U.S. adding first tidal plant

July 27, 2012

Under President Barack Obama's "all of the above" energy strategy, the U.S. has placed a renewed emphasis on diversifying its power supply. Natural gas-fired power plants have taken on a growing portion of the burden from coal, while solar panels and wind turbines are cropping up on rooftops and horizons all around the country.

But one of the most promising new power sources for the U.S. is also the one that will go unseen by most Americans.

According to The Boston Globe, Maine-based Ocean Renewable Power Co. has started work on the first ever tidal power project, but by the time it is completed early this fall there will not be much left for people on the shore to see.

Harnessing the tide

Hydroelectricity has been a significant part of the world's energy picture for more than a century at this point, but there are two types of power technology that researchers have recently begun looking at to take advantage of the tremendous energy available in the ocean.

First is wave power, which uses the motion of water as it rises and falls. These systems can function in a variety of ways, either with static generators in anchored platforms or more recently by pumping water to shore to power a traditional turbine.

The sometimes lower-profile tidal power instead makes use of the motion of water into and away from the shore, relying on the steady and sometimes dramatic movement of the tides to spin a turbine and power a generator. At the strongest point, the media outlet reports, tidal currents can move as fast as seven miles per hour.

Reliability the key

While the U.S. Department of Energy reports that the windiest parts of the country can average wind speeds of more than 22 miles per hour, the difference with tidal power lies in the mass of the fluid. With water being heavier than air, it requires more energy to move at higher speeds, allowing even slower-moving tides to provide greater amounts of energy.

This improved energy density allows Ocean Renewable Power to offer greater amounts of energy with more compact turbines, reducing costs and increasing the potential energy for the footprint of a given plant. In addition, because these turbines are relying on the deeper tidal waters, the projects are effectively invisible from the shore, which helps avoid hassles such as the objections from residents near Massachusetts' planned Cape Wind.

More importantly, however, tidal power differs from so-called intermittent energy sources like wind and solar. Whereas those technologies rely on often unpredictable weather patterns, the U.S. National Oceanic and Atmospheric Administration maintains detailed projections for tidal currents, including time and speed.

"That’s highly valuable to the folks who have to manage the generation and transmission system," Paul Jacobson, project manager at California nonprofit Electric Power Research Institute, explained to the Globe. "To know how much power they can expect to get from a system over time is valuable."

One project in growing field

The Ocean Renewable Power Co. pilot project includes only a single turbine for the time being and is scheduled to be completed this September. According to Technology Review, the one turbine will produce 150 kilowatts of power at its peak, powering around 1,200 homes. After operating for about one year, the company hopes to add several more turbines.

However, Reuters reports a new study from the Carbon Trust estimates that the rapidly growing U.K. tidal power industry could see power prices fall by half when compared to offshore wind in the next 13 years, offering a promising alternative to an oft-troubled industry.