Making Waves in Sustainable Energy

Can nets and nanotechnology make the "blue energy dream" come true?
20 February, 2017
From Scotland's western coast to Australia or southern Africa, the shoreline may offer more than sun and sand.
The ocean can potentially become a tremendous source of sustainable energy once scientists learn to harness its power more efficiently. That is precisely what research scientist Zhong Lin Wang hopes to achieve.

In a recent piece for the journal Nature, the physicist described a new way of capturing wave energy using floating nets of sensors. The approach is based on principles that researchers already use to harvest energy for lights, phone chargers and other applications using what is essentially friction. They're getting much better results than piezoelectric materials, which generate energy when pressed, have in the past.
This "triboelectricity" is essentially the same static energy people occasionally encounter in their homes, and it can be drawn off using electrodes to create a pulse of current. Zhong's team has used the principle since 2011 to deliver energy performance as efficient as electromagnetic generators.

So the nanotechnology might theoretically be applied to help create commercial wave farms, which currently do not exist. Some small projects exist in Portugal, the world's first, or in Australia, but they rely on heavy equipment and complex, expensive and technically difficult processes. Zhong wants to radically change that with balls of floating motion sensors – easily made with conventional materials, including rubber, silicon and aluminium foils – that create a "nanogenerator network" when attached to create nets stretched across waves. As balls the size of oranges roll with the motion, they create energy.
"Power is generated according to how fast the nanogenerator moves with the waves," Zhong explains. "The direction does not matter. If agitated two or three times per second, each unit produces a little power (and) many devices can be linked with conducting cables to generate more." So far, his Georgia Tech team has demonstrated the concept works by linking 400 nanogenerators over 4 square meters.

Is it worth it? In terms of renewable energy, waves are constantly in motion, regardless of whether the sun is up or it's the middle of the night. On top of that, the ocean covers 70 percent of the surface of the earth. The energy source doesn't change, nor does it have to be anticipated and stored as systems that rely on solar do.

There is also a lot of it. Whereas wind energy's potential resources are usually measured and described in gigawatts, wave and tidal potential is always described in terawatt hours per year (TWh/yr). That is significant when one realizes that estimates for just one TWh/yr would power almost 100,000 average American homes.
Image: Tikalon
While many people understand the value of hydropower, they envision that as a renewable resource limited to dam construction and therefore land-dependent. The wave energy concept makes offshore operations possible, and according to Zhong, presents little safety or security concern and at least theoretically, less environmental impact than dams and other methods for harvesting hydropower.

The biggest challenges are in material design, to ensure that the nanogenerators are durable, and in placing the "wave nets" of connected units strategically so they do not interrupt shipping traffic, marine life, or ocean-based livelihoods and leisure. Careful consideration of the environment includes ensuring that fish and other marine life are not trapped in the networks, and linking systems to the shore are both safe and efficient.
Banner image: Pinterest