Coming Soon! A site dedicated to wave energy in Ireland
- A technical resource for those interested in wave energy
- A forum for the promotion of a wave energy knowledge industry in Ireland
Easy Tiger The economics and technology of taming Atlantic waves
Could the creation of an ocean energy industry in Ireland help sustain our maturing tiger economy, ease energy security woes and reduce Ireland’s Kyoto shortfall?
Achill Island: Plentiful Wave Energy along Ireland's west coast
As Ireland looks to the creation of a credible knowledge economy to substitute its ailing manufacturing competitiveness, what better solution than to stimulate a cutting edge research knowledge base while helping to exploit our regions untapped renewable energy resources. The Atlantic waves that incessantly crash on Ireland’s western shores are constantly dissipating energy. On average about 50GW of power, or 20 times the electrical power consumed by the entire Irish grid, is dissipated uselessly as heat. If even 1% of this could be converted to useful electricity, it could provide 20% of Ireland’s needs. A report produced by ESBi and the Marine Institute has estimated that, allowing for technological and accessibility limitations, about three quarters of the Irish electricity requirements are potentially realisable, with a current market value of about €2bn per annum. All of this can be achieved from an infrastructural deployment that will have a small or positive environmental impact and will likely meet minimal public resistance. If the development plan outlined by the Marine Institute and Sustainable Energy Ireland is followed, it is estimated that wave energy could be worth €270M to the Irish economy by 2020 and would only expand after that with the global market estimated to be worth in the order of €50 to €200bn. However, there are some technical hurdles and economic uncertainties that need to be addressed before investors will feel safe backing this rosy prospect. The trouble is that addressing such hurdles requires huge investment in itself. Does Ireland have the courage to cough up the cash and fill that funding gap?
The Irish Wave Energy Resource: Power diminishes closer to the coastline but in the green band there is still 50kW for every metre of contour.
(source: Marine Institute GIS www.marine.ie )
The technology of wave power:
The solar energy falling on our planet heats the atmosphere and converts some of the solar power to wind energy. The wind in turn imparts some of its energy into the oceans, where it is stored mechanically as wave energy. As the energy from the sun trickles down through this sequence, its “intensity” is increased. In Ireland, the average amount of solar energy incident with any square meter of surface is only enough to light a few light bulbs. The energy available from the wind passing through an imaginary vertical square meter is about three times as much. In ocean waves however, there is on average over 2kW passing through each square metre of ocean, plenty enough to power an entire home. The resource might be impressive, but practical and affordable methods of converting this chaotic form of energy into convenient electricity have so far been much more illusive than for wind or solar energy.
The idea of extracting useful energy from ocean waves has been tantalising inventors and engineers ever since Stephen Salter of the University of Edinburgh highlighted its true potential in “Wave Power” published in the scientific journal “Nature” in 1974. Early pioneers of wave energy established the fundamental theories of primary wave energy extraction, that is to say the scientific understanding of how a physical interface with the ocean could extract the mechanical energy that the ocean stores. “To absorb a wave is paradoxically to generate a wave”, the very personable author on the subject, Prof Johannes Falnes, sternly reminded the next generation of wave energy enthusiasts, gathered at a conference celebrating his 75th birthday in Trondheim last December. Any oscillating body bobbing in the sea is capable of generating a wave field outwards across the sea surface. The trick is to radiate a wave field that cancels out as much of the incident ocean waves as possible, thereby absorbing the equivalent energy into the bobbing body. Falnes and his colleague Kjell Budal at NTNU Trondheim discovered this “antenna effect”, where a floating “point absorber” could theoretically absorb far more wave energy from the sea than that which is directly incident upon its geometry, analogous to a radio antennas ability to absorb radio waves. The upshot of this effect is that, in order to absorb a maximum amount of wave energy, the body must be driven in an oscillating “resonant” condition where it will absorb and store the energy from the sea around. The body’s motion must then be controlled within practical limitations, by introducing “power take off” (PTO) machinery which can deliver this mechanical power to the electricity grid.
In a scaled laboratory test in an Edinburgh wave tank, Stephen Salter managed to absorb over 90% of a regular wave using his famous “duck” floater. In the test, this specially designed geometry pitched about a fixed central axis where an electrical generator then converted the relative motion to electricity. Note in Fig 2 that the circular orbits of wave particles on front of the duck device are completely diminished behind the duck, indicating near total absorption of the wave’s mechanical power.
A time exposure of Salter’s duck in motion in an Edinburgh laboratory wave tank. Note the orbits of tracer fluid showing wave motion in front of the duck to the right. This is completely diminished behind the duck. The power has been completely absorbed.
