The turbine takes water from the Talybont reservoir, which was originally built in the 1930’s the provide drinking water for the City of Newport. At that time, there was no mains electricity in the valley, and the original turbine provided electricity for the water works. It was decommissioned when mains electricity reached the valley in the 1950’s. In 2001, Talybont energy approached Welsh Water with a proposal to reinstate the turbine and restore a continuous supply of renewably generated electricity to the National Grid. The turbine you see today was installed and commissioned in April 2006.
The reservoir drains a catchment area of about 32 square kilometres, 2½% of the Brecon Beacons National Park. It was formed by damming the River Caerfanell above the village of Aber. Above the reservoir, the river drops over a spectacular series of waterfalls. Below the reservoir, it is broader but still quite fast-flowing, joining the River Usk just below the village of Talybont.
Welsh Water is obliged to maintain the flow of the River Caerfanell at statuary levels, and a proportion of this “compensation flow” is channelled through the turbine. In winter, from November to April, the turbine flow is about 230 litres a second, but in summer it drops to about 115 litres per second. The flow is constant, so the output of the turbine can be accurately predicted.
The turbine “head” – the distance between the surface of the reservoir and the turbine house – is about 24 metres (or 80 feet). The theoretical Wattage available is therefore:
Flow in Litres/second × Head in metres × Gravitation Constant
230 × 24 × 9.82 = 54.2 kW (winter flow)
In practice our turbine produces a maximum of 33kW in winter – i.e. about 60% efficient – and 19kW in summer. But this power is produced 24 hours a day, seven days a week, so the turbine produces between 220 and 250 megaWatt hours annually. The average electricity consumption of a UK household is reckoned to be about 4800 kWh annually or just over 13kWh per day, so in winter the turbine can power about 60 houses, and in the summer about 30, but these are gross daily figures. It requires only eleven electric kettles to take all the power of the turbine at maximum output!
In 2009, the Talybont Turbine produced 241 megaWatt hours of electricity, saving about 127 metric tonnes of fossil CO2, and generating about £30,000 gross income for Talybont energy to invest in sustainable living projects in our community. Example projects for this year (2010) include installing photo-voltaic panels on the village hall, and starting a zero-carbon car-sharing club with an electric and a 100% bio-diesel car.
The Talybont Turbine Catchment Area
The Water Power we Miss
Most of the water flowing into the Talybont reservoir goes into Welsh Water’s mains to be consumed by the thirsty residents of Newport, but a “compensation flow” is fed back into the River Caerfanell below the dam, in order to maintain the river in a healthy state. This compensation flow goes through our turbine, and generates our electricity.
However, when it rains heavily (and this can happen even in summer in the Brecon Beacons!), the reservoir fills up and then we have the distressing sight of water overflowing down the spillway and back into the river, bypassing our turbine. It is frustrating to think of all the hydro-electric power we lose, but unfortunately it wouldn’t be economic to attempt to harness the overflow, which is sporadic if potentially massive. At least it makes for a spectacular (and noisy) sight!