Hydropower

Riding the Waves: Developments in Marine and Tidal Power

Issue 4 and Volume 11.

The UK currently dominates the emerging marine and tidal stream sector, but it is far from alone in pursuing the development of such technologies. As a number of other countries strive to catch up, the race is on to see which players will ultimately emerge as commercially successful, writes David Appleyard.

A visit to the seashore on all but the calmest of days instantly reveals the abundance of energy potentially available, as waves continuously crash and froth, rising and ebbing as far as the distant horizon. For engineers and clean energy advocates, extracting energy from such an enormous resource is a long-held dream. Obvious it may be, but to quantify, the European Ocean Energy Association in Brussels estimates that the global resource for wave energy lies between one and 10 TW, while total energy production from all sources is about 13 TW currently.

Despite our age old relationship with the sea, it is only fairly recently that technologies that can extract this energy in a usable form have been actively pursued. And, because marine and tidal energy technologies are still at such an early stage of development, there is no clear consensus over which types of generators can produce electricity from the ocean most efficiently and cheaply, and remain sufficiently robust to survive conditions at sea. Rather, there are a large number of competing models and designs for producing wave and tidal power.

Nonetheless, there are some exciting areas of development and some encouraging signs that, before long, marine and tidal energy systems will be contributing a significant percentage of our energy demand.

Marine energy development

There is a multitude of differing designs for extracting marine energy, but these generally fall into two camps, wave and tidal. Tidal devices may be further divided into two types, either barrage-type in which water lifted by the action of the tides is retained and released later through conventional hydro turbine technology, or tidal stream devices which rely on the movement of water in tidal currents to rotate subsurface turbines.

Wave energy devices, meanwhile, rely on the rise and fall of waves either to extract mechanical energy or to compress air or water which is then used to rotate a turbine. For example, in 2000 Inverness-based Wavegen installed the world’s first commercial wave power device on the Scottish island of Islay. This 500 kW device — the Limpet — uses generators built into the shore. As waves crash against the shoreline, compressed air is forced through turbines, generating electricity. Wavegen (acquired in May 2005 by Voith Siemens Hydro) has teamed up with a Faroese utility company to try to develop a larger wave farm built into the cliffs of the Faroe Islands. More recently, RWE Innogy has submitted a planning application for a 4 MW Wavegen pilot plant that will be installed in Siadar Bay on the Isle of Lewis. Construction could begin in 2009.

One of the better known mechanical designs for wave power devices is the Pelamis, a 750 kW, 160 metre long, snake-like machine developed by Edinburgh-based Ocean Power Delivery (OPD). Following a period of testing at the European Marine Energy Centre (EMEC) in Orkney, plans are now under way to build several multi-megawatt wave farms using this device. The first of these is a 2.25 MW development in Portuguese waters with energy company Enersis. Under this deal, OPD will deliver three Pelamis machines, with options on another 30. Commercial operations are expected to commence in September this year.

Back in the UK, utilities ScottishPower and AMEC, along with CRE Energy, are also looking into building a small pre-commercial Pelamis array at EMEC, with work possibly being completed this year. ScottishPower has already been granted planning permission for the farm by the Scottish government. The £10 million (US$20 million) project will see four floating generators, expected to have a combined capacity of around 3 MW when commissioned, positioned off the coast of the new European Marine Test Centre.

Meanwhile, Ocean Prospect, a division of Wind Prospect, has announced its intention to build a 7 MW wave farm using 10 Pelamis P-750 machines. Looking further ahead, OPD has also expressed interest in building a 30 MW wave farm in South Africa and is looking into a development near Vancouver in conjunction with BC Hydro.

Tidal current energy

As with wave energy, there’s a variety of competing devices which generate electricity from tidal currents. Again 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. Scottish and Southern Energy (SSE) has recently teamed up with Aquamarine Power and plans to be the first company in the world to deploy both wave and tidal devices on a commercial scale and has been developing an underwater tidal turbine demonstrator. SSE plans to finalize the design and install a 2.4 MW demonstrator at EMEC in 2009. It is also working with Aquamarine on its Oyster wave power device, which generates power by pumping high pressure water on-shore which is then used in conventional hydro technology.

Certainly, the pace of marine energy development has accelerated over the past 12 months. In October 2007 E.ON UK and Lunar Energy announced plans to develop an 8 MW tidal stream project off the Welsh coast of the UK. The new project will use horizontal-axis systems, developed by Rotech Tidal Tubines, which are mounted on the sea-bed and are invisible from the surface. If approved, it is anticipated that the plant would be operational by 2010 or 2011.

Lunar Energy subsequently announced an agreement with Korean Midland Power Co, to create a giant 300-turbine field in the Wando Hoenggan Water Way off the South Korean coast by December 2015. Full resource research and feasibility is due to be completed as REW goes to press, with the installation of a 1 MW pilot plant by March 2009.

