Slashdot Mirror

← Back to Stories (view on slashdot.org)

Energy From Vibrations

Posted by Hemos on from the making-better-use-of-energy dept.

JN writes "Now here's a nifty invention. What started off as a Small Business Innovation Research grant from the Navy to a MIT professor has turned out to become a great mechanism that harnesses running machines' minute vibrations into energy. The possibilities are limitless. Aside from the obvious, imagine the ultimate cellphone - one that charges the battery every time it rings/vibrates, hence promising extended talktimes, and giving operators all the more reasons to get their customers to use their devices. How cool is that? Do I see 3G applications with a vibrate() call mandatory every couple minutes? "

11 of 520 comments (clear)

  1. This could be sweet. by OwnerOfWhinyCat · · Score: 5, Funny

    On a Harley block these could power my Microwave!

    1. Re:This could be sweet. by GRH · · Score: 5, Interesting

      I'm in the HVAC controls industry. Many sensors are required in ventilation systems (primarily air handlers) to control them properly. This is costly, not because of the cost of the sensor, but because of the wiring and conduit required to reach the sensor. We have little choice about the location of the sensor (it has to be able to do its job).

      There has been talk of trying to build wireless sensors (some do exist) and actuators, but the killer is the power. It either needs to be brought in on wires or battery powered. Batteries are not very good because they don't last that long (these systems are designed to run for over 10 years) and some sensors are difficult to access.

      So, this could be looked at as an enabling technology, in that it could allow wireless sensors to become practical (by running off the ductwork vibration).

      In a mid-sized office building, the installation savings from this would be around $100k. Look around at how many buildings there are...

      GRH

    2. Re:This could be sweet. by CmdrWass · · Score: 5, Insightful

      To paraphrase the parent post's comments:

      A cell phone will use more energy to create the vibration than it will be able to regain from that vibration.

      Due to the laws of thermodynamics and energy,(particularly the law that energy can neither be created nor destroyed), the device that generates energy from vibration would then (by definition) have to absorb some of the vibration's energy. Therefore, in order for this mechanism to "produce" any amount of valuable energy, the source (the cell phone) would have to increase its vibration. However, it will always be the case that the cell phone uses more energy than it gains back (otherwise the phone wouldn't vibrate). Therefore, it would be more condusive of the cell phone to focus its energy on notifying its owner of an incoming call, and do so in the most efficient way.

      Basically, (as stated in the parent post) this invention at MIT doesn't do much for the cell phone industry. Cell phones would be better off being more efficient with the energy they have rather than trying to regain some of the energy expelled while producing environmental feedback.

  2. Indeed by inertia187 · · Score: 5, Interesting

    Reminds me of this article. But seriously, wouldn't the daily movement of the cell phone user also be useful? Granted, it's not as vigorous as the vibrate feature, but it has to account for something.

    "Crud, I dropped my cell phone. But now I have ten more minutes of talk time! Gotta love solid state!"

    --
    A programmer is a machine for converting coffee into code.
    1. Re:Indeed by agentkhaki · · Score: 5, Informative

      Unless the phone happens to be one of those nifty wrist-based one, the answer is no, this won't work. The kinetic watches work on the theory that you a) swing your arms, however so slightly or greatly, when you walk b) you tend to walk around quite a bit (even if it's just going to the fridge to grab another barrel of soda) and c) even when you're not walking around, your arms are moving.

      Contrast that with a cell phone, which is either a) attached to your hip or b) sitting on your desk. When you're walking around, you might be able to harness some energy, the amount of which would increase the farther down your leg you carried it, but when you're just sitting around, or when you're doing your filing, or whatever, you wouldn't be doing anything for the phone.

      Furthermore, any gain would quickly be balanced out by the fact that, just like the watches, you would need an electric device that constantly moves the phone around when you're not going to be using it for a certain period of time (longer than overnight, I believe).

