Solar energy

Jay-qu · 11-05-2005

Quote:

Originally Posted by alexander

we could always just send 2 satellites up in space and connect them with a wire and harness the power of the earth's magnetic field...

which isnt much power... The field is weak and its fading - it is at most 60microTesla on the surface, Im not sure if its stronger or weaker in space...

CraigD · 11-06-2005

Quote:

Originally Posted by alexander

we could always just send 2 satellites up in space and connect them with a wire and harness the power of the earth's magnetic field...

There’s a problem with the basic Physics of a “power tether” schemes like alexander describes. Such a system is essentially just a DC electric generator – it’s not extracting energy from the Earth’s magnetic field, but from the kinetic energy of its armature – the satellites and tether. To maintain the satellites in orbit requires that they be boosted, presumably with the usual hydrazine or combustible rocket propellants, which, unless the satellites are launched with huge masses of fuel, must be periodically refueled via supply rockets. However it’s done, the mechanical parts of the system and all the fuel it uses must be boosted into orbit, which requires a lot of propellant and other pricey stuff, not to mention safety and pollution concerns. In addition to its generating and orbit-maintaining parts, it needs parts to “beam” the energy back down to the ground.

All the system is, in essence, is an inefficient, expensive rocket-powered electric generator, not much good for generating power to be used on the Earth’s surface.

For generating electricity to be used by the orbiter, power tethers appear to be promising – they can generate a lot of it, and might be mechanically simpler than other generators, such as solar cells, fuel cells, or conventional generators. They’re also potentially very versatile – like any electric generator, they can be “run backwards” to be a motor, allowing an orbiting spacecraft to be maneuvered, even de-orbited into atmospheric reentry, using nothing but electricity. In fact, most interest in orbital tethers is currently focused on their tether propulsion potential.

Actual experiments with tethers in orbit have proven them tricky to keep from power surging, shaking, and breaking, but who doesn’t like an engineering challenge

alexander · 11-07-2005

i never said it was supposed to be easy, but then what in this world is easy?

CraigD · 11-08-2005

Quote:

Originally Posted by alexander

i never said it was supposed to be easy, but then what in this world is easy?

Please allow me to clarify post #12.

Generating power using 2 orbiting satellites connected by a wire is innately not a good way to generate electric power to be used on the ground – you’d do better to burn the fuel you’d use to launch them and maintain their orbit in a conventional powerplant generator.

It’s potentially a good way to generate electric power to be used on the satellites, and an even better way to use electric power on them. To realize this potential, several seemingly tricky – and rewarding - engineering challenges must be met.

The payoff of working out the problems of tether propulsion is big. Imagine …

a solar powered satellite with limitless maneuvering energy, able to change orbits at will. As long as it doesn’t mechanically wear out, such a satellite would last forever, never falling to Earth because of a decayed of orbit.
a vessel able to quickly rendezvous with satellites in many orbit, carrying people, performing maintenance, etc., but requiring no expendable reaction mass.

Tether power is less promising as a generator of power than as a consumer of the ample solar power available in earth orbit.

alexander · 11-08-2005

what if there was a possibility of wirelessly transmitting electrical current without loss, say through a controlled wormhole...

CraigD · 11-08-2005

Quote:

Originally Posted by alexander

what if there was a possibility of wirelessly transmitting electrical current without loss, say through a controlled wormhole...

It matters not. The system is still an electric generator that requires a lot of energy (a launch into orbit) before it can begin requiring energy to maintain its orbit, which is converted into electricity.

The only way to get “free energy” via the Earth’s magnetic field, as near as I can tell, is to erect a rigid, conductive, 300 km pole from its surface to the ionosphere. This would then allow electricity to be generated by slightly reducing the Earth’s rate of rotation (so it’s not really “free”, just abundant – the earth has about 2*10^29 joules of kinetic energy – enough for 10^16 seconds (300 million years) of power at current world power demands. The material engineering challenges of erecting a 300 km tall rigid tower capable of withstanding the force of generating a substantial fraction of the worlds total power demands, however, are daunting!

Erasmus00 · 11-08-2005

Quote:

Originally Posted by alexander

what if there was a possibility of wirelessly transmitting electrical current without loss, say through a controlled wormhole...

Regardless, magnetic fields don't do work, so any power you gain comes from power you put in. Sattelites would generate electricity by slowing down (or using fuel to increase their thrust). Its not extracting energy from a magnetic field, its extracting energy from sattelite fuel, which we can burn on the ground.
-Will

learnin to learn · 11-09-2005

Quote:

Originally Posted by alexander

we could always just send 2 satellites up in space and connect them with a wire and harness the power of the earth's magnetic field...

lol that would be awsome.... but is it possible?

learnin to learn · 11-09-2005

What about nuclear fusion? I know we do not yet the technology to accomplish this amazing feet but, do yall think it is even logically possible for us to use nuclear fusion here on earth?