Based on an article written in 2002 by Alison Colls and reviewed by Alan Wells, FRS, inventor of the Wells turbine for converting waves to electricity. A comprehensive overview of the development of wave energy technology.

Introduction

Waves represent an enormous potential source of renewable energy, which could reduce the UK's contribution to global warming. It is estimated that there could be sufficient recoverable power around the UK to generate enough power to exceed domestic electricity demands. Here we provide a comprehensive overview of wave energy full of fascinating information for anyone new to the subject.

 Photo: www.claudiaferrari.com

Sections in this article

• How waves are created

• Global potential

• Background- a history of wave power in the UK

• Renewed interest

• Technology

• Environmental impacts

• Commercial potential

• Are there any major barriers to it expanding?

• Where Next- further sources of information on wave energy

How waves are created

Waves are generated by winds blowing over the ocean surface.  Wave energy is effectively a stored and concentrated form of solar energy since the winds that produce them are caused by pressure differences in the atmosphere caused by the sun's differential heating of the earth's surface. Waves can efficiently transport energy for thousands of miles and retain their energy long after the winds that first created them have died down, which makes waves one of the most concentrated and consistent sources of renewable energy. 

Most of their energy is released when the waves hit shallow water, beaches and cliffs, over time eroding the coastline. Waves can be immensely powerful; the force exerted by a large wave on an exposed coast is estimated to be nearly ten tonnes per square metre, and even greater during storms.

Global potential

Globally, the potential use of wave power is, unsurprisingly, limited to areas of the world where there are waves. On a global scale, this is dictated by global wind patterns, with the result that waves are more prevalent in the mid-latitudes (40-60(N/S), than nearer the equator where the lack of ocean wind is referred to as the 'doldrums'.  Interestingly, this potential for wave power contrasts with that of solar power, which is more effective in lower latitudes.

Within the mid-latitudes, wave energy is greatest in areas where waves have travelled a long distance, in practice across large oceans. Western Europe, the West Coast of USA, and the coasts of New Zealand and Japan are particularly suitable. Sheltered coastlines are less suitable; applications of wave energy in the Mediterranean and Germany, for example, are less viable.

Background- a history of wave power in the UK

Despite its huge potential, the development of wave energy lags behind that of other renewables, such as wind or solar power.  This is not because it is a newer technology or concept - on the contrary, the exploitation of ocean waves as a source of energy has been the subject of extensive research in the UK.  In 1974 the Government established a major wave energy R&D programme in response to the oil crisis and the need to find alternative sources of secure energy.  The Government invested a considerable amount of money and support in the development of wave energy.  But the initial targets of the programme were over-ambitious and researchers failed to meet them.  The wave energy sector consequently suffered from scepticism about its capability and perceived high costs.  Furthermore, an internal and unpublished Government report inaccurately reported that wave energy could never be economically viable.  The Government's R&D programme was radically scaled down in 1982 and finally abandoned in 1994, which the DTI now acknowledges was a mistake.

Wave energy's credibility was not helped by the fact that several of the early wave energy prototype generators were destroyed in storms, fuelling the doubts of the reliability of generating electricity in such a hostile environment. Despite this, a number of wave energy schemes proceeded in the 1980s and 1990s. Queen's University, Belfast, for example, operated a small, near shore, pilot device on Islay for nearly ten years.  Yet, it has been suggested that the UK's failure to develop its considerable wave energy potential, impacted on the optimism and motivation of other countries to exploit their own wave energy resources (House of Commons 7th report).  David Ross presents a more detailed account of the history of wave power development in The Power from the Waves, (Oxford University Press, 1995). 

Renewed interest

Climate change has put renewable energy firmly back on the agenda because of its role in helping to reduce fossil fuel emissions.  While solar, wind, biomass and hydropower are expected to meet the 2010 renewable targets, it is widely anticipated that other types of renewable resources, including wave energy, will need to be developed in order to meet more challenging targets beyond 2020.  In 1999, the Government relaunched its wave energy R&D programme (though on a much smaller scale than its programme during the 1970s) to help assess the extent to which wave power could help meet our energy needs. 

In the same year, three wave energy companies (Wavegen, Ocean Power Delivery, Sea Power International) were chosen as part of the third round of the Scottish Renewables Obligation, to supply electricity to the National Grid for approximately twenty-five years.  Of the three, Wavegen currently run the world's only commercial-scale wave power facility on the shoreline of Islay, in west Scotland. Called LIMPET (Land-Installed Marine-Powered Energy Transformer), it is demonstrating the viability of wave energy and contributing 500 kilowatts of electricity into Islay's power grid, enough to light 400 homes.

Wavegen's LIMPET (Land-Installed Marine-Powered Energy Transformer).

Ocean Power Delivery and Sea Power International are expected to launch their wave energy devices later this year, off the island of Islay and the Shetland Islands respectively. Wavegen have, in addition, received Government funding to help them develop an offshore wave power facility, off the island of Orkney, which once operational will supply enough electricity to power 1400 homes.

Technology

Wave energy conversion is a comparatively young technology, and a wide variety of possible wave energy technologies have been developed.  Most of these remain in the research stage but a significant number shoreline, near-shore, and offshore demonstration projects have been built around the world and a number of companies are planning their first commercial schemes.  All the current competing technologies convert wave action into energy by providing some way for the wave to transfer its kinetic energy to a piston or turbine, either storing this energy briefly or passing it immediately into a generation device.

