Hybrid energy harvester generates electricity from vibrations and sunlight

Apr 17, 2013 by Lisa Zyga feature
(a) Diagram of the silicon nanopillar solar cell. (b) Diagram of the hybrid energy harvester consisting of a piezoelectric nanogenerator integrated on to of a silicon nanopillar solar cell. Credit: Dae-Yeong Lee, et al. ©2013 IOP Publishing Ltd

(Phys.org) —Devices that harvest energy from the environment require specific environmental conditions; for instance, solar cells and piezoelectric generators require sunlight and mechanical vibration, respectively. Since these conditions don't exist all the time, most energy harvesters don't generate a constant stream of electricity. In order to harvest ubiquitous energy continuously, researchers have designed and fabricated a hybrid energy harvester that integrates a solar cell and piezoelectric generator, enabling it to harvest energy from both sunlight and sound vibration simultaneously.

The researchers, Dae-Yeong Lee, et al., from Sungkyunkwan University and Samsung Advanced Institute of Technology, both in South Korea, have published their study on the hybrid harvester in a recent issue of Nanotechnology.

"By using the hybrid energy harvester, two different can be utilized in one platform," coauthor Hyunjin Kim at the Samsung Advanced Institute of Technology told Phys.org. "Thus the total output power from the hybrid harvester can be increased compared to each separate harvester. Furthermore, by harvesting two energy sources in one device, continuous output can be generated even when only one energy source is available."

To design the harvester, the researchers turned to silicon nanopillar solar cells for the sunlight harvesting half of the device. Previous research has shown that silicon nanopillar solar cells are promising candidates as due to their low reflection, high absorption, and potential for low-cost .

After fabricating the cells using a plasma etching technique and annealing processes, the researchers coated the top of each cell to prepare it for placement of the piezoelectric generator, which was stacked on top using a spin coating method. Last, top and bottom electrodes sandwich the device.

The entire harvester has a height of just a few hundred , with the bulk of the height coming from the 300-nm-tall nanopillars in the solar cell.

In tests, the energy harvester could generate electricity from the with a 3.29% conversion efficiency. At the same time, the harvester could generate 0.8 V of output voltage when exposed to a 100-dB sound.

The hybrid device suggests that harvesting both solar and vibration energies can enable more efficient harvesting in certain environments compared to a device that harvests just one kind of energy.

"This energy harvester can be very useful where there is no electric grid connected," coauthor Won Jong Yoo at Sungkyunkwan University said. "For example, this device will be useful in moving vehicles such as moving boats, trains, automobiles, etc. The output of 0.8 V is just preliminary data. If we optimize the device structure and fabrication condition, the output power will be increased significantly."

In the future, the researchers plan to fabricate all-flexible hybrid energy harvesting devices using plastic substrates in order to harvest mechanical energy more efficiently.

Explore further: Team finds electricity can be generated by dragging saltwater over graphene

More information: Dae-Yeong Lee, et al. "Hybrid energy harvester based on nanopillar solar cells and PVDF nanogenerator." Nanotechnology 24 (2013) 175402 (6pp). DOI: 10.1088/0957-4484/24/17/175402

Journal reference: Nanotechnology search and more info website

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MR166
2.2 / 5 (6) Apr 17, 2013
WOW!!!!! I am impressed a mere 30DB below the threshold of pain and the device can generate perhaps a milliwatt of power. Yep, definitely another green energy triumph.
Irukanji
5 / 5 (1) Apr 17, 2013
WOW!!!!! I am impressed a mere 30DB below the threshold of pain and the device can generate perhaps a milliwatt of power. Yep, definitely another green energy triumph.


It's in its early development. If it can generate energy from sound, perhaps it could generate energy from the vibrations of a vehicle on a road? Or a bicycle? With some research, in 5-10 years time it could be considerably more efficient, and cheaper.
Eikka
5 / 5 (3) Apr 17, 2013
perhaps it could generate energy from the vibrations of a vehicle on a road


While at the same time being able to collect sunlight? Hardly any of the vibration energy reaches the exposed surfaces of a car for a good reason: the occupants of a vehicle would go deaf from the noise if there was such vibrations in the chassis.

It's very hard to imagine a situation where sunlight would alternate with a 100 decibel noise or other vibration. Well, except for certain vulgar scenarios.

SteveL
not rated yet Apr 17, 2013
Were a vehicle to generate this much noise energy, we could acquire far more energy savings by addressing the waste of energy at the source than you could ever recover by recapturing, converting and storing that lost energy.
Whydening Gyre
1 / 5 (1) Apr 18, 2013
Forget putting it on a vehicle. instead just have a series of collection devices by train tracks or runways or even on the side of the road? Then port the energy to storage devices or to the grid. We could recover so much of the wasted energy we now "throw away".
antialias_physorg
not rated yet Apr 18, 2013
Couple of years ago, when these nanopiezo actuators were first reported, I went to our national institute for earthquake monitoring(which just happens to be 150 meters down the road) and had a bit of a chat with them.
Got some data on the natural background vibration of the Earth (microearthquakes, which are going on all the time)...
Was surprising for them as they usually only study large earthquakes.

The intent was to find out if one could harvest the energy of those microearthquakes efficiently (simply by making a power spectrum and looking at how much energy would be contained in the best suited frequencies)

Turns out the energy content is too low to be of much use in large scale applications (i.e. power generation in general). But there still are scenarios where this can be useful, like embedded sensors that harvest energy over time, e.g. charging a capacitor, and then use that power once every day or so to transmit a burst of data.
alfie_null
not rated yet Apr 18, 2013
WOW!!!!! I am impressed a mere 30DB below the threshold of pain and the device can generate perhaps a milliwatt of power. Yep, definitely another green energy triumph.

Glad you're impressed. Since you sound like you really know what you are talking about, I'm curious how you calculated that one milliwatt figure?
MR166
1 / 5 (1) Apr 18, 2013
WOW!!!!! I am impressed a mere 30DB below the threshold of pain and the device can generate perhaps a milliwatt of power. Yep, definitely another green energy triumph.

Glad you're impressed. Since you sound like you really know what you are talking about, I'm curious how you calculated that one milliwatt figure?


Your right, I just guessed. It could be a just few microwatts. One thing is for sure, if it was a substantial amount of power, say enough to power a LED they would have mentioned the power output of the device. Power is a much more meaningful parameter than voltage.
MR166
1 / 5 (1) Apr 18, 2013
I have to say one positive thing about this. It is the first product that is able to harvest energy from the dying screams of it's bankrupt investors.
Eikka
not rated yet Apr 23, 2013
This whole thing is actually very similiar to the physics problem of how long would you have to shout at a cup of coffee to heat it up.

Sound intensity at 0 dB is 10e-12 W/m^2. Let's assume that we're measuring 100 dB at 1 meter distance from the source. 100 dB intensity is 100 mW/m^2 and the surface area of the unit sphere is 4 pi, so we got a sound source that outputs approximately 1.26 Watts of acoustic power. To harvest, or at least absorb, all that power would require 12.6 square meters of material surrounding the source at that 1 meter distance.

So that explains why they're only getting microwatts of power out. There's really very little power to harvest in the first place.

That's right - you don't need a whole lot of power to make loud sound. The reason why big loudspeakers need more of it is because you're not listening at 1 meter distance, and because ordinary speakers are really really inefficient at turning electrical power to sound.

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