Wave energy technology utilizes the rising and falling crests of surface waves driven by tidal forces on the ocean to generate electrical power, either from the direct flow of water or through the pressure effect that the water can have on surface air currents. While wave energy technology offers the promise of being essentially free energy and completely renewable, its impact on the marine environment is largely unknown. The technology is also in a developmental stage, where prototypes are being tested that could eventually be scaled up to provide large amounts of power for coastal cities.
One example of wave energy technology using wind energy has been developed in Australia and is being tested off the coast of Hawaii in the US as of 2008. Arriving waves enter a chamber that forces air in and out of a central tube, which is used to drive a turbine. The turbine is designed to shift rotation in response to waves rising or falling as they alter the flow of air so that it turns continuously. The process does generate a lot of noise, however, which is one of its major drawbacks.
Another method uses large, floating, oblong pelamis tubes that bob up and down on the surface as waves pass underneath them. This moves a lever attached from each tube to a hydraulic pump that drives electrical generators. A similar hydraulic design uses equipment that sits on the sea floor, attached to floating units that move like a piston as the waves rise and fall, to pump seawater through generators. The oyster shell wave energy technology also uses the pumping action of waves to open and close a hydraulic panel that pumps fluid to a shore station, where the pressure is again used to drive an electrical generator.
In the US as of 2007, experimental wave energy projects off of the coast of Oregon have a completion date of between 5 to 10 years, and are projected to produce enough power at peak capacity to supply 60,000 households. The devices use wave capturing buoys placed in the Pacific Ocean, and complement similar experiments by the states of Washington, Hawaii, and New Jersey. The testing is being done while simultaneously attempting to assess the environmental impact of the systems as they operate.
While US programs are largely experimental, Europe is leading in the development of wave energy technology. Throughout the European sector, wave energy technology has been studied for over 25 years with varying levels of public support and success. Problems with scaling up tidal energy systems to practical levels include irregularity in wave size and direction, structural capabilities to handle extreme ocean weather patterns, and matching the design of equipment so that it is efficient at utilizing slow and irregular wave motions.
The ability to harness energy from waves is directly proportional to the square of their amplitude, or period of time between crests, and their size. This makes waves generated in the latitudes of 30° and 60° north and south latitude around the globe the most energetic. The European nations with the highest potential to tap into this energy source are Iceland, the United Kingdom, and Ireland, as well as northern Spain and southern Norway.
Estimates are that the total amount of ocean power available along European coastlines is in the magnitude of 320 gigawatts. The coastline of the UK is projected to have the capacity to produce 67 gigawatts of electricity from wave energy technology. By comparison, the UK, as of 2008, had an electrical energy production capacity of 76 gigawatts of power from traditional oil, gas, and renewable sources.
The environmental concerns from the placement of a wave energy generator focus on five broad areas. The effects of multiple wave energy devices on littoral, or shoreline dynamics, and benthic ecosystems at the bottom of shallow regions of water, are under study. Research into the electromagnetic fields that wave energy technology generate and have on surrounding fish habitats and migration patterns is also under investigation. Overall effects on the local life cycles of marine mammals and seabirds is also being studied.
Additional concerns with wave energy farms along the shoreline involve their effect on recreational activities, their noise pollution, and the potential hazard to ship navigation. Despite these drawbacks, as of 2008, global prototypes were producing two megawatts of power. Projected worldwide production has been estimated at 2,000 gigawatts a year, or 10% of the world's entire electrical energy consumption in 2008. To actually reach such a level of production, the investment cost has been estimated at €820,000,000,000 Euros ($1,173,830,000,000 US Dollars).