Rival utility 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 developing tidal farms of 100 MW or more. Manufacture of the prototype will commence in 2008, with installation during 2009.

One of the most high-profile of the UK tidal companies is Bristol-based Marine Current Turbines (MCT). Its 300 kW single rotor SeaFlow device was first installed off Devon in 2003, and, following a period of testing, the company is looking to develop several commercial-scale projects.

The first of these is a MW-scale project in Strangford Narrows off Northern Ireland, which has been developed with funding from the UK government. The company has recently installed MCT’s new SeaGen device, a two-rotor machine capable of generating 1.2 MW — the device has already exported power to the grid and will be the first commercial-scale tidal turbine installed and operating anywhere in the world when fully commissioned this summer.

Looking ahead, MCT intends to manufacture and deploy a series of SeaGen devices in projects off Anglesey and on the Canadian seaboard within the next two to four years.

Indeed, UK utility company npower and MCT have already announced a partnership to develop a commercial-scale tidal stream project, off the coast of Anglesey, north Wales. A newly created development company, SeaGen Wales, would execute the 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 the island. The scheme will consist of seven 1.5 MW SeaGen turbines. Subject to successful planning consent and financing, the tidal farm could be commissioned as early as 2011 or 2012, a statement says.

MCT is also looking into developing a second, 10 MW, tidal farm in the Bristol Channel called the Lynmouth SeaGen Array, consisting of 12 SeaGen devices, and has signed an agreement with Canada’s BC Tidal Energy Corporation to install at least three SeaGen tidal energy turbines in Vancouver Island’s Campbell River by 2009. The agreement is 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 4000 MW.

The announcement comes on the heels of MCT’s agreement with Canada’s Maritime Tidal Energy Corporation (MTEC) to develop a tidal power project in Nova Scotia’s Bay of Fundy, located on Canada’s eastern seaboard.

While MCT remains the leader in the deep tidal market, there are a number of competitors including the Tidel machine developed by Newcastle-based SMD hydrovision. This is a twin turbine device which floats in the tidal current, turning to face the flow as the tide turns. The advantage of this system is that the device requires no support structure and is simply moored to the seabed making it easy to install and maintain. SMD is looking into building a 1 MW prototype in the next couple of years.

Another entrant to the field is the Pulse Stream 100, being developed by a BMT and IT Power venture called Pulse Tidal Ltd. The Pulse Stream converter uses a pair of hydrofoils which oscillate across a tidal flow — enabling the extraction of tidal energy from shallow water (10-30 metres), an area not yet exploitable by conventional tidal generators. The company has been granted planning permission for a prototype tidal stream generator to be tested in the UK’s Humber Estuary near Grimsby. The pulse generator will be capable of generating up to 150 kW and, if successful, will be used to develop larger 1 MW units which could be deployed in arrays each generating up to 100 MW. EDF has recently unveiled plans to develop a new tidal current project in Brittany.

Tidal barrage and other marine technologies

In addition to tidal flow systems, there are a number of very large-scale tidal barrage devices being considered. Proposals for such schemes around the Severn Estuary in the south-west of England have been mooted for well over a hundred years, but recently the UK government moved the project forward by appointing a consortium, led by consulting firm Parsons Brinckerhoff, to determine the potential of a tidal energy generator in the Severn Estuary, estimated at up to 7 GW.

There is a precedent for such schemes, with the world’s most successful tidal barrage plant — the 240 MW La Rance development in France’s Brittany which was designed in 1959. The station comprises a retaining basin, a dam and 24 low-head bulb turbines. Both ebb and flood currents can be used to generate electricity.

Another recent development is the proposal for a tidal energy project off the South Korean coast, expected to be the largest in the world. Known as the Sihwa Tidal Power Plant, the project would generate 260 MW from the flow of water in and out of a coastal bay.

The tidal power plant, expected to be completed by 2009 at a cost of approximately $250 million, will consist of a barrage and a powerhouse for 10 bulb-type turbines. VA Tech Hydro has been awarded a contract by Daewoo Engineering & Construction for engineering and delivery of the electromechanical main components for the plant.

Policy drivers and international hotspots

Recognizing an opportunity for the UK to become a world leader in marine and tidal technology, government support has been relatively high when compared with other sectors. This state support takes several guises.

