BRIAN VANITY, insurgent49, September 1, 2006
As any mariner knows, the oceans are packed full of energy. The energy contained in the seas can destroy ships but, if harnessed correctly, can also be used to generate electricity.
There are several types of energy, which can be extracted from the Alaska’s ocean waters, the two most promising being tidal, and wave energy. Tidal energy is derived from the cyclic rise and fall of the ocean’s tides, while wave energy is harnessed from rapid rise and fall motion of the ocean waves, which are mostly created by the wind. Ocean current energy is extracted from deep-level currents, which are caused by the thermal circulation of the earth’s weather system.
Tidal, wave, and ocean current energy are directly related to conventional hydroelectric power, in that they are all variations of the mechanical energy of moving water. Offshore wind energy is also considered ocean energy, and several offshore wind farms have been built in Europe’s North Sea. In Alaska today, the only wind energy proposals in the state involve on-shore projects.
Tidal power uses the energy of the moving ocean tides, which are driven by the gravitational pull of the moon and, to a lesser extent, the sun. The power output is variable, but predictable years in advance.
The natural ebb and flow of the tides potentially offers a huge future energy source for Alaska. In contrast to other variable renewable energy sources such as wind power, the tides are predictable.
Although tidal energy was first used in European grain mills hundreds of years ago, only a handful of tidal power plants exist in the world today, so operational experience is limited. These existing tidal plants are barrage-style, which involve the capital-intensive construction of large tidal dams across an estuary or inlet. Such large structures that block tidal flows usually have significant environmental impacts, similar to those of large dams on rivers.
The largest existing tidal power plant, a 240-megawatt MW facility on the La Rance estuary in northern France, has caused negative environmental effects since being completed in 1966. The only other large-scale tidal power plant in operation today is the 20 MW Annapolis Royal facility, located along the Bay of Fundy in Nova Scotia.
Tidal current energy, also called ‘in-stream’ or ‘hydrokinetic’ tidal energy, is a different form of tidal power generation that does not require barrages or dams. In constricted ocean channels or inlets, the changing tidal water level can create strong tidal currents. Low-impact tidal current turbines, which and resemble underwater versions of wind turbines, are still under development. Research, development, and capital costs are high since the technology is mostly in the experimental stage, and have borrowed from many advanced in wind energy technology.
Several tidal energy sites are under investigation across the USA. In Washington, the city of Tacoma is investigating the tidal energy potential of the Tacoma Narrows of Puget Sound. The company Verdant Power (www.verdantpower.com) is installing six 36-kW tidal turbines in the East River of New York City, with the installation of the first two turbines to be completed by the end of this year. The six tidal turbines will power a shopping center and parking garage on Roosevelt Island, which is located between the boroughs of Queens and Manhattan.
In Europe, an array of tidal turbines is also being built in northern Norway (www.e-tidevannsenergi.com), with 540 kW of generation capacity to be installed by the end of 2006. Lunar Energy (www.lunarenergy.co.uk), HydroVenturi (www.hydroventuri.com) and Marine Current Turbines (www.marineturbines.com) are three promising tidal current turbine upstart firms from the UK, where the government is very supportive of ocean energy research.
Both wave and tidal energy devices will soon begin tests at the new European Marine Energy Centre (www.emec.org.uk), which is located in the Orkneys Islands north of Scotland. The Scottish government has pledged that the country generate 18% of its power from renewable resources by 2010, and this new marine energy testing center will be the largest such facility in the world.
Alaska has many sites with strong tides along its lengthy coast, including both large tidal ranges between high and low tides, and strong tidal currents. Parts of the Alaska coastline have some of the strongest tides in the world, including the upper Cook Inlet around Anchorage. Bristol Bay, Cordova, Seldovia, Angoon and other locations in Southeast Alaska also have strong tidal currents.
The tidal power potential of Alaska has been studied since the 1950s, although no tidal energy systems yet exist in Alaska. Over the past several decades, a number of tidal energy studies have been conducted on Cook Inlet. All of these proposed the construction of large concrete barrages (seawater dams) and the use of conventional bulb-type, “low-head” hydropower turbines. Various ‘barrage schemes’ for upper Cook Inlet were studied up until the early 1980s.
Tidal Electric of Alaska’s tidal energy feasibility study for Cordova proposed a large, concrete-enclosed ‘tidal tank’, a modification on the traditional tidal barrage, and would have still used conventional bulb-type turbines. A 1998 feasibility study conducted in Cordova estimated a $14 million initial cost for a 5000-kW system, or $2800 per kW of installed capacity. Electricity generated from the nearby 6000-kW Power Creek hydroelectric project, which was completed in 2001, was found be more economical. The Cordova tidal energy studies between 1998 and 2000 were the most recent investigations conducted, though did not lead to any development.
Hydrokinetic or in-stream current energy has only recently been under investigation for use in Alaska. The Underwater Electric Kite Corporation (www.uekus.com) has proposed an in-stream turbine installation for the town of Eagle on the Yukon River, with 270 kW to be installed. This project was first proposed in 2003, though still has not received funding. Next door in British Columbia, the provincial electric utility BC Hydro commissioned a 2002 study on tidal current energy, which concluded that the theoretical tidal current power potential of the BC coast is just over 2200 MW.
