Space-Based Solar Optics to Power and Protect Earth
June 24, 2007 - 5:36 pm | Filed under: solar, conservation, greenhouse, planet, tree hugger, defense, ecology, earth, environment, economics, Miscellaneous, energy, Technology
Further brainstorming over a solar array / weapons defense system did produce one interesting possibility: a low-cost space-based mirror array for CSP (concentrated solar power). The idea seems silly at first glance because it seems far easier to place the optics on earth close to the energy converting apparatus - however some out-of-the-box thinking (as shown below) reveals that space-based optics could be far easier, cheaper, maintenance free, and effective than an earth-based solution (note that optics can be the biggest cost and maintenance for CSP):
1) Orbiting the earth are giant concave mirrors (parabolic in shape), each 7 square miles in area made from ultrathin reflective fabric (like mylar) stretched between 3 structural points (2 miles between each point in this example). Each mirror keeps its parabolic shape by solar wind. Secondary optics are also located at the focal point of the mirror and continually adjust to redirect the beam of concentrated light back to a receiving solar plant on the earth where the suns rays would be converted to usable energy.
Oh yeah, another thing … this can indeed also be used as an anti-missile defense system if multiple arrays are used, providing round-the-clock protection, while being tons cheaper than any other Star-Wars type technology. It overcomes all the problems of the Solar Missile Defense scenario posed below and has countless advantages.
Also, nighttime surveillance in other parts of the would could be as easy as turning on a light bulb, and can you imagine the psychological effect it could have on the enemy?
1) Orbiting the earth are giant concave mirrors (parabolic in shape), each 7 square miles in area made from ultrathin reflective fabric (like mylar) stretched between 3 structural points (2 miles between each point in this example). Each mirror keeps its parabolic shape by solar wind. Secondary optics are also located at the focal point of the mirror and continually adjust to redirect the beam of concentrated light back to a receiving solar plant on the earth where the suns rays would be converted to usable energy.
Above: a small section of a giant array of parabolic reflective fabric mirrors.
2) Innumerable additional 7 sq.mile mirrors can be simply added, each requiring only one additional structural point, 7 more square miles of reflective fabric, and optics at the focal point of each mirror to send the concentrated solar power to a receiving solar plant on earth.
3) The incoming solar power would be distributed among receiving solar plants strategically placed on earth, so each plant would receive the maximum amount of suns possible without damaging the energy conversion facilities. Maintenance could be performed on these earth-based solar plants at night.
The solar reflectors, being in the vacuum of space, would never require any kind of maintenance. Periodic adjustments can be made to keep them approximately facing the sun via temporarily collapsing one mirror to let solar wind push the array back into orientation. The focal point optics necessary to send each mirrors rays to the right location on earth would be powered by solar power of course.Oh yeah, another thing … this can indeed also be used as an anti-missile defense system if multiple arrays are used, providing round-the-clock protection, while being tons cheaper than any other Star-Wars type technology. It overcomes all the problems of the Solar Missile Defense scenario posed below and has countless advantages.
Also, nighttime surveillance in other parts of the would could be as easy as turning on a light bulb, and can you imagine the psychological effect it could have on the enemy?
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The only possible glitch I see here is keeping the secondary optics from overheating. Space is a vacuum and vacuum is an insulator. It may radiate enough heat to stay cool, but I just don’t know.
Comment by — June 25, 2007 @ 9:22 am
My math was wrong on point #2. With each additional structural point two (not one) 7 mi^2 solar panels can be added depending on the geometry.
I also think the challenge of overheating optics can be addressed by using only reflective optics (mirrors) with nearly perfect reflectivity - which is entirely possible. Given an overheated condition a bimetal contraption could move them out of the focus point until sufficient heat has radiated into space afterward the bimetal system would naturally bring the optics back into play.
Comment by — July 11, 2007 @ 6:37 pm
How will a 7 sq mile parabolic umbrella avoid all that space debris?
Comment by Sadler — September 11, 2007 @ 9:24 am
Interstellar material will go right through it, leaving a hole no bigger than the material. This should have a negligible impact over it’s lifetime. Space junk would be a bigger problem. It would need to be well outside of the envelope of space junk. One possibility would be for it to not orbit the earth, but rather trail the earth as the earth revolves around the sun. If placed correctly this should prevent it from being pulled into the earth and will indefinitely maintain it’s relative position.
Japan is proposing a similar system, where the sunlight is converted into a laser beam before it is sent to earth: http://www.treehugger.com/files/2007/09/orbiting_space.php
I’m thinking the system I proposed would have to do something like this as well especially if we’re talking about the distances I’m proposing here.
Another thing to consider: using these beams to propel spacecraft. This has already be proposed with the “solar sails” attached to the spacecraft, but rather than put a bunch of huge sails on the spaceship … the spaceship would only have one small sail that would collect the concentrated rays as sent by the huge solar array I’m proposing.
Comment by Dave Austin — September 11, 2007 @ 8:30 pm