The tides will turn

The oceans naturally play a critical role in moderating the Earth's weather and climate -- keeping temperatures of coastal communities milder in winter and cooler in summer than their inland counterparts.

Now that the global energy/climate crisis has even the United States Congress understanding the need to wean ourselves from fossil fuels, there will undoubtedly be a lot of attention focused on the oceans as a source of clean renewable energy. Offshore wind burst upon the stage in a flurry of controversy in the United States seven years ago with the proposal by Cape Wind Associates to construct 130 wind turbines off the coast of Cape Cod.

Some opponents of offshore wind energy were quick to offer tidal and wave energy as more acceptable forms of ocean-based renewable energy, primarily because they promised to have less visual impacts. Some tidal and wave projects have already been constructed and more are on the drawing board. For a variety of reasons (some mentioned in the following article), I think siting of large-scale tidal projects may actually prove trickier and thornier than offshore wind.

Our goal should be to responsibly site offshore wind, wave, tidal and ocean thermal projects and create a sustainable portfolio of diverse ocean-based renewable technologies (GW)

The Next Wave

Ken Silverstein
EnergyBiz Insider
June 22, 2007

The next wave of hydropower may be tidal power, or harnessing the energy of the oceans and rivers to generate pollution-free electricity. It's a budding sector. And producers have come up with a host of new technologies that they say will speed development.

The products that create electricity from the tides include everything from spinning turbines to floating buoys. Like all emerging technologies, those within the tidal power sector are vying with other entities for investment dollars. But firm commitments are necessary not just from utilities to include it as a fuel mix, but also from governments to help the technology get over the hump and into the marketplace -- just as some nations are now trying to foster advances in nuclear and coal technologies.

The Electric Power Research Institute (EPRI) performed feasibility studies in this area. The Palo Alto, Calif.-based research arm of the electric utility sector said that unlike hydropower, tidal energy does not require the permanent impediment of water flow and the subsequent harm to aquatic life. Existing tidal plants, it adds, impound the water before releasing it into generators. And newer tools are even more progressive and use underwater turbines that ultimately connect to cables to transport the power.

Existing tidal power plants include a 240 megawatt facility in France, a 20 megawatt plant in Nova Scotia and a 0.5 megawatt one in Russia. EPRI says that not only would new tidal projects create electricity, but they would also bring about a host of new jobs and new economic development. With the proper permitting, it says that the power source is environmentally benign -- a necessity, given the rigors of getting new plants up and operating today. And, furthermore, ocean currents are a lot more predictable than other green energy forms such as wind and solar.

"A relatively minor investment today might stimulate a worldwide industry generating billions of dollars of economic output and employing thousands of people while using an abundant and clean natural resource," says Roger Bedard, ocean energy leader for EPRI. Bedard adds that widespread commercial use of the technology is a decade away. It could supply 10 percent of the nation's energy mix by mid-century, he adds.

In this country, New York's East River is home to the latest tidal power pilot project. There, the tides come in at about 6 feet per second and turn 2 underwater blades that are hooked to a generator to create the electricity. The power is then channeled into cables affixed to the seafloor and then into the electric grid. Right now, the project is just 35-kilowatts and feeds only a couple of businesses. But the project's developer, Verdant Power, says that if all goes well, it will install after 18 months about 200 more turbines that could produce as much as 10 megawatts of electricity.

Those developers add that they have implemented sophisticated tools that continually monitor the area to ensure that no fish are harmed. Since December 2006, none have been displaced or hurt, they say.

Miles-to-Go

As the world's largest solar collectors, oceans in particular generate thermal energy. Waves are unending and therefore have the ability to produce power around the clock. Moreover, seawater is 832 times as dense as air, providing a six mile-per-hour ocean current with more kinetic energy than a 217 mile per hour wind, say experts. To bring the idea into the mainstream, however, scientists and engineers must still show that their work can be done on a large-scale basis.

Like other power projects, they have to go through a painstaking permitting process spearheaded by the Federal Energy Regulatory Commission. Verdant, for example, started that process in 2002 and must spend $2 million to study the effect of its technology on fish.

According to FERC, the last five years have been slow. But the tide is turning. In 2006, it received about 40 applications. That's almost four times more applications than it received in the previous five years. Pacific Gas & Electric is the first major utility to file a permit. It is considering a tidal plant underneath the Golden Gate Bridge.

Meantime, Portugal is home to a couple of tidal projects. One project, developed by Ocean Power Delivery, will provide about 2.25 megawatts of wave power. Another is to be built by Norsk Hydro. Annapolis Royal Station in Nova Scotia, Canada, meanwhile, already generates about 20 megawatts of power using tidal power.

But rough waters lay ahead. Environmentally, tidal power plants can impede sea life migration and can affect local ecosystems. The optimal solution, the Department of Energy says, is to carefully select sites that preserve scenic shorelines.

And, economically, there are barriers. Operating tidal plants is reasonable. But building and maintaining them is expensive. Therefore, the return on investment takes a long time. It is furthermore problematic when it comes to getting the power to shore.

The regulatory hurdles, in combination with the difficulty of attracting capital, are significant issues. But they can be overcome. If the current commercial and pilot projects are proven to be successful, then it would encourage other developers to get on board. With more experience and with the mass production of the essential technologies, prices would come down. At the same time, newer technologies that are around today are less problematic and don't block migratory paths.

"We've done our due diligence, and we think this has promise," says Kevin Walsh, who heads renewable energy for GE Energy Financial Services, in a USA Today story.

Without a doubt, tidal power's status has been lifted. Needless-to-say, it has much further to go. But scientists and engineers are working hard to develop newer and better tools to harness this never-ending source of energy. If they are triumphant, then wave power could become another arrow in renewable energy's quiver.

More information is available from Energy Central:

The Promise of Wave Power, EnergyBiz, March/April 2005

The Power of the Tides, EnergyBiz, March/April 2007