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The Shannon hydroelectric Scheme was a major development by the Irish Free State in the 1920s to harness the power of the River Shannon. Its product, the Ardnacrusha power plant, is a hydroelectric power station which is still producing power today and is located near Ardnacrusha within County Clare approximately from the Limerick border. It is Ireland's largest river hydroelectric scheme and is operated on a purpose built headrace connected to the River Shannon. The plant includes fish ladders so that returning fish, such as salmon, can climb the river safely past the power station. Completed within 7 years of Irish independence in 1922 at a cost which was equivalent to one fifth of the Irish state's annual budget, the plant enabled an enormous surge in demand for electricity across the country and demonstrated the ability of the new government to develop during a difficult financial period. The plant was constructed by the German company Siemens-Schuckert, although much of the design was done by Irish engineers and Ireland provided most of the labour force. The scheme involved changes to the flow of the whole river, multiple dams and bridges and the construction of a national power grid. The generating plant at Ardnacrusha is composed of three vertical-shaft Francis turbine generators (commissioned in 1929) and one vertical-shaft Kaplan turbine generator (commissioned in 1934) operating under an average head of 28.5 metres. The scheme originally was designed for six turbines, with four turbines fitted. The 85 MW of generating plant in Ardnacrusha was adequate to meet the electricity demand of the entire country in the early years. The full output equates to about 332,000 MWh generated on an annual basis. Ardnacrusha generates at 10.5 kilovolts (kV) but this is transformed to 40 kV for local distribution and to 110 kV for long distance transmission. ==Background== The first plan to harness the Shannon's power between Lough Derg and Limerick was published in 1844 by Sir Robert Kane.〔The Industrial Resources of Ireland, Dublin 1844〕 Inspired by Nicola Tesla's 1896 project at Niagara Falls, "Frazer's Scheme" proposed a head-race canal ending at Doonass, and was sanctioned by the 1901 "Shannon Water and Electric Power Act". This envisaged a seasonal scheme with a back-up steam turbine to generate electricity in the summer, but the overall cost was considered too great and the Act was shelved. In 1902 SF Dick proposed a sharper fall at Doonass. The British Board of Trade appointed a committee in 1918 which approved proposals by Theodore Stevens and published a report in 1922. This envisaged altering upper lake levels to create extra storage of 10,000 million cubic feet, at a cost of £2.6m.〔Report on Water Power, Dublin 1922〕 At the same time the First Dail saw the possibilities, and Sean Wall, Chairman of Limerick County Council in 1920 and commander of the East Limerick IRA, asked the Council to make another survey of river levels but was killed in a gunfight at Annacotty in May 1921. At the end of 1923, the engineer Dr. Thomas McLaughlin approached the new Irish Free State's Minister for Industry and Commerce Patrick McGilligan with a proposal for a much more ambitious project. Dr McLaughlin had started working for Siemens-Schuckert, a large German engineering firm, in late 1922, and his scheme would exploit the full height difference between Lough Erne and the sea. He drew on the analysis of 25 years of flow at the weir at Killaloe published by John Chaloner Smith, an engineer with the Commissioners of Public Works. McGilligan was enthusiastic although W. T. Cosgrave, the premier, was more cautious. The scheme was published by Siemens in September 1924 and the government appointed a team of experts from Norway and Switzerland to check its viability. It caused considerable political controversy as the cost of £5.2m was a large part of the new state's entire budget in 1925 of £25m and interests in Dublin preferred more localized solution. But the experts supported the centralized solution which would require a distribution grid all over the country but recommended a two-stage implementation of the power generators. The government accepted this and by April 1925 had introduced the Shannon Electricity Act, 1925 in the Dáil.〔(Shannon Electricity Act, 1925 ) Irish Statute Book〕〔North Munster Antiquarian Journal 1987, vol.29, essay by Paul Duffy, pp. 68-92.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Shannon hydroelectric scheme」の詳細全文を読む スポンサード リンク
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