Wave after wave – ocean energy in Ireland

Renewable resources

Here’s a fact: The day will come when all the energy we consume will come from renewable resources, simply because reserves of oil, gas and coal will run out. Renewables include wind and solar power, and also ocean energy, which has the potential to supply immense amounts of sustainable energy. The Carbon Trust estimates there is a practical global resource potential of between 2.000-4.000 Twh/yr, enough to supply 10-20% of current world energy consumption.

PHOTO: Ireland’s ocean energy strategy

West coast of Ireland
Waves contain energy, lots of it. And waves are better at retaining energy than wind, being able to retain up to 1.000 times as much kinetic energy. Just how much energy a wave contains depends on factors such as wind speed, how long the wind blows, and the distance over which it blows – the ‘fetch’. Facing the Atlantic Ocean, the west coast of Ireland has a very long fetch, producing a very powerful wave climate with the highest average wave power in Europe.

Investing in ocean energy
The total energy resource available off the Irish coast could amount to 34 GW, according to studies by the Sustainable Energy Authority of Ireland (SEAI). Therefore, a combination of government, utility and wave technology companies are working to harness its potential.

ESB is Ireland’s leading utility company, with 7,000 employees and an annual turnover of EUR 3 billion. Colm de Búrca is the Manager of Ocean Energy at ESB

PHOTO: Colm de Búrca, Manager of Ocean Energy, ESB

Experienced man at the helm
Colm de Búrca has experience of working in the fields of power generation, retail supply and business development, as well as power contracting. Since 2008 he has been responsible for setting up ESB’s ocean energy business, with the long-term goal of positioning the company for growth after 2020.

The technologies

Technologies united by diversity

If there is one thing that unites the devices used to harness ocean energy it is their diversity. While they all function by converting the action of the waves into movements that power generators use to produce electricity, the manner in which they do this differs greatly. They might utilise buoys, terminators, overtopping, surface following or oscillating water columns, as well as pneumatic or hydraulic power take-off.

Four technologies ahead of the pack
In Ireland, ESB is working with four companies with four different technologies to develop an initial wave energy project for Ireland. The four devices utilise near-shore attenuation, oscillating water column (OWC), a point absorber and an articulated attenuation device. All four are currently undergoing development and testing and are all designed for commercial deployment in large offshore arrays.

Wavebob
Wavebob is an Irish company who design and manufacture the Wavebob wave energy converter (WEC). The converter is an axi-symmetric, self-reacting point absorber comprising an inner float and an outer ring which react differently to the passage of waves. Waves cause the inner float to move relative to the outer ring and the energy of this relative movement is captured to create electricity. The Wavebob will automatically adjust its response to suit the prevailing wave climate and is especially designed to recover power from ocean swell. The full-size Wavebob has an approximate diameter of 20 meters and a submerged body 65 meters below water.

OceanEnergy Buoy
OceanEnergy Limited is an Irish company who design and manufacture the OceanEnergy Buoy, a floating single unit Oscillating Water Column (OWC) wave energy converter. It utilises wave energy to compress air in a chamber trapped by seawater and pumps it through an air turbine system. Each rising wave forces the air in the chamber through the aperture above the water column which leads to the turbine and generator, turning the turbine. As the water inside falls again, air pressure is reduced, drawing air back through the turbine, which continues to turn.


"The delivery of ocean energy projects is crucially dependent on commercially viable technology being proven on a utility scale."

Colm de Búrca, Manager of Ocean Energy, ESB

Pelamis
Pelamis Wave Power Limited design and manufacture the Pelamis wave energy converter, a 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 fluid through hydraulic motors via smoothing accumulators. An algorithm controls the resistance in the hydraulic rams, decreasing it when waves are small and increasing it when they are large, ensuring that energy production is maximised whatever the sea state. The hydraulic motors drive electrical generators to produce electricity. Current production versions are 180 meters long and 4 meters in diameter with 4 power conversion modules per machine.

Aquamarine Power Oyster
Aquamarine Power design and manufacture the Oyster wave energy converter. This employs a single buoyant hinged flap, which is almost entirely underwater, whose movements drive two hydraulic pistons which push pressurised seawater onshore, to drive a conventional hydroelectric turbine and generate electricity. The Oyster is a near-shore device that operates in water less then 20 metres deep, typically around half a kilometer from shore. In essence, the Oyster is a large pump that provides the power source for a conventional onshore hydroelectric power plant.

 

Do all four ocean energy technologies need to develop into commercially viable solutions for ESB to meet its targets for 2020 and beyond?

Colm de Bùrca: Not necessarily as there will be other technologies that may be developed in the coming years. However, the delivery of ocean energy projects is crucially dependent on commercially viable technology being proven on a utility scale.

