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Foyers hydropower schemes
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Foyers hydropower schemes
There are two hydropower schemes at Foyers, Highland, Scotland, which is located on the south-eastern shore of Loch Ness about half-way along its length. There is a conventional 5 MW hydropower scheme taking water from the River Foyers, and a 300 MW pumped-storage hydro-electric scheme using Loch Ness as the lower reservoir and Loch Mhòr for the upper.
The first hydropower scheme was built in 1895 by the British Aluminium Company to power an aluminium smelting plant on the shore of Loch Ness. This had a rated power of 3.75 MW, and took water from a dam on the River Foyers above the Falls of Foyers, significantly reducing the flow over the falls. The Aluminium smelter closed in 1967, and the hydropower scheme was then taken over by the North of Scotland Hydro Electric Board (now SSE). The scheme was upgraded to 5 MW in 1968, has a gross head of 108 m (354 ft), and is referred to as Foyers falls or Foyers 5 MW.
The Hydro Board promoted plans for the pumped storage scheme in 1968, with work commencing the following year. It has two reversible 150 MW turbines, which can pump water uphill at times of low demand for electricity, then generating when demand is high. The pumped storage scheme has a gross head between the lochs of 179 m (587 ft) and was completed in 1974.
The scheme was designed with sufficient storage to operate on a weekly cycle, with additional hydropower generation from the inflow to the reservoir. It therefore operates as a hybrid scheme, with about 25% of the planned output coming from inflow to Loch Mhòr. As part of the new development, some flow of the River Fechlin was diverted via a tunnel into the River E upstream of Loch Mhòr, increasing the inflow into the reservoir, and thus the amount of power which could be produced.
The British Aluminium Company identified Foyers as a possible site to build a hydropower scheme to produce electricity for an aluminium smelter. The scheme takes water from the River Foyers above the Falls of Foyers, it is diverted via a tunnel and cast iron penstocks to the generating station and smelter located on the shore of Loch Ness. The power station originally had five Girard turbines on vertical shafts with Oerlikon direct current generators
To provide a more continuous flow of water, a reservoir was constructed upstream of the intake. This combined Loch Garth and Loch Faraline just upstream, into a new reservoir named Loch Mhòr, raising the water level of Loch Faraline by 20 feet (6.1 m). A bathymetrical survey in 1903 noted that in the summer, the reservoir level may drop back to the original level.
The company identified the Falls of Foyers as a possible site, and bought the Lower Foyers estate, covering some 8,000 acres (32 km2), together with water rights from neighbouring areas. This allowed them to create a hydro-electric scheme without needing to obtain Parliamentary approval, and to ignore public opposition to the effects it would have on local amenities. The River Foyers ran through a gorge to the almost vertical Lower Falls, which was a beauty spot, and was a stopping point for tourists using the MacBrayne pleasure steamers running along the Caledonian Canal from Fort William to Inverness.
Construction began in 1895. Loch Garth was modified by a concrete and masonry dam at its south-western end, together with an earth embankment. The concrete section is 690 feet (210 m) long and around 23 feet (7 m) tall, or possibly 760 feet (232 m) long and around 30 feet (9 m) tall. The dam raised the water level of Loch Garth by 20 feet (6.1 m), resulting in it joining Loch Farraline, and the combined storage reservoir, which was 4.5 miles (7.2 km) long, was renamed Loch Mhòr. Water from the reservoir was conveyed along the original course of the River Foyers to the top of the Upper Falls of Foyers. From there a tunnel was cut through solid rock for 0.5 miles (0.80 km) and the water continued through cast iron pipes to the generating station. The pipes were 30 inches (76 cm) in diameter, and were laid in a trench, to be covered with sand. This provided a head of 350 feet (110 m) to the turbines, and although there was some debate as to whether cast iron pipes could withstand such pressure, no issues were experienced. The water drove five Girard turbines connected to Oerlikon direct current generators, which could produce a total of 3.75 MW.
