How Archie works
What are the Components?
1 – River Goyt; 2 – River Sett; 3 – Torr Weir; 4 – Headrace (water intake); 5 – Powerhouse; 6 – Fish Pass; 7 – Reverse Archiemedes Screw Turbine a.k.a Archie; 8 – Tailrace (water outlet); 9 – Leaping Salmon Carving; 10 – Ruins of Torr Mill; 11 – Torr Bridge.
(This is the view from the Union Road Bridge.)
So How Does it Work?
Water flowing in from the Rivers Sett and Goyt is held by the blades of the turbine. Gravity pulls the water down, rotating the turbine and the attached generator to produce clean, green electricity.
How Much Power?
With a 3m head and a 3m/s flow, the force due to gravity 9.81ms2 and the density of water 1000 kg/m3 gives a theoretical maximum output of 63kW after friction and generation losses. The actual output will be slightly lower due to the water taken off by the fish pass and various other technical factors.
Where Does the Power Go?
The local Cooperative Food Superstore buys all our electricity. Any power surplus to its needs is sold through the national grid.
How Efficient is Archie?
Archie extracts over 70% of the potential power of the site when running at peak generating power (maximum power output). An average annual output of 240 000kWh is our target. This implies a load factor (the ratio of average to maximum output) of 43.5%. By comparison a typical load factor for a well sited modern wind farm would be 30%.
What About the Environment?
Torrs Hydro works very closely with the Environment Agency, the guardian of the nation’s rivers. They funded the fish pass incorporated into the scheme to allow upstream access for migratory fish. This will help the salmon which now enter the Mersey, downstream of the Goyt, access more spawning grounds.
The slow rotating nature of the turbine itself is inherently fish friendly. There is no need to screen fish as they can pass through the turbine unharmed. See video evidence of this surprising but true fact!
Water flow is controlled to ensure the weir does not run dry. By virtue of our regular visits to the site, the volunteers of Torrs Hydro were able to alert the Environments Agency to a spillage of red diesel into the River Sett upstream of the site in autumn 2009, helping to avert a serious contamination event.