The United Kingdom has been a pioneer in hydropower development, using water for electricity generation since 1879 when the first 4.5 KW hydroelectric generator was put into operation to provide electricity for a single incandescent lamp.
Today the UK has a total hydropower installed capacity of over 4,700 MW, including over 2,800 MW of pumped storage. The vast majority of installed capacity is located in the wet and mountainous regions of Wales and northwest Scotland.
Over the past 30 years, the proportion of electricity generated by hydropower has remained around 2 per cent of total power generation. Hydropower has however increasingly been called upon to support the development of the UK’s variable renewable sector by providing peaking, balancing and other grid services, especially as wind generation has increased over ten-fold since 2007.
The UK’s energy transition has its foundations in the 2008 Climate Change Act, which is a legally binding commitment by the UK government to reduce total GHG emissions by at least 80 per cent of 1990 levels by 2050.
Despite an estimated 2.4 GW of viable hydropower potential in the UK, hydropower expansion is likely to be limited to small-scale applications (up to 5 MW), with the exception of pumped storage projects.
The UK hosts four pumped storage projects in Scotland and Wales. The largest such project, Dinorwig in north Wales, was commissioned in 1983 with a capacity of 1,728 MW. Since the 1960s, only one non-pumped storage project greater than 20 MW has been commissioned: the 100 MW Glendoe project in 2009.
While these pumped storage projects were initially developed to provide peaking and balancing support for coal and nuclear, the changing energy generation landscape is shifting how pumped storage is utilised.
The addition of wind and gas, replacing coal, means that many pumped storage assets in the UK are no longer operating on daily cycles, pumping at night and generating during peak daytime hours. Rather, pumped storage assets have substantially increased ramping and sometimes cycling up to 60 times a day.
Small-scale hydropower projects, including community-led projects, are being developed across the UK. Innovations in small hydropower turbines have allowed for some hydropower to be applied at sites with very low heads and low flows by utilising the Bernoulli principle, including the River Mill in Cambridgeshire, England. Other notable community-led projects include the 100 KW Bethesda scheme in Wales, which allows residents to purchase generated power for half the average price of UK electricity, and reduces losses due to transmission.
The UK’s current interconnection capacity rests approximately at 5 per cent of total installed capacity, about half of the recommended 10 per cent benchmark proposed by the European Commission. A number of new interconnection projects are underway, most notably the North Sea Link, a 1,400 MW HVDC interconnection with Norway, which takes advantage of Norway’s hydropower while providing an off-taker for excess UK wind production.
Read our country profile in the 2018 Hydropower Status Report.