Knik Arm has the potential of being a good site for a tidal current power plant, with strong currents four times each day. Also, Elmendorf Air Force Base, on the east side of the arm, has significant electrical infrastructure and demand for power. The site also has a close proximity to the Port of Anchorage, which would serve as a base of operations for both construction and maintenance.
The currents and depth are good for the site, but there is are several other concerns that could derail a project, most importantly concern over marine mammals in Knik Arm. Upper Cook Inlet’s Beluga whale count was low this year, worrying marine biologists. A recent report by the Electric Power Research Institute (EPRI) recommended that ‘Alaskan stakeholders’ commission a studies on sub-surface ice behavior, future trends in seabed movement, conduct a site-specific regulatory and environmental assessment, and more detailed tidal current velocity measurements. Deploying an array of tidal current turbines at the Cairn Point site in Knik Arm could produce an average of 17 MW or power from the tidal currents, enough to power over 10,000 average Anchorage homes.
The Alaska tidal energy rush has already started. One upstart tidal energy developer, the Miami-based Ocean Renewable Power Company (www.oceanrenewablepower.com), has recently applied for preliminary permits with the Federal Energy Regulatory Commission (FERC) at seven Alaska locations. However, they already have a bad reputation within the close-knit tidal energy industry.
If approved, a preliminary FERC permit gives a developer three years exclusive access to a site. In the case of these two firms, it is likely that they only intend to “bank” the sites and auction them off for its own private gain when tidal technology matures a few years down the line. Many in the industry are accusing the Oceana and Ocean Power Renewable companies of blocking access to prime sites by applying for permits with no intention of developing them.
Sean O’Neill, president of a new trade group called the Ocean Renewable Energy Coalition recently told Bloomberg News that “Speculation, and the fact it could hold up a site for anywhere from three to six years, that certainly is not good for the industry… Any company that is banking sites should be tarred and feathered.” So in all likelihood, lawsuits over Alaskan tidal energy sites are quite possible for the near future. For more information, read the Bloomberg News article on the web: (www.renewableenergyaccess.com/rea/news/story?id=45668&src=rss).
Though often co-mingled, wave power is a diffierent technology than tidal power generation. However, like tidal energy technology, wave power generation is not yet a widely employed technology, with only a few experimental sites in existence. Worldwide, wave power could yield much more energy than tidal power.
The Earth’s total tidal dissipation (friction, measured by the slowing of the planet’s rotation) is 2.5 terawatts, or about the same amount of power that would be gennerated by 2,500 typical nuclear power plants. The energy potential of waves is certainly greater, and wave power can be exploited in many more locations than tidal energy.
Large wave energy potential is estimated for Alaska’s, thousands of miles of coastline, which is more than the length of coast for the other 49 states combined. Some of the most powerful waves in the world are found in Alaska, and the southern Pacific coastal arc of Alaska (stretching from Ketchikan to Attu) has a theoretical wave energy potential estimated to be 1,250 TWh per year, or 300 times more electricity consumed by Alaskans today.
There are a wide variety of wave energy conversion technologies being tested, ranging from “bobbing corks” to giant metal “sea snakes”. The Pelamis Wave Energy Converter is being developed by an upstart wave energy technology company from Edinburgh, Scotland (www.oceanpd.com/default.html ).
Ocean Power Delivery (OPD), developer of the Pelamis device, has secured over $23.6 million of new investment from a consortium of new and existing investors. In May 2005, OPD signed an order with a Portuguese consortium to deliver the initial phase of the world’s first commercial wave-farm. OPD recently delivered the first three production machines to Portugal, where they will be installed following final assembly and commissioning by the end of 2006. The three units are planned to have a total generating capacity of 2.25 MW, or about enough to power a town of 1000 people.
Another upstart wave energy company, the AquaEnergy Group (www.aquaenergygroup.com ), is working on a four-“bouy” installation with one MW of capacity, to be located three miles offshore of Makah Bay, Washington. The wave energy upstart Ocean Power Technologies (www.oceanpowertechnologies.com ) has already deployed its PowerBouy in Hawaii and New Jersey, and is planning an installation in northern Spain. Other wave power generation projects are under development off the coasts of Italy, Spain, South Africa and Oregon.
The Future for Ocean Energy in Alaska
Knik Arm is the most promising commerical tidal energy site in the state, due to its close proximity to Anchorage. Also, offshore wind or tidal turbines mounted on abandoned oil and gas platforms in Cook Inlet, though new underwater electric transmission cables would be needed. To find more promising sites, a statewide study of Alaska’s tidal and wave energy potential is needed. In the future, utility-scale tidal power could also help the urban Alaska energy situation, which is faced with looming increases in natural gas prices. Tidal energy research and development in Alaska could establish the state as a world leader in ocean power technology.
Given the length of its coastline and the strength of the seas, both wave and tidal energy are well worth exploring for Alaska’s future energy needs