Project description:

This site is owned by Natural Resources Wales (previously the Environment Agency Wales) and used as a salmon hatchery. There was keen interest from the fisheries team in harnessing the surplus flow of water in the former mill leat which now supplies the fish rearing tanks to offset the energy consumption at the site. As the site is often left unattended, it was important that a system was installed which could be relied upon to work with little supervision.

An overshot waterwheel was quickly identified as an appropriate solution which also made most sensible use of the existing infrastructure which was of course originally designed to incorporate a similar wheel.

The scheme required planning permission, Environment Agency licensing and CDM regulations to be precisely followed during the installation. Nevertheless, the project was successfully commissioned and handed over to the Environment Agency staff within 6 months of the contract being signed with Pico Energy Ltd.

Project description:

A sawmill in a previous life, Currypool Mill was renovated by its new owners and converted into a family home. Options for power generation including a crossflow turbine and an overshot waterwheel were compared in terms of cost, power output and suitability for integration with the surrounding buildings. The simplicity, overall efficiency and lack of screening required favoured reinstatement of a waterwheel.

An old badly broken ‘Armfield’ turbine was removed and a new launder was installed along with an overshot wheel made from Corten steel, which was carefully dimensioned to fit the existing wheel pit.

The system operates without active flow regulation under normal generating conditions. During shutdown the flow is diverted behind the wheel via a trap door sluice in the launder. If the power is interrupted, the hydraulic circuit which normally holds the sluice shut, is de-energised and the door opens under its own weight. This provides a failsafe means of controlling the system.

The power produced is exported to the grid on a net metering basis. This enables the power to be consumed in the building if sufficient demand exists or otherwise exported. The system has been registered with OFGEM for the awarding of ROCs since 2006.