Off the western coast of Scotland, on the Isle of Islay, science teacher Ray Husthwaite turns on the light in his classroom. The electricity comes from a power cable that runs to the mainland. But it also comes from the ocean. A few miles from the school, wave action compresses and decompresses air in a chamber. The moving air powers a turbine, which generates electricity. It is pleasant ... to sit beside the gray, concrete structure and listen to the rising and falling of the waves, driving air through the turbines like the breath of a great sea monster," Husthwaite said. "It seems insane to me to be investing in nuclear power stations and gas turbines when there are endless, free energy resources in the rivers, oceans and the wind." Ocean power gradually is joining the ranks of wind and solar power as a source of renewable energy. Islay's wave-power converter, the Limpet 500, has been operating since 2000. In Hawaii, the Navy has been churning up electrons with the help of a floating buoy. And in Portugal, engineers are installing snakelike tubes designed to convert the sea's motion into electricity. Some designs, like the Limpet, use waves to push air through a column. Others convert the sea's up-and-down motion into mechanical energy. One wave-power company executive told a congressional committee last year that several hundred square miles off the California coast could supply the electrical needs of all of the homes in the state.