Today in Mad Science News

High-flying kites could power New York
"There is a huge amount of energy available in high altitude winds," said coauthor Ken Caldeira. "These winds blow much more strongly and steadily than near-surface winds, but you need to go get up miles to get a big advantage. Ideally, you would like to be up near the jet streams, around 30,000 feet."

"We found the highest wind power densities over Japan and eastern China, the eastern coast of the United States, southern Australia, and north-eastern Africa," said lead author Archer. "The median values in these areas are greater than 10 kilowatts per square meter. This is unthinkable near the ground, where even the best locations have usually less than one kilowatt per square meter."

Several technologies have been proposed to harvest these high altitude winds, including tethered, kite-like turbines that would be floated to the altitude of the jet streams at an altitude of 20,000-50,000 feet and transmit up to 40 megawatts of electricity to the ground via the tether.

Nokia developing phone that recharges itself without mains electricity
A new prototype charging system from the company is able to power itself on nothing more than ambient radiowaves - the weak TV, radio and mobile phone signals that permanently surround us. The power harvested is small but it is almost enough to power a mobile in standby mode indefinitely without ever needing to plug it into the mains, according to Markku Rouvala, one of the researchers who developed the device at the Nokia Research Centre in Cambridge, UK.

The difference with Nokia's prototype is that instead of harvesting tiny amounts of power (a few microwatts) from dedicated transmitters, Nokia claims it is able to scavenge relatively large amounts of power -- around a thousand times as much -- from signals coming from miles away. Individually the energy available in each of these signals is miniscule. But by harvesting radiowaves across a wide range of frequencies it all adds up, said Rouvala.

The trick here is to ensure that these circuits use less power than is being received, said Rouvala. So far they have been able to harvest up to 5 milliwatts. Their short-term goal is to get in excess of 20 milliwatts, enough power to keep a phone in standby mode indefinitely without having to recharge it. But this would not be enough to actually use the phone to make or receive a call, he says. So ultimately the hope is to be able to get as much as 50 milliwatts which would be sufficient to slowly recharge the battery.

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23 Responses:

  1. jwm says:

    See also: Pomegranate Phone. Be sure to review all the special features.

  2. vordark says:

    On the kite/wind front, maybe someone can explain something to me: How come humans can't breathe at 30K feet, but there's still wind? I'm not disputing anything, I'm just curious as to how these two (seemingly contradictory) points are resolved.

    • dmlaenker says:

      For the same reason jets can intake enough oxygen to fly at 30K feet, I'm assuming.

    • andr00 says:

      Humans are fragile wusses that can't survive outside a very narrow range of environmental conditions. It's not that there's no atmosphere up there - it's just not good enough for prissypants sapiens.

      • vordark says:

        Given this, and the earlier comment about jet engines, I am deeply disappointed by our race. If the atmosphere is good enough to supply enough oxygen to drive 170+ tons of metal (the pre-passenger weight of a 747), it should be good enough to keep my fat ass alive.

        • If I'm not mistaken there's enough oxygen to keep your fat ass alive but not to run the really awesome smart part of your brain.

        • I think if you were moving at just under Mach 1 and had your mouth wide open, the problems you would have with survival would not be due to a lack of air.

    • kowh says:

      Looks like it's not the amount of oxygen that is the problem as much as the pressure of the oxyxgen. Too low and we can't get the oxygen into where it needs to go.

      As far as I can tell, the range we can support is roughly 0.16 bar to around 1 bar of partial oxygen pressure (the total air pressure * the fraction of the air that is oxygen). By way of comparison, the partial pressure of oxygen at sea level is about 0.21 bar.

      Too low and we get hypoxia, too high and we get hyperoxia. I agree, we need aftermarket upgrades to handle things like this.

      • lionsphil says:

        Aren't those called "breathing apparatus"?

        There's something to be said for the squishy brainmeats being able to develop their own extensions to their support infrastructure.

      • anyfoo says:

        Sure it's not the other way around? If we can't get enough oxygen, wouldn't that be hypoxia? And hyperoxia would be too much?

        • kowh says:

          Isn't that what I said? Partial pressure too low -> can't get enough oxygen -> hypoxia. Partial pressure too high -> get too much oxygen -> hyperoxia.

          • anyfoo says:

            > Too low and we get hypoxia, too high and we get hyperoxia.

            Ah. Sorry. I read "too low" and "too high" with respect to altitude, not air pressure, wondering how you'd get hyperoxia from being too high in the sky where there's less pressure %)

            • kowh says:

              Heh. Is it even possible to get hyperoxyia just from altitude?

              If air pressure was the only factor you would have to be over 16 km below sea level and the deepest mine in the world seems to be about 4 km.

  3. strathmeyer says:

    Why, why don't they power phones with kinetic energy, like they do watches?

  4. skington says:

    I read something about this a few months ago, where they were talking about how you engineer a tethered wind turbine that's designed to sit 30,000 feet up in the air, and, particularly, what happens when the wind slackens. At this point, you reverse the flow of current through the tether cable, powering the blades of the turbine, so it turns (briefly, until the wind flow picks up again) into a helicopter.

  5. aris1234 says:

    Wasn't 'power from the airwaves' busted by Mythbusters some years ago?

  6. lionsphil says:

    My concern with this kind of stuff is what the climate effects of slowing the jet stream down are (by forcing it to do work turning turbines) at the kind of scale you'd need to deploy this to make it anything other than a local curiosity.

    • djquack says:

      Exactly. We're going to fight climate change by using alternative energy sources which...change the climate? What?

    • leolo says:

      I strongly suspect that the amount of energy we'd remove from the jet stream would be staggerlingly small, compared to the amount of energy present.