(source: University of Edinburgh Wave Power Group http://www.mech.ed.ac.uk/research/wavepower/ )
At small scale in a laboratory, an electric generator was directly able to absorb the wave energy. However, one of the considerable difficulties is how to create this power take off force at full scale and out in the open and often violent Atlantic ocean. There are two main complications. Firstly, the force must be reacted by the relative motion with a second body. This could simply be the shoreline for on-shore devices, or a connection to the sea floor in shallower water. An offshore device can also be “self-reacting”, for example by using two floating bodies to react against each other as they move, or by using a large weight inside the floating structure to react against. This requirement leads to mechanical complexities and in some designs, an “end stop” problem where, under extreme waves, the power take off machine must necessarily run out of stroke, causing a bump and inducing large unpredictable loads in the structure. Secondly, mechanical power is a product of force and speed. The nature of wave power is one of very high forces and slow speeds. As well as the fact that high forces require stronger structures, electrical generators also much prefer higher speeds than waves naturally provide. Wind energy suffers the same problem and requires very troublesome gearboxes that convert turbine windmill speeds as low as 1 revolution every 5 seconds up to the electrical generator shaft speeds 100 times faster.
There are a number of methods being considered for this power take off application. Stephan Salter decided that high pressure oil hydraulics was the preferred option, similar to a digger bucket being used in reverse (i.e. the waves wiggle the bucket!). High pressure hydraulics can carry huge amounts of power with only relatively small equipment compared to electrical motors and generators. Not content with the efficiency of hydraulic machines available on the market, Salter led a team at the University of Edinburgh to produce a highly efficient hydraulic machine. They also found a way of providing the required reaction forces using the gyroscopic forces of heavy spinning discs inside the device, the same force that keeps a bicycle vertical. This can be sealed inside the device and has no “end stop” problem.
An Oscillating Water Column (OWC) using a Wells Turbine to convert wave energy to electricity
(source: http://www.offshorecenter.dk )
Another power take off option is to use air turbines. This is where entrapped air in a chamber above the sea surface is compressed by the waves outside, causing oscillating airflows through a turbine duct. The concept is called an Oscillating Water Column (OWC). Such power will be familiar to anyone who has listened to large waves entering partly submerged caves at the coast. The wells turbine, invented by Prof. Wells of Queens University Belfast can be applied in an OWC. A wells turbine is capable of extracting shaft power in a constant rotational direction despite the oscillating airflow. Some designers tout the relative simplicity of this solution and its ability to convert huge wave forces at slow speeds into very fast shaft speeds for electricity generation. Others however, highlight its inefficiency where an absolute maximum of 40% of the available pneumatic power can be converted to shaft power. Efforts to improve efficiency usually add considerable cost and complexity.
Another big challenge for developers is how to bring the power they generate to the market. The wave resource is often remote from large population centres where it is required and where the electrical grid is strong enough to cope. Long submerged electrical cables are an extra cost and can be a headache for grid managers. Furthermore, though less variable than wind energy, the wave resource is still variable and must be backed up by other energy sources on days when there are no waves. This limits wave energy’s potential contribution to an isolated Irish grid. However, such problems are not unique to wave power and other forms of renewable energy have to contend with similar issues. Ireland has the advantage that along its Atlantic coastline is a strong grid and sizable energy demand, with the country’s largest power station at Moneypoint, only about 30 km from the exposed Clare coastline. The variable delivery problem is also much improved if the supply is connected to a single larger grid, such as a Britain and Ireland grid for example. The stabilising influence of Britain’s nuclear resources and power supply smoothing infrastructure could play a vital role in increasing the renewable contribution from more isolated regions in Ireland and Scotland.
The challenges are therefore not insurmountable and development teams in Edinburgh and elsewhere had achieved good success until the oil shocks of the early 1980’s receded and interest and support for the UK wave energy programme dwindled. “The requirement at the time was for a large scale energy source, competing with nuclear power. Off the shelf technology at that time was not up to the task. It was like the Wright brothers building a jumbo jet”, recalls Stephen Salter. Once financial support was cut, development could not be sustained. All was not in vain, however, and much of the hydraulics technology conceived at that time is still being developed by a spin off company called Artemis, while wave tank laboratory design also led to the creation of a company called Edinburgh Designs. More recently, there is a resurgent interest in wave energy and new developers as well as Stephen Salter himself have been picking up where they left off.
Facing commercial realities:
The funding gap left a generation gap in the wave energy research community. This is obvious at any European wave energy meeting today, where young enthusiastic researchers and developers are to be seen mingling with their more mature and invariably wiser colleagues. The new generation are making their mark, however. They find themselves sitting on the fence between the existing theoretical ideals and the commercial realities of the world around them.
