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Wearable Device Generates Electricity From Walking Knee Movements

Posted by timothy on from the walk-to-work dept.

Zothecula writes "If you've ever worn a knee brace, then you may have noticed what a large change in angle your knee goes through with every step you take, and how quickly it does so. A team of scientists from the U.K.'s Cranfield University, University of Liverpool and University of Salford certainly noticed, and decided that all that movement should be put to use. The result is a wearable piezoelectric device that converts knee movement into electricity, which could in turn be used to power gadgets such as heart rate monitors, pedometers and accelerometers."

26 of 99 comments (clear)

  1. Or.. by busyqth · · Score: 5, Funny

    It could be used to power a truly awesome joy buzzer.

    1. Re:Or.. by __aaltlg1547 · · Score: 2

      The really cool stuff is going to have to wait for a device that extracts food (sugars or fats) and oxygen from blood and makes usable electricity so it's directly powered by food. And it would have to give priority to your body, although perhaps you could program it to help you control your weight.

    2. Re:Or.. by p0p0 · · Score: 2

      Already done. Search slashdot for it. It'll be used to power small implants and uses sugar from the blood.

    3. Re:Or.. by Jeremi · · Score: 5, Insightful

      Already done. Search slashdot for it. It'll be used to power small implants and uses sugar from the blood.

      That's somewhat useful, but what we Americans really need is a device that runs on the energy stored in body fat. People could connect their home gaming rig to their beer belly's AC socket, and emerge at the end of their 8-hour Skyrim session significantly slimmer than when they started.

      --


      I don't care if it's 90,000 hectares. That lake was not my doing.
    4. Re:Or.. by amoeba1911 · · Score: 2

      you know some people will abuse it, plugging a hair dryer into their beer belly's AC socket and end up with hypoglycemia.

  2. Bending, not lateral movement by QuasiSteve · · Score: 2

    You could actually read the article.. only takes a few seconds.

    Known as the pizzicato knee-joint energy harvester, the device fits onto the outside of the knee. It is circular, and consists of a central hub equipped with four protruding arms, surrounded by an outer ring bearing 72 plectra (a plectrum is a plucking tool, such as a guitar pick). The ring rotates about a quarter of a turn with every bend of the knee, causing the plectra to pluck the arms. This causes the arms to vibrate (not unlike a guitar string), and itâ(TM)s those vibrations that are used to generate electrical energy.

  3. Travel! by rbowen · · Score: 5, Funny

    You could even use the power generated by your knees to travel from one place to another!

    --
    Apache guy, Open Source enthusiast, runner
    1. Re:Travel! by rbowen · · Score: 4, Funny

      I was talking about "walking." It was funny. Now it's not any more. Thanks a lot.

      --
      Apache guy, Open Source enthusiast, runner
    2. Re:Travel! by lobiusmoop · · Score: 3, Interesting

      Quick comparison with a regular AA battery... they are usually around 2000mAh, 1.5V, or about 3Wh energy. So about 1500 hours of constant knee movement at 2mW. Assuming a generous 4 hours/day of walking, this generates the equivalent of a single AA cell every year. Meh.

      --
      "I bless every day that I continue to live, for every day is pure profit."
    3. Re:Travel! by Anonymous Coward · · Score: 2

      It's not quite as bad as your math. For one things, AA batteries do not stay at 1.5v, they slowly drop eventually reaching close to 1v when they are dead. A better estimate would be 1.2/1.3v. Also, this is the initial stage, they want to eventually improve it to "provide at least 30 milliwatts" which is quite better then the 2mW figure you are using as it's not like this will be out on the market right away.

      But yes, I really don't see the point. Those small lithium cell batteries would provide years of life for this scale of power while being simpler and less annoying then a wearable device that may eventually break. This device provides no extra benefits, is more complex, and in the end, feels pretty gimmicky. I also have trouble seeing it being cheaper though admittedly, those small lithium batteries can be pricey sometimes.

  4. Re:More power by Anonymous Coward · · Score: 5, Informative

    Finally, a way to power our future borg implants.

    Except that we already had this technology in 2008. And /. user Promatrax161 called out the idea in 2005. But then he may have adapted it from a shoe based version in 2001.

  5. Failure by hort_wort · · Score: 4, Insightful

    I'm willing to go out on a knee here (sorry) and declare this experiment a failure. They have generated 2 milliwatts. Milliwatts -- my spellchecker doesn't even recognize that. For $15, I could get a 1,000 milliwatt solarpanel, tape it to my dang knee, and just sit there. Peizoelectric tech has amazing applications, but this one appears to be a dud.

    1. Re:Failure by Yosho-sama · · Score: 2

      "So far, the device has been able to harvest about two milliwatts of power. The researchers, however, believe that it should be a relatively easy to improve its performance to the point that it is able to provide at least 30 milliwatts – this ought to be enough to power a GPS tracking system, and to allow for advanced signal processing electronics, plus more frequent and longer wireless transmissions."

      Put that into perspective for whoever is giving this guy mod points. This device is in prototype stage. It has functional applications at a level which the inventors think would be an easily accomplished goal. Solar or batteries can be unavailable/cumbersome. I think the idea of this project is functionality at any time necessary.

      --
      My kingdom for a donkey!
  6. Re:More power by AngryDeuce · · Score: 3, Interesting

    I was thinking more along the lines of the stillsuit, which if I recall correctly was powered in via movement.

