A look at the wave, tidal and ocean current power renewable energy technologies, the companies and project news during 2008.
While much of the attention on renewable energy in recent years has focused on solar and wind technologies, awareness has been growing around the enormous energy generating potential of the Earth’s oceans. The first ocean power system connected to the grid opened in Orkney, Scotland, in August 2004; it’s a test system producing 750kW. Orkney will eventually be home to 40 such systems in a “wave farm,” producing 30MW of power.
A 2005 report from the Electric Power Research Institute stated that wave power properly and effectively harnessed, would likely have minimal environmental impact, and be much less visible on the landscape, than competing technologies. At the same time, waves possess the advantage of being more predictable than either wind or solar, which in principle makes it a more reliable source of energy. It is also estimated that the theoretical global wave power resource is between 8,000 and 80,000 TWh/year. A tremendous amount of energy that is several times greater than the actual global electricity demand.
The rapidly expanding field of wave power is rife with innovation and an extraordinarily diverse range of approaches. Several technologies have been, and are being, developed and tested in coastal regions around the world. So far however, technical challenges involved in engineering a sufficiently inexpensive, efficient and reliable method of extracting this energy have proven difficult enough that as yet there is no agreed upon ‘best way’ to do it.
Among the significant difficulties facing engineers of commercially viable wave power have been durability in storms, and low generating capacity factors resulting from the difficulties of extracting a steady load from constantly shifting wave motions. Irregular and alternating wave motions lead to large variations of the power produced, severely limiting the power output of many Wave Energy Converters (WEC).
Mikael Sidenmark, founder of Ocean Harvesting Technologies, and the inventor of the Ocean Harvester (pictured above), has developed a method of generating electricity from waves that offers compelling and cost-efficient solutions to these problems.
As Sidenmark explains:
A buoy follows the wave motions at the surface. When the wave rises, a drum inside the buoy is rotated by a mooring line wound around it, converting vertical motion into a rotation. This is a very efficient way of extracting energy from waves that is independent of the wave sizes and has been used in earlier technologies.
What is unique with the Ocean Harvester is the way a counterweight is used to achieve a leveled and controlled load on the generator. As a result, excess energy from larger waves can be accumulated and used to compensate for shortage from smaller waves. In combination with the flexible mooring, this also composes a simple and efficient storm protection system.
Together, these characteristics result in an exceptionally high capacity factor.
The system should produce a consistent level of power throughout the wave motion, over changing wave sizes, and even in storms. Besides generating efficiently and evenly, the simplicity of its design will allow the Ocean Harvester to be easily protected in rough conditions, and make its manufacture impressively cost-efficient.
Ocean Harvesting Technologies is currently planning a two-year scale model testing period, slated to begin in March 2009 in the coastal Blekinge region of Sweden, on the Baltic Sea. The company expects the Ocean Harvester to enter the commercial market in 2013.
Pelamis Wave Energy Converter
The Pelamis Wave Energy Converter is a technology that uses the motion of ocean surface waves to create electricity. The machine is made up of connected sections which flex and bend as waves pass; it is this motion which is used to generate electricity.
Developed by the Scottish company Pelamis Wave Power (formally Ocean Power Delivery), it was the world’s first commercial scale machine to generate electricity into the grid from offshore wave energy and the first to be used in commercial wave farm project. The first full scale prototype was successfully installed and generated electricity to the UK grid at the European Marine Energy Centre in Orkney, Scotland in August 2004. The first wave farm, located off the coast of Portugal, was officially opened in September of 2008.
The Portuguese minister of the economy officially opened the worlds first wave farm, consisting of three Pelamis wave energy converters, on the 23 September 2008. The farm is located at the Aguçadoura Wave Park near Póvoa de Varzim in Portugal. It has an installed capacity of 2.25MW, enough to meet the average electricity demand of more than 1,500 Portuguese homes. A second phase of the project is now planned to increase the installed capacity from 2.25MW to 21MW using a further 25 Pelamis machines.
In the US, the wave energy company getting the most attention has been Finavera with it’s AquaBuoy system, which has received preliminary approval to build a 100 MW facility off northern California (and has signed a power purchase agreement with PG&E for part of this). At hasn’t all been plain sailing for Finavera however, with a test AquaBuoy device sinking off Oregon late last year.
The Electric Power Research Institute (EPRI) estimated that waves off the Washington, Oregon and California coasts could produce from 250 to 500 terawatt-hours per year – around 12% of US energy demand. Finavera also has approval for a project in Washington state, along with others in South Africa and Canada.