Is there really a market for this electricity? What future electricity price are we competing with? Should we aim for maximum efficiency or should we concentrate on demonstrating survivability and reliability first? What support can we count on from the government? What assurances can we give investors in such a high risk, long term venture? What regulatory bodies do we have to deal with? As the new generation attempts to answer these questions, the deepening concern over energy security and increasingly entrenched consensus on the need to act against global climate change is providing some of the answers. The ability to talk the commercial language, court investors and compromise on technical ideals is starting to take effect.
Ocean Power Delivery Ltd (OPD), set up by Richard Yemm, a former student of Stephen Salter, is an Edinburgh based commercial company set up in 1998 that is developing the Pelamis concept (see Fig). It is probably the most advanced commercial outfit in wave energy, employing over 70 people. They received funding from a consortium of private venture capital, including funding from energy giant General Electric as well as some funding from the UK’s Carbon Trust. After a successful demonstration of their full scale prototype at the European Marine Energy Research Centre (EMEC) in Orkney, they were awarded their first commercial contract to deploy 3 devices in a demonstration project in Portugal in 2005. OPD’s strategy has been to use 100% 'available technology' and system components that are available 'off the shelf' and introduce new technology to improve efficiency only after reliability has been demonstrated. ‘Survivability before power capture efficiency…these two essentially conflicting aspects are often approached from the other direction’ stresses Richard Yemm, now the company’s managing director.
Ocean Power Delivery’s “Pelamis” device. A snake-like self-reacting device with hydraulic machinery to extract power at each of its joint
(Source: www.oceanpd.com )
While OPD are continuing efforts centred in Scotland, it is by no means a one horse race. Inverness based Wavegen, recently acquired by German engineering firm Siemens, has been developing air turbine technology for wave energy applications. Their turbines have been tested at full scale in the Limpet oscillating water column (OWC) on the Scottish island of Islay. Further afield, another experimental OWC has been developed by Portuguese developers on the island of Pico in the Azores. AWS Ocean Energy, now based in Inverness are hoping to commercialise a device called the Archimedes Wave Swing (AWS). This fully submerged device with zero visual impact was developed by a Dutch company, “Teamwork Technology”. It has already been tested at full scale off the Portuguese coast. In Norway, a shore based OWC was built as well as a shoreline tapered channel device where waves ramp up and “overtop” into a raised reservoir before being let back to the sea through a hydro turbine. In Denmark, a one quarter scale prototype of a floating overtopping reservoir device called Wave Dragon has been deployed with plans to build a full scale version off the Welsh coast. Uppsala University in Sweden are experimenting with smaller devices with a unique linear electric generator for power extraction. Although efforts have been concentrated in Europe, numerous other ideas have been pursued around the globe, including in Japan and North America. There are seemingly endless ideas for how best to extract ocean wave energy and as yet there is no clear winner. Wind energy went through a similar stage of development about 20 years ago before the 3 bladed horizontal axis turbine, synonymous with wind energy today, was accepted as the industry standard configuration.
Irish efforts to date:
Efforts in Ireland have also been significant. The Hydraulics and Maritime Research Centre (HMRC) in Cork, recently bolstered by funding from the Marine Institute under the “Blue Power” project now employs over 15 researchers and technicians. The HMRC has been involved in European wave energy development since 1979 and are leading members of the EU funded Co-ordinated Action on Ocean Energy (CAOE). The HMRC has an “ocean basin” laboratory where scale models can be tested in realistic ocean sea states. Many of the prominent international projects have used the HMRC’s facilities and knowledge at some stage in their development. The HMRC have also outlined a protocol for how wave energy devices should be developed, which provides a useful guideline for developers and investors. Queens University Belfast have an ongoing wave power research group and were responsible for the development of a full scale shoreline OWC device called ”Limpet” on the Scottish island of Islay. They also have a shallow water wave tank and are now concentrating on solutions to be deployed in near-shore regimes. The University of Limerick’s Wave Energy Research Team (WERT), based within the department of mechanical and aeronautical engineering have also carried out world leading research on air turbines for wave energy applications. Finevera Renewables, a publicly floated Irish investment company dedicated to developing renewable energy has also taken a bet on wave energy. It has acquired 100% of AquaEnergy, originally a Swedish developed technology but now mostly operating in North America.