  7. Re:Next up ... by PNutts · · Score: 5, Funny

    Sex Power!

    Well, since this is /. you're talking about something that mounts to one wrist.

  8. The human dynamo by namgge · · Score: 4, Interesting

    Walking is a very low-energy form of movement that relies on some highly evolved bio-mechnics. Attempting to harvest a useful amount of energy introduces dissipation in parts of the 'mechanism' that have not evolved to handle it. The result can be anything from mild discomfort to quite serious injuries. So, such techniques are limited to a few mW, and are in most respects inferior to using a battery.

    It's been years since I saw a bicycle with a dynamo on it for similar reasons.

    1. Re:The human dynamo by olau · · Score: 2

      Reelights and Free Lights are examples of non-friction (in the mechanical sense) dynamos that are becoming quite popular. They don't generate an awful lot of power, but enough for LED safety lights, which is all you need if you live in a city with street lamps.

  9. Good luck... by fahrbot-bot · · Score: 3, Funny

    ...wearing that through a TSA checkpoint and onto a plane.

    --
    It must have been something you assimilated. . . .
  10. Perspective by subreality · · Score: 2, Interesting

    At 2 mW, you'd have to walk for over 1000 hours to generate the energy held in 1 AA battery. Rather than strapping a wonky device to my knee, I'd rather just carry a spare battery.

    Related, my bug out bag doesn't contain a hand-crank radio or flashlight. It has a couple packs of AAs, which are much lighter than the food to replace the energy I'd expend cranking. They'll last me at least a few weeks. If civilization can't reestablish itself in that time, I'm probably fucked, regardless of electricity.

    1. Re:Perspective by bemymonkey · · Score: 2

      Ah ok, I wouldn't like to carry that around either... I'm considering a fold-up 10W panel right now, which should weigh in at a similar weight, but I'm assuming I'll get 5W out of it at best... I suppose you use yours solely for charging a battery, which then powers the radios?

      I'm hoping to somehow transform up to 19V and then charge my Thinkpads (which idle just under 5W) with the 10W panel... might actually be enough to charge on particularly bright days, and enough to maintain charge level on not so sunny days.

    2. Re:Perspective by subreality · · Score: 2

      Yes, I just charge a small 12v gel cell and then use DC-DC converters to get whatever voltage I need.

      I'm not sure if the Thinkpads will charge from a 10W panel. The power port doesn't connect directly to the battery. There's a charging circuit which regulates current to the lesser of what the battery or power supply can handle. So if you connect a 65W power supply, the charging circuit pulls until it sees the voltage start dropping (which happens sooner than a 90W power supply), then just holds that charge rate. The trouble is the charging circuit may decide something is wrong when the voltage starts dropping when it's only pulling 10W.

      Fortunately, it's easy to try out! What you need is a "dc-dc boost converter", aka a "step up converter". Like this: boost converter. Warning, Chinese seller; it'll take a couple weeks to arrive, but I've bought buck converters (convert DC down instead of up) from them a couple times and never had a problem. Take one of those and try converting up from a 12V wall wart and see if it works before you get the panels.

      One potential problem: the voltage out of the solar panels will vary with load. Mine goes up to about 20V with no load. The boost converter will not convert down. There are two ways to address it: either add a small gel cell battery to hold the voltage near 12V, or use a buck-boost converter. That's just what it sounds like: boost the voltage up to say 35V, then convert back down to 19V. Of course you take a double hit on conversion efficiency doing this. It's likely not a real problem though; the laptop probably won't care, and as soon as it starts pulling power it'll go right back into the range the boost converter can handle.

  11. I used to generate electricity like you ... by dbIII · · Score: 4, Funny

    I used to generate electricity like you, but then I took an arrow to the knee.

  12. Re:More power by thesuperbigfrog · · Score: 3, Informative

    You are correct.

    "It's basically a micro-sandwich -- a high-efficiency filter and heat-exchange system. The skin-contact layer's porous. Perspiration passes through it, having cooled the body ... near-normal evaporation process. The next two layers . . . include heat exchange filaments and salt precipitators. Salt's reclaimed. Motions of the body, especially breathing and some osmotic action provide the pumping force. Reclaimed water circulates to catchpockets from which you draw it through this tube in the clip at your neck... Urine and feces are processed in the thigh pads. In the open desert, you wear this filter across your face, this tube in the nostrils with these plugs to ensure a tight fit. Breathe in through the mouth filter, out through the nose tube. With a Fremen suit in good working order, you won't lose more than a thimbleful of moisture a day..."

    --
    42
  13. Re:More power by Tastecicles · · Score: 2

    meh. Now, where's my spare Illudium Pu-36 explosive space modulator...?

    --
    Operation Guillotine is in effect.
  14. Re:A similar method to harness body heat? by Anonymous Coward · · Score: 2, Informative

    There's wristwatches that do that -- look up seiko thermic.

  15. Re:More power by ongelovigehond · · Score: 4, Informative

    Sweat cools because the phase transition from liquid to vapor absorbs a lot of energy to break the bonds. This energy is provided by the skin, so as a result, the skin gets cooler. Likewise, if you condense the vapor back into a liquid, the exact same amount of energy is released again. If that condensation happens inside the suit, the suit will get warm, defeating the purpose of sweating in the first place. It would be like running in the desert in a raincoat.