So there are other promising technologies?

Colm de Bùrca: Yes there are and ESB is involved in monitoring and evaluating a number of promising technologies that could be deployed on future ocean energy projects.

Deployability
Part of the technological challenge involves finding the right site and conditions for ocean energy projects. The technology itself – the devices – need to match the site when it comes to water depth, the seabed and geotechnical requirements, and so-called bathymetric factors.

Survivability
The greatest technological and design challenge is probably survivability in a hostile – and at times, extremely hostile – environment. On the one hand, wave energy devices need to be designed for a particular wave climate and its wave spectra variations, directionality, spreading and alignments. These are predictable factors.

However, what cannot be predicted are extreme waves; even in areas with average wave power levels of 30-70 kW/m, extreme levels in excess of 2.000 kW/m have been recorded. Constructing devices with a 25-year lifespan that can withstand such extreme forces is a challenge faced by everyone in the ocean energy industry.

Challenges

Resource, strategy and commitment

A number of factors played a central role in the decision to invest in ocean energy in Ireland. In addition to the resource available off of the West coast of Ireland there was also a clear government strategy and commitment, enabling ESB, in its role of utility company, to include a substantial amount of renewable energy in its energy portfolio in the coming years.

How much of Ireland’s electricity requirements could be provided by ocean energy in 2030 or 2050?

Colm de Búrca: The amount of electricity that could be produced from wave energy is vast and by 2050 the majority of Ireland’s marine renewables will likely be exported to other EU countries and may not be consumed in Ireland. However it is likely that a sizeable share of Ireland’s electricity portfolio may come from wave energy by 2030. The government’s targets of 500 MW by 2020 are just a signal to a much greater ambition towards 2030 and beyond.

Challenges include reducing the cost of technology, improving the reliability of technology, getting access to the foreshore, getting access to the grid, ensuring the supply-chain is sufficiently developed and ensuring appropriate funding.

Colm de Búrca, Manager of Ocean Energy, ESB

What are the major challenges facing the commercial development of ocean energy in Ireland?

Colm de Búrca: Challenges include reducing the cost of technology, improving the reliability of technology, getting access to the foreshore, getting access to the grid, ensuring the supply-chain is sufficiently developed and ensuring appropriate funding for pre-commercial and commercial-scale projects.

WestWave
To meet these challenges, the WestWave project was established to promote collaboration. WestWave is a project being led by ESB where technology developers, utilities, supply chain companies and government bodies can collaborate and share knowledge on the road to developing commercial-scale ocean energy projects in Ireland.

 

Combining resources

Could the future be wave + wind?

With its wave climate, Ireland has the potential to generate very significant amounts of energy. One option could be to combine resources such as offshore wind and ocean energy. For example, a recent study by the Offshore Valuation Group estimated that just one third of the total offshore resources of the UK could generate energy equivalent to current UK North Sea oil and gas production, which is around one billion barrels of oil per year. And Ireland has even better natural offshore resources.

What about the possibility of combining offshore wind and wave energy in Ireland?

Colm de Búrca: In terms of scale there is a very attractive offshore wind energy resource available in Ireland in addition to the wave energy potential. Wind energy is an established renewable technology; wave energy is the next generation of renewables after wind.

PHOTO: Wave and wind

Could wave energy catch up with offshore wind?

Colm de Búrca: It will take a number of years for costs to fall as the technology matures and for larger projects to bring about economies of scale and lower costs. One of our long-term goals is to match the costs of offshore wind, which we would expect to happen by 2030. Offshore wind energy is also continuing to evolve and floating offshore wind concepts offer a great opportunity to further reduce costs in offshore wave projects.

Learning from one another
Establishing ocean energy projects faces challenges common to offshore wind projects. These include gaining access to the sea, such as licensing, permitting and environmental aspects, as well as connecting to the electricity grid. Working together to overcome these challenges will be essential going forward.

Competitive
Ocean energy faces the classic commercial issue, that of costs. The demand for renewable energy is huge and constant – what ocean energy is working towards is becoming relatively cost effective and competitive in terms of kWh prices.

The industry is sometimes compared to the onshore wind industry 15 or 20 years ago, with many competing technologies. In the wind industry, a few technologies won out, parts were standardised and costs fell. Ocean energy could be on the verge of going through the same process, but with the experience of wind energy to draw upon, things can be expected to move a lot faster, both in Ireland and elsewhere around the world.


"In terms of scale there is a very attractive offshore wind energy resource available in Ireland in addition to the wave energy potential. Wind energy is an established renewable technology; wave energy is the next generation of renewables after wind."

Colm de Búrca, Manager of Ocean Energy, ESB


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