Page 328 - Alternative Energy Systems in Building Design

302 OCEAN ENERGY TECHNOLOGIES

faster than sea creatures can swim. There is no significant risk of leakage of noxious
substances, and the risk of impact from the rotor blades is extremely small. This is so
because the flow spirals in a helical path through the rotor, and nature has adapted
marine creatures so that they do not collide with obstructions (marine mammals gener-
ally have sophisticated sonar vision). Another advantage of this technology is that it is
modular, so small batches of machines can be installed with only a small period
between investment in the technology and the time when revenue starts to flow. This
is in contrast to large hydroelectric schemes, tidal barrages, nuclear power stations, or
other projects involving major civil engineering, where the time between investment
and gaining a return can be relatively large.
It is expected that turbines generally will be installed in batches of about 10–20
machines. Many of the potential sites investigated so far are large enough to accom-
modate many hundreds of turbines. As a site is developed, the marginal cost of adding
more turbines and of maintaining them will decrease, as will the economy of scale as
the project grows.
Marine Current Turbines, Ltd., is currently in the process of starting a program of
tidal turbine development through research and development (R&D) and demonstra-
tion phases for use in commercial manufacture. An initial grant of 1 million euros has
been received from the European Commission toward R&D costs, and this has been
followed by a grant toward the cost of the first phase of work from the U.K. govern-
ment worth 960,000 euros. The German partners also received a grant worth approx-
imately 150,000 euros from the German government.
The company’s plan is to complete the initial R&D phase by 2006 and to start com-
mercial installations at that time. It is planned that some 300 MW of installations will
be completed by 2010, and after that, there is a far larger growth potential from a mar-
ket literally oceanic in size.
Phase 1 involved the installation of the first large monopole-mounted experimental
300-kW single 11-m diameter rotor system, off Lynmouth in Devon, U.K. (Fig. 9.10).
The installation uses a dump load in lieu of a grid connection (to save cost) and gener-
ally will operate with the tide in only one direction. The cost is approximately
3.3 million euros.
Phase 2 involved the design, manufacture, installation, and testing of the first full-
size twin-rotor system, to be rated at 750–1200 kW (each rotor being slightly larger
than in the phase 1 system—the variation depends on the rated velocity for the site
chosen). This will be grid connected and will function with the flow in both directions.
It will, in fact, be the prototype and test bed for the commercial technology. This phase
is expected to cost approximately 4.5 million euros, including grid connection.
Installation of the first small farm of tidal turbines, interconnected with the phase 2
system, probably will involve three to four extra units in order to give an aggregate
power of about 4–5 MW for the system—the actual amount depends on how many
units and the rated power for the site.
The project will be partly self-financing, through revenue generated from the sale
of electricity. However, it still will very much be the final phases of the R&D program
form, which means that much will need to be learned about operating several
machines together in an array.