6 Rance tidal power station

6.1 General Information

The Rance Tidal Power Station (enclosure figure 3-4 ) is the world's first tidal power station and also the world's second biggest tidal power station. The facility is located on the estuary of the Rance River, in Brittany, France. Opened on the 26th November 1966, it is currently operated by Électricité de France, and is the second largest tidal power station in the world, in terms of installed capacity. With a peak rating of 240 Megawatts, generated by its 24 turbines, it supplies 0.012% of the power demand of France. With a capacity factor of approximately 40%, it supplies an average 96 Megawatts, giving an annual output of approximately 600 GWh. The barrage is 750 m (2,461 ft) long, from Brebis point in the west to Briantais point in the east. The power plant portion of the dam is 332.5 m (1,091 ft) long. The tidal basin measures 22.5 km2 (9 sq mi).

6.2 History Of Rance Tidal Power Station

An early attempt to build a tidal power plant was made at Aber Wrac'h in the Finistère in 1925, but due to insufficient finance, it was abandoned in 1930. Plans for this plant served as the draft for follow-on work. Use of tidal energy is not an entirely new concept, since tidal mills have long existed in areas exposed to tides, particularly along the Rance.

The idea of constructing a tidal power plant on the Rance dates to Gerard Boisnoer in 1921. The site was attractive because of the wide average-range between low and high tide levels, 8 m (26 ft) with a maximum perigean spring tide range of 13.5 m (44.3 ft). The first studies which envisaged a tidal plant on the Rance were done by the Society for the Study of Utilization of the Tides in 1943. Nevertheless, work did not actually commence until 1961. Albert Caquot, the visionary engineer, was instrumental in the construction of the dam, designing an enclosure in order to protect the construction site from the ocean tides and the strong streams. Construction necessitated draining the area where the plant was to be built, which required construction of two dams; an effort which took two years. Construction of the plant commenced on the 20th of July 1963, while the Rance was entirely blocked by the two dams.

Construction took three years and was completed in 1966. Charles de Gaulle, then President of France, inaugurated the plant on the 26th of November of the same year. Inauguration of the route crossing the plant took place on 1 July 1967, and connection of the plant to the French National Power Grid was carried out on the 4th of December 1967. In total, the plant cost ₣620 million (approximately €94.5 million).

7 Grand coulee dam

Grand Coulee Dam (enclosure figure 5) is a gravity dam on the Columbia River in the U.S. state of Washington built to produce hydroelectric power and provide irrigation. It was constructed between 1933 and 1942, originally with two power plants. A third power station was completed in 1974 to increase its energy production. It is the largest electric power-producing facility in the United States and one of the largest concrete structures in the world.

The proposal to build the dam was the focus of a bitter debate during the 1920s between two groups. One wanted to irrigate the ancient Grand Coulee with a gravity canal and the other supported a high dam and pumping scheme. Dam supporters won in 1933, but for fiscal reasons the initial design was for a "low dam" 290 ft (88 m) high which would generate electricity, but not support irrigation. The U.S. Bureau of Reclamation and a consortium of three companies called MWAK (Mason-Walsh-Atkinson Kier Company) began construction that year. After visiting the construction site in August 1934, President Franklin Delano Roosevelt began endorsing the "high dam" design which, at 550 ft (168 m) high, would provide enough electricity to pump water to irrigate the Columbia Basin. The high dam was approved by Congress in 1935 and completed in 1942; the first water over-topped its spillway on June 1 of that year.

Power from the dam fueled the growing industries of the Northwest United States during World War II. Between 1967 and 1974, the Third Powerplant was constructed. The decision to construct the additional facility was influenced by growing energy demand, regulated river flows stipulated in the Columbia River Treaty with Canada and competition with the Soviet Union. Through a series of upgrades and the installation of pump-generators, the dam now supplies four power stations with an installed capacity of 6,809 MW. As the center-piece of the Columbia Basin Project, the dam's reservoir supplies water for the irrigation of 671,000 acres (2,700 km2).

The reservoir is called Franklin Delano Roosevelt Lake, named after the United States President who presided over the authorization and completion of the dam. Creation of the reservoir forced the relocation of over 3,000 people, including Native Americans whose ancestral lands were partially flooded. The dam has also blocked the migration of salmon and other fish upstream to spawn.