18 September 2009
Interest in wave and tidal energy systems is gathering pace as a huge number devices move from the drawing board, through prototype and testing phases and on to commercial developments.
Like many of the current crop of ‘cutting edge’ renewable energy technologies, the concept of extracting energy from waves and tides is not a new one. Indeed, it is well over 100 years since the first tidal wheel was built and the 240 MW La Rance tidal barrage project in Brittany, France, has been operating for well over 40 years. What has changed over the intervening years is the level of urgency with which such projects are now being addressed and the technical achievements by some manufacturers which are making tidal and wave energy a reality.
Alongside growing interest in the UK, USA, and Portugal, countries such as Canada, South Korea, Australia, New Zealand, Brazil, Chile, Mexico and other nations are also expressing support for ocean energy development.
Blessed with one of the longest coastlines of any country in Europe, large tidal ranges and strong winds, it is perhaps obvious that as the home of one of the largest marine energy resources, the United Kingdom should also sport by far the largest concentration of marine power companies in the world. However, while the UK has taken a lead, it is far from alone. According to the IEA-OES, also known as the Implementing Agreement on Ocean Energy Systems which functions within a framework created by the International Energy Agency (IEA), by the end of 2008, more than 25 countries were involved in ocean renewable energy technology development activities. With the deployment of multi-unit wave technology in Portugal, and the commencement of construction of a 260 MW tidal power plant in South Korea standing out as noteworthy.
However, although government support from a few countries has to some extent enabled the ongoing commercialization of ocean energy technologies, a lack of targeted national priorities and policies remains a major barrier. Certainly, the stakes are potentially high.
For example, some analysis suggests that the accessible resource in waters around the UK, taking into account constraints on available sites for a wide variety of reasons, could be as much as 700 TWh per year. Similarly, it has been estimated that the North American marine energy resource could realistically supply some 10% of US electricity demand.
Policy and Government Support
Government engagement with marine technology has been something of a mixed bag. In the UK, for example, support has been relatively high when compared with other sectors. However, Denmark, for instance, ended its wave energy development programme in 2002, leaving the country without a dedicated policy.
Resource assessment is a key step in building marine energy capacity and in one of the more significant developments for the UK industry over the past year, a study to determine the potential for marine energy in English and Welsh waters was announced by the government in April 2009. The new scoping study will look at wave, tidal-stream and tidal range technologies along the English and Welsh coastline. (See caption and credit information for image by clicking on it in the image gallery at the end of this article.)
The devolved Scottish government, meanwhile, is further along, having already produced a preliminary Strategic Environmental Assessment (SEA) for marine energy in Scotland. And, in September 2008, the Crown Estate outlined the application and consent procedure for wave and tidal energy projects in the Pentland Firth, in Scotland, which contains some of the best locations for wave energy in the world. The Firth is the first UK marine power site to be opened up for commercial-scale development, with the aim of developing an installed capacity of more than 700 MW by 2020. The process of granting options for lease over areas of seabed in the Pentland Firth and surrounding area is due to be concluded in the summer of 2009, with deployed as early as 2010 or 2011.
Announcing the decision for England and Wales, the minister for sustainable development and energy innovation, Lord Hunt, said: ‘The marine energy sector has reached a pivotal stage with more and more devices ready to go into the water.’
However, even in the UK the support available has faced criticism. For example, in 2009, the first companies are expected to qualify to receive funding under the Marine Renewables Deployment Fund, which provides £50 million (US$75 million) to support wave and tidal stream technologies in the UK. This sounds positive, but the industry is concerned that the support is only available to companies which have been operating a full-scale prototype for at least three months, a measure which has been criticized given that devices have only recently entered the water. Parliamentary questions found that the entire budget for the Wave and Tidal-stream Energy Demonstration Scheme has remained unspent since it was announced in 2004. Nonetheless, it does set a premium of £100/MWh for electricity produced from marine energy, and this is on top of the retail price of electricity and the Renewables Obligation (RO), which requires utility groups to source a growing proportion of their electricity from renewables. The main support scheme for renewable electricity projects in the UK, the RO is to be revised upwards for marine energy when the government introduces banding for emerging technologies which require more support, such as marine and offshore wind.
In a move first mooted in 2007, ocean energy systems are due to receive 2 ROCs for each MWh produced, double the current level.
