Dear EarthTalk: Alternative energy sources like wind power, hydrogen and biofuels are getting a lot of headlines these days, but what about efforts to generate electricity from the ocean's waves?
—Tina Cook, Naples, FL
As any board or body surfer will tell you, the ocean's tidal currents pack considerable wallop. So why wouldn't it make sense to harness all that formidable power, which is not too unlike that of the rivers that drive hydropower dams or the wind that drives wind turbines, to make energy?
The concept is simple, says John Lienhard, a University of Houston mechanical engineering professor: "Every day the moon's gravitational pull lifts countless tons of water up into, say, the East River or the Bay of Fundy. When that water flows back out to sea, its energy dissipates and, if we don't use it, it's simply spent." According to Energy Quest, an educational website of the California Energy Commission, the sea can be harnessed for energy in three basic ways: using wave power, using tidal power, and using ocean water temperature variations in a process called "ocean thermal energy conversion" (OTEC).
In harnessing wave power, the back-and-forth or up-and-down movement of waves can be harnessed, for example, to force air in and out of a chamber to drive a piston or spin a turbine that can power a generator. Some systems in operation now power small lighthouses and warning buoys. Harnessing tidal energy, on the other hand, involves trapping water at high tide and then harnesses its energy as it rushes out and drops in its change to low tide. This is similar to the way water makes hydroelectric dams work. Already some large installations in Canada and France generate enough electricity to power thousands of homes.
An OTEC system uses temperature differences between deep and surface waters to extract energy from the flow of heat between the two. An experimental station in Hawaii hopes to develop the technology and someday produce large amounts of electricity on par with the cost of conventional power technologies.
Proponents say that ocean energy is preferable to wind because tides are constant and predictable and that water's natural density requires fewer turbines than are needed to produce the same amount of wind power. Given the difficulty and cost of building tidal arrays at sea and getting the energy back to land, however, ocean technologies are still young and mostly experimental. But as the industry matures, costs will drop and some analysts think the ocean could power nearly two percent of U.S. energy needs.
Several companies now work at the cutting edge of ocean power technology. Scotland's Ocean Power Delivery Ltd. has a wave system called Pelamis that it hopes to install in waters off of California's wave-battered central coast. And Seattle, Washington's Aqua Energy has installations off the coasts of Oregon, Washington and British Columbia and is in talks with utilities about providing the Pacific Northwest with hundreds of megawatts of ocean energy within the next decade.
Tidal energy pioneers are also hard at work on the U.S. Atlantic coast. The New Hampshire Tidal Energy Company is developing tidal power in the Piscataqua River between New Hampshire and Maine. And a company called Verdant Power is providing Long Island City, New York with electricity through tidal river turbines and has begun installation of tidal power systems in New York City's East River.
Dear EarthTalk: There has been so much attention paid to designing environmentally friendly cars. Is there a similar effort to replace gas-guzzling boats?
—Brita B., via e-mail
The U.S. has been regulating fuel economy and emissions in cars and trucks for decades but got a late start addressing similar issues with boats. In 1996, though, recognizing a growing problem of boat engine pollution, the Environmental Protection Agency (EPA) issued new rules to "bring forth a new generation of marine engines featuring cleaner technology and providing better engine performance to boat owners."
Even small quantities of fuel and exhaust discharged by boats can disrupt the balance of nutrients, oxygen and clean water in both freshwater and marine ecosystems. Indeed, the cumulative effect of millions of inefficient motorboats plying our waterways has been devastating to marine life and our water supplies. Under the new EPA regulations, which will phase in over the next 30 years, new marine engines will burn gas much more efficiently and generate much less pollution than most models out on the water today.
According to the EPA, traditional two-stroke boat engines waste significant amounts of gasoline and oil, spilling as much as 30 percent of their fuel into the water and air either unburned or partially unburned. In the water, unburned hydrocarbons increase concentrations of benzene, methyl tertiary-butyl ether (MBTE) and other toxic substances that pollute water ecosystems. In the air, they help form smog, which causes a host of health problems and disrupts visibility everywhere from our cities to our national parks.
Those looking to buy a boat today should choose one with a four-stroke or direct fuel injection (DFI) two-stroke engine. These pollute about 75 percent less than their traditional two-stroke predecessors and use as much as 50 percent less gas and oil. They cost more than traditional two-stroke engines, but owners soon make up the difference in fuel and oil savings. They are also easier to start and maintain, and are quieter.
New generations of electric boat motors are also coming on line, and promise to significantly cut pollution if adopted widely. Wooden, sport and leisure boats are now all available with electric engines that are quite comparable to traditional engines in performance and looks. They are also non-polluting, quiet and can cruise where gas motors are not permitted. Some leading makers include Beckman, Budsin, Cobalt Marine, Electric Launch, Duffy, Electracraft, Griffin Leisure, Pender Harbour and Spincraft.
The only catch is that the energy that powers the batteries for electric boats most likely comes from a coal-burning power plant that spews mercury, carbon dioxide and other pollutants into the skies and waterways. A handful of manufacturers—such as Australia's Solar Sailor and Canada's Tamarack Lake—now make solar-powered or solar-assisted electric boats to help overcome this environmental hurdle.
Of course, the ultimate energy source for any recreational activity is elbow grease. But for those who need more than a canoe or kayak to get around, Nauticraft hybrid boats employ human pedal power to augment a small electric motor. And the Italian-made Shuttle Bike puts a new spin on pedal boats: Owners affix two inflatable pontoons to their mountain bikes, and they can then pedal around their local lake or harbor.