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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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While it's nifty that they can focus EM radiation to a smaller point now, I'm not following how this will enable wireless power transfer.
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.
Two wrongs don't make a right, but three lefts do.
If the limits on a CD are because of conventional lenses, and this can get 10 times the best a lens can do, it follows that a superlens-based CD, DVD or Blu-Ray system could get 10 times the capacity per track and 10 times as many tracks (in other words, 100 times the capacity). That would be some serious storage space.
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We're just trying to work out all the bugs :p
which is totally what she said
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It's interesting to consider whether power beamed down from orbit even has much of a future. If space elevators ever become a reality, it seems much safer just to have power from orbital solar arrays wired back down the elevator than beam it, where anything passing through could be fried.
Firstly, it's horribly inefficient. There are significant losses over the signal path that hand waving won't make go away. And then there's the real show-stopper: high power microwave beams would be a hazard to aviation, shipping, or anything or anyone else who got in the way.
There'd be enough scattering of the beam to spread the danger around. Sure, this technology is possible - but there just don't seem to be any practical applications for it. Wire is much more efficient and airmen have a chance to see and avoid it. They'd never know that microwave beam was there until they entered it.
Beaming power in from space is a perennial favorite - but nobody ever seems to be able to get around the atmospheric effects. And I'd prefer to not have any randomly scattered ionizing radiation impinging on my home, thanks.
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.
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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.
Didn't we try this in Sim City? Look how well that worked out.
The energy in question is coming from the sun, and was going to enter the biosphere anyway.
To a certain extent, the effect will be the exact opposite of what you are thinking, as the sunlight would have most assuredly heated the land, sea and air, but beamed down to the electrical grid, it will be stored in other forms, such as the potential energy of a high-rise building, or in places where the increased warming isn't terribly important, like the area immediately around a ski lift.
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.
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Actually, NASA's study got it exactly right. The amount of solar-collecting material you'd need to place into orbit is large enough that you'd spend a lot more energy and money getting it into orbit then you'd ever get back from it once it was functional. Things may have improved since then (more efficient rockets, lighter solar panels, etc), but I doubt they've improved so much as to make the plane feasible yet. I'd re-do the feasibility studies after the space elevator is up and working, getting enough mass into orbit will be a lot cheaper then
I don't care if it's 90,000 hectares. That lake was not my doing.
No, the problem is that carbon dioxide is acting as a blanket, trapping too much heat beneath it.
How is adding more energy to the equation going to do anything but make it worse?
It's not a heat beam, it's a microwave beam. There's a big difference between the two. The amount of heat generated by the beam when it reaches the receiver would be insignificant, and it would generate no heat when going through the atmosphere, because the wavelength chosen would be one that is transparent with respect to air. So the net effect would be practically zero added heat. (Even if you count the heat generated by the motors powered by the resulting electricity, it's still insignificant compared to the heat trapped by CO2 in the atmosphere) And if we use that device to replace traditional fossil fuels, then its net effect would be a significant reduction in CO2 output.
There are good reasons why in-orbit solar power isn't a good idea at this time, but your reason isn't one of them.
I don't care if it's 90,000 hectares. That lake was not my doing.
... replacing our entire energy consumption with external sources only increases the energy flux striking the Earth by about 0.01%.
Actually, replacing ground-generated electricity with space solar power REDUCES the heat load.
First: Ground generated electricity is made with big heat engines, limited by the carnot cycle. In addition to the heat released by using the energy, there's the heat released on the cold side of the heat engine. The total is a lot more than you bought and used.
But with space solar power the cold side of the heat engine is in space, radiating toward the sky (with it's black body temperature of 4 degrees absolute). The dumped heat misses the earth. All you heat with is the useful power and a few percent losses. (The sky-to-ground system is estimated to run in the range of 90% efficient and only part of its losses are on the ground.
But far more significant: Fuel-driven ground generators release carbon dioxide, which continuously traps solar power as heat until it's eventually scrubbed from the atmosphere decades or centuries later. That is a big multiple of the useful power actually delivered. No fuel burned on Earth, no CO2 pumping the greenhouse.
The main problem will be keeping us from sliding into an ice age over the next 400 to 1,200 years. (According to one model the current interglacial peaked at about the dawn of agriculture and we've been essentially regulating the earth's temperature as the "furnace" output has been curving down for the last 6,000 years or so, with a slight bump since industrialization. Stop the CO2 and we'd quickly crash back onto the steepening slope of the cooling curve.) But that takes decades to centuries. So we can decide what to do about it in a few generations, when we start to get below the old "regulated" temperature.
One nice thing: If we need to bring in more heat from space we'll have the infrastructure to do it. B-)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
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.
So if the energy efficiency of the panel/beam is greater than about 100%-37%-5% = 58%, then this system will result in more heat than would normally occur from the sunlight.
Of course, even if it does significantly increase the amount of heat generated for the fraction of sunlight that it captures, that is still a tiny fraction of the sky that is covered, and the net result will be completely negligible compared to just about anything else.
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