WASHINGTON - Scouring the Earth for new sources of clean, renewable energy, scientists and engineers are exploring some unusual nooks and crannies.

Kites, waves, tides, ocean currents, geysers, garbage, cow manure, old utility poles, algae and bacteria are being enlisted in the effort to lower the world's reliance on climate-warming coal and oil.

Researchers are even trying artificial photosynthesis, producing electricity by imitating the way green plants exploit the sun's energy.

Most of these ideas may never make economic or technological sense. It's always possible, however, that a daffy-sounding scheme could turn out to be the next Google, GPS, Facebook or similar breakthrough.

Many exotic proposals would be expensive, at least at first, and of uncertain reliability. They mostly depend on government subsidies, and probably the continued high price of oil, to make them competitive with the old standbys.

Here are some of the innovative ideas that researchers -- and venture capitalists hoping for profit -- are working on:

WAVES

People have always been amazed at the enormous power of waves, especially those pounding the U.S. coastlines. Now they're trying to harness some of that wasted energy to generate electricity.

The European Wave Energy Centre, based in Lisbon, Portugal, lists 63 such projects with catchy names such as Wave Dragon, WaveRoller, Manchester Bobber and Poseidon's Organ.

Some use floating devices that bob up and down with the waves. Others try to capture energy from the surf along beaches. A "wave swing" hanging below the sea's surface generates electricity from the rising and falling pressure of waves passing overhead.

The up-and-down or back-and-forth motion of these experimental devices produces energy to drive electrical generators, provided they can be scaled up to work at high volume and reasonable cost.

"No design has yet emerged to be the winner," said Chang Mei, an ocean engineering expert at the Massachusetts Institute of Technology in Cambridge.

One project is the Pelamis Wave Energy Converter, based on the Orkney Islands north of Scotland. Pelamis resembles a huge snake made up of four 40-meter (about 130-foot) steel tubes, linked end to end, riding on the sea surface. Waves make the segments flex against each other, driving hydraulic rams that, in turn, drive electric generators. By next year, the operator, Pelamis Wave Power Ltd., hopes to supply the power that 10 percent of Orkney's 20,000 inhabitants need.

TIDES

Suitable tidal currents are scarcer but more dependable than waves, Mei said.

An ambitious scheme being developed at Florida Atlantic University in Boca Raton would anchor a fleet of turbines to the sea floor under the Gulf Stream, 13 to 15 miles off the east coast of Florida.

The vast, untapped power of the Gulf Stream would spin the turbines as it flows north at a steady 5 mph. Underwater cables would carry electricity to shore. A prototype turbine is being tested in a laboratory before it goes into the water next year, assuming that questions about the environment and the safety of fish are settled.

"Florida is the best location in the world to develop ocean current energy," said Susan Skemp, the executive director of Florida Atlantic's Center for Ocean Energy Technology, the project's sponsor. When fully deployed, she said, the Gulf Stream project could produce as much electricity as four to eight nuclear power plants, enough to serve 5 million homes.

The United Kingdom is weighing a plan to place a 10-mile-long "barrage," a sort of dam, across the Severn Estuary between Wales and southwest England. The rise and fall of the estuary's 48-foot tides would spin turbines, like a hydroelectric dam, but it would work both ways, as the tide roared in and out.

Next page >

Get $150+ in coupons in every Sunday N&O. Click here for convenient home delivery.