Wave Power

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Wave power

The oceans are an enormous reservoir of energy. One form in which that energy appears is waves. The energy in waves is derived from the wind energy that generates them. Since wind currents are produced by solar energy , wave energy is a renewable source of energy.

Humans have invented devices for capturing the power of waves at least as far back as the time of Leonardo da Vinci. The first modern device for generating electricity from wave power was patented by two French scientists in 1799. In the United States, more than 150 patents for wave power machines have been granted.

Harnessing the energy of wave motion presents many practical problems. For example, while the total amount of wave energy in the oceans is very great, the quantity available at any one specific point is usually quite small. For purposes of comparison, an wave that is 8 ft (2.4 m) tall contains the same potential energy as a hydroelectric dam 8 ft high.

One technical problem inventors face, therefore, is to find a way to magnify the energy of waves in an area. A second problem is to design a machine that will work efficiently with waves of different sizes. Over a period of days, weeks, or months, a region of the sea may be still, it may experience waves of moderate size, or it may be hit by a huge storm. A wave power machine has to be able to survive and to function under all these conditions.

Wave power has been seriously studied as an alternative energy source in the United States since the early 1970s. An experimental device constructed at the Scripps Institute of Oceanography, for example, consisted of a buoy to which was attached a long pipe with a trap near its top. As the buoy moved up and down in the waves, water entered the pipe and was captured in the trap. After a certain number of waves had occurred, enough water had been captured to drive a small turbine and electrical generator. One of the first Scripps devices consisted of a pipe 8 in (20 cm) in diameter and 320 ft (98 m) long. It was able to generate 50 watts of electricity. Scripps researchers hoped eventually to construct a machine with a pipe 15 ft (4.5 m) in diameter and 300 ft (91.5 m) long. They expected such a machine to produce 300 kilowatts of energy in 8-ft (2.4 m) waves.

Research on wave power in the United States essentially died out in the early 1980s, as did research on most other forms of alternative energy sources . That research has continued in other countries, however, especially in Japan, Great Britain, and Norway. The Norwegians have had the greatest success. By 1989, they had constructed two prototype wave machines on the coast west of Bergen. The machines were located on the shore and operated by using air pumped into a large tower by the rise and fall of waves. The compressed air was then used to drive a turbine and generator. Unfortunately, one of the towers was destroyed by a series of severe storms in December 1989. The Norwegians appear to be convinced about the potential value of wave power, however, and their research on wave machines continues.

Great Britain has had a more checkered interest in wave power. One of the most ambitious wave machines, known as Salter's Duck, was first proposed in the early 1970s. In this device, the riding motion of waves is used to force water through small pipes. The high-pressure water is then used to drive a turbine and generator.

The British government was so impressed with the potential of wave power that it outlined plans in April 1976 for a 2,000-megawatt station. Only six years later, the government changed its mind, however, and abandoned all plans to use wave power. Fossil fuels and nuclear power had, meanwhile, regained their position as the major—and perhaps only—energy sources in the nation's future.

Then, in 1989, the British government changed its mind yet again. It announced a new review of the potential of wave power with the possibility of constructing plants off the British coast. One of the designs to be tested was a modification of a Norwegian device, the Tapchan (for "tapered channel"). The Tapchan is designed to be installed on a shoreline where waves can flow into a large chamber filled with air. As waves enter the chamber, they compress the air, which then flows though a valve and into a turbine. The compressed air rotates the turbine and drives a generator. The prototype for this machine was installed at Islay, Scotland, in the early 1990s.

Wave power has many obvious advantages. The raw materials (water and wind) are free and abundant, no harmful pollutants are released to the environment , and land is not taken out of use. However, the technology for using wave power is still not well-developed. It can be used only along coasts, and is still not economically competitive with traditional energy sources.

[David E. Newton ]