Actions
Forum Thread Details
  • Replies 2 replies
  • Subscribers 6 subscribers
  • Views 414 views
  • Users 0 members are here
Related

Piezo resonator electric power generator

claudiu.neamt

Hi guys. Someone asked me for help for a project. She wants to build a device that can produce about 5W out of a piezo resonator that can resonate at the walking frequency . she wants to build a device that can be trapped to your leg and produce electric energy. Anyone heard about anything like that and how can we do this?   we need a high power resonator with a low resonating frequency or a variable resonating frequency

Parents

  • 5 W is equivalent to lifting about 3.7 pounds 1 foot up every second, which is a lot of power for this technology and will be a significant expenditure of energy by the person generating it. Imagine wearing shoes that weigh 4 pounds each and lifting your feet 1 foot on every step. Assuming you are okay with this work load during walking you would likely need a mechanical spring or cantilever that got kicked or "pumped" synchronously on every step taken. The spring would need a relatively heavy weight to keep the spring oscillating until the next step. It would only need to oscillate 2 or 3 mm but it would need to oscillate at a frequency of 50 or 60 Hz. For every 10 grams of piezo material you might get 6 mW of power, so you need about 8 or 9 kg of piezo benders to generate 5 W, in addition to the spring and weights. To bend these piezo elements 3 mm would take about 100 pounds and it needs to happen 50 times per second. It is possible to eliminate the weights and spring using a machine to convert leg motion into a 100 pound, 50 Hz vibration, but it is likely to be a machine with gears and crankshafts. Think of a bicycle that has an extra wheel geared up to 3000 RPM that uses another crank to push a 100 pound lever 3 mm on every revolution. In the case of a bicycle, it would be easier to install a small rotary generator.

    The bottom line is 5 W from walking is possible and there are some real applications, but be prepared to do quite a lot of development work as well as quite a lot of work while you walk. Of course, there are commercial power scavenger systems that convert leg motion to power, usually using a generator for higher power applications, but they normally use the collected power to charge a battery that evens out the cyclical nature of walking.

  • in reply to dougw

    I'll second Douglas' remarks -

     

    Here's a link to a Thesis paper by one JY Hayashida who actually built  a mechanical generator. It manages only 60mW average although the peak power was over 1W. He put a lot of effort into the design. The paper quotes some interesting background data as well. It's a bit old (2000) but well worth a read.

     

    http://www.media.mit.edu/resenv/pubs/theses/JEFFHAY-Thesis.pdf

     

    MK

Reply Children
No Data