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Thu 7 Oct, 2004 10:54 am
This is about SPS = solar power satellite and alternative energy. I love to analyze. An important consideration is most communities need about twice as much electricity near sunset as the average for the rest of the day = the peak demand period. This is about the time surface solar stops making electricity. Like nuclear, geo-stationary SPS has the same output 99% of the time, so costly polluting, gas turbines are run about an hour per day to make the extra power for peak demand and rare down time emergencies and maintenance.
If we orbit the SPS at about 1/2 the GEO-synchronous altitude, the satellite stays over the sunshine terminator, or close by. This is called a solar synchronous orbit. Closer means the transmitting antenna on the satellite can be smaller, saving perhaps 100 billion dollars construction cost. This SPS beams the energy to the communities where it is needed most. I believe the transmitting antenna can be designed to produce three beams up to 1000 miles apart, each separately steerable and of equal or unequal power. This may make the SPS practical up to about two gigawatts = 2000 megawatts where the cost per megawatt-hour may be least.
There are, of course, other considerations: More rectennas are needed which are typically only used an hour or two per day. Very costly but it does allow other uses for the square mile plus perhaps 22 hours per day. There will be brief periods when the SPS is over the Atlantic or Pacific ocean, when only a small portion of the 2000 megawatts can be safely sent to a rectenna. Co-operation of many countries will be needed as the rectennas are needed in nearly every tropical and semi tropical nation. The SPS can swing briefly away from the Equator in a semi polar orbit, but I think that will mean one, likely more, days per month that the SPS will be too close to the horizon to safely beam the needed amount of electricity to a rectenna in the temperate zone. I have not been able to think of a quick way to turn off the 2000 megawatt beam, except at very high cost, so it will occasionally pan (defocused perhaps) across densely populated area. Options for interrupting 5000 megawatts dc are more complex than flipping a switch. It tends to arc horribly even in the vacuum of space. I say 5000 megawatts as I think the various losses are much higher than the optimistic projections, and I recommend 50% efficient traveling wave tubes/klystrons, instead of 70% efficient magnetrons, as the former can be modulated with wide band data which can be received with a modest antenna over 1/2 of the solar system plus 1/2 of Earth's surface. Neil
I was just thinking about this last night for some reason. Weird. I am a complete imbecile when it comes to science, but I'm interested.
Thanks for the thread
Re: SPS = solar power Satellite
neil wrote:This is about SPS = solar power satellite and alternative energy. I love to analyze. An important consideration is most communities need about twice as much electricity near sunset as the average for the rest of the day = the peak demand period. This is about the time surface solar stops making electricity. Like nuclear, geo-stationary SPS has the same output 99% of the time, so costly polluting, gas turbines are run about an hour per day to make the extra power for peak demand and rare down time emergencies and maintenance.
If we orbit the SPS at about 1/2 the GEO-synchronous altitude, the satellite stays over the sunshine terminator, or close by. This is called a solar synchronous orbit. Closer means the transmitting antenna on the satellite can be smaller, saving perhaps 100 billion dollars construction cost. This SPS beams the energy to the communities where it is needed most. I believe the transmitting antenna can be designed to produce three beams up to 1000 miles apart, each separately steerable and of equal or unequal power. This may make the SPS practical up to about two gigawatts = 2000 megawatts where the cost per megawatt-hour may be least.
There are, of course, other considerations: More rectennas are needed which are typically only used an hour or two per day. Very costly but it does allow other uses for the square mile plus perhaps 22 hours per day. There will be brief periods when the SPS is over the Atlantic or Pacific ocean, when only a small portion of the 2000 megawatts can be safely sent to a rectenna. Co-operation of many countries will be needed as the rectennas are needed in nearly every tropical and semi tropical nation. The SPS can swing briefly away from the Equator in a semi polar orbit, but I think that will mean one, likely more, days per month that the SPS will be too close to the horizon to safely beam the needed amount of electricity to a rectenna in the temperate zone. I have not been able to think of a quick way to turn off the 2000 megawatt beam, except at very high cost, so it will occasionally pan (defocused perhaps) across densely populated area. Options for interrupting 5000 megawatts dc are more complex than flipping a switch. It tends to arc horribly even in the vacuum of space. I say 5000 megawatts as I think the various losses are much higher than the optimistic projections, and I recommend 50% efficient traveling wave tubes/klystrons, instead of 70% efficient magnetrons, as the former can be modulated with wide band data which can be received with a modest antenna over 1/2 of the solar system plus 1/2 of Earth's surface. Neil
How do you propose to beam the energy back to earth? How are you going to generate a 2000 MW beam in space? Where is this energy coming from, how will you harness it, then how will you transfer this energy to earth, through the atmosphere. Remember, the atmosphere contains water particles which also scatter light.
I'm not debunking your premise, but some more information would be helpful if you want to have a discussion about the feasibility of the project.
Hi Joe: Those are all reasonable questions and concerns. I'm doubtful that SPS will ever send even 1% of Earth's energy from space. I love to analyze and some of the concepts will have important future applications.
The 25 million dollar study about 1985 mostly considered microwaves, perhaps 455 megahertz, as we have built almost a billion microwave ovens at that frequency. With recent advances, we might consider 100 times that frequency or more. This should cut the cost of the transmitting antenna, and perhaps deliver the energy with greater precission. Lasers have been considered, but not too seriously, likely due to the absoption losses being higher than the microwaves passing though the atmosphere.
Several square miles of photo voltaic panels is the usual source of energy, but a giant mirror has been been considered that focuses the energy on a boiler making high temperature, high pressure steam which drives a turbine which turns an alternator. The main problem with the latter is several humans are likely necessary on the satellite 24/7, while there is hope the solar panel installation and repair can be fully automated. A laser beam could be aimed at an ordinary photo voltaic array on Earth's surface, except one square mile plus and tilted to the South for locals in the North temperate zone.
The micro wave receptor is typically called a rectenna, also a square mile plus with up to a billion dipole antennas, each driving a fullwave voltage doubler. Perhaps 300 of these doublers in series drives an inverter. Several hundred inverters in series drives a high voltage power line connected to the grid. Two other series strings drive the other two phases of the grid. The series output connections can be avoided by using transformers, but this looses another 10 to 15% as the transformers must have very high voltage insulation. Neil
sry man i think your getting to far ahead of yourself, besides there are simpler solutions to the problem that are far more feasible. Such as wind power i believe that if you were to build a sky scraper like cage and have it filled with wind genirators you would be better off.
the size of the building would account for wasted ground space( as you likely know wind generators tend to be space consumming) also do to the hieght of the building i think it would provide more powerful winds to your generators.
You could just strap a turbine onto John Kerry's mouth and keep D.C. up and running no problem.
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