I've been saying for years (in company with many sages of science fiction writing, who first postulated the idea decades ago) that the future of our energy needs lies with the Sun. Not solar power cells on Earth, you understand, but much larger and more efficient ones in orbit. In theory at least, a network of energy (i.e. electricity-generating) satellites could provide all the energy our planet needs, with plenty to spare.
Now it seems that the first steps are being taken to make this a reality. Popular Science reports:
Japan has serious plans to send a solar-panel-equipped satellite into space that could wirelessly beam a gigawatt-strong stream of power down to earth and power nearly 300,000 homes.
The satellite will have a surface area of four square kilometers, and transmit power via microwave to a base station on Earth. Putting solar panels in space bypasses many of the difficulties of installing them on Earth: in orbit, there are no cloudy days, very few zoning laws, and the cold ambient temperature is ideal.
A small test model is scheduled for launch in 2015. To iron out all the kinks and get a fully functional system set up is estimated to take three decades.
There's more at the link. The project costs are estimated at $21 billion at present; not small change, to be sure, but I guess such startup costs are inevitable. However, if the experiment works, and the technology can be scaled up, the costs can be recovered through fees charged for the electricity it will generate. After all, running costs of production will be minimal - sunlight's essentially free for the taking. All the expense is in providing the hardware, both in orbit and on the ground.
This will bear watching . . . and one hopes NASA will get in on the act. It'd be galling in the extreme to have to pay Japan for most of our electricity, just as we currently pay OPEC for most of our oil!
Peter
5 comments:
It will be REALLY interesting for them to try to get environmental permits for megawatt microwave... That will knock airplanes down, kill birds, and kill people...
What he said. Wireless power transmission exists now, but is only really practical for small loads, like a TV or cell phone (of course they use electro-magnetic induction instead of microwaves). This is a neat idea, but considering how some react to a few dead bats around a wind turbine, it may not go over too well when cooked geese start raining out of the sky (Christmas dinner, anybody).
You really do not want to stand in the beam of a gigawatt microwave beam. Even one spread over four square klicks.
The real problem with microwaves is rectification of 3 to 30 billion cycle per second (3 to 30 gigahertz) RF into DC. The diode rectifiers currently available are good for a few volts and could probably be stretched to a few hundred and still operate at microwave frequencies. That would need to be stretched to a megavolt plus "headroom" before such a system became truly practical.
From a practical standpoint, a solar mirror/metal vapor boiler setup would be both simpler and cheaper. After all, lift is the most expensive part of the operation.
If you go with microwaves you must convert infrared into microwaves. Meaning you must lift the solar boiler PLUS the AC or DC generating equipment, and addition to the DC powered microwave generator into orbit. That would be very heavy - and require a lot of lifting capacity.
With the solar mirror, the only thing you lift is the basic mirror, with a much longer focal length (flatter), plus the positioning equipment. And that is much cheaper in the long run.
With that setup, you will need a minimum of 36 square miles on the terrestrial side, largely for a buffer zone so the reflected energy does not fry Phoenix or some such.
Stranger
The power density can be reduced to levels that are safe for birds, planes or walking through. In turn, that requires more acres on the ground, which will have to be in shade all the time.
This idea has been around for quite some time, and there was a big article on it in (now defunct) "The Industrial Physicist" around 5 years ago. I always thought of it as the Microwave Power Amplifier Engineer's Full Employment Program.
One of those oddities of physics is that there is less power loss in free space propagation than in wires for microwaves. Low frequency AC (of course) won't go anywhere without wires. Otherwise, those microwave point to point links wouldn't use towers, they'd string cables.
That would be money better spent on fusion, or advanced fission plants, or damn near any other thing.
Jim
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