Ocean Waves Now Being Used to Produce Clean Power
Wave energy conversion can be used to generate electricity, safely replacing our need for toxic fossil fuels and dangerous nuclear power plants, and reducing millions of pounds of carbon dioxide, sulfur dioxide and nitrogen dioxide emissions that are produced from coal generated electricity.
Clean electricity generation offers the additional benefit of saving millions of dollars on health care related costs due to air pollution. This abundant, renewable energy resource is produced 24 hours a day, 365 days a year and is 80 percent efficient.
Wave energy conversion can be accomplished with various technologies, including; onshore devices, near-shore devices, floating (moored) devices and offshore (submerged) devices, like tidal power turbines.
Onshore wave devices such as The LIMPET located on the Isle of Islay, Scotland, trap the waves crashing to shore in an inlet, bay or estuary. The LIMPET uses an inclined oscillating water column (OWC), which was further developed by WaveGen Corp.
Graeme Mackie, Senior Engineer at WaveGen, recently spoke at the Ocean Energy2004 Conference, introducing us to the facility. The LIMPET has been in operation for over three years, and is located on the shoreline off the west coast of Scotland.
It is an automatically run, unmanned remote operation that utilizes a pair of fixed pitch contra- rotating Wells turbines. The device has a rating of 500kW.
According to the WaveGen website “the World Energy Council estimates that the energy that can be harvested from the world’s oceans is equal to twice the amount of electricity that the world produces now”.
Scotland currently generates approximately 12 percent of their electricity from renewable sources, and they plan to increase that to 40 percent by 2020.
The technology already exists to extract the energy from their energetic shoreline, and the technical problems have been solved. The challenge that is left is to make the technology work at a cost that is acceptable to consumers.
Another type of onshore system is the tidal power plant, also referred to as a barrage system, the oldest running unit located in La Rance, France.
The only tidal power plant located in North America can be found in Nova Scotia. The Annapolis Tidal Generating Station, the first and only modern tidal power plant in North America, is located in the Bay of Fundy, Nova Scotia. Using the largest straflo turbine in the world, it produces more than 30 million kW hours per year-enough to power 4000 homes.
Put simply the incoming and outgoing tides are used to generate electricity by building a dam across a bay or estuary. The incoming tide is allowed to fill up a basin, the floodgates are closed behind it, topping off the water in the basin.
When the ocean level outside the basin has fallen, the water is released back to the sea through conventional hydroelectric turbines which generate electricity.
The electricity is then transmitted back into the grid and distributed to the end user. Suitable sites for tidal power plants situated around the world can be found in: France, the United Kingdom, Russia, Canada, and the United States.
During the last week in August the operators of the Annapolis plant had to shut it down temporarily because a humpback whale had wandered up the Annapolis River.
While not being in any direct danger from the power plant, the noise from its operation may have scared the whale farther up the river. The whale eventually found its way back to sea with no harm
The environmental impact of the barrages on the tides along the eastern seaboard, the inter-tidal zones, and the sedimentation (understanding its biological function and effects on marine life) have yet to be studied at length.
In a recent correspondence Mr. Foerd Ames, with Ocean Wave Energy Company, wrote” Negative environmental impact is not specific to just OWEC®.
Perhaps a sobering outlook, but a de facto philosophy is that any human activity or construct changes the hitherto pristine natural environment in which it exists.
Some of the most well intended works, particularly shore bound constructions, have subsequent effect often of detrimental quality that was not predetermined.
Within ocean environs, onshore, near-shore littoral zones comprise biodiverse processes that are best left undisturbed. OWEC® deployment is intended for offshore application where such perturbation would be minimized.
Offshore systems placement, whether OWEC® or other, also has intrinsic effect which may comprise negative or beneficial attributes. Within the context of wide scale OWEC® deployment…., prudent thought considers, for example, barnacle and seaweed encrustation that would engender habitat change and subsequent marine life redistribution, sunlight blocking of upper layers, aeration cycle (H2O, O2, CO2) manipulation, and other considerable factors.
It could be that the change is actually positive with careful monitoring and control but, generally, my point was that we need exercise a careful approach.”
The largest tidal power plant in the world is located in the estuary of La Rance, France, generating 240 MW it utilizes double effect generation, meaning both the incoming and outgoing tides are used.
The embassy of France in Australia reports that although the dam controls the tidal waters, fish can pass freely from the sea to the basin and back without injury to the fish.
The initial damage to the maritime environment caused by the underwater construction fully recovered its biological diversity, of both plants and animals, according to the maritime Laboratory in Dinard.
