SUMMARY

Location:                                   Gants Mill,

Rating:                                      12kW

Turbine:                                    300mm Crossflow turbine

Gross head:                               4.8m

Design flow:                              495 litres/sec

Year of commissioning:               2004

Further information:                   www.gantsmill.co.uk

OVERVIEW

Gants Mill on the River Brue in Bruton is part of the South Somerset Hydropower Group, a group of 10 mill-owners working together to install electrical generating equipment in their mills.

In 2004 a new turbine and electricity generator were installed at Gants Mill, to complement the 1888 Armfield turbine. Over the centuries the mill has been adapted to society's changing requirements, as a corn mill, fulling mill, silk mill, then corn mill again, and is now a fine example of a small-scale hydropower scheme, producing electricity from a renewable resource. Visitors are able to see it as part of their tour of the mill.

DESIGN ASPECTS

The new crossflow turbine was built by Valley Hydro of Cornwall, and the electronic control system and mains connection unit by GP Electronics from Devon. The automatic control system operates the turbine valve so as to adjust water flow through the turbine and maximise power output while maintaining a minimum reserve flow of water in the main river. The turbine can operate down to one third of maximum flow.

The equipment is designed to produce up to 12 kW of electricity which is  fed into the local grid. The actual output depends on river flow, being naturally greater during winter than in the summer months.

The system was designed to fit into the old waterwheel pit within the mill, while also allowing the continued function of the Armfield turbine. All the pieces of the pipe work, turbine and generator were lowered into the old wheel pit using specialised heavy lifting gear. Assembly of the parts required particular attention to the stresses and weights involved, with around 2 tonnes to be supported by RSJs slotted into the walls of the wheel pit.

Installation began in September 2003 and the turbine and generator's working life started in April 2004.

Gants Mill	General arrangement of the equipment
Crossflow runner and casing	Penstock and transition piece
Cross-flow turbine lowered into position	Turbine with belt-drive and generator installed