The reservoir at Glendevon flows into the River Devon, a tributary of the River Forth in Clackmannanshire, Scotland

Low-cost green energy generated at Scottish reservoir in pilot scheme

Image credit: ABB

A renewable energy scheme has been unveiled as part of upgrades to a Scottish reservoir. Torishima Service Solutions Europe Ltd, using an ABB generator and regenerative drive on their turbine, has provided a scheme producing green energy which is returned to the grid.

A hydroelectric generation solution, comprising a reversible-pump turbine, generator and regenerative variable speed drive (VSD), has been installed at Lower Glendevon reservoir’s compensation measuring house, in a pilot scheme involving Torishima Service Solutions Europe Ltd (TSSE), Scottish Water and ABB.

The installation produces enough renewable electricity to power some 100 homes in the local area, while fulfilling the reservoir’s primary purpose of providing the statutory minimum flow to the River Devon.

“In the first three months of operation, we have generated over 113,000kWh of electricity, which we have been able to return to the grid and puts us on course to save at least the equivalent of 93 tonnes of carbon dioxide annually," said Tom Coutts, senior project manager for TSSE.

When the reservoir at Glendevon is at full capacity, water cascades over into the River Devon, via a spillway. A 15in outlet pipe is sized to deliver the desired minimum compensation flow of 242 litres per second (l/s), directly to the river, as stipulated by the Scottish Environment Protection Agency (SEPA).

The 15in pipe passes into the compensation measuring house, where it connects to a reverse-pump turbine from Torishima Japan, which in turn powers an 85kW ABB asynchronous generator. When reservoir levels are high, a secondary 24in pipe becomes active, providing additional power generation capability. A 90kW ABB regenerative VSD converts the generator's output into electricity suitable for transfer to the grid.

Water flows into the compensation measuring house where it powers a reverse-pump turbine which in turn powers an 85 kW ABB asynchronous generator. An ABB regenerative VSD then converts the energy into grid electricity.

Image credit: ABB

The drive was supplied by ABB Value Provider EDC Scotland, who also offered engineering and commissioning support during the installation, while the panel was built by Kilmarnock-based electrical engineering firm Aird Walker & Ralston.

If the grid no longer needs additional electricity or a connection is lost, a separate brake chopper and resistance bank can be activated to divert the generated power and dissipate it as heat. Without them, a lost connection could cause the turbine and generator to accelerate to around twice their normal speed, which would then send surge waves back upstream, potentially damaging the old pipeline.

"A regenerative drive is the ideal solution for capturing energy and feeding it back to the grid, allowing flexibility on the variation on flow,” said Jim Dow, ABB's regional sales manager in Scotland. “The drive requires simplified cabling, which makes the installation quick. There are fewer components, which improves the drive's reliability and provides a smaller footprint, which helps optimise space."

Scottish Water is benefitting from the integration of remote operation and monitoring at the facility. Previously, the team faced 90-minute journeys to the remote location site, so being able to control the valves and monitor real-time data around flow levels, temperatures and power generation remotely has proved beneficial.

The installation produces enough renewable electricity to power some 100 homes in the local area, while fulfilling the reservoir’s primary purpose of providing the statutory minimum flow to the River Devon.

Image credit: ABB

Torishima’s solution, combined with ABB's technology, is helping Scottish Water achieve its own net-zero target by 2040. “Work began on the project in 2017 with a feasibility study, looking at many potential sites for hydro schemes. The installation at Lower Glendevon was effectively a trial and has proven the concept, which gives us the confidence to look at other sites where we can introduce this technology," said Coutts.

Around 69 per cent of Scottish Water's carbon footprint is created through its electricity demands and it has identified 25 sites where renewable energy schemes can help offset its energy usage.

“These schemes are, by their nature, weather-dependent so it can be difficult to accurately predict performance into the future,” added Coutts. “We have been impressed with what we have seen so far, though, which has given us confidence to start identifying other facilities where we can look at introducing renewable power generation.”

Dow added: “The project at Lower Glendevon is a good example of how existing infrastructure, in this case the reservoir’s compensation measuring house, can be used to contribute towards net-zero targets. While the scheme itself is relatively small, it proves the concept and highlights how ABB’s drive and motor technology can play an important role in the journey towards decarbonisation.”

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