Ocean renewable energy

The free flow turbine from Verdant Power

Have you ever been knocked down hard by a rouge wave? Then you know that the water in the oceans packs some serious power, in the form of waves, tides, and currents. The first commercial electric projects to harness this power are going to come online in the US next year.  I put together a slideshow of technologies for generating renewable electricity from the power of the oceans, that’s up on Discovery.com this week. Check it out.

In reporting for this story, I learned a lot more about ocean renewable energy technology then I was able to fit into the Discovery story. First off, unlike wind and solar, the oceans provide a constant source of power, so you don’t run into the same intermittent resource problems. Here’s some other interesting aspects to ocean renewables.

1. Dam ocean! Dams have also been built in to harness the energy of the oceans.  Marine dams are built in estuaries with a large difference between high and low tide. They exploit the vertical change in the water using gates so that water can flow freely through the dam in one direction, and the water flowing in the opposite direction can push turbines. The first ocean power plant was built in France in 1966.

La Rance Tidal Hydropower Dam, by London Looks, via flickr

Generating power in this way requires large scale infrastructure.  In South Korea, the construction cost reached nearly $300 million, for the new 254 MW tidal power dam  that opened on August 4, 2011. This project, the Lake Sihwa Tidal Power Plant, used an existing dam in the estuary.  There is a significant vertical difference between the high tide levels reaching the dam and the lower level of the reservoir behind, so they employ turbines to capture the power of the tidal waters entering reservoir. Then, water flows back out to sea at lower tide. This in-flow turbine design is less efficient  for power generation then the design at La Rance, in France, which uses out-flow turbines, but it was the best fit for the Lake Sihwa location. Generating power with dams does cause significant disruption to the marine ecosystem, preventing movement of animals, sediments, and natural water flow.

2. The tidal turbines can also work in rivers! A smaller version of the turbine generator unit that Ocean Renewable Power installs in estuaries can be used in small rivers. Designed to fit in a standard shipping crate, they hope to use these units to provide power to remote communities, like Alaskan villages, that otherwise rely on expensive, shipped in diesel for generators. These local electric projects could be a first step in a broad shift in how and where we produce power.

“Heretofore, what the world has been doing is building big electrical generation projects,” Trey Taylor, CEO of Verdant Power, a tidal energy company, said.  “We’re moving away from centralized to decentralized power.  Most cities are near moving water. You can build clean power plants right next to where people live.”

3. Fish don’t get whacked by turbines! Unlike windmills, which have been known to strike and kill migrating birds, fish swim around the underwater turbines, unharmed. All of the pilot projects in the US have been accompanied by environmental impact studies which show that the effects of turbines in the water is negligible.

“What we’ve learned since [the prototype] was installed in 2006 is that the fish just swim around, not through,” said Trey Taylor.

School of fish, by Frank Starmer

The fish can sense changes in pressure of the water, which helps them navigate and avoid predators. They sense the pressure as the turbine blades spin slowly, and they respond to the pressure by swimming away.

4. The turbines have to be spaced out so that they don’t slow the water down too much. As Verdant’s turbines spin in the water column, the water that passes through the blades is slowed down, because the turbine literally takes the energy out of the water.

“There’s a real art to understanding how to place these,” Taylor said. “We can take no more than 15 percent of the energy out of the water current. We have to allow a significant distance between rows so the water current can regain speed.”

5. The U.S. industry could produce 36,000 jobs by 2030. The industry, officially known as  marine hydro-kinetics (MHK) is represented in Washington D.C. by the Ocean Renewable Energy Coalition, and they released an industry roadmap on November first, outlining how the industry expects to grow in research, development, and production in the next twenty years. Once the permitting process for these types of projects speeds up, they expect to be installing projects on both coasts in the next few years. Here in Wisconsin, we may be stuck with wind power, but in NYC, Maine, Oregon, and Alaska, these technologies will be providing power soon.


One thought on “Ocean renewable energy

  1. Hi Kate, I liked this post. I learned some new things about wave powered turbines. Thanks!

    I am paying “blog calls” to each @scio12 attendee to say “Hi” and give your blog a shoutout on twitter (I’m @sciencegoddess). I look forward to meeting you in January!

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