Nigel Blackaby, Features Editor
British companies are at the forefront of the development of wave and tidal technologies but this young industry desperately needs funding if its dream of commercialisation is to be realised. PEi examines the state of the industry and some of the most promising power generation devices.
Depending on your point of view, marine renewable technologies (devices capable of producing electricity from wave or tidal energy), either represent an important potential source of clean power capable of rivalling wind power in the future or are a collection of bizarre-looking gadgets which stand little or no chance of ever becoming commercially viable. If a recent poll carried out through PEi’s website is any indication, the majority view is that marine technologies will make a small contribution to renewable power, although 35 per cent of respondents believed that the technologies have the potential to one day rival the electricity production from wind power.
Wavegen’s Limpet oscillating water column unit located on the Isle of Islay
Presently, the UK leads the way in the field of marine renewable technologies. Its coastline and seas offer some of the best wave and tidal natural resources in the world. In addition, the UK is able to boast considerable technical expertise in the field, built on experiences in the offshore oil and gas and wind power industries. If devices can be developed in the UK that harness the energy contained in the tides and waves around the coast on a commercial scale, this could make an important contribution to greenhouse gas reduction targets. It would also be a valuable contributor to the country’s economy.
The British Renewable Power Association hosted the 2004 Wave and Tidal Symposium (WATTS) in London in March. This was an opportunity for the industry to contemplate its future as well as to provide an update on how the leading marine power technologies were progressing. The message emerging from the conference was a clear one: marine technologies hold much promise but commercialization will not become a reality without significant additional financial support.
One of the biggest supporters of the UK’s marine power industry is the Carbon Trust, the government-backed independent company, which helps foster the low carbon economy by encouraging renewable technologies. It has funded the Marine Energy Challenge (MEC), a à‚£2.5 million ($4.6 million) programme which is currently helping eight marine power developers achieve cost and performance improvements. The MEC aims to establish a benchmark à‚£/kWh cost of generation and see how far this can be reduced through engineering design. It also aims to identify ‘generic’ components, establish key areas of cost reduction and performance improvement and to highlight required areas of Research & Development by providing research programmes with feedback.
“Marine energy has great promise,” says Tom Delay, chief executive of the Carbon Trust. “This is a very young industry and, as a result, there is considerable uncertainty. This uncertainty has meant that private investment has not been forthcoming. The Carbon Trust aims to be a catalyst for marine renewable technologies, helping it develop its huge potential.”
The atmosphere at the WATTS conference reflected the uncertainty to which Delay referred. On the one hand, there was a sense of excitement at being involved at the very outset of an industry with huge latent possibilities in which the UK excels. On the other, speakers at the conference spoke of the risk of losing this competitive advantage, in the same way as the UK failed to exploit its initial know-how in wind technology. Adequate funding to enable marine technologies to move towards commercial operation remains the main concern. Since 1999, the UK government has provided à‚£15 million to the industry. The UK Department of Trade and Industry (DTI) has said that, while more funding will be available, the marine renewables industry should not rely on the government for funding but also look to enter into partnerships with entities like the Carbon Trust, research councils and other R & D interests. The Renewable Power Association has estimated that funding of around $150 million will be needed over the next five to ten years
The Stingray generator is mounted on the seabed in water depths of up to 100 m
One of the marine renewable technologies that has benefited from DTI funding is the Stingray tidal stream generator, being developed by The Engineering Business (EB). The Stingray is designed to harness the flow of the tidal stream over a hydroplane causing an oscillating motion, which is used to directly operate hydraulic cylinders to produce a flow of oil. This can be used to drive a hydraulic motor, which in turn drives an electrical generator. Tests in waters off the Shetland Islands have shown that the device is capable of extracting ten per cent of the available tidal energy. An array of the submerged devices connected to a common distribution network would be required to generate electricity on a commercial basis.
Stingray is one of a number of marine-related engineering solutions designed by The Engineering Business in the northeast of England. The future development and exploitation of Stingray is the responsibility of Tidal Energy Business, a joint venture between EB and the UK’s New and Renewable Energy Centre, based in Blyth, Northumberland, which has made a à‚£1 million investment in the new venture. TEB has plans for a 5 MW pre-commercial Stingray farm that, funds permitting, will be installed in 2005.
The DTI has also been one of the backers of the Seaflow Project, along with the European Commission and German government. Marine Current Turbines Limited (MCT) is undertaking an initial $3.5 million programme to design, build and test this tidal turbine system, with a view eventually undertaking their commercial manufacture. Testing of the Seaflow Project device off the coast at Lynmouth, Devon, UK has been ongoing since last year
Marine current turbines are, in principle, much like submerged windmills. They will be installed in the sea at places with high tidal current velocities, to take out energy from the huge volumes of flowing water. The technology under development by MCT consists of twin axial flow rotors of 15 m to 20 m in diameter, each driving a generator via a gearbox much like a hydroelectric turbine or a wind turbine. The twin power units of each system are mounted on wing-like extensions either side of a tubular steel monopile some 3 m in diameter, which is set into a hole, drilled into the seabed from a jack-up barge.
The next stage of the project is to build a 1 MW prototype twin-bladed machine at a cost of à‚£4.5 million leading on to the development of a 5 MW tidal farm by 2005-6.
