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
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
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
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