Water power at Morden Hall Park
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Funding from Heritage Lottery and Thames Water have enabled us to conserve one of the waterwheels to what it may have looked like 200 years ago and to install an Archimedes' screw hydroelectric turbine in the River Wandle.
Originally two waterwheels turned in the river, driving the machinery in the snuff mills. The river was channelled towards the mills and the flow of the river was controlled by a metal gate. When the gate opened the torrential pressure of the water struck the lower paddles of the waterwheels forcing them to turn.
This wheel is now unable to turn. Most of the machinery was removed at the start of the Second World War because of the need for scrap metal. We investigated renovating the wheel to generate electricity but, due to the low level of water, it would only generate enough for a single light bulb.
The Archimedes' screw
Behind the waterwheel, an Archimedes' screw hydroelectric turbine has been installed. This modern waterwheel works on a low head of water and harnesses the power of the river to generate enough electricity to power 18 average households.
Archimedes was a Greek mathematician and engineer who invented the Archimedes' screw pump. This was used to draw water up to higher levels to irrigate fields and pump out boats.
Archimedes' screw turbines use a similar principle but backwards. Water enters the top of the screw and pushes on it causing it to rotate and allow the water to fall to the lower level.
The top of the screw is connected to a generator that converts the rotating energy to electrical energy. Our turbine generates 59,000 kWh a year, enough to power 18 average households.
Keeping wildlife safe
The Archimedes' screw turns slowly and is large enough to allow fish to pass safely down it. Migratory fish such as salmon and eels also need to move upstream to breed. Unfortunately man-made obstructions such as our weir prevent this. We have installed fish and eel passes next to the screw so that they can travel up the river to suitable habitats.