Dolgarrog Power Station in

Dolgarrog Dolgarrog is a village and community (Wales), community in Conwy County Borough, in Wales, situated between Llanrwst and Conwy, very close to the Conwy River. The village is well known for its industrial history since the 18th century an ...

, Wales was originally built in 1907 as part of an

aluminium smelting Aluminium smelting is the process of extracting aluminium from its oxide, alumina, generally by the Hall-Héroult process. Alumina is extracted from the ore bauxite by means of the Bayer process at an alumina refinery. This is an electroly ...

plant. It uses

water turbine A water turbine is a rotary machine that converts kinetic energy and potential energy of water into mechanical work. Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now, t ...

s to drive electricity

alternator An alternator (or synchronous generator) is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field wit ...

s. Public supplies began in 1922 when power lines were constructed to transmit electricity from the power station to

Colwyn Bay Colwyn Bay () is a town, Community (Wales), community and seaside resort in Conwy County Borough on the north coast of Wales overlooking the Irish Sea. It lies within the historic counties of Wales, historic county boundaries of Denbighshire (h ...

Conwy Conwy (, ), previously known in English as Conway, is a walled market town, community and the administrative centre of Conwy County Borough in North Wales. The walled town and castle stand on the west bank of the River Conwy, facing Deganwy ...

and

Llandudno Llandudno (, ) is a seaside resort, town and community (Wales), community in Conwy County Borough, Wales, located on the Creuddyn peninsula, which protrudes into the Irish Sea. In the 2021 United Kingdom census, 2021 UK census, the community � ...

. The station was vested in the

British Electricity Authority The British Electricity Authority (BEA) was established as the central British electricity authority in 1948 under the nationalisation of Great Britain's electricity supply industry enacted by the Electricity Act 1947. The BEA was responsible for ...

and its successors following

nationalisation Nationalization (nationalisation in British English) is the process of transforming privately owned assets into public assets by bringing them under the public ownership of a national government or state. Nationalization contrasts with priv ...

in 1948. It is currently (2025) operated by

RWE RWE AG is a German multinational energy company headquartered in Essen. It generates and trades electricity in the Asia-Pacific region, Europe and the United States. In July 2020, RWE completed a far-reaching asset swap deal with E.ON first ...

NPower UK.

History

Dolgarrog hydro-electric power station was commissioned in 1907 by the Aluminium Corporation of Dolgarrog to supply electricity to its adjacent aluminium smelting plant. The smelting of the mineral

bauxite Bauxite () is a sedimentary rock with a relatively high aluminium content. It is the world's main source of aluminium and gallium. Bauxite consists mostly of the aluminium minerals gibbsite (), boehmite (γ-AlO(OH)), and diaspore (α-AlO(OH) ...

to make aluminium is an energy intensive process requiring a large amount of electricity. The availability of cheap hydro-electric power was therefore attractive. The construction of the power station was sanctioned under the provisions of the ''North Wales Electric Power Act 1904''. Water was drawn from Llyn Cowlyd and Llyn Eigiau, via a system of

leat A leat (; also lete or leet, or millstream) is the name, common in the south and west of England and in Wales, for an artificial watercourse or aqueduct dug into the ground, especially one supplying water to a watermill or its mill pond. Othe ...

s and tunnels. There are two 48-inch (1.22 m) diameter pipelines providing a working head of 830 feet (253 m) and 1130 feet (344 m). The Aluminium Corporation of Dolgarrog acquired a controlling interest in the North Wales Power and Traction Company in 1918. Ownership of the power station was transferred in 1920 to the Power Company which was subsequently renamed the North Wales Power Company Limited. The Power Company also owned and operated the power stations at Cwm Dyli and Maentwrog. In 1924–25 the North Wales Power Company increased the capacity of the power station by adding two

Pelton wheel The Pelton wheel or Pelton Turbine is an Impulse (physics), impulse-type water turbine invented by American inventor Lester Allan Pelton in the 1870s. The Pelton wheel extracts energy from the impulse of moving water, as opposed to water's dead w ...

s coupled to 5 MW

s. This was known as No. 2 station. In the mid-1930s the Company sought to further expand the power station. The

Electricity Commissioners The Electricity Commissioners were a department of the United Kingdom government's Department for Transport, Ministry of Transport, which regulated the electric power industry, electricity supply industry from 1920 until nationalisation in 1948. ...

gave consent to the addition of a new 6.5 MW generating set. A new 6-feet (1.83 m) diameter pipe was installed to extend the existing 48-inch (1.22 m) pipe to Cowlyd dam. The North Wales and South Cheshire Joint Electricity Authority (JEA) supported the North Wales Power Bill which increased the share capital of the Power Company to £3 million. Money was therefore available to finance the extension. The power bill was enacted as the ''North Wales Electric Power Act 1936''. The British electricity supply industry was nationalised in 1948. The North Wales Power Company Limited and the JEA were abolished and ownership of Dolgarrog power station was vested in the

and its successor organisations. The '' North Wales Hydro-Electric Power Act 1952'' (15 & 16 Geo. 6 and 1 & 2 Eliz. 2. C. cxlvi) provided for the extension of the Dolgarrog and Maentwrog catchment area including a 10 MW extension to the plant at Dolgarrog power station. This was No. 3 Station. The British electricity supply industry was privatised in 1990. At that time the net capability of Dolgarrog power station was 27 MW from four machines. The station was designated Dolgarrog High-Head power station (18.4 MW) and Dolgarrog Low-Head power station (14.98 MW). Ownership was vested in

National Power National power is defined as the sum of all resources available to a nation in the pursuit of national objectives. Assessing the national power of political entities was already a matter of relevance during the classical antiquity, the Middle Ages ...

in 1990 which demerged as Innogy plc in 2000. This was acquired by RWE of Germany in 2002. The station is currently (2020) operated by an Innogy subsidiary Innogy Renewables UK.

Plant and equipment

The power station was developed in stages as outlined above; technical details are as follows.

No. 1 station

Commissioned in 1909, comprising a Boving Pelton wheel with Bruce Peebles 1.2 MW, 6.6 kV alternator.

No. 2 station

Commissioned in 1924–25 and comprising 2 Pelton wheels driving 2 × 5 MW AC alternators. In 1936 a third Pelton wheel was installed coupled to a 6.5 MW alternator.

No. 3 station

Commissioned in 1957, comprising one Boving-Bruce Peebles 10 MW set operating at 750 rpm and with a working head of 750 feet (229 m). There were Ferranti step-up transformers from 6.6 kV to 20 and 33 kV.

Plant summary

In 1979 the plant at Dolgarrog power station comprised 2 × 5 MW; 1 × 6.5 MW; and 1 × 10 MW turbine & alternator sets giving a net capability of 27 MW. The oldest machine had been installed in 1924. The generator sets are currently (2020) are numbered 2, 3, 4 & 5; all are

Francis turbine The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The pro ...

s manufactured by Weir, Weir, Boving & Gilkes respectively, with alternators by GEC-Alsthom (Nos. 2, 3 & 5) and Peebles (No. 4).

Operations

In 1921–23 the electricity statistics for the North Wales Power Company's Dolgarrog power station were: Operating data for the period 1921–86 was:''CEGB Statistical Yearbook 1972'' to 1986, Central Electricity Generating Board The output in GWh is shown graphically. The station is currently (2020) operated by Innogy Renewables UK.

References

{{reflist Hydroelectric power stations in Wales Dolgarrog