The Archimedes Screw water turbine was ceremonially ‘switched on’ by Lord Egremont at the annual evening opening of the Coultershaw Beam Pump just outside Petworth.
The water turbine, which generates ‘green’ electricity from a renewable source, is believed to be the first of its kind in the south east. The project has been masterminded by Robin Wilson, chairman of the Coultershaw Trust and a past president of the Institution of Civil Engineers.
“The screw is traditionally attributed to have been invented by Archimedes in the third century BC,” said Mr Wilson. “It was used in irrigation to lift water from a lower level. It is in the form of a giant corkscrew set at an angle down which water flows from a higher level. The screw is slow turning and drives a generator through a gearbox.
“It is ‘fish friendly’ and needs only a coarse screen from which floating debris can be removed manually.”
The six-ton screw complete with gear box and generator was lifted into the wheel pit of the old corn mill in March. It was then connected to the grid and is now generating power. It is expected to generate 65,000 kWh a year and save 50 tonnes of carbon dioxide.
The work to repair the sluices and modify the wheel pit to take the turbine began in July last year and was not without difficulty.
“The temporary cofferdam to enable the work to be carried out in the dry failed twice,” said Mr Wilson. “A munitions contamination survey had to be carried out to check sheet piling would not disturb a suspected unexploded bomb.
“Divers placed over 50 tons of cement grout and concrete in voids under the sluice and the original wheel pit, back-filled with rubble from the last corn mill, was excavated by hand and re- filled with mass concrete.”
The project began in 2008 when Lord Egremont sponsored a pre-feasibility study. With a grant from the South Downs Joint Committee, the Coultershaw Trust then commissioned the outline design and obtained the necessary planning approval and Environment Agency licences.
The Archimedes Screw water turbine is another chapter in the long history of waterpower at Coultershaw, which has been the site of a fulling mill, several corn mills and the water wheel-driven Beam Pump. It is open to the public on the first and third Sundays and all bank holiday Mondays, 11am-5pm from April to September.