Page 325 - Alternative Energy Systems in Building Design

CURRENT TIDAL GENERATION TECHNOLOGIES 299

Tidal stream technology has the advantage over tidal barrages when comparing eco-
logic issues. The technology is also less intrusive than offshore turbines or tidal bar-
rages, which create hazards to navigation and shipping.

TIDAL TURBINES
Tidal turbines (Fig. 9.7) do not pose a problem for navigation and shipping and require
the use of much less material in construction. They are also less harmful to the envi-
ronment. They function best in areas where the water velocity is 2–2.5 m/s. Above this
level, the turbine experiences heavy structural loads, and below this level, not enough
generation takes place.

Economics The tidal stream technologies (Fig. 9.8) have been in developmental
stages for several years and thus far have been shown to have a significant potential to
harvest renewable energy. The cost of using tidal streams is in general site-specific and
depends on the type of technology used.
Once installed, electricity is produced with no fuel costs and with complete pre-
dictability. The only operational cost will be turbine maintenance, which will depend
on the technology used.
There are only a few places on earth where this tide change occurs. Some power
plants are already operating using this idea. One plant in France makes enough energy
from tides to power 240,000 homes.

Figure 9.7 Stream-energy turbine test. Courtesy of J. A. Consulting, UK.