Australian company Oceanlinx (previously known as Energetech) has had a 450 kilowatt wave power unit running at Port Kembla in NSW for a number of years, and plans to connect to the commercial power grid in early 2008. Oceanlinx is also at the advanced permitting stage for a project in Portland, Victoria which would deploy eighteen 1.5MW units for a total capacity of 27MW, which the company claims will be the largest wave energy project in the world.
The company has other projects planned in Rhode Island, Hawaii and Namibia, and intends to participate in the South West of England Regional Development Agency’s “Cornwall Wave Hub” in the UK.
Power Purchase Agreement (“PPA”) has been signed with Australian utility Integral Energy for the supply of electricity from the prototype 450kW unit currently deployed at Port Kembla (New South Wales, Australia).
Both wave energy devices developed and installed so far by Oceanlinx can be viewed in high resolution on Google Earth. It is believed that Oceanlinx is the first wave energy developer to have two different devices in the water concurrently. Both devices are offshore from Port Kembla. The bottom mounted MK 1 device can be viewed at 34° 27’ 07.6” S, 150° 54’ 06.8” E. The floating MK 2 device is positioned at 34° 28’ 16.7” S, 150° 54’ 56.5” E. Simply type these coordinates into the Fly To section, in the upper left hand corner of the Google Earth page.
TIDAL and OCEAN CURRENT POWER
Tidal power stations can take the form of a dam (or barrage) built across a narrow bay or river mouth. As the tide flows in or out, it creates uneven water levels on either side of the barrier. The water flows through the barrier, turning turbines to generate electricity. Underwater turbines can also be used on their own to harness both tidal power and ocean current power. The turbines (sometimes called aquanators) are similar to wind turbines. In water moving between 6 and 9 km per hour, a 15 m diameter water turbine could generate as much energy as a 60 m diameter wind turbine. Given the smaller amount of infrastructure required and the larger range of possible sites that this technology could be deployed to, it seems likely that underwater turbines will become much more widespread than tidal barrage style generation.
SeaGen, the world’s first commercial scale tidal stream turbine, designed and developed by British tidal energy company, Marine Current Turbines, has for the first time generated at its maximum capacity of 1.2MW. This is the highest power so far produced by a tidal stream system anywhere in the world and exceeds the previous highest output of 300kW produced in 2004 by Marine Current Turbines’ earlier SeaFlow system, off the north Devon coast.
SeaGen works in principle much like an “underwater windmill”, with the rotors driven by the power of the tidal currents rather than the wind. It was deployed in Northern Ireland’s Strangford Lough in May of this year and since then has undergone commissioning trials. As SeaGen has now reached full power it will move towards full-operating mode, for periods of up to 22 hours a day, with regular inspections and performance testing undertaken as part of the project’s development programme.
The power generated by SeaGen is being purchased by Irish energy company, ESB Independent, for its customers in Northern Ireland and the Republic of Ireland. SeaGen has the capacity to generate power to meet the average electricity needs of around 1000 homes.
Drawing on its experience of Strangford Lough, Marine Current Turbines’ next project, announced in February 2008, is a joint initiative with nPower renewables to take forward a 10.5MW project using seven SeaGen turbines off the coast of Anglesey, north Wales. It is hoped the tidal farm will be commissioned around 2011/2012.
Using its SeaGen technology, the company is also investigating the potential for tidal energy schemes in other parts of the UK and Ireland, and in North America.
On the west coast of Canada, Marine Current Turbine and BC Tidal Energy Corporation plan to install at least three 1.2 MW tidal energy turbines in Vancouver Island’s Campbell River by 2009. This the first step in a plan to develop larger tidal farms off British Columbia’s coast, which the company says have a tidal energy potential of up to 4,000 MW.
Hydro Green Power
The USA’s first commercial hydrokinetic turbine, which harnesses the power from moving water without the construction of a dam, has splashed into the waters of the Mississippi River near Hastings, Minnesota.
Although not strictly speaking ocean power technology I thought it was worthy of inclusion in this review.
The 35-kilowatt turbine is positioned downstream from an existing hydroelectric-plant dam and — together with another turbine to be installed soon — will increase the capacity of the plant by more than 5 percent. The numbers aren’t big, but the rig’s installation could be the start of an important trend in green energy.