Their geomorphology laboratory reported the sedimentary balance in the estuary remained stable. Because toxic wastes aren’t dumped into the environment from this plant, the overall operations displayed environmentally sound results.
The last and smallest tidal power plant, coming in at a 0.5 MW capacity, is located at Kislaya Guba on the White Sea, Russia.
Nearshore submerged devices are placed on the seabed in shallow water, for example the Sea Dog, which not only generates electricity without pollution, but can be used to act like an artificial reef, improving the environment for fish.
Mark Thomas, President/CEO of Independent Natural Resources Inc., a Minnesota based company, announced that they have successfully tested their new wave pump device, dubbed The Sea Dog.
The pump is a point absorbing wave energy converter that is potentially capable of generating 755 MW of hydroelectric energy for every one square mile pump field, assuming ocean swells of nine feet.
The pump sends seawater to a reservoir or water tower. The water is sent back to the oceans through hydroelectric turbines, generating electricity. The company plans to test a “wave farm” with either 14 or 200 Sea Dog pumps working in concert, according to their vice president, Doug Sandberg.
Wave Energy Conversion is a system that captures the pneumatic motion of waves using one of the many floating devices available, such as; The Pelamis, The Aqua Buoy, The PowerBuoy, The Salter Duck, articulated rafts, and compressed floating bags, to name a few.
Max Carcas, of Ocean Power Delivery, Edinburg, Scotland, has been in the renewable energy industry since 1998. His company was presenting The Pelamis Wave Energy Converter, a floating wave device that generates 750 kW, enough energy to power over 500 homes.
The device, measuring 150 m in length, 3.5 m diameter, and weighing 750 tons, was recently installed at the European Marine Energy Center in Scotland.
The machine operates utilizing the articulation of wave energy, which is transmitted through hydraulics, run through the accumulator, to the turbine and into the generator.
Their chief concerns with The Pelamis are: environmental concerns, socio-economic concerns, and the security of the energy supply.
Alla Weinstein, of Aqua Energy, presented their new project located in Makah Bay, WA. AquaEnergy has developed a new offshore point absorber wave energy conversion device called the AquaBuoy, composed of four devices linked together with cable.
They combine a Swedish Hose-Pump with the buoy to harness the motion of the waves, moving the pistons up and down, causing the pressurization of water, which turns the turbines.
The electricity which is generated is sent along the submerged cable to land. It is a closed loop which generates some 2,200 mWh of power annually.
Some of the problems in completing the construction were:
- Permitting problems, FERC licensing requirements ask a 30 year license for a two-year project, and there’s much confusion over which agency is in charge of the permitting. They ended up dealing with at least 13 agencies for the environmental impact studies alone.
- Not much support from government funding, because no one in government seems to know how this technology works, therefore they considered it an unknown.
- Unknown long-term environmental impacts; some of the environmental problems noted thus far are rocks breaking or entangling the cables, and seaweed and kelp beds entangling the cables.
- And of course the enormous monetary output necessary to construct and maintain these projects per year.
For more information, click on their website at: www.aquaenergy.com.
Dr. George Taylor, president and CEO of Ocean Power Technologies, has been in the renewable energy industry since 1984, and announced that OPT was the first wave power company to take its stock public on London’s Alternative Investment Market.
PowerBuoy wave power technology is best located above the tropic of Cancer, not in tropical areas, as it works better in colder climates.
Offshore wave technology can be located closer to population centers, therefore cutting down on transmission costs to the end user. The environmental advantages of wave energy over conventional energy generation include: no carbon emissions, no noise or visual pollution, no negative impact on marine life.
The machine, installed at a 30 m depth looks like a steel column buoy, anchored into the sea bed, like a steel tube on a pogo stick. The cylinder is about 48 feet long and 14 feet in diameter.
Divers attach the buoys to anchors, and a yellow computer station at that the top of the steel column reads the energy output and status of the machinery. A power line then transmits the energy to the power station onshore.
O.P.T. is currently building a 1MW wave power station for the US Navy, at the Kane’ohe Marine Corp base on Oahu, Hawaii. They have also contracted with Iberdrola, the largest renewable energy utility in Europe, to build a 1.25MW wave power station on the northern coast of Spain.
The project will use 10 of the PowerBuoys, which utilize smart technology that can sense fluctuating wave conditions and automatically switch off the generator when the power of the ocean begins to damage the equipment.
The generating capacity for the buoys are at between 80-90 percent efficiency compared to conventional coal and oil generation at between 30-45 percent efficiency.
The last in this series on ocean energy recovery will cover tidal turbines, offshore wind farms, and hybrid technologies.