Project Overview

Electrical energy generated by two hydro turbines and a solar array is stored in a large battery bank. Energy is delivered from the battery to the various loads on the site (cafe, visitor centre, warden’s accommodation). Solid state inverters convert the electrical supply from 48Vdc as stored in the battery to 230Vac for efficient distribution and so that standard appliances can be used around the site.


Sensitive and sympathetic system design lessened the impact of the modern energy equipment on the fabric of the building. All changes to the buildings had to be approved by National Trust committees in addition to obtaining the necessary planning permissions for this grade 1 listed building. Information is presented both to the site warden and to visitors to the site about the power being generated from the various sources and consumption around the site. In addition, a “fuel gauge” provides continuous feedback about the amount of energy availability from the battery bank. This detailed feedback enables the site warden to manage the various energy demands in response to the available hydro and solar energy and the visitor schedule for the days ahead.

Gibson Mill is a unique building. Its size, function and lack of connection to the National Grid all added to the complexity in making the site work efficiently on renewable energy. Dulas’ expert knowledge and years of experience were significant in the transformation of this site into a focal point for groups looking to do similar projects. The renewable energy schemes will help pull hundreds of extra visitors into this area, every year.

Guy Laurie, National Trust

The multi award winning flagship project for the National Trust is now 100% self-sufficient in renewable energy.

Technical Overview
Intake Structure Drop Bar side intake
Pipeline Leat to Mill pond
Head 16ft
Powerhouse Original Mill Building
Turbine 1929 Gilkes wallplate
Generator 15kVA, single phase, 1500rpm
Tailrace and Outfall Original stone calvert
Solar PV 4.32kWp
Battery 2300 Ah