Hydropower and Ocean Energy
From rushing rivers to waterfalls to waves breaking on the beach, water energy is all around us. Hydroelectric power plants at dams or alongside rivers use moving water to turn turbines to create electricity. And researchers are currently testing many other ways of tapping into waves, tides and currents.
Water power is...
Hydroelectric generators release almost no CO2, but some experts argue that plants and other organic matter decaying in the lakes behind dams produce significant amounts of greenhouse gases.
Though start-up costs can be high, hydroelectric power plants have been providing low-cost electricity to much of the world for decades.
Water flows all day and night, so hydropower provides a constant source of electricity. Droughts, however, can interrupt this power supply.
Since electricity can only be generated in certain spots, hydropower best serves those living close to waterways.
Dams can force people and animals to resettle and can damage river ecosystems.
15% of the world's electricity is generated by hydropower
Hydroelectric power plants currently provide the world with about 15 percent of its electricity, but there's not much room for big new hydroelectric plants.
Researchers are working on ways to tap into the ocean's energy. Here, linked cylindrical generators, each about the size of a train car, wriggle back and forth in the waves. A resistance system inside each section generates electricity.
Projects that harness the ocean's energy are for the most part experimental, and they are unlikely to provide a substantial portion of Earth's electricity over the next few decades. But one of the simplest methods has been around for decades: since 1984, the Annapolis Tidal Generating Station in Nova Scotia has opened gates in a dam to allow a basin to fill with water during high tide. As the tide recedes, the outgoing water flows through turbines, generating electricity for thousands of local homes and businesses.