And that could mean more of these “wind turbines for the water” will be generating clean energy soon.
“We don’t require that massive dam construction, we’re just using the natural flow of the stream,” said Mark Stover, a vice president at Hydro Green Energy, the Houston-based company leading the project. “It’s underwater windpower if you will, but we have 840 or 850 times the energy density of wind.”
Hydrokinetic turbines like those produced by Hydro Green and Verdant capture the mechanical energy of the water’s flow and turn it into energy, without need for a dam. The problem for companies like Hydro Green is that their relatively low-impact turbines are forced into the same regulatory bucket as huge hydroelectric dams. The regulatory hurdles have made it difficult to actually get water flowing through projects.
Tidal Power Projects by Country
In the United States, at the southern end of the Bay of Fundy, lies Passamaquoddy Bay, which has long been a target for a tidal power development – first initiated in 1935 by the Public Works Administration under the Roosevelt administration, then halted by Congress a year later. John F Kennedy revived the 550 MW project in 1963, however the plan died with him.
Further south, in the Martha’s Vineyard area, two underwater turbine projects are trying to get started – one a 300 MW proposal from Oceana Energy Company and the other from Natural Currents Energy Services. Other projects are being considered in the Cape Cod and New Bedford areas – part of a “gold rush” for good tidal power sites (the most desirable ones usually have hourglass figures, to get maximum force in the incoming tide) which has seen the FERC issue 47 preliminary permits for ocean energy projects (and generated mainstream news coverage on the NBC network).
New York’s East River is the location of one of the more high profile tidal power experiments currently underway, with Verdant Power experimenting with underwater turbines there. The first attempt eventually ended in failure, with the strong tides breaking the devices.
The Gulf Stream has also caught the eye of hopeful ocean energy companies, particularly in Florida, with the 30 mile wide current pushing 8.5 billion gallons of water along per second and prompting some observers to consider the prospect of “Infinite Underwater Energy“.
Californian utility PG&E is also investigating tapping tidal power in San Francsico Bay, with some observers talking about a plant of up to 400 MW in size.
In the UK, another bay famous for its tides is the Severn river estuary in Britain, with a tidal range of 14 metres. Plans for damming the Severn estuary or Bristol channel have existed since the 19th century (with tidal power generation being just one proposed application). The UK government recently proposed a new barrage design, which could produce 5% of the UK’s electricity requirements, with a peak rate of 8.6 GW. A feasibility study is expected to be complete by 2010. An alternative proposal, by Tidal Electric, involves a series of lagoons, the first of which would be built in Swansea Bay. Some observers have noted underwater turbines may be more appropriate than a barrage.
Pentland Firth in Scotland is another UK location that is considered to have a large amount of tidal power potential – a DTI study in 1993 indicated that if all potential sites were developed, the total UK tidal stream resource could be about 60 TWh. Of this, almost half (28 TWh) could come from the Pentland Firth. The water depth is 60m or more, making potential energy capture huge but technically difficult – 63% of the tidal stream resource is estimated to be in waters deeper than 40m.
Marine Current Turbines launched the world’s first underwater turbine project off north Devon in 2003. MCT also began installing a 1.2 MW “SeaGen” tidal current turbine in Northern Ireland’s Strangford Lough in 2007, with the company planning to scale up to build a 10MW tidal power farm off Anglesey in North Wales, and to have 500MW of tidal capacity by 2015. Also in Wales, Lunar Energy and Eon are hoping to build an underwater tidal project off Pembrokeshire.
Another UK tidal power proposal is part of a plan by Metrotidal to build a tunnel under the Thames, currently under fire from environmental groups. There is also talk about regions like the Isle Of Wight and the Humber estuary harnessing tidal power as part of initiatives to become energy self-sufficient (like other “Transition Towns”).
Norway has also begun investigating the use of tidal power, with an experimental facility opening in Hammerfest in 2003. The company that developed that technology, Hammerfest StrÃ¸m, is working with Scottish Power to develop a project near the Orkney Islands (the islands have also been a test site for another venture by Lunar Energy and Rotech).
In Australia the Kimberly region has long been a target for would be developers of tidal power projects, due to its enormous potential (a tidal range of 11 metres). Thus far all of the proposed projects have been stymied by the remoteness of the location from the Western Australian and national electricity grids and by environmental concerns. A number of possible sites have been identified, including Secure Bay, Walcott Inlet, George Water and St. George’s Basin.
