From what I’ve read, harnessing the energy of a star requires building a “dyson swarm” of solar panel satellites that encircle the sun. How would this energy be sent back to earth though?
In the original idea of a Dyson Sphere (as thought up by Dyson) one doesn’t build solar collectors around the sun and beam the energy back. Rather, one builds space stations around the sun with solar collectors pointed at it, and you build so many space stations that you block out the sun completely from outside. Dyson’s hypothesis was that such a civilization would be undetectable via visible means, but that you might find one by searching for infra-red radiation given off by the structures.
Anywho, if your goal is to get energy out of the thing, one way would be to use the solar power to collect comets, electrolysize the ice, and extract the hydrogen into a canister of some kind, then shoot the canister at the earth to be collected.
Another strategy is to beam the energy back with highly-directional microwaves. The disadvantage is you need stationary receivers on the earth and if your aim is off you end up cooking people.
One really long extension cord.
This is a fairly major obstacle to the whole idea. There are a few ideas being kicked around, like using the solar power to run a huge microwave generator. The microwaves would be beamed down to earth to heat up water, which would run a turbine. One obvious problem with this is targeting. If the aim is just slightly off, that would have some rather suboptimal consequences. Another problem is that a lot of the power would be absorbed by the atmosphere.
Another idea I’ve heard is to use the solar power to split water into hydrogen and oxygen. The gasses could then be sent down to earth and combusted, releasing heat to drive a turbine and only water vapor into the atmosphere. The problems with this are, first, safely getting the gasses down to earth, and secondly, supplying the orbiting power stations with water.
Yep. A superconducting one.
By the time you get to a Dyson swarm, you don’t even have the option of beaming all that energy back to Earth because you’d fry the Earth. Missing microwave receivers isn’t even the issue. All that energy coming in means waste heat at every step that you use it - waste heat converting microwaves to steam, waste in converting steam to electricity, waste as you transport and use the electricity. Everything winds up as heat, and the Earth can only radiate it away at a certain speed. By the time you’re even 1% of the way to a Dyson swarm, there’d be too much energy on the Earth and the waste heat from our devices would cook the whole planet.
So the only way to keep expanding is to leave the Earth behind altogether, and that solves the transmission problem. Each part of the swarm collects and uses its own energy.
No - the microwaves are beamed into a rectenna (rectifying antenna) for direct conversion to DC current. This can be up to 90% efficient.
If you built a full dyson sphere absorbing the entire solar output you wouldn’t want to ship the energy back home as it would burn the earth to a cinder. For more modest goals, say powering a city, you could concentrate it into a microwave beam and send it back to a collector on earth. Just don’t miss.
all well and good and theoretical is important to consider, but, folks, we have plenty of unused southwestern desert perfect for setting up solar farms that will take care of our needs for as long as we can speculate we will be around. Enough unjustifiable money in the defense budget every year to execute the project over the next 30 years and, with the right storage technology (looks more promising every year) get rid of HC based fuels entirely, reserving the HC’s for chemical feeds.
Economics, today say to forget solar, it is still too expensive compared to marcellus gas, etc. but it won’t always be, and the problem is more a geopolitical one, national security, etc., than it is economic. Self-sufficiency is a great goal for the country and for each of us individually.
Isn’t one of the ideas of a Dyson sphere that you actually live on the surface of the thing? So there’s no question about how to “beam” the power back home, it’s already there. Just plug your solar panels into the (superconducting) power grid.
What are you doing with all that energy? Just put whatever your energy consumers are (superpowerful computers?) out in space right next to the solar panels.
Hmmm. Yes? No? It’s not a solid sphere, like a spherical version of the Ringworld. As friedo said, it’s an enormous number of space stations. If it were a solid sphere, gravity from the Sun would pull you off the surface, into the Sun. I guess you could live on the outer surface, but gravity would be too weak to maintain an atmosphere, so it would need pressurized rooms anyway. So you might live at the surface, but not on the surface.
Microwavescould transmit the power. Could.
I have no idea what the efficiency would be at 93 million miles.
NASA also worked on using lasers to transmit power across space.
Spin the sphere and you’ll have gravity and atmosphere on a sizable portion of it. The land mass would be incredible. The polar regions will have little/no atmosphere or gravity and make for nice rapid transportation hubs for inside of the sphere. Launch craft destined for the outside from the equator and get free kinetic energy.
Move the panels out of the way and let the sun shine directly on Earth.
BTW, Is there enough material in the Earth to even build a Ringworld, let alone a Sphere?
Instead of using the energy to power devices, why don’t we just use it to create matter (m = E/c[sup]2[/sup] … I’m sure we’ll have something worked out by the time we’re worrying about Dyson swarms) for more Dyson swarm space stations? No waste heat that way.
If you are building a Dyson sphere, you are going to disassemble the Earth anyhow. So that isn’t going to be an issue.
No. But you will probably have mined out the planets and asteroid belt for additional construction material by that stage, anyhow. The question of whether the solar system has enough silicon for a sun encompassing set of PV cells is another question. You would have to use direct conversion, I think. Using mirrors to focus light on a thermal generation system in space would lead to heat-management issues, I would expect.
^Additionally I don’t see a requirement for blanketing the sun. If we did even a fraction it would still be impressive.
Is a network of battery charging stations & transportation to/from earth conceivable?
And would they sell Slurpies?
Regards,
Shodan
Battery tech would have to get way better for that to be a good idea. I think the best batteries right now only store about 400wh/kg. So a ton of batteries would equal about 400kwh, or about $40 in electricity. Sending a ton of batteries to/from the sun to obtain $40 in energy isn’t going to be worth it. Like I posted earlier though, NASA has considered using lasers to transmit power. You collect the power, use it to shoot a laser (or microwave) at a receiving station and the station converts it back into power.
Lasers are also a potential method of interstellar travel. You have a spaceship with a large solar sail, and you have a laser on earth or in earth’s orbit, and you use the laser to hit the solar sail.
Again, I’m not a physicist. So I don’t know if microwaves or lasers would have high efficiency over the kinds of distances they would need to go to do this. The earth is 93 million miles from the sun, interstellar travel will require trillions of miles of distance.
On another note, there is enough potential energy on the earth via wind (including high altitude wind and offshore wind), solar, geothermal and nuclear to power hundreds of human civilizations. Energy demands in the developed world only go up about 1-2% a year, because increases in energy efficiency drive down demand. Refrigerators today use about 1/4 as much energy as they did a few decades ago, so even if more people buy them it still takes less energy.
So even if the entire world had western energy demands, that would only increase global energy demands by 200-400%. If current trends continue, those demands would grow by 1-2% a year, doubling every 40ish years from then on out. And again, since we have enough power on the earth to power hundreds of civilizations, I see no reason why we would need to create a dyson sphere unless we find some new technology that is insanely energy intensive and we lack the tools to make it energy efficient. An interstellar spaceship that expands and contracts spacetime could require a lot of energy. Aside from that, I don’t think we’d need dyson spheres anytime soon.