The energy of this water is no longer going to waste
How much energy do we produce?
Water available to generate energy
Head (pressure in metres)
The maximum height of water in the reservoir is 37 metres above the level of the basin below. This will means the effective head is up to 31 metres, which will be available 90% of the time.
The water company is legally obliged to deliver a compensation flow of 16 million litres per day to the river immediately downstream of the embankment. That is equivalent to 185 litres per second.
Theoretical maximum power
Power = mass per second x g x height
= 185 x 9.8 x 31
= 56203 W
This never actually happens in normal flow.
For some of the year the reservoir is in overflow so we can get more water flowing through the turbine.
Averaged throughout the year, with a 55 kW turbine we expect to generate 43 kW of electricity for 90% of the time.
Equivalent number of homes.
Mean domestic annual consumption of electricity in the UK is about 4000 kWh
Generation of 43kW gives 43 x 24 x 365 x 90% kWh per year
= 339012 kWh
339012 divided by 4000 = 84.75
We provide enough power for 85 average homes.
Assuming about 0.5 tonnes per MWh gives about 170 tonnes of CO2 per year.
The site for the turbine is next to the basin below the reservoir. The turbine is situated below ground level to allow underground pipework from the United Utilities' pump house and maximise the head of water available.
Cross section of the turbine
Electrical energy is generated by a cross-flow turbine.
The turbine gets its name from the way the water flows across the rotor.
Cross-flow turbines are widely used on UK micro hydro sites with power outputs from 5 kW to 100 kW. They work best with heads from 2 to 40 metres and flows between 40 to 10,000 litres per second.
More information on turbines at http://www.renewablesfirst.co.uk/hydropower-hydro-turbines/
The control system has to ensure that the compensation flow is maintained at all times. It is unusual for a turbine to have constant flow but variable head (as the reservoir level goes up and down).
The level of water in the stilling basin (the area which the water passes through before flowing into the river) is monitored continuously. The system uses the inlet guide vane to control the amount of water flowing through the turbine to keep the required level. This required reprogramming of the software that controls the hydraulics.
If the turbine is out of commission or trips out, there is a bypass outlet which is activated automatically allowing water to go directly to the stilling basin.
The control panel is programmed to send an email to the volunteer maintenance team in the event of any faults occurring.
The control panel also monitors and records the output to the grid.
The system can be operated remotely from a smart phone app.