The UK government’s future projections of renewable energy production do include a contribution from marine technologies, albeit that it represents just a small slither of the government’s projected renewables pie for 2015. Director of the Energy Innovation and Business Unit of the DTI, Claire Durkin, said that wave and tidal power was part of the mix of renewable technologies envisaged under the government’s Energy White Paper. “Wind power will not be enough. We will need a variety of renewable technologies if we are to achieve our goals,” said Durkin. The government expects that wind power, along with small hydro, biomass and landfill projects will be the technologies to achieve the ten per cent renewables target by 2010 but that a wider spectrum of renewables will be needed as it moves towards its aspiration (and likely target) of 20 per cent renewables by 2020.
The UK government points to its recently extended Renewables Obligation as a mechanism which provides support and certainty to renewable power producers. But while developers of new renewable technologies can do so in the knowledge that electricity suppliers will have to include a proportion of ‘green’ power, this fails to offer assistance to those who have yet to reach the stage of commercial generation. The industry argues that, although wave and tidal power is cheaper than wind power was at the same stage of its development, some form of transitional funding will still be required.
Concern has been expressed over the lack of practical support in the government’s recent Renewables Innovation Review. Philip Wolfe, the Renewable Power Association’s chief executive commented, “We are impressed with the government’s declared commitment to this sector, but the detail of the Innovation Review just doesn’t back this up. Our member companies are pioneering a whole new industry with exciting developments every month. Meanwhile the government seems to think it can wait until the 2020s before helping the market to emerge.”
For many, wave and tidal power remains an unproven technology. The energy is difficult to capture and the problem of reliability and survivability of devices in hostile sea environments need to be overcome. So far, the technology has yet to be shown to be cost-competitive and this is a major key to attracting private capital. Utilities like Scottish & Southern Energy, the UK’s biggest renewable energy provider, are prepared to invest in mature technologies. “The progress of R & D towards the commercial application of marine technologies is very slow,” said David Sigsworth, Scottish & Southern’s generation director. Sigsworth believes that a large-scale demonstration of the technologies is what is needed to attract political attention to the sector. “What is needed is a breakthrough at commercial scale,” said Sigsworth.
Pelamis is towed back to Edinburgh following its successful offshore sea trials
One of the devices that show the greatest promise of commercial potential is the Pelamis wave energy converter. Edinburgh-based Ocean Power Delivery is developing Pelamis, which has recently undergone a successful offshore sea trial. Built on technology developed for the offshore industry, the Pelamis has a similar output to a modern wind turbine.
Pelamis is a 120 m-long, semi-submerged, articulated structure composed of cylindrical sections linked by hinged joints. The wave-induced motion of these joints is resisted by hydraulic rams, which pump high-pressure oil through hydraulic motors via smoothing accumulators. The hydraulic motors drive electrical generators to produce electricity. The first full-scale pre-production prototype is currently being built and will be tested at the European Marine Energy Centre in Orkney later this year.
“We are working with a couple of the large renewable players with a view to the development and deployment of Pelamis in Scotland,” said Ocean Power Delivery’s founder and managing director, Dr. Richard Yemm. “Portugal is also a target market as a fixed rate for electricity derived from wave energy is available.”
However, one shore-based marine technology is already up and running. Limpet is the name given to the world’s first commercial-scale wave energy device that generates power for the grid, designed and operated by Inverness-based Wavegen and located on a rocky coastal strip on the Isle of Islay. The Limpet unit has an inclined oscillating water column (OWC) that couples with the surge-dominated wave field adjacent to the shore. The design of the air chamber is important to maximise the capture of wave energy and conversion to pneumatic power. The turbines are carefully matched to the air chamber to maximise power output.
The performance has been optimised for annual average wave intensities of between 15 and 25 kW/m. The water column feeds a pair of counter-rotating turbines, each of which drives a 250 kW generator, giving a nameplate rating of 500 kW.
A à‚£7 million joint venture with SEV, the Faroese electricity company, is planned based on a OWC design but using tunnels cut into the cliffs on the shoreline to form the chamber which captures the energy.
Computer image of Mermade situated at the bottom of a wind turbine monopile
At the other end of the development spectrum is a device that may prove cost-effective, because of the way in which it takes advantage of existing infrastructure. Offshore services company, Oceantecs, is developing a tidal flow/current turbine, Mermade, capable of being mounted vertically or horizontally, in shallow waters either in the open sea, rivers or lakes, if there is sufficient flow. One of the main advantages of Mermade is that it can be used in conjunction with other offshore/subsurface structures, such as wind turbines, bridge supports, jacket legs etc. or it can be installed as stand alone units in an array, forming a field of turbines.
Existing offshore wind farms are approximately 55 per cent efficient due to either lack of or too much wind. One idea is that Mermade would be mounted at the bottom of the wind turbine monopile, thereby providing long-term predictable power output to supplement the output from the wind turbine, using the same infrastructure. Mermade is currently in its development stage but Oceantecs plans to construct a scale model in 2004 for wet and dry testing.
Comparisons between the development of the marine energy and the wind power industries are frequently made. Indeed the British Wind Energy Association (BWEA) has begun championing the emerging wave and tidal sector with the launch of a joint national conference with Regen SW in Bristol in February. Marcus Rand, CEO of the BWEA said, “While wind energy has entered the phase of delivery, wave and tidal power are in the phase of proof. I sincerely hope that with our 25 years experience, knowledge and commitment, we can play our part in fast tracking the commercialization of these exciting new technologies.” And fast track it will have to. It has taken the wind industry around 20 years to get from where the marine renewable sector is today. Wind and tidal technologies are unlikely to be afforded the same luxury.