Hi, this is Alex from MinuteEarth. The ocean is covered with literal waves of
energy, and if we could convert this energy into electricity, we could power all of humanity's
electrical needs. But for now that’s just a dream. That’s because we haven’t yet figured
out an efficient way to use waves to spin turbines, and spinning a turbine is the best
way we know of to convert the mechanical energy of a moving substance into electrical energy. Aside from solar panels, pretty much all our
electricity comes from spinning turbines. Wind turbines and water turbines are the most
obvious, but even our coal, gas and nuclear power plants use turbines - the fuel is just
there to heat water into steam that can flow and spin a turbine. A wave, on the other hand, is not the flow
of a substance as a whole. Instead, it’s just the local, oscillating
motion of small regions of the substance. It’s like how at a stadium when the crowd
does The Wave, the wave moves through the crowd but the people don't move sideways - just
up and down. If the entire crowd was, say, walking around
the stadium, you could imagine everyone helping twist a single big turbine on the field. But if people were just standing up and sitting
down, you’d need a more complicated system to move the turbine. So, back in the ocean, most attempts at harnessing
wave energy try to turn waves into something else that can spin a turbine. We’ve made caverns in which waves rise and
fall, pressurizing air that flows past a turbine. We’ve made big floating pipes whose joints
flex in the waves, driving pumps that pressurize fluid that can spin a turbine. And we’ve created what are essentially big
floating bags that waves pile up into, and that water flows out of, spinning a turbine. We’ve also realized that at the edge of
the ocean, when waves break, their water flows quickly enough to spin a turbine, but only
for a few seconds at a time. So far, though, we haven’t been able to
get any of these turbines to spin fast enough or consistently enough to make electricity
- at least cheap electricity; building things in the ocean is expensive, and then whatever
you build gets exposed to saltwater, sand, debris, barnacles, and storms, so you have
to spend a lot of money repairing it. As a result, there’s no commercially successful
design for capturing energy from waves. We may yet be able to figure out how to make
turbines commercially viable, or we may move past the turbine paradigm; we’ve come up
with some designs that don’t rely on turbines - like buoys whose bobbing movement pulls
on a generator - but their electricity ends up being just as expensive as from the designs
that rely on turbines. Hopefully, a new wave of wave-energy will
arrive someday soon, but so far, wave energy is barely making a ripple. This video was sponsored by the Okinawa Institute
of Science and Technology Graduate University , an international graduate school devoted
to the advancement of science, education and innovation in Japan and throughout the world. OIST offers a fully-funded PhD program and
research internship opportunities that attract talented young scientists from around the
world to work with researchers like Professor Tsumoru Shintake, whose Wave Energy Project
is tackling the challenges discussed in this video. So far, innovations in their turbine design
have already improved power output, which is essential if wave power is ever going to
become a viable energy source. To learn more about OIST, visit admissions.oist.jp.
<sigh> This isn't about why wave power isn't working, but rather a partial explanation of why most wave energy isn't cost efficient to harvest.
A better technical explanation would be to describe the available energy. Generally speaking, wave energy is low specific energy per square meter of surface. A wall of moving water, like when a large wave strike a pier has tremendous momentum. Yes, that particular wave has a lot of energy, but how long until the next wave - the next storm ? Most useful (to us) waves are at the transition from deep water to shallow, which compresses the wavelength, forcing the amplitude up (shorter distance between wave crests, taller waves). But such areas are typically waterfront used for other things other than energy harvesting.
The video does present the obvious drawbacks: salt water and metals generally don't mix, particularly moving/sliding/rotating pieces of metal. devices that move and then stop are particularly at risk. Off shore energy is particularly difficult to get to shore and off shore wind energy is much more practical from a maintenance perspective.
Wind drives waves, so it makes sense to grab that wind energy, particularly when climate change is looking to push more energy into the atmosphere, so wind speeds, particularly at higher elevations are expected to rise.