Perhaps at least as significant for the industry’s long-term development, in December 2008, the government published a new Marine and Coastal Access Bill, designed to give greater confidence and economic benefits for marine developers through simplification of the legislative framework, and balance the interests of conservation, renewable energy and other marine interests. Through the legislation, the government intends to set up a new Marine Management Organisation (MMO) to oversee the majority of marine planning applications and the bill will also create a strategic marine planning system.
Elsewhere in Europe, in Portugal for example – which boasts the world’s first commercial marine energy installation – a feed-in tariff for wave energy was established in 2007 mandating a euro260/MWh price for the first 20 MW installed. While in the US, members of both houses of Congress are calling on the Department of Energy (DOE) to allocate $250 million of the $2.5 billion in stimulus funding for renewable energy research and development to the emerging marine renewable energy industry.
And, in a 2009 Earth Day speech President Barack Obama announced that the Department of the Interior has now finalized a long-awaited framework for renewable energy production on the US Outer Continental Shelf (OCS). The framework establishes a programme to grant leases, easements and rights-of-way for orderly, safe and environmentally responsible renewable energy development activities, such as the siting and construction of wave farms on the OCS. Alongside growing interest in the UK, USA, and Portugal, countries such as Canada, South Korea, Australia, New Zealand, Brazil, Chile, Mexico and other nations are also expressing support for ocean energy development.
Wave Energy Generators
Though still at an early stage of development, the marine energy sector has already seen a number of technologies progressed to the point of commercial installation. The rapid emergence of new machines, continuous development of more established ones, and the wealth of on-going R&D leaves no real consensus over which designs will ultimately emerge to produce electricity from the ocean most efficiently and cheaply, and yet which remain sufficiently robust to survive the rigours of a life at sea. Indeed, a large number of competing, sometimes unexpected, designs for producing wave and tidal power all but swamp the horizon.
Oscillating water column (OWC) is one technology that is being explored by a number of companies.
For instance, Orecon’s wave to energy buoy is based on a multi-resonant chamber (MRC) oscillating water column and a HydroAir bi-directional air impulse turbine supplied by Dresser-Rand Company Ltd, the two have also signed a memorandum of understanding to optimise the design for the device. Orecon has also signed an agreement with Portuguese developer Eneólica to establish a Joint Venture company to build and deploy Orecon’s first full-scale 1.5-MW MRC buoy in a grid-connected installation. Once the first unit is commissioned, two further MRCs will be added, increasing output to 4.5 MW and making it the world’s largest operating wave farm to date. The partners say they intend to develop further sites in Portugal over the next 10 years.
Another OWC design that is subject to advanced testing and planning is the Danish development Wave Dragon. A prototype project was installed in Nissum Bredning as early as 2003 and Wave Dragon plans to deploy a 7-MW Wave Dragon off the coast of Milford Haven in Wales in the spring of 2010. The company also plans to install 10 machines in Portugal between 2011 and 2012 and an additional 10 machines in an array off Wales in 2013. OWC-type machines of various designs and to varying degrees of success have also been built in Australia, Scotland, Norway, Japan, India, and Portugal.
One of the most commercially advanced offshore wave power devices is the Pelamis machine (see image, above), a 750 kW, snake-like machine developed by Edinburgh-based Pelamis Wave Power (PWP). Following a period of testing at the European Marine Energy Centre (EMEC) in Orkney, the world’s first commercial wave energy installation, a 2.25-MW development in Portuguese waters has been developed with energy company Enersis. The three machines, near Póvoa do Varzim some 5 km offshore, are known as the Aguçadoura wave farm.
Another example comes from New Jersey, USA-based Ocean Power Technologies (OPT) and its PowerBuoy. It is due to install one of 150 kW devices at EMEC, while in the longer term it intends to develop a 5-MW wave farm, consisting of buoys arranged in a grid, planned as part of the UK’s Wave Hub project. The device, which uses waves to move the buoy up and down converts the resultant mechanical stroking via a power take-off to drive an electrical generator, is expected to be ready for deployment and grid connection in 2009. In the past year OPT says it has reached two major manufacturing milestones in the development of its flagship PB150 PowerBuoy device with projects at locations including Reedsport in Oregon, Victoria, Australia and in the UK.
The design is similar in concept to that of Wavebob Ltd of Ireland, which has signed a co-operation agreement with Vattenfall AB for the possible development of a 250-MW demonstration project using its Wavebob device.