For instance, the UK government has part-funded various key infrastructure projects such as EMEC and the New and Renewable Energy Centre (NaREC), which have proved invaluable in providing a test bed for prototype wave and tidal devices. More recently, a further step on the road to commercialization has been taken with planning approval for the so-called Wave Hub, an electrical offshore ‘socket’ that will allow wave devices to feed energy to the national grid. The £28 million ($56 million) project off the coast of Cornwall will be funded by the Regional Development Agency (RDA). Designed by Halcrow, it will be about 16 km offshore and will allow four devices of up to 10 MW each to connect. Four companies are already lined up, including Ocean Prospect, Ocean Power Technology, Fred Olsen and Australia-based Oceanlinx. Up to 30 wave energy technologies are expected to be deployed at Wave Hub when it becomes operational, which is now not due until spring 2010.

The UK government also introduced the £50 million ($100 million) Marine Renewables Deployment Fund (MRDF), on top of the Renewable Obligation Certificate (ROC) scheme, to help marine energy companies bridge the gap between prototype and commercial deployment. However, while the UK may have gained an early lead, other players are catching on to the potential goldmine washing about their shores.

For example, the US Department of Energy (DOE) recently announced that up to $7.5 million in federal funding is now available for research and development to help advance such technologies. This development followed December’s signing of the Marine and Hydrokinetic Renewable Energy Research and Development Act, which authorizes an annual $50 million from 2008-2012 to carry out R&D and the provision of grants to universities for the establishment of National Marine Renewable Energy Research, Development, and Demonstration Centers. The west-coast state of Oregon is looking to take the lead and has invested through Oregon State University (OSU). In January the Oregon Wave Energy Trust, or OWET, received the first part of its $4.2 million budget approved by the 2007 state legislature.

Meanwhile, a number of projects are also under way in the US, notably in Hawaii. Oceanlinx has announced plans to provide up to 2.7 MW of electricity to the Maui Electric Company from two to three floating platforms off Pauwela Point on the north-east coast of Maui. The $20 million project could be operational by the end of 2009.

New Jersey-based Ocean Power Technologies (OPT) has already installed its 40 kW PowerBuoy devices at a US naval base in Hawaii and off the coast of New Jersey. The company is also developing a further 1 MW in Hawaii and is working on a number of products for Lockheed Martin, using wave energy to power radio buoys.

Such developments are also attracting considerable attention from international utility companies. For example, in mainland Europe, OPT has reached an agreement with Spanish utility Iberdrola to install 1.4 MW off the coast of Spain in Santona, Cantabria. The installation will ultimately comprise 10 buoys.

In June, Iberdrola and Tecnalia Corporación Tecnológica announced an agreement to develop the Oceantec project which will involve a joint investment of around €4.5 million with expectations that the device will be built and pass testing through 2009.

France’s EDF Energies Nouvelles, meanwhile, has signed a partnership agreement with Renewable Energy Holdings plc (REH) covering the development and deployment of CETO wave energy technology, which uses a submerged piston to deliver high-pressure water on shore, which is then used in conventional hydro technology. REH recently deployed a second CETO II Wave Energy prototype off its test site, at Fremantle in Western Australia, and a third unit will be deployed shortly. EDF Energies Nouvelles and REH are actively planning for the commercial roll-out beginning next year.

Irish company Wavebob, which recently announced the opening of US operations in Annapolis, Maryland, has signed a research and development agreement with Swedish utility group Vattenfall AB. The two companies will collaborate on bringing the prototype Wavebob device to readiness for a full-scale commercial wave farm.

Lars Strömberg, vice president of R&D at Vattenfall commented: ‘Wave power is now mature enough to be demonstrated at commercial size… the technology must still be further developed and optimized… before [it] can be commercially introduced at larger scale.’

A number of other utility and oil companies are securing positions in the emerging wave energy sector. This includes Pacific Gas and Electric, the large Northern California utility, which has signed a power purchase agreement for the output from a 2 MW wave farm which Finavera will build 4 km off the coast near California’s Humboldt County using its Aquabouy technology. The wave farm is expected to start producing power in 2012.

In December, Finavera was granted an operating licence for its Makah Bay Offshore Wave Pilot Project in Washington State by the United States Federal Energy Regulatory Commission (FERC).

Tidal Race

While the UK appears to have a head start in the initial development of marine renewable energy — possibly as a result of its strong offshore engineering heritage and huge marine resources — it remains to be seen if it will be able to maintain its position as this technology moves towards commercialization. Certainly other countries such as the US, South Korea, Portugal, France, Spain and South Africa are working hard to catch up and some have established feed-in tariffs for marine renewable energy, as well as a series of other support measures to encourage the technology’s development. And, while commercial success remains some way off, the potential of the oceans to provide huge quantities of renewable energy is expected to see such technologies emerge as strong players in years to come. Not all the products emerging from the current surge in the development of marine and tidal energy devices will become commercially successful, but given the level of interest from developers, governments, and utilities, the pursuit of such technologies is clearly no albatross.

David Appleyard is Associate Editor of Renewable Energy World magazine.
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