Nuclear hare and the hydro tortoise
The hydropower station at Maentwrog has been generating electricity since 1928, and is planned to continue operating until 2088. It’s only half-way through its working life. This compares with the twenty-six years of the nuclear power station at Trawsfynydd, which stopped generating in 1991 and will not be totally decommissioned until 2098!
The Maentwrog station was built in 1928 by the North Wales Power and Traction Company, which also built hydro stations at Dolgarrog and at Cwm Dyli, between Beddgelert and Capel Curig. Why “Traction”? In the early 1920s North Wales Power had controlling interests in the Ffestiniog, Welsh Highland, and Snowdon railways and the idea was to supply them with electricity.
When it opened it had sufficient capacity to satisfy the electricity requirements for all of North Wales. Today we use a great deal more electricity, and the station supplies just the areas in and around Porthmadog, Blaenau Ffestiniog, Dolgellau and Harlech.
As I walked from the car park to the entrance someone had pressed the button, releasing the water with a huge gurgle and whoosh as it rushed down the hill into the turbines. From that point the electricity for our homes was coming from the power of local water as opposed to via the anonymous national grid.
The water for Maentwrog comes from the Trawsfynydd reservoir which, measured in acres, is the largest in Wales. Seventy per cent of the water is from the Afon Prysor and the rest from a series of leats which extend the catchment area to thirty-five square miles.
Depending on how wet the ground is, one inch of rain equates to between twelve and eighteen inches on the dam wall. Each inch in the reservoir converts to two hours of generation, and in a year of average rainfall there’s enough to generate eight hours every day.
The dam walls were extended and raised in 1958 when Britain’s only inland nuclear station was built. The reactors needed thirty-five million gallons of water a minute to stop them overheating!
Hydro is capital-expensive but very low-cost to run with minimal manpower. These days the workforce is down to just seven people working a Monday to Friday day shift. If there’s a need to start or stop generating in the middle of the weekend, this can be done remotely by the station manager’s laptop over a mobile phone.