Another device that uses the linear motion of waves to generate energy is Trident Energy’s machine. This machine is solidly anchored, rather than self-reacting using inertial forces like OPT and Wavebob, and floats are used to drive linear generators. Trident Energy is currently in the final stages of preparing for a year-long deployment of a fully functional test rig in the North Sea off England’s east coast. The test rig will generate about 20 kW from eight full scale linear generators.
Other designs of wave energy devices include the Archimedes Wave Swing developed by Scotland’s AWS Ocean Energy, Voith Siemens Hydro Power Generation’s WaveGen and Isle of Man-based Renewable Energy Holdings plc (REH) with its CETO device.
The CETO uses a submerged piston to deliver high pressure water to shore which is then used in conventional hydro technology. Test deployment of a full-scale CETO III unit is due for completion in 2009, with commercial rollout anticipated shortly thereafter.
In April 2009 Aquamarine Power announced that it is to commence installation of its 350-kW Oyster wave energy machine at EMEC in the summer of 2009 and with Airtricity, the renewable energy division of Scottish and Southern Energy, a deal is place to develop sites capable of hosting 1 GW of marine energy by 2020. The device consists of an oscillating flap, which, as with the CETO design, pumps high pressure water through an on-shore turbine to generate electricity. (See image, left.)
Many novel wave devices, such as the Green Ocean Energy Ltd Wave Treader machine, which attaches to offshore wind farm monopiles and shares infrastructure, or the rubbery submarine-like tube that is the Anaconda from Checkmate Seaenergy Ltd are at far earlier stages of development than other designs. Nonetheless, they represent interesting avenues for the development of commercial wave energy.
Tidal Current Energy
As with wave energy, there are a variety of competing devices which generate electricity from tidal currents. These can broadly be divided into those that operate in shallow shoreline water and those that work in deep fast-moving tidal channels. Most of the devices approaching commercialization are in this second category.
One of the most commercially advanced of the tidal companies is Marine Current Turbines (MCT). The company has installed its new SeaGen device, a two-rotor machine capable of generating 1.2-MW, in Stangford Narrows in Northern Ireland. In July 2008, having briefly exported power the grid, it became one of the world’s first commercial-scale tidal turbines installed and operating.
MCT intends to deploy a series of SeaGen devices in projects off Anglesey and on the Canadian seaboard within the next few years, and has already secured backing of npower Renewables to execute plans for a 10.5 MW-tidal farm scheme in an area of 25 metre-deep open sea known as the Skerries, off the north-west coast of Anglesey. Subject to successful planning consent and financing, the tidal farm could begin commercial operations as early as 2011 or 2012. It has also agreed a partnership with Canada’s Minas Basin Pulp and Power Company Ltd for a demonstration project in the Bay of Fundy, Nova Scotia.
The company followed this up by applying for a lease from the Crown Estate to deploy up to 50 MW of its machines in the Pentland Firth. Subject to financing and securing the necessary approvals, the company says it expects to install up to 50 MW by 2015.
In another tidal turbine development, utility group Scottish Power has teamed up with Hammerfast Strøm of Norway to install a 1-MW full-scale prototype tidal turbine in Scotland, with a view to eventually developing tidal farms of 100 MW or more. Manufacture of the prototype began in 2008, with installation during 2009. Using the device Scottish Power also plans to install three tidal energy farms off Scotland and Northern Ireland with a total capacity of up to 60 MW, which could be operational by 2011, the company says. The facility will use the Lànstrøm tidal turbine, developed by Hammerfest Strøm AS.
Meanwhile, Irish company Open Hydro has been testing their 250 kW open centred, rim generator device, at EMEC in the Orkneys since September 2008. And, in April 2009, the company awarded a contract to Cherubini Metal Works of Dartmouth, Nova Scotia, for the supply of a subsea base to support the installation of its first tidal turbine in Canadian waters. The unit is scheduled for deployment this autumn in the Minas Passage of the Bay of Fundy and the project is being developed in partnership with Nova Scotia Power and with support from Sustainable Development Technology Canada (SDTC). Work is expected to complete in August 2009. Open Hydro has also partnered with EDF in plans to install four to 10 of their turbines off the coast of Brittany and the company has also announced that it has secured a contract to develop a pilot project for Snohomish County Public Utility District, a public utility in Washington State, USA. The contract to develop a tidal project in the Admiralty Inlet region of the Puget Sound involves the installation of up to three turbines. Installation is expected to begin as early as 2011.
