Select Committee on Science and Technology Appendices to the Minutes of Evidence


Memorandum submitted by the Institution of Civil Engineers


  It is suggested that the Science and Technology Committee ask ETSU for a full report on the work they commissioned in the mid to late 1970s when they were funding design work to try to make practical prototypes out of the half dozen or so laboratory models developed in the universities. This report should explain why they all failed and the Committee would then be able to decide whether the present workers have solved the fundamental problems which were identified at the time.

  A member of our ICE Energy Board was seconded to work at Edinburgh University for 18 months on the "Salter" nodding duck design and comments, to some degree, are based on personal experience.


  There are two basic designs

    1.  Devices designed to capture the energy from the deepwater offshore waves. These devices are the only ones which could make a serious contribution to the national energy supply. In deep water the waves are not affected by the influence of the seabed and the devices are designed to capture the energy from the rotary motion of the circular waves. These devices are typically floating on the surface and moored to the seabed. The preferred location is in a line 200 to 300 miles long and west of the Hebrides where the wave energy is greatest.

    2.  Two shoreline devices designed to capture the energy from the changing water surface level as the wave breaks when it runs into shallow water. In shallow water the seabed interferes with the circular motion of the wave causing it to break, and if the boundaries of the run up channel are converging the effects is to magnify the raise and fall of the water level. This design is a special case which is suitable only at a few particular locations where the right natural conditions exist or can be built. Devices at such locations are small, inefficient and expensive and although they may be helpful for a small local community they are useless for supplying the national demand. The wave energy machine on Islay is an example of this type.

    My comments will be restricted mainly to the first type of device.

Non-barrier tidal Energy

  These devices would make use of the longitudinal flow of the current as distinct from the circular motion of the waves. Although they may be technically easier than wave energy devices there has been little work done on them, partly because there has been little work done on assessing the potential energy available, which is probably much smaller than for wave energy. Some of the comments about wave energy apply also to these devices.

  Answers to committee's questions:

  1.  Technological viability? No. The major technical problems are:

    —  Survival in extreme wave conditions, ie waves caused by gale force winds. In January 2000 there were three days when the wind west of the Hebrides was force 12. Structures and their moorings to survive these conditions would be prohibitively expensive;

    —  Maintenance of structures and machinery in a corrosive environment. Large sections of the 200 mile length of devices would need to be removed and brought back to dry docks for maintenance regularly. This would be a major running cost for the devices;

    —  Design and construction of flexible power cables to carry the energy from the floating wave devices to the shore;

    —  Wave energy in this country is in the wrong place. The waves are off the NW coast whereas the demand centres are 800 miles away in the south east. The power from devices off the west coast would need to be carried by submarine cable to the island of Lewis, then by submarine cable to the mainland and then by overhead line along the west coast of Scotland to the main 400KV grid connection outside Glasgow. This overhead line would cause environmental problems.

  2.  Commercial viability? No. It is impossible to consider commercial viability until the technical problems have been solved.

  3.  Current projects. Past projects failed because they failed to solve the technical problems. Present devices appear to be no more successful than those in the past.

  4.  Renewable strategy. None until the technical problems have been solved. If they are ever solved then the role of wave energy would depend on its commercial viability.

  5.  Research and Development. Very little R&D at present. No more money should be spent on this until innovators have demonstrated that they can solve the technical problems.

  6.  Environmental aspects. Floating devices will attract crustaceans, which may interfere with their operation, but they are not otherwise likely to have much effect on marine life. They would need to be marked as a hazard to navigation. The main environmental problem is likely to be the construction of the overhead transmission lines from the point where the power is landed ashore to the load centres.

  7.  International comparisons. Few other countries are working on wave energy partly because many of the developed countries that may be short of power do not have coastlines with significant waves, and conversely many countries with long coastlines are not short of conventional sources of power.

  No country appears to have yet developed a reliable wave energy device.

27 February 2001

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