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Lanark Hydroelectric Scheme
Falls of Clyde, Clydesdale, South Lanrkshire, Scotland, UK
associated engineer
Buchan & Partners
date  1926 - December 1927
era  Modern  |  category  Power Generation  |  reference  NS883416
ICE reference number  HEW 1627
Lanark Hydroelectric Scheme is the UK’s oldest major plant to generate hydroelectricity for public supply. The scheme consists of a pair of similar power stations — Bonnington and Stonebyres — on the River Clyde in South Lanarkshire, built in the Modernist style and still delivering electricity to some 17,000 homes.
The stations were built for the Clyde Valley Electrical Power Company near three waterfalls — Bonnington Linn, Corra Linn and Stonebyres Linn — which provide the energy needed. Ideas for the hydroelectric scheme came from several engineers, including Sir Edward MacColl who later designed the Cruachan Hydroelectric Scheme (1965). It was designed by Buchan & Partners and the site agent was Guy Maunsell, working for Sir William Arrol & Co. Parliamentary approval for the scheme was granted in 1924 and work began in 1926.
Bonnington Power Station is a single storey reinforced concrete building with a flat roof, large round-topped arched windows and smaller rectangular windows. It has extension blocks in the same style the same height but containing two and three storeys. Stonebyres Power Station has a similar layout.
Water is abstracted at intakes above from Bonnington Linn and Corra Linn by an automatic tilting weir that regulates the flow and maintains a head of water. It has three pivoting counter-balanced gates. Water is conveyed through 3m diameter tunnels and penstocks (total length 1.1km and 58m drop) to Bonnington Power Station, where twin turbo-alternators each generate 5.5MW of electricity.
At downstream Stonebyres Power Station, water is abstracted above Stonebyres Linn and delivered over a 30m drop by a similar configuration of weir, tunnels and penstocks. Its two generators each produce 3.2MW of electricity.
All four turbo-alternators have vertical shaft Francis turbines rotating at 375 rpm connected to 50Hz three phase 11.2kV generators. Their output travels along the local transmission lines to a remote substation for stepping up to a grid voltage of 132kV.
Water levels in the falls allow almost year-round operation and there are no reservoirs in the scheme. After the energy has been extracted from the water it is returned to the river. The stations are stood down for maintenance on a handful of days between April and October each year, temporarily restoring the Falls of Clyde to their former power.
Both stations were automated in 1970, when induction generators replaced the original synchronous generators.
In 1991-2, gas-operated circuit breakers were installed instead of the original oil-filled ones. Three electrical stators were replaced in 1994-95. In the late 1990s efficiency was improved by 10% and output by 14% following replacement of the turbine runners with custom-built stainless steel parts. Control systems were modified to allow both stations to be operated from Stonebyres Power Station, using programmable ‘intelligent’ logic controllers.
Refurbishment was carried out 2002-4 so that both stations qualified for Renewable Obligation Certificates. This included replacement guide vanes and turbine runners. In 2006-7 the 1.98m internal diameter steel penstocks (pipelines) that deliver water to the stations were grit blasted and repainted at Bonnington (230m) and replaced completely at Stonebyres (21m).
Recent and current work includes replacing the weir’s bridge deck and painting the steel intake screens at Bonnington, and replacing the weir gates at Stonebyres — the new ones are each 2.75m by 11.6m and weigh 6 tonnes.
New Lanark was founded in 1786 as a centre for cotton milling, harnessing the power of the river to drive the mill machinery. It is now a UNESCO World Heritage Site and a location along the Clyde Walkway (2005). Land around the hydroelectric scheme is a Scottish Wildlife Trust nature reserve, and there is a Site of Special Scientific Interest near Bonnington Power Station. Scottish Power now runs both stations.
Site agent (for Sir William Arrol & Co): Guy Anson Maunsell
Contractor (1926-7): Sir William Arrol & Co
Arrol chief engineer: Adam Hunter
Contractor (2006-7): DCT Engineering
Hydroelectric plant: English Electric Company Ltd
Weir gates: Ransomes & Rapier, Ipswich
Research: ECPK
bibliography
"Gazetteer: Hydroelectric Schemes in Scotland 1890-1975” in Power to the People, p.95, undated, available at www.celebratingscotlandsarchitecture.org
“Lanark Hydro-Electric Scheme” undated leaflet, available at www.scottishpower.com
“Obituary: Guy Anson Maunsell” in ICE Proceedings, Vol.22, Issue 3, pp.347-348, London, July 1962
“Environmental Performance Report 2004/2005” by Scottish Power, available at www.scottishpower.com
"Lanark Hydros Planned Projects 2009/2010" by Scottish Power, Issue 02/2009, available at www.spenergywholesale.com
"Lanark Hydros Technical Factsheet” by Scottish Power, Issue 01/2010, available at www.spenergywholesale.com
http://canmore.rcahms.gov.uk
www.nce.co.uk
www.newlanark.org
www.scottish-places.info
www.scottishpower.com
reference sources   CEH SLB
Location

Lanark Hydroelectric Scheme