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Foyers hydropower schemes
There are two hydropower schemes at Foyers, Highland, Scotland, which is located on the south-eastern shore of Loch Ness about half-way along its length. There is a conventional 5 MW hydropower scheme taking water from the River Foyers, and a 300 MW pumped-storage hydro-electric scheme using Loch Ness as the lower reservoir and Loch Mhòr for the upper.
The first hydropower scheme was built in 1895 by the British Aluminium Company to power an aluminium smelting plant on the shore of Loch Ness. This had a rated power of 3.75 MW, and took water from a dam on the River Foyers above the Falls of Foyers, significantly reducing the flow over the falls. The Aluminium smelter closed in 1967, and the hydropower scheme was then taken over by the North of Scotland Hydro Electric Board (now SSE). The scheme was upgraded to 5 MW in 1968, has a gross head of 108 m (354 ft), and is referred to as Foyers falls or Foyers 5 MW.
The Hydro Board promoted plans for the pumped storage scheme in 1968, with work commencing the following year. It has two reversible 150 MW turbines, which can pump water uphill at times of low demand for electricity, then generating when demand is high. The pumped storage scheme has a gross head between the lochs of 179 m (587 ft) and was completed in 1974.
The scheme was designed with sufficient storage to operate on a weekly cycle, with additional hydropower generation from the inflow to the reservoir. It therefore operates as a hybrid scheme, with about 25% of the planned output coming from inflow to Loch Mhòr. As part of the new development, some flow of the River Fechlin was diverted via a tunnel into the River E upstream of Loch Mhòr, increasing the inflow into the reservoir, and thus the amount of power which could be produced.
The British Aluminium Company identified Foyers as a possible site to build a hydropower scheme to produce electricity for an aluminium smelter. The scheme takes water from the River Foyers above the Falls of Foyers, it is diverted via a tunnel and cast iron penstocks to the generating station and smelter located on the shore of Loch Ness. The power station originally had five Girard turbines on vertical shafts with Oerlikon direct current generators
To provide a more continuous flow of water, a reservoir was constructed upstream of the intake. This combined Loch Garth and Loch Faraline just upstream, into a new reservoir named Loch Mhòr, raising the water level of Loch Faraline by 20 feet (6.1 m). A bathymetrical survey in 1903 noted that in the summer, the reservoir level may drop back to the original level.
The company identified the Falls of Foyers as a possible site, and bought the Lower Foyers estate, covering some 8,000 acres (32 km2), together with water rights from neighbouring areas. This allowed them to create a hydro-electric scheme without needing to obtain Parliamentary approval, and to ignore public opposition to the effects it would have on local amenities. The River Foyers ran through a gorge to the almost vertical Lower Falls, which was a beauty spot, and was a stopping point for tourists using the MacBrayne pleasure steamers running along the Caledonian Canal from Fort William to Inverness.
Construction began in 1895. Loch Garth was modified by a concrete and masonry dam at its south-western end, together with an earth embankment. The concrete section is 690 feet (210 m) long and around 23 feet (7 m) tall, or possibly 760 feet (232 m) long and around 30 feet (9 m) tall. The dam raised the water level of Loch Garth by 20 feet (6.1 m), resulting in it joining Loch Farraline, and the combined storage reservoir, which was 4.5 miles (7.2 km) long, was renamed Loch Mhòr. Water from the reservoir was conveyed along the original course of the River Foyers to the top of the Upper Falls of Foyers. From there a tunnel was cut through solid rock for 0.5 miles (0.80 km) and the water continued through cast iron pipes to the generating station. The pipes were 30 inches (76 cm) in diameter, and were laid in a trench, to be covered with sand. This provided a head of 350 feet (110 m) to the turbines, and although there was some debate as to whether cast iron pipes could withstand such pressure, no issues were experienced. The water drove five Girard turbines connected to Oerlikon direct current generators, which could produce a total of 3.75 MW.