As well as having a strong foothold in the knowledge of wave energy, Ireland’s policy makers and financers have also been making noise of late. In 2002 Sustainable Energy Ireland (SEI), in conjunction with the Marine Institute, published the public consultation document on “Options for the Development of Wave Energy in Ireland”. The document lays out three options going forward. The first one aims to take all the risks necessary to ensure that Ireland becomes an all out technological leader in the field and to be in a position to benefit from any large export industry. The second is to ensure that Ireland will be in a position to utilise wave energy while having a small core of exportable research excellence. The third option is to play an observational role in international developments and to simply “buy in” the fruits of foreign work. While the public response generally favoured the first option, the result since then has resembles more option 2. In 2005 a follow up document “Ocean Energy in Ireland” has been rubber stamped by the Department of Communications, Marine and Natural Resources. It outlines a more concrete commitment to wave energy with a 4 phase strategy culminating in a competitive market readiness for large scale Irish wave energy deployment by 2020. Ambitions of having over 2200 Irish jobs in ocean energy by 2025 are also expressed. The report claims that the policy “could also see Ireland positioned with the potential to become a world leader in the manufacture and use of ocean energy systems.”
Phase 1 of this plan has already been underway since 2005. This phase is “to support national developers of wave energy devices through concept validation, model design optimisation and scale model testing.” SEI have been able to make some R&D funding available to developers and the Marine Institute have set up a wave energy test side off Spiddal in Galway Bay. This is a benign site, sheltered by the Aran islands and is suitable for testing ¼ scale devices in the sea. Two indigenous Irish prototype devices have already been deployed. Wavebob, invented by Irish physicist William Dick, is a 2 body, self-reacting buoy, floating largely underwater. Like OPD’s Pelamis, it uses hydraulics for power take off. The developers are Clearpower Technology Ltd, based in Northern Ireland where they are backed by the UK’s Carbon Trust, Ireland’s Marine Institute and Norwegian shipping and energy magnate Fred Olsen. The scaled prototype was tested during 2005 at the Marine Institute’s test site. A second device, the OE Buoy is being developed by Michael Whelan of Ocean Energy Ltd in Cork. This device uses the oscillating water column concept applied to a floating device where use is made of the relative motion of the buoy and the entrapped air column. Because it is a floating device, it can be deployed further offshore where the wave resource is much better then at the shoreline. Their prototype was deployed at the Marine Institute test site since autumn 2006, where it has successfully survived very severe weather.
¼ Scale Wavebob in position at the Galway Bay Test Site
Artists Impression of the OE Buoy. A ¼ scale device has been in Galway Bay since Autumn 2006.
Towards the future
So it seems that, in principle at least, wave energy is being taken seriously in Ireland and there is consensus about its potential benefits to this country. The opportunity to do with wave energy what Denmark did with wind energy is an enticing prospect for any government. Wind energy related activities now make a valuable contribution to the Danish economy and have created in excess of 20,000 Danish jobs. The trouble for wave energy, as it was for wind energy, is that in the current economic climate it is not possible to compete directly against conventional energy production. In order to be truly economically viable, wave power will require an economy of scale with hundreds, if not thousands of machines being deployed in “wave farms”. As this happens, it could be expected that the rising prices of depleting gas resources could make wave power a very attractive, if not a necessary, solution for powering Ireland’s economy. This could especially be the case if Kyoto commitments prompt EU taxes to be levied on carbon emissions from more conventional power production. As it is, the short term return for wave energy technology development is almost non-existent so private investors tend to shy away. Britain committed £50 million of public money to wave and tidal energy, but this is a drop in the ocean compared to, for example the £15 billion required to develop a nuclear power plant. The relatively little public funding that is available tends to be diluted among numerous projects with legitimate claim to fund their development. These funding problems can be overcome with a “feed in tariff” such as that introduced by Portugal, where successful projects initially get far above the market rate for the delivery of ocean energy to the electricity grid. This can motivate investors and is almost certainly the reason for Scottish based OPD having their first commercial deployment in Portugal.
The success of wave energy hinges on its perceived strategic benefit to the future of a particular society. Isn’t the time ripe for Ireland to prove its metal in the industrial world as a leader in technical innovation? Perhaps more importantly, as one of the highest per capita energy consumers in the world and with an enormous wave resource in our back yard, there is a moral duty on us to contribute to this field. Surely we are not content to sit on our laurels and simply hope that someone else will continue to solve impending problems for us? The next phase in the Irish strategy will be to go to full scale ocean prototype testing of one or more devices in the full rigour of the Atlantic. This is due to begin from 2008 onwards. That will require resources far beyond lip service. The ability to commit the very significant funding required for this phase and then to deliver a successful test, will be a true measure of Ireland’s ability to meet the wave energy challenge. One can only hope that the Irish decision making community and investors have the courage, and that researchers and engineers possesses the knowledge, to ensure that this island will stand to harvest the rewards of a potential energy revolution.