What’s the scoop here?
The November 2008 edition of The Journal of Offshore Mechanical Arctic Engineering – I didn’t even know such a thing exists – showed that it is possible to generate electricity from vortex-induced vibrations (VIV). They devised a proof of concept machine which they called VIVACE which is short for Vortex-Induced Vibration Aquatic Clean Energy – quite catchy if you ask me. In short, this contraption can make electricity out of natural movements of the water.
Ehhh but what is a VIV again?
Those were the same questions I had when I read about the title because I am a Biologist and not an Engineer. To answer the first question, when air, or liquid passes by a cylindrical object vortexes are formed. Wikipedia again has a nice image of the beautiful vortexes you can get:
VIVs are the kind of vibrations that result from the vortexes you see above. Because this sounds a bit abstract, I searched for how VIVs actually look. I found a video that shows VIVs created by a stream of air.
VIVs are generally considered bad side-effects in many applications. It’s what civil engineers are concerned about when they build a bridge: The fast streams of water flowing around the legs of a bridge can create such vibrations. If the right frequency is hit, the signal can get so much amplified within the structure of the bridge that it will simply collaps. As a famous example, I found information on the
Airplane engineers are also concerned about these. When airplanes fly at high speeds, many vortices are generated along the span of the wing. VIVs can severely drag down an airplane, and in larger airplanes with long wings, these VIVs could in theory rip the wings off an airplane. This is not happening of course because airplane engineers are smart. Did you ever notice that the wings of an airplane has pointy extensions along the wing? These extensions were put there to redirect and reduce the amount of VIVs to mostly those flexible tips. Drag is reduced, and so is the vibration.
And how is VIVACE such a big deal?
Well, let’s think of how hydroelectric energy is normally generated. Hydroelectric energy makes use of water movements. Traditionally, in a river-setting for example, water from a higher elevation flows to a lower elevation, turning a turbine that runs the generator.
Tidal energy generators work in a similar way. These technologies though straightforward have a few disadvantages. First, they require relatively fast moving water (5 knots and above). Second, they may be quite obstructive. You may already have seen how big these dams are. In ocean environments, they may be harmful to marine life. Just try to imagine what will happen if fish get chopped off by the turning, spinning rotors.
Obviously, a lot of research is going on those fronts (like rotor design) too. But with VIVACE, no rotors are needed at all. No fish need be afraid of being chopped into pieces. And because VIVACE relies on tiny vibrations that are generated even when there is just a little water movement (2-3 knots), no fast streams are needed to generate electricity. If you wonder how such a contraption may look, gizmo.com has a nice concept art drawing which you can see below:
And there is a video of a working prototype on the newly formed company website:
What did I learn from here?
Who would have known that electricity can be generated from just vibrations. Energy is all around us. It will take a flexible mind to find these ways. A traditional argument against alternative energy sources has always been cost.
Cost and efficiency are always valid concerns. solar power currently costs 48 cents/kwh because of expensive material and production costs of solar panels. Furthermore, solar power can only be used during the day. Wind power now only costs about 8 cents/kwh, but has the disadvantage of not being reliable because the wind does not always blow. Just as a comparison, for coal this turns out to be about 4 cents/kwh. How well does VIVACE compare? The authors estimate that a VIVACE converter can generate electricity as cheaply as 5 cents/kwh.
Since "Change" was the slogan in a recent election campaign, it may be time to change the way we think about energy. As some have suggested already, there is no single magic energy source that will replace all others. Rather a healthy energy mix of renewable energy sources could compensate for the short comings of the other. For instance, often times when it's sunny, it's not windy. When it's windy, the weather is usually bad - at least that's what I observed in Germany. Combining solar, wind, and now hydro-electric energy like the VIVACE converter could perhaps provide us with enough clean energy for the future.