Elsewhere in the USA, a number of marine current energy trials are underway, for example Verdant Power has tested six of its 35-kW turbines in New York’s East River, but it is only in the last year that the first commercial hydrokinetic turbine has been installed. Hydro Green Energy LLC completed the installation of one of two surface-suspended turbines at what it claims is the United States’ first-ever commercial hydrokinetic power project, near the City of Hastings in Minnesota, in late 2008.
Another tidal stream turbine comes from Lunar Energy. The company has forged an alliance with EON to develop an 8 MW project off the Welsh coast using 1-MW horizontal-axis systems developed by Rotech Tidal Tubines (RTT). The development follows Lunar Energy’s March 2008 agreement with Korean Midland Power Co (KOMIPO), to supply a giant 300-turbine field in the Wando Hoenggan Water Way off the South Korean coast. The field is expected to supply electricity by 2015.
In the southern hemisphere, in March 2009 Singapore’s Atlantis Resources Corp signed a co-operation agreement with Norwegian utility group Statkraft to develop tidal current electricity generation projects in Europe using its 400-kW Nereus II and 500-kW Solon turbines. In December 2008, Atlantis signed the world’s largest tidal energy generation agreement with Hong Kong-based CLP Group, increasing Atlantis’ electricity-generating project pipeline to 800 MW. The commercial launch of a 2-MW Solon turbine is expected soon.
A Creative Explosion
One key characteristic of the marine energy sector which makes it all but impossible to pick a winning technology is the burst of creativity that has seen a wealth of novel designs emerge.
As with wave energy devices, a number of novel designs have emerged which seek to generate energy from tidal currents. One such device is under development by Australia’s BioPower Systems. The so-called bioSTREAM is based on the highly efficient propulsion of Thunniform-mode swimming species, such as shark, tuna, and mackerel and the machine mimics the shape and motion characteristics of these species, but is a fixed device in a moving stream. In this configuration the propulsion mechanism is reversed, and the energy in the passing flow is used to drive the device motion against the resisting torque of an electrical generator. Systems are being developed for 250 kW, 500 kW, and 1 MW capacities to match conditions in various locations.
Meanwhile, World Energy Research and Blue Energy Canada have signed a joint agreement under which World Energy Research would finance the development of Blue Energy Canada’s first 200 MW commercial tidal power project at a cost of roughly $500 million using a novel vertical-axis hydro turbine.
There are also other types of ocean energy that have yet to be explored to any great extent and which include technologies such as those which exploit an osmotic gradient or so-called Ocean Thermal Energy Conversion (OTEC) systems, which rely on a thermal gradient. It may be hard to pick a technology winner, but the vast quantities of energy potentially available suggests that a winner will indeed emerge.
David Appleyard is associate editor of Renewable Energy World.
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Sidebar: Tidal Barrage Development
The precise predictability of the tides and the vast quantities of energy potentially available has prompted continued interest in tidal barrage technologies.
Although only a very few tidal barrage projects of any size are currently operating, alongside La Rance is the 18 MW Annapolis Royal Tidal plant in Canada’s Bay of Fundy which has been operating since 1984, a number of smaller schemes do exist. In China, for example, the IEA reports that there are at least seven tidal barrage plants with a capacity of 5 MW or more.
In addition, plans for more tidal barrage development are well underway. In South Korea, the Sihwa Tidal Power Plant project would generate 260 MW, making it the largest such project in the world. The approximately $250 million project is already under construction and will consist of 10 turbines and is expected to be completed in 2009. South Korea has also announced plans for other tidal barrage schemes, including the 520 MW Garolim Bay development. This installation is expected to be completed some time in 2014.
Other countries blessed with large tidal ranges and suitable geography include the USA, India, Mexico and Canada.
In the UK, the Severn Estuary with its 14-metre tidal range has been the site of proposed tidal barrage schemes for well over 100 years and with a potential generating capacity estimated at more than 8 GW, some 5% of current UK requirements.
Subject to an on-going two-year feasibility study led by consulting firm Parsons Brinckerhoff, significant environmental, not to say engineering and financial, challenges remain.
So far, a public consultation has arrived at a proposed shortlist of five schemes from 10 original proposals, which includes a mixture of barrages and tidal lagoon schemes.
Elsewhere in the UK, feasibility studies have considered tidal barrage schemes in the Eastern Irish Sea, the northwest of England – including the Solway Firth, and the estuary of the River Mersey, among other locations.
via Renewable Energy World Magazine
Marine Energy Systems 