 

The potential for generating electricity is much higher out at sea where the waves are bigger and contain more energy. The offshore environment is, however, incredibly hostile.  Any wave energy device must be constructed to survive severe storms and other challenges including salt-water corrosion, growth of algae, marine fouling (barnacles, seaweed, etc) and access difficulties. Many of these challenges have already been overcome, at high costs, by existing offshore industries with correspondingly high revenues: namely oil and gas and shipbuilding.  Subject to necessary economies, the experience, skills and technology acquired by these industries should be transferable to the wave energy sector. Furthermore, the oil and gas and shipbuilding industries are both expected to decline over the next few decades. Wave energy could provide an important alternative source of work, as these industries seek to diversify. 

Electricity for use ashore need not be the only output from wave power plants.  Treated seawater at high pressure could be used to increase the yields of oil wells by injection and displacement. This would more than offset some of the higher costs associated with working offshore. On the thousands of islands worldwide, directly compressed air from wave power turbines could be expanded on shore and used for refrigeration and air conditioning. 

Environmental impacts

Wave energy technology is clean and sustainable and, with careful siting, has little impact on the environment. Most wave energy conversion devices would be invisible from the shore although there could be visual and environmental impacts associated with the line required to transmit electricity to shore and to the grid. Some wave energy devices may affect the natural flow of sand and other beach sediment and so would require sensitive siting but the installations could also potentially benefit the environment by creating safe havens for fish and helping to reduce coastal erosion. As with most renewable energy sources, wave devices have no emissions during generation but the energy associated with the construction of the device does have small associated emissions.

Costs and reliability

Wave energy is at an early stage of development and is therefore still relatively expensive when compared to other sources of electricity.  The House of Commons Science and Technology Committee concluded in 2001 that a true picture of the likely cost of wave power will only be available after the industry has matured and large devices have been operating for some time.  However, the cost of wave energy has fallen over the past 10 to 15 years and ongoing technological developments mean the predicted costs of wave energy are continually being reduced.

Wave energy is already competitive in niche markets, such as remote islands, which are often reliant on expensive (and environmentally detrimental) diesel generators.  The development of wave energy alongside other technologies - fish farms, harbour defences, desalination plants or wind farms could further reduce costs.  In addition, there are potentially many opportunities for the wave energy sector to collaborate with the wind power industry, both on joint projects (e.g., combined offshore facilities) and by addressing common problems such as connecting the electricity they generate to the National Grid.

Wave energy is dependent on the weather and consequently varies substantially. However, the variability in wave energy broadly corresponds to electricity demand. Furthermore, maritime data, collected over centuries, makes it possible to predict peaks and troughs of supply at least six hours in advance.  The House of Commons Science and Technology Committee concluded in 2001 that this allows much easier integration into the Grid than some other renewables.  In terms of the technology, few wave energy devices have been operating for long enough to demonstrate long-term performance and reliability.

Commercial potential

In addition to the UK's domestic demand for renewable energy, there is potentially a huge (£500 billion plus) export market for wave energy devices, especially for those companies that develop the technology first.

The UK currently has a small technical lead in the wave energy sector, but internationally, the industry is experiencing rapid growth and other countries (e.g., Denmark, Japan, Australia, Ireland, Netherlands, Portugal) are also developing wave energy technology.  Some of these are pilot schemes, while others are commercial projects.  An American company, Ocean Power Technology, for example, has tested a large scale floating wave energy device in the Eastern Atlantic and is currently building commercial schemes in Australia and in the Pacific.

Photo: http://www.claudiaferrari.com/

Are there any major barriers to it expanding?

Since most wave energy technologies have yet to develop a proven track record (e.g. reliability, efficiency and reparability) it is essential that the current demonstration schemes are successful, to reassure future investors. The most important objective is to deploy full-size demonstration schemes in order to gain greater confidence in the most developed technologies (as in the EU's Atlas project).  They will need to be adequately funded to minimise risks.

Before wave power can contribute significantly to the UK's electricity needs, it will be necessary to significantly improve the network connections to the electricity suppliers.  This is because the optimum sites for generating wave energy (and often other renewables such as wind or tidal) are located far away from the network demand centres.  Reinforcing the electricity network will be very expensive and a central issue will be how these costs are met.  With this in mind, the Scottish Executive has recently initiated a detailed study of the electricity grid in Scotland to determine its capacity to carry further renewable generation capacity, to look at areas where strengthening may be required, and to assess the costs.

Another obstacle is that unlike wind energy or other renewables, wave energy does not yet have a central, co-ordinating body.   The UK wave energy R&D teams are all relatively small and working independently because commercial considerations force them to keep their ideas secret.  However, a report by Arup Energy in 2001 concluded that this secrecy compounds the slow progress and delays any return on their good ideas.

At the time of writing in early 2002, Brian Wilson, the Energy Minister, has just announced plans for Wavegen to develop a cluster of offshore wavepower stations in the western Isles.  They will be supplying Scottish Southern with electricity while acting as demonstration plants.

Where Next- further sources of information on wave energy

On ClimateX.org

One man's struggle to convert waves into electricity is documented in the case study ‘Well's Waves', also available in this section.

Other recommended sources

Latest news on wave energy technologies and projects in the UK can be found at the British Wind Energy Association (see Where Next) at http://www.bwea.com/marine/devices.html.

The House of Commons Science and Technology Select Committee 2001 Report on ‘Wave and Tidal Energy'  ,used in preparation of this article.

Wavegen, Seapower International and Ocean Power Delivery are all energy companies with a particular interest in wave power.

The British Wind Energy Association is the UK trade association for wind, wave and tidal renewable energy technologies. See http://www.bwea.com/marine/index.html

Claudia Ferrari has some great photos of Hawaiian waves on her website: http://www.claudiaferrari.com/.

Or you can read the following book:

Power from the waves, David Ross, 1995, Oxford University Press.