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Each solar array on the International Space Station can generate a maximum of about 32KW. Each solar array has a mass of 15,824 kg. (source) For the purposes of simple math, we'll say that we can get about 2KW per metric ton of solar array. A good-sized power plant's electrical output is often at least several hundred megawatts, if not several gigawatts. 1GW is a good round number. So about 500 metric tons, or 500,000kg of solar arrays (not counting microwave rectenna, or thrusters to keep the satellite in position, or any of the other structure that would be necessary). Assuming we use the not-yet-built Falcon Heavy rocket, and assuming a projected payload cost of $1,000/lb, or roughly $2,200/kg (and that's generously assuming SpaceX gets everything right with their plans for reusability), it would cost about $1.1 billion dollars just to lift the solar arrays to orbit. But wait, it gets a lot worse. Because that's the cost to low Earth orbit, or LEO, where our bigger-than-the-entire-ISS satellite would be whizzing around the planet once every 90 minutes or so. That's not really suitable for power generation; we need to get it to a much higher orbit, which is much costlier. The projected maximum payload for Falcon Heavy is 53 metric tons to LEO, but only 19 metric tons to a geostationary transfer orbit! We'll be generous again and assume that this ratio applies to the final payload to geostationary orbit itself. This effectively raises our launch cost by a factor of at least 2.8, meaning it would cost about 3.1 billion dollars - again, this is only to lift the mass of the solar arrays into orbit. This doesn't cover actually building a modular solar array satellite bigger than the International Space Station, nor does it cover building the receiving antenna or power infrastructure on the ground. Better hope you can design it to be remotely assembled without a human presence, because manned missions will rapidly inflate your costs too. Additionally, you're not going to get 100% efficiency from transmission either, meaning that your 1GW maximum solar array will not translate to 1GW of electricity on the ground. Palace of Hate posted:we could just build like 100 nuclear power plants instead of this stupid rear end bullshit exactly CommieGIR posted:We already do that, it called a solar concentration and the most powerful one is 344 MW and takes up more space than 4 nuclear plants. Ivanpah also winds up burning a shitload of natural gas
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Apr 15, 2015 17:20
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Rebel Blob posted:If you can keep the costs under $20 billion, it would still be less than what the US military spent annually on air conditioning during the Iraq & Afghanistan wars. This is all just to build one solar power satellite with a hypothetical 1GW capacity, and assumes that it would not run into massive cost overruns due to unforeseen difficulties (and also that there would be minimal transmission losses, and that it would be roughly as simple as throwing up a half metric kiloton of solar panels, plugging them into a big microwave transmitter, and aiming it at a rectenna on the ground). We also haven't discussed what happens if a huge solar flare hits the solar power satellites. I like the idea of a constellation of solar power satellites, and maybe eventually the engineering would get worked out, but even as a huge space nut I firmly believe we'd be better off spending that money on building fleets of nuclear reactors on the ground.
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May 5, 2015 19:56
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