      --
      Ack!
    2. Re:Indeed by dev_sda · · Score: 5, Interesting

      That was my thinking, too. That sort of "recharge" has been available in wrist watches for some time (no winding necessary, your wrist movements do it). For a cell phone with small power needs, it would seem a simple thing to accomplish.

      Its the same basic concept but the degree of difference between the levels of energy generated by the daily movements of a person compared to the power required by a cellphone is huge. The amount of 'vibration energy' you release on a daily basis would probably add 10 minutes of talk time to a low powered cell phone a day. I also like the submitter's misconception of general physics:

      How cool is that? Do I see 3G applications with a vibrate() call mandatory every couple minutes?

      Right. Energy for free! Unfortunately the mythical +100% efficiency machine has yet to be built (and never will). This technology only recovers percentages of energy lost due to machine inefficiency and friction. The day x amount of energy generates y amount of energy where y > x is the day the universe implodes.

    3. Re:Indeed by Torqued · · Score: 5, Funny

      "Unless the phone happens to be one of those nifty wrist-based one, the answer is no, this won't work."

      1: Momentum powered wrist cell phone
      2: Porn
      3: !!!!!!!!!
      4: Profit! (or at least unlimited power!) :)

  3. nothing new here by kin_korn_karn · · Score: 5, Funny

    I know plenty of women that get energy from vibrating objects.

  4. Not perpetual motion by Plastik · · Score: 5, Interesting

    This is a way to power small, low-power devices parasitically from the vibrations of a much larger engine. Actually very interesting.

  5. Re:Wow! by pcol · · Score: 5, Informative

    Actually there is a way to store the energy when a vehicle brakes into a flywheel and then use it to re-acelerate the vehicle after the stop. It's called a regenerative braking system.

    No violation of conservation of energy. You are simply storing part of the energy that would have gone into heat and re-using it later.

    Take a look at: Urenco Power Technologies - they've been doing this for years.

  6. Re:2nd Law of Thermodynamics by grEchelonSurge · · Score: 5, Informative

    Of course, one can't get any more energy. Duh.

    But exactly how much energy could one get out of a vibration? Are we talking powering an LED by the San Andreas fault? Or are we talking powering San Francisco from the vibrations on an air conditioning shaft?

    Let's see:
    We'll consider the vibrations to be simple harmonic motion (because it is relatively accurate, and anything else is near impossible to calculate without a beowolf cluster).

    Let's look at the vibration when your car goes over a speed bump. This should have a relatively large energy associated with it, since the energy in a object due to vibration is:

    E = 0.5 K A^2

    Where k is the spring constant (in metric, it would be N / m ).

    K can be determined by calculating how far your car is lowered when you get in (your weight, in newtons, divided by how far your car is lowered, in meters).

    Let's assume that you weigh 150 lbs. This is about 70 kilos, or 670 Newtons. Let's also assume that your car is lowered by about an inch when you get in (0.0254 m).

    This makes the spring constant for your car's suspension:

    670 N / 0.0254 m = 26,378 N / m

    This is to say that if one were to depress your car's suspension by one meter, you would be exerting a force of 26,378 Newtons.

    Let's also assume that, when going over the speed bump, your car bounces 10 inches. Thus, the amplitude of your car's motion is 5 inches, or 0.127 meters. Putting this information, and the spring constant into the first equation for energy:

    E = 0.5 ( 26,378 N ) ( 0.0127 M ) ^ 2

    E = 213 Joules.

    Great. How does this relate to power needed for powering some electronic device?

    Power = Energy / Time.

    Let's assume that this vibrations to energy device in the article can absorb your car's vibrational energy in 10 seconds. Thus, the power going into the device is:

    213 J / 10 s = 21.3 J /s = 21.3 W.

    That's right. 21 watts. Barely enough to power a small lightbulb. And that is coming from a whole car!

    Thus, I think that we can safely say that we're not going to be replacing our power plants any time soon. But for, say, a low-powered electronic sensor, which wirelessly broadcasts it's data in bursts every ten seconds, it would be fine.