Wave Hub looms off the Cornish coast

A renewable energy project is about to be built off the coast of Cornwall. Wave Hub could generate power for 7,500 homes, and save thousands of tonnes of CO2

In May, the UK’s South West Regional Development Agency (SWRDA) announced the fourth and final recipient of a berth on its Wave Hub. This is a groundbreaking renewable-energy project off the Cornish coast, which aims to create the UK’s first large-scale offshore facility for the demonstration of wave energy generation devices.

Australian firm Oceanlinx will take its place alongside Ocean Power Technologies, Fred Olsen and WestWave in what will be one of the world’s largest wave farms, with funding of £28M from the SWRDA.

Although some smaller wave energy projects have been run in the UK before, this project signifies that tidal energy now really has arrived in the UK.

The idea of converting the energy of ocean surface waves into useful energy forms is not new. There are patents relating to the concept dating back to 1799 in France. The commercial focus on wave energy conversion began in earnest after the oil crisis in 1973. Several European countries with substantial wave power resources considered wave energy as a possible source of renewable energy, and introduced support programmes for wave energy. Research programmes with government and private support started around that time in Denmark, Ireland, Norway, Portugal, Sweden and the UK.

The amount of energy carried by wave and tidal streams that is convertible to electricity has been estimated in a variety of studies. The Carbon Trust White Paper in 2003, Options for UK Renewable Energy, identified an accessible worldwide wave energy resource of between 2,000 and 4,000TWh a year. And the UK practical offshore wave energy resource has been estimated at 50TWh a year – about one seventh of current UK electricity consumption.

Three years later, in its 2006 report, Future Marine Energy, the Carbon Trust gave some indications of the market’s size. Environmental and engineering consultancy Entec estimated that the value of worldwide electricity revenues from wave and tidal stream projects could ultimately be between £60B and £190B a year. Meanwhile, the Department of Energy’s Energy Technology Support Unit (ETSU) report (1999), A Brief Review of Wave Energy, estimated that total investments of more than £500B would be necessary for wave energy to contribute 2,000TWh a year worldwide.

Deployment zone

Wave Hub will be situated in a deployment zone about 18.5km off Hayle in Cornwall, in about 50m of water. Safety zones up to 500m around the Wave Energy Converters may be established to prohibit certain activities, such as navigation by commercial shipping, to ensure that the devices operate safely.

The project will have a power generation capacity of 20MW, with each berthholder being entitled to generate a maximum of 5MW from its own array of devices. The infrastructure comprises an onshore substation connected to offshore electrical equipment on the seabed via a 25km-long sub-sea cable. Wave Hub’s onshore substation will be situated adjacent to the existing substation facilities at Hayle, located behind the Hayle Towans sand dunes, linked by the sub-sea cable to the deployment zone.

The hope is that Wave Hub could be built as early as next year, subject to planning approval. Apart from the huge environmental benefits, the project could generate £76M over 25 years for the regional economy. The indirect benefits of such an industry are calculated at potentially hundreds of new jobs and many millions of pounds a year to the regional economy by 2010, and rising thereafter.

To put the significance of this project into an environmental context, Wave Hub could generate enough electricity for 7,500 homes, saving 24,300t of CO2 every year when displacing fossil fuels. In local terms, this translates to around 3% of Cornwall’s domestic energy requirement. This would support South-west England’s stated target of generating 15% of the region’s power from renewable sources by 2010.

The government is committed to increasing the amount of electrical energy generated by renewable energy sources to 10% by 2010 and 15% by 2015 with an aspiration to 20% by 2020. With one of the largest wave energy resources in Europe, the UK is well placed to generate a substantial proportion of this from waves. Allowing for technical, practical and environmental limitations, wave energy could generate up to one sixth of the UK’s electricity consumption. By 2020, the wave energy market in the UK could by worth £200M.

The fourth berth of the Wave Hub will be filled with the unique technology of Oceanlinx, a Sydney-based ocean wave technology company founded in 1997 by Dr Tom Denniss. Its technology is based on the well proven Oscillating Water Column (OWC) designs but solves two fundamental hindrances in cost-effective extraction of wave energy from earlier OWC designs. Firstly, the turbines used in the earlier designs were inefficient in extracting energy from the oscillating, bi-directional air flow resulting from wave motion on OWCs. Secondly, they were designed mainly for deployment at or near the coast, where the wave power levels were much smaller than in deeper waters.

Simple solution

Oceanlinx’s solution to this situation is simple. It uses variable-pitch turbine blades, which maintain the optimum angle of the blades to extract energy efficiently regardless of the direction of the airflow being created by the waves. It has also developed a floating OWC that can be moored in deeper, more energetic waters.

Of the Oceanlinx technology, Tom Thorpe, renowned oceanics academic and director of Oxford Oceanics, says: “OWCs are a proven technology, with a track record of providing a safe, green and reliable source of electricity. Oceanlinx has clearly developed this technology further to greatly improve its economics for electricity generation. They have demonstrated the significantly increased efficiency of their turbine and shown how moving to a floating structure can reduce costs while increasing output.”

The technology was developed by working with the University of Sydney’s Department of Aeronautical Engineering to establish proof of concept of the performance of the variable blade pitch turbine, and with the Australian Maritime College in Tasmania to confirm performance of a floating OWC, as well as other experts in various related fields.

Oceanlinx’s first full-scale prototype Wave Energy Converter at Port Kembla near Sydney has a peak electrical capacity of 500kW, and a small commercial sweet-water production capacity of 75l/h from its reverse-osmosis desalination system. The planned full-scale desalination unit will produce 3Ml a day.

This prototype design has now been further refined and a floating, catenary-moored device is now under development. A one-third scale model of this design is currently undergoing sea trials at the company’s Port Kembla site prior to the deployment of a number of full-scale devices near Portland, Victoria in Australia in 2008 and 2009.

The market attraction to wave energy has steadily improved since 2002 and is illustrated by the UK, Portugal, Spain and Ireland, which are lending full governmental support to wave energy initiatives in the form of generous financial grant and revenue support mechanisms. All have recognised the potential of wave energy as a means of diversifying away from an over reliance on unsightly wind power, with potential for local employment.

The first commercial project in Portugal has feed-in tariffs of £159 per MWh for the first 20MW of wave capacity. And there are good prospects in the UK where the government is finalising the terms of a £50M marine energy deployment fund. There is no premium price legislated in Australia. But Oceanlinx has secured a favourable premium for the Port Kembla prototype and has indications that it would receive the same for its Portland project.

The UK government has targets for deployment of new renewables for 2010 and beyond, most of which is expected to be provided by wind. The licensing process, however, and appeals by campaigns against onshore wind in the UK have resulted in significant delays to approval for these windfarms, which puts this target in doubt.

Sustained high fossil fuel prices leading to a high base cost of electricity will bring forward the time when wave and tidal stream energy become cost-competitive. And it will reduce the necessary costs of support. In addition, a rising oil price or shifts in domestic and imported fossil fuel supplies in the UK could raise interest in both the indigenous nature and the absence of fuel price volatility of marine renewables. This would raise the profile of wave energy and its strategic and environmental benefits.

It is possible that a large share of the Wave Energy Converter deployment envisaged across Europe could occur in the UK. If this happened, up to one sixth of the UK government’s aspiration for 20% renewable energy by 2020 could be met by marine renewables. The likes of Oceanlinx and its Wave Hub partners are here to stay.

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