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Focused Microwaves Could Enable Wireless Power Transfer
esocid alerts us to news out of the University of Michigan, where physics researchers have found a way to focus microwaves to a point 20 times smaller than their wavelength using a new 'superlens'. Such resolution was thought to be impossible until recent years, and it could bring about the capability to transfer power wirelessly.
"No matter how powerful a conventional lens, it cannot focus light down to more than about half its wavelength, the 'diffraction limit'. This limits the amount of data that can be stored on a CD, and the size of features on computer chips. The new lens is a 127-micrometer-thick plate of teflon and ceramic with a copper topping. 'The beauty of these is that they're planar,' Grbic says, 'they're easy to fabricate.' The lenses can be made through a single step of photolithography, the process used to etch computer chips."
I know what you mean, messing with wireless power is a seriously bad idea. Tesla tried it too, and look what happened to him. He's DEAD!
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What I remember from studying this technology 15 years ago was that it was possible to create a beam sharper than the diffraction limit, but the result was diffuse spill-over. That is, one could create an extremely sharp main lobe in the beam pattern, but one had to suffer higher side-lobes. That's OK for imaging and lithography applications -- the spill-over is diffuse enough not to cause too many problems. But for power applications it means both inefficiency (power lost to the side lobes) and irradiation for people who think they aren't in the beam.
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We're just trying to work out all the bugs :p
which is totally what she said
Back in the 1960's. Diode grid to rectify the beamed power. Bad idea.
Actually it was a very GOOD idea. But NASA blew it.
The plan was to site solar power satellites in geosync orbit and bring the power back via microwaves.
Unlike microwave ovens (which are tuned to a frequency that is strongly absorbed by water), these would be tuned to a frequency where water - clouds, rain, birds, cows, people - is essentially transparent. This is good both for getting the power through the atmosphere and avoiding rains of roast duck.
I could go into detail on why there's no problem from the millimeter waves, but that would take time. Short form: System failures defocus the beam so much it becomes just radio interference in directional antennas pointed at the satellites. Even when fully focussed it's not an issue for tissue: You can grow crops and graze cattle under the (rather spindly) rectennas, so they don't even use up the chunk of land they're on.
Benefits:
- Enough power to completely replace fossil fuel AND nuclear plants and absorb forseeable energy use expansion for decades.
- 'Way cheaper, too. (Even at '60s fuel prices.)
- Essentially no pollution at ground level.
- Bootstraps a space program that can then move other manufacturing processes, and THEIR pollution, off the planet as well.
NASA blew it by doing a study that purported to show it would be too expensive. But they did that by splitting the design teams for the rockets and the power plant. The power plant designers made a turbine very large to get a couple extra percent of efficiency. Then the rocket designers came up with a heavy lifter sized to take the biggest piece. Result: Enormous rockets with few trips to ammortize the design/construction costs, rather than moderate sized ones with many trips. Cost skyrockets versus a properly integrated design with a small turbine and a fleet of smaller lifters.
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Depends on how much the power is needed, and how soon. The space elevator seems like it's a long time away, still in need of new materials to be invented, and so on. On the other hand, solar power in space is feasible now, at least technically.
Without power people die. So the risks of catastrophic failure of microwave power transmission from space, must be weighted against the possibility of many people not getting electricity. It might be safer to build powerplants now, than to wait for a hypothetical space elevator.
The issue with wires is that you will have IR drop and I^2R power losses. If you make the wires thicker to cut the resistance and losses, you have now made the wires heavier. Plus, you have to somehow support the weight of all that wire which means the tensile strength must be huge.
On the other hand, if you beam the energy down, you will have much lower losses provided the atmosphere is transparent at the wavelength you use to send the energy. All you will get from beam spread will be a lower energy density but the same total amount of energy (aside from absorption and scatter losses) will be available.
Beaming power down is probably a much more efficient way to go depending on conversion losses at the source, the scatter and absorption losses, and the conversion losses again at the receiver.
I don't know about the efficiencies and losses of beaming but would guess they would be much less than however many miles of cable would be required and would bet the cost would be lower as well.
You would just need to make damn sure you switch the beam off if it quits tracking the target receiver. Bu as the other person commented, I think this isn't intended to beam power from space.
I don't know if he's correct, but even a small amount of thought should show you a lot of possible ways.
* No exposure to the elements, thus reduced maintenance cost from wind/weeds/corrosion
* No land cost
* No clouds, no day/night cycle
* Cost is based on weight, not on land, potentially allowing for use of extremely large light cheap panels instead of smaller denser more expensive ones
Does it make up for the difference? I couldn't say. But there's four ways in which space beats land in terms of efficiency.
Breaking Into the Industry - A development log about starting a game studio.
What I was referring to was current squared times resistance which equals power. The R was resistance and not radius. V = I * R, and W = I * V. Therefore, W = I * I * R.
Likewise, the IR drop is also just Ohm's law which equals voltage. The resistance will have some value per unit length and the longer the length, the more voltage drop.
The way to drop the current, so the I^2R (watts) losses can be reduced is to increase the voltage. But as you go to higher voltage, and higher altitude, where the air pressure starts getting low enough to support a plasma discharge, insulation starts getting important which just leads to more weight, etc.