1.25 Megawatt Oscillating winds generate power from waves

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Wuxi InfiMotion Technology Co., Ltd.

Harvesting energy from waves is not always easy. Point absorbers, wave energy converters, or systems with air chambers are just some of the solutions available on the market. In Hawaii, a wave power plant using the air chamber principle is now being connected to the grid.

Air turbine technology is one of the most efficient ways to generate electricity from waves. An Oscillating Water Column consists of a structure partially submerged underwater, placed on the coast or on a floating platform at sea. This structure has an air chamber that is open at the top and dips into the water at the bottom. When a wave hits the structure, water is pushed into the lower opening of the chamber. The motion of the water level within the chamber then causes a compression of the air in the chamber.

The compressed air then flows through an opening at the top of the chamber. In this opening, there is a turbine, often a Wells turbine, which always turns in the same direction regardless of the direction of air flow. This turbine is connected to a generator, which converts the mechanical energy of the turbine into electrical energy.

There are two cycles that generate energy:

Rising Wave: As the wave rises, water is pushed into the chamber, the air is compressed and pushed out through the turbine, driving the turbine.

Falling Wave: When the wave falls, the water level in the chamber drops, creating a vacuum. Air is sucked into the chamber through the turbine, which drives the turbine again.

The continuous alternation of compressed and relaxed air ensures a constant movement of the turbine. The Wells turbine is particularly efficient because it always turns in the same direction regardless of the direction of air flow, which allows for consistent energy generation.

The Irish company Ocean Energy has built a facility for Hawaii with its US subsidiary. Here, OE-25 type wave generators are used. The approximately 38 x 18 meter (124.7 x 59.1 ft) facility, about 9 meters (29.5 ft) of which is supposed to be underwater, is set to generate around 1.25 megawatts and costs about 12 million dollars. The electrical energy saves 3,600 tons of CO2 annually and is expected to supply up to 18,750 households with electricity. On July 19, the facility was brought to its destination, the Mōkapu Peninsula, and will be connected to the grid there.

The location of the facility is in the U.S. Navy Wave Energy Test Site (WETS). The US Navy's testing ground is located north of the Mōkapu Peninsula, Marine Corps Base Hawaii, Kaneohe Bay, O'ahu, Hawai'i. The water depth in the area is between 60 (197 ft) and 80 meters (262 ft).

The test will show whether wave energy plants have the potential to play a significant role in future energy supply. They can generate high amounts of energy in a small area and could significantly contribute to the reduction of CO2 emissions. However, they face challenges such as high initial and maintenance costs, the need for further technological developments, and geographical restrictions to coastal regions. Overall, wave energy facilities could be an important addition to other renewable energy sources, but their widespread adoption depends on overcoming these hurdles. (mr)