Powering up Trew’s Weir

The hydro project at Trews Weir has been progressing well. We’ve had our first meeting with the Environment Agency and during that meeting they suggested the disused radial canal might be a possible site for the turbines, rather than in the main weir next to the existing fish pass. We extended our feasibility investigations to include this option and it was good news to learn that both options were both technically and financially viable. The advantages of the radial channel include cheaper construction costs, less noise, and less visible which might be appreciated by river users and walkers.

Trews Weir showing radial channel

Two types of turbines have been considered; the Kaplan and the Archimedes Screw, and although the Kaplan would give us higher generation potential the additional cost for screening to prevent fish entering the turbine makes it less financially viable. We have therefore submitted our EA pre-application on the basis of using the Archimedes screw. It’s a technology more than 2,000 years old named after the ancient Greek genius designed for irrigation. For electricity generation, the flow of water passing down the screw-shaped shaft inside the pipe turns it to generate clean electricity that doesn’t cause pollution or global warming.

Local consultants Hydromatch Ltd, chief executive Gill Wyatt and director and hydroelectric engineer Hertha Taverner-Wood are all working to progress the project that could generate around 500 megawatt hours (MWh) of electricity per year, enough to power 125 homes. Leases will be arranged with Exeter City Council and the Environment Agency, who are the landowners and both are willing in principle.

Engagement with the local community and river users is important to ECOE, we want to know about peoples’ concerns and make sure we are addressing them within the design. We have already had meetings with the Exeter River and Canal Users group and the River Exe and Tributaries Association and we will be organising a community meeting for all to attend in September. The existing Larinier fish pass recently constructed should not be affected by the design and the Archimedes screw should also allow them to pass safely.

The scheme has an important educational opportunity. We hope to be able to raise additional funds to build an Interpretation centre for Energy Over The Ages in Exeter and at least have interactive display boards.
We will need to be ready to pre-accredit the scheme with OFGEM by the end of March 2019 to secure the Feed-in-Tariff (FiT) for a further two years. This is necessary as FiT is due to end 31st march 2018. That would give us a further two years to complete construction and be fully operational. It’s an ambitious project with potential costs of £800,000 – twice the value of the previous ECOE share offer. We plan to raise the money by another community share offer and through loans. Our community finance model shows it will still pay for itself in 20 years and provide over £200,000 for ECOE’s Community Fund.

Trews Weir