You need somewhere suitable. In particular, you need to be able to >>>> store large amounts of water at two levels that are at sufficiently >>>> different elevations. >>>> >>>> Sylvia. >>> You mean like in Wales? >> It needs to be reasonably close to where the power will be consumed. The >> UK is small, and Wales is reasonably close to most of it. Wales is useful >> in the UK, but is hardly a general solution. >> >> Sylvia. > Your historical, geographical and political knowledge is somewhat > lacking. > The Prince of Wales is the Queen's son, I'd suggest to you that > Wales was most definitely part of the UK. Did I say otherwise. My stomach is reasonable close to all parts of my body. Sylvia.
From: David Spain on 19 Dec 2009 01:33 Pat Flannery <flanner(a)daktel.com> writes: > David Spain wrote: >> >> Yes, GEO satellite do not actually remain fixed at a point, but do a little >> figure 8 in the sky, unnoticable by the antennas that receive their signals. > > Since Earth's axial tilt is 23.44 degrees, if I'm figuring this right, that > means the SPS will have go through a total of 46.88 degrees up and down > movement in the sky daily to completely avoid its shadow (actually a little > less as the shadow tapers as it gets further away from the Earth due to the > fact that the sun isn't a point source of light, but has a visible angular > size in the sky), however, I think this ends up with it getting into the > Earth's shadow on a almost daily basis rather than just around the Spring and > Fall equinoxes. > > Pat Some references that might help. First, Dr. T.S. Kelso's guide on GEO satellites: http://celestrak.com/columns/v04n09/ and some interesting comments on how to best make SPS pay by Geoffrey Landis at Glenn which also talks about the alternative of placing a SPS at L2 instead of GEO to supplement ground-based solar: http://www.nss.org/settlement/ssp/library/2004-NASA-ReinventingTheSolarPowerSatellite.pdf Dave
From: Pat Flannery on 19 Dec 2009 12:01 David Spain wrote: > > Some references that might help. > > First, Dr. T.S. Kelso's guide on GEO satellites: > > http://celestrak.com/columns/v04n09/ That's a good description on the shadow problem, but that 25% power drop-off in 7 years is troubling from a economic viewpoint, and makes me wonder if the reflector/heat engine approach isn't superior to the solar cell arrays as a way of doing things. As has already come up, switching to batteries during eclipse isn't practical because of the weight that would be involved to keep microwave power transmission levels constant. Sylvia's multiple SPS constellation with the individual satellites widely spaced certainly has simplicity on its side. > > and some interesting comments on how to best make SPS pay by Geoffrey Landis > at Glenn which also talks about the alternative of placing a SPS at L2 instead > of GEO to supplement ground-based solar: > > http://www.nss.org/settlement/ssp/library/2004-NASA-ReinventingTheSolarPowerSatellite.pdf At GEO it's already a long way to the rectenna on the ground; sticking it clean out in a L2 halo orbit beyond lunar distance is going to make the focusing of microwave beam onto a reasonable sized rectenna even more difficult. The idea of the relay satellites is interesting, but then you run up power loses unless you make them into some sort of simple reflectors rather than microwave receiver/transmitters. The part that hits me as really odd though are the inflated solar collector/microwave transmitter elements; these do not seem like something that's going to stay inflated long once some micrometeoroids start hitting them. I did come up with one little idea though that might help on the Earth side of things. The closer the incoming microwave beam can hit the rectenna to a ninety degree angle the smaller in size the rectenna can be. Assuming a circular incoming beam, in North America the rectennas would have to be ovoid in shape to capture all the beam, particularly as you got further north on the continent. Using the concept of "If you can't raise the bridge, lower the river" rectennas built not on flat land, but rather on the south-facing sides of mountains would present a more perpendicular aspect to the incoming microwave beam from a SPS in the southern sky. Pat
From: David Spain on 19 Dec 2009 14:59 Pat Flannery wrote: > > At GEO it's already a long way to the rectenna on the ground; sticking > it clean out in a L2 halo orbit beyond lunar distance is going to make > the focusing of microwave beam onto a reasonable sized rectenna even > more difficult. Similar problem with the micro-power sats. It isn't desirable to have to build a 1-2km wide rectenna in order to obtain only 50kW of power. For a micro-power sat to work with any reasonable ground antenna size, you probably have to move up to millimeter wave RF. Only problem there is you start to get into serious atmospheric interference and rain fade issues. Starts to sound really non-compelling vs. just having ground based solar cells. The idea of the relay satellites is interesting, but > then you run up power loses unless you make them into some sort of > simple reflectors rather than microwave receiver/transmitters. You will still see losses with passive reflectors, but they are far simpler ergo more reliable. > I did come up with one little idea though that might help on the Earth > side of things. > The closer the incoming microwave beam can hit the rectenna to a ninety > degree angle the smaller in size the rectenna can be. Assuming a > circular incoming beam, in North America the rectennas would have to be > ovoid in shape to capture all the beam, particularly as you got further > north on the continent. Yes, all the designs I've seen feature that shape. > Using the concept of "If you can't raise the bridge, lower the river" > rectennas built not on flat land, but rather on the south-facing sides > of mountains would present a more perpendicular aspect to the incoming > microwave beam from a SPS in the southern sky. > Wouldn't that work regardless of which hemisphere it's constructed in North or South? For that matter, since height isn't that serious a criterion, you could just build the rectenna on the surface of a properly angled constructed pyramid, ala PAVE/PAWS only much much much bigger. That would help efficiency, but the other goal of the ground rectenna is to minimize environmental impact, ergo most of the designs I've seen have it about 10-20ft off the ground, made mostly of wire and posts, with screening below the passive antenna elements to provide shielding to those working below, maintenance folks or grazing cattle ;-).... Dave
From: Pat Flannery on 19 Dec 2009 19:16
David Spain wrote: > >> Using the concept of "If you can't raise the bridge, lower the river" >> rectennas built not on flat land, but rather on the south-facing sides >> of mountains would present a more perpendicular aspect to the incoming >> microwave beam from a SPS in the southern sky. >> > > Wouldn't that work regardless of which hemisphere it's constructed in North > or South? Yeah, in North America it would probably be out in the Rockies facing south; in South America in the Andes facing north. > > For that matter, since height isn't that serious a criterion, you could > just > build the rectenna on the surface of a properly angled constructed pyramid, > ala PAVE/PAWS only much much much bigger. Considering that the smallest rectenna size for a GEO SPS I've seen is around 3 km in diameter, this thing would start getting pretty big pretty fast. I imagine you could stick it on the slanted roof of a Arcology super-building. > That would help efficiency, but > the other goal of the ground rectenna is to minimize environmental impact, > ergo most of the designs I've seen have it about 10-20ft off the ground, > made mostly of wire and posts, with screening below the passive antenna > elements to provide shielding to those working below, maintenance folks > or grazing cattle ;-) Although it might disfigure the side of a mountain, the higher you could get the rectenna above sea level the less atmosphere the beam has to pass through. Pat |