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Is Triboelectricity the Next Harvesting Source?

We're always looking for a new source of energy to harvest, and why not? It's often free (ignoring the up-front cost), convenient, and solves many practical installation/replacement issues. But before the energy can even reach the harvesting electronics and load, there are two front-end problems to resolve: finding a consistent physical phenomenon available for harvesting and having a reasonably efficient and reliable transducer to actually capture its energy (such as a piezo-based component for vibration, blades for air flow, or a water-diving vehicle that uses temperature gradients).

Among the well-known potential sources (sorry about that pun) are solar radiation, of course, along with temperature differences, sound, vibration, air flow, and motion. There's one more possible source that is truly ubiquitous but has been hard to capture: static electricity due to friction (it often appears as ESD — electrostatic discharge — and is considered a bad thing). But some recent work at the Georgia Institute of Technology may change that.

According to the Georgia Tech press release, a team including that school has developed inexpensive, flexible polymer materials that are very good at developing a charge through rubbing, then holding it until it can be extracted as current flow. While static electricity is not a new development, it's tricky to generate, hold, and extract (think of the Leyden jar).

The image shows how power is generated by triboelectric generation, by sliding two materials together and then creating a gap between them.(Source: Inertia Films)

The image shows how power is generated by triboelectric generation, by sliding two materials together and then creating a gap between them.
(Source: Inertia Films)

This is certainly interesting, but how much harvestable energy is there via this mechanism? Here's where the analysis gets a little tricky.

The press release cites a power output as high as 300 W, which is pretty significant. But energy harvesting is about energy on the capture side, while it is about power delivery on the load side. You collect energy in random dribbles when you can, but you have to spend it as power (the rate at which the energy is expended), because any real load requires some minimum threshold of power to function. That 300 W figure may translate into barely meaningful energy levels, and the lower the energy level available to be harvested, the harder it is to actually collect it with acceptable losses.

Still, the Georgia Tech work sounds impressive and intriguing. They claim a volume power density of more than 400 kW per cubic meter, along with efficiency of greater than 50%. How this translates into real-world applications is hard to say but is certainly worth keeping an eye on.

The researchers also say that their materials can be used to harvest energy from contact with flowing water. That certainly opens up new opportunities, since there are many hidden flow sources, such as sinks and faucets, which perhaps could be tapped, as well.

It will be interesting to check back in a few years and see what has become of this source. Is there enough energy available to make it viable for the electronics which must extract it effectively? Will the material and associated physical embodiment of the transducer be reliable and cost-effective? Will it become a mass-market source, or a highly specialized one such as the thermoelectric generator (TEG) which uses thermocouples to extract energy from a heat source?

Are there any other untapped harvesting sources you'd like to see explored? Any reasons you think they have not been exploited thus far?

This article originally appeared on EBN's sister publication EDN .

10 comments on “Is Triboelectricity the Next Harvesting Source?

  1. prabhakar_deosthali
    March 3, 2014

    One of the energy harvesting source that I can think of is the water supply piping in a building.

    Normally water is stored in the overhead tanks and it gushes down the pipes whenever somebody opens a basin tap, takes a shower and starts a washing machine.

    This flowing water thorugh the pipes generates some kind of friction and therefore some heat. If this energy is harvested , may be it could be used to pump the water up in the overhead tank.

     

     

  2. t.alex
    March 3, 2014

    This is pretty good idea. All of these small flows can be combined into a big one which can easily drive a decent turbine for electricity generation.

  3. Adeniji Kayode
    March 3, 2014

    @ t.alex, Good point, but is turbine generated electricity not old fashion now?

  4. prabhakar_deosthali
    March 4, 2014

    I was not thinking on the lines of “turbibe”, but  about the heat generated by the friction of the water flow thorugh the pipes – potentially that could be converted to some kind of energy

  5. Ariella
    March 4, 2014

    @Prabhakar I suppose it can and should. If it is not channeled in a positive way, wouldn't it likey form a problem of heat that has to be eliminated? 

  6. Daniel
    March 4, 2014

    “There's one more possible source that is truly ubiquitous but has been hard to capture: static electricity due to friction (it often appears as ESD — electrostatic discharge — and is considered a bad thing). But some recent work at the Georgia Institute of Technology may change that.”

    Bill, that's great news but how far it's possible to generate, collect and distribute this frictional energies? How about its amplitude, frequency and volts for domestic use.

  7. Daniel
    March 4, 2014

    “I was not thinking on the lines of “turbibe”, but  about the heat generated by the friction of the water flow thorugh the pipes – potentially that could be converted to some kind of energy”

    Prabhakar, energies are formed at various instances and occasions, due to many activities like walking, driving the automobiles, by flow of water etc. but as of now there is not any proper mechanism to harvest such energies.

  8. Hailey Lynne McKeefry
    March 9, 2014

    Earlier this week, I was speaking with an IEEE engineer and he mentioned that some engineers are working on buidling components that could literally harvest electricity from a WiFi signal. That would mean that cellular phones, for example, might be able to go weeks between charges and smaller devices that draw less power could conceivably never have to be charged. I think there's some interesting stuff coming down the pike that we can barely imagine.

  9. Adeniji Kayode
    March 28, 2014

    @Hailey, Is this going to be at extra cost or free service by the operators.

  10. Hailey Lynne McKeefry
    March 30, 2014

    @Adenjii, as I understand it it will be a feature of the phone, the ability to self-charge by harvesting electricity from the WiFi. It would work automatically whenever the phone connects to a wireless network. Sounds very cool right? Stay tuned, we are planning to write something about this soon.

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