Page 319 - Alternative Energy Systems in Building Design

CURRENT TIDAL GENERATION TECHNOLOGIES 293

ROAD
RIVER

SEA

TURBINE

Figure 9.5 La Rance tidal barrage. Courtesy of Popular
Mechanics.

the power plant. Turbine technology is inherently similar to hydropower turbines, and
the construction of barrages in general requires extensive civil engineering design.

La Rance tidal barrage The construction of the La Rance tidal barrage began in
1960 (Fig. 9.5). The system consists of a dam that is 330 m long and a basin with a
tidal range of 8 m. It incorporates a lock to allow for the passage of small craft. During
construction, two temporary dams were built on either side of the barrage to ensure
that it would remain dry; this was for safety and convenience. The work was com-
pleted in 1967, when twenty-four 5.4-m turbines, rated at 10 MW, were connected to
the 225-kV French transmission network.
This barrage uses bulb turbines, described earlier, that were developed by Electricite
de France to allow for power generation on both ebbs of the tide.
Bulb-type turbines have been popular with hydropower systems and have been used
on mainland Europe in dams on the Rhine and Rhone rivers. Estimates of power gen-
erated from the La Rance power station, which provides electricity to a large majori-
ty of homes in Brittany, is calculated as follows: The turbines are rated at 10 MW and
therefore have a total capacity of 240 MW.

Maximum electricity generated per annum in kWh = 240,000 × 8760 (hours in a year)
= 2,102,400,000 kWh

Wave energy is like most other forms of renewable energy in that it cannot be relied
upon 100 percent of the time. This means that the value just quoted almost certainly