Project description:

The current owners had been planning a hydropower scheme at this former mill for 20 years before the system was finally installed in 2010. Previous feasibility studies had considered various low head turbine options but all were unsatisfactory from both a cost and a planning perspective. Plans to sympathetically update the mill with a new waterwheel system were proposed and permission was eventually granted to remove the existing listed wheel which was well beyond repair and unsuitable to adapt for electricity generation.

A layout was designed which enables as much of the historic infrastructure as possible to be preserved by positioning the new drive and generator on the opposite side of the wheel to where the old pit wheel is positioned. This now sits on a reinforced wall between the wheel pit and relief channel alongside.

The mill and surrounding area flood on occasion due to downstream flow restrictions. It is possible that future flood levels could reach the height of the wheel axle. With this in mind, the gearbox unit has been designed with labyrinth seals which prevent water ingress if temporarily submerged.

Under the guidance of Hydromatch Consulting, the scheme owners carried the site preparation and building work themselves. The scheme is accredited for FITs.

Project description:

The listed former textile mill situated on the River Lea is the head office of Ramblers Holidays Ltd who undertook a program of significant refurbishment in order to provide a modern business premises for their 45 full-time staff prior to moving in in 2005. A feasibility study showed that hydropower could meet a significant part of the buildings energy consumption and compared to options using conventional turbines with a modern waterwheel. It was decided that a modern waterwheel was the most appropriate solution due to the considerable aesthetic benefit as well as cost-effectiveness compared to the turbine options. The new wheel dimensions are very similar to those of the original, which had disappeared and enabled a close fit into the existing wheel pit.

The wheel operation is regulated by a control system, which monitors the upstream water level. It adjusts the position of an overshot sluice gate along with a second relief channel sluice gate. An auxiliary power system enables the inlet sluice to close and water levels to be maintained upstream via the relief sluice in the event of disruption to mains power. The system is simple to operate and requires very limited maintenance.

The power produced is exported to the grid on a net metering basis. This means that the power is consumed in the building if sufficient demand exists and otherwise exported. The system has been registered with OFGEM for the awarding of ROCs since 2006. The building refurbishment with waterwheel was both regional and national winner of the British Council for Offices awards 2007 in the ‘small project’ category.