Some Kimberly tidal power advocates have also tried to base the idea of a “hydrogen economy” on the resource, though this seems a lot more far-fetched than a grid link (the grid link could also potentially include large scale CSP solar in the western australian deserts, which are one of the best solar resources in the world) .
The Bass Strait area is also considered to have significant potential for tidal / ocean current power generation (one estimate claiming there is potential for 3000 MW of generation in the channel between King Island and Cape Otway).
New Zealand is another country with large tidal resources but without any existing tidal energy generation. According to TVNZ, there are at least 24 wave and tidal power projects currently under development. Trying to get a handle on who might be behind these projects isn’t easy – there is an NZ wave and tidal power association, but it doesn’t list members or projects – according to their latest newsletter they have 59 members. Crest Energy seems to be the most prominent local company, with a plan for a 200 MW plant in Kaipara Harbour using underwater turbines. Other potential locations include Manukau and Hokianga Harbours, and Tory Strait and French Pass in the Marlborough Sounds. The harbours produce 5 to 6-knot currents and tidal flows of 100,000 cu m a second from the flood and ebb tides, with tidal volumes 12 times greater than the flow in the largest local rivers.
The Phillipines is another potential location for tidal power, with a 2.2GW tidal fence proposed for the Dalupiri Passage using the Davis turbine, from the Blue Energy company and an estimated cost of $US 2.8 Billion is unfortunately on hold due to political instability.
South Korea also has ambitions to generate power from ocean currents, with pilot underwater turbines being installed at Uldolmok, in the country’s south-west. Researchers at the Korea Ocean Research and Development Institute (KORDI) chose the site because it has flows up to 12 knots, believed to be among the fastest in Asia. The strong currents have resulted in a number of accidents, hampering progress. KORDI is also trying to improve the efficiency of more conventional barrage-type tidal power plants. The primary project involves building a power plant with a capacity of 250 MW at Lake Sihwa, with another plant up to 520 MW being considered for Garolim Bay.
Taiwan is another Asian nation considering the the possibility of large-scale ocean current power generation. There have been discussions about using the strong Kuroshio current off the east coast of Taiwan to generate up to 1.68 trillion kilowatt-hours per year (compared to Taiwan’s current annual demand of electricity of around 98 billion kilowatt-hours).
Probably the most exciting bit of Hydropower news this year was the news of a new technology that can generate electricity in water flowing at a rate of less than one knot – about one mile an hour – meaning it could operate on most waterways and sea beds around the globe.
This new device utilises a novel approach to extract energy from flowing water currents. It is unlike any other ocean energy or low-head hydropower concept. VIVACE is based on the extensively studied phenomenon of Vortex Induced Vibrations (VIV), first observed 500 years ago by Leonardo DaVinci in the form of “Aeolian Tones.” For decades, engineers have been trying to prevent VIV from damaging offshore equipment and structures. By maximizing and exploiting VIV rather than spoiling and preventing it, VIVACE takes this ‘problem’ and transforms it into a valuable resource for mankind.
The system, conceived by scientists at the University of Michigan, is called Vivace, or “vortex-induced vibrations for aquatic clean energy”.
Michael Bernitsas, a professor of naval architecture at the university, said it was based on the changes in water speed that are caused when a current flows past an obstruction. Eddies or vortices, formed in the water flow, can move objects up and down or left and right.
“This is a totally new method of extracting energy from water flow,” said Mr Bernitsas. “Fish curve their bodies to glide between the vortices shed by the bodies of the fish in front of them. Their muscle power alone could not propel them through the water at the speed they go, so they ride in each other’s wake.”
Such vibrations can cause damage to structures built in water, like docks and oil rigs. But Mr Bernitsas added: “We enhance the vibrations and harness this powerful and destructive force in nature.
“If we could harness 0.1 per cent of the energy in the ocean, we could support the energy needs of 15 billion people. In the English Channel, for example, there is a very strong current, so you produce a lot of power.”
Engineers are now deploying a prototype device in the Detroit River, which has a flow of less than two knots. Their work, funded by the US Department of Energy and the US Office of Naval Research, is published in the current issue of the quarterly Journal of Offshore Mechanics and Arctic Engineering.
This new technology along with all the other exciting developments in Hydropower mark out 2008 as a landmark year. It should be a very exciting 2009.
If any readers know of any projects, companies, or technologies that I have failed to cover here, please let me and all our other readers know about them using the comments.