Articles & Case Studies

Pump used as turbine – making optimum use of hydropower with KSB

Posted: Tuesday 23rd October 2012

A pump as turbine can use water power to its full potential. It generates additional energy in systems by reducing pressure differences or by making use of heads and water flow.

KSB Limited, with South West Water as the end user, has successfully supplied, via May Gurney, the largest ‘Pump as Turbine’ (PaT) to date as part of a hydro-electric scheme.

The scheme - at Avon Dam near Buckfastleigh in Devon – comprises two PaTs supplied by KSB, one of which generates on the compensation flow and a larger unit which generates on spill flows in the winter months.

The smaller compensation flow turbine passes 60l/s at 26.7m head, generating an average of 11kW of electrical power at an overall efficiency of 70% - 24 hours a day and almost 365 days per year. The only down time is for scheduled maintenance or any faults or loss of mains connection. The unit therefore has the potential to generate 96,000kWh per annum.

The larger spill turbine passes 650l/s at 26.7m head, generating 140kW of electrical power at an overall efficiency of 80.5%. This unit was sized to make maximum use of potential spill volumes in winter months and during prolonged wet periods. Based on historic spill data at the site, the unit will run on average for 2,560 hours per annum, generating 358,400Whr. Combined, the two turbines will provide enough power to meet the average annual needs of 137 homes*.

KSB’s Water & Wastewater Project team worked alongside May Gurney’s design team to put forward the most cost effective solution, while at the same time ensuring maximum power generation for South West Water’s budget.

The scheme is located within a former meter house at the foot of the dam. May Gurney undertook civils works to redirect the 700mm reservoir outlet source pipework to the meter house, with new discharge pipework from the two turbines being taken into the stilling chamber at the base of the dam.

With the spill KSB PaT offering over 80% efficiency, this solution compared exceptionally well against other turbine suppliers. The installation exceeded expectations in power generation, asset cost and our key goal to minimise noise implications within sensitive sites. Due to the simplified design of the KSB PaT the overall operation and maintenance costs will also be kept to a minimum for our clients.

A bespoke control panel allows the system to be operated remotely from South West Water’s Avon Water Treatment Works. In the event of power outage from the local distribution network operator (DNO), the system’s control software ensures that the turbines are taken off line and that the water course downstream is protected, by maintaining control of the compensation flow through a battery backed bypass valve.

The Avon scheme is the latest in a series of hydro-generation schemes for South West Water, and KSB along with May Gurney are in the process of scoping and tendering for additional works for South West Water and other water utility companies.

Stuart Wallis, KSB’s General Manager for Water & Wastewater said:

“With rising energy costs and finite conventional energy resources calls for alternatives and solutions have become louder. This is why KSB have increased their already strong focus on the renewable market. The Hydro projects we have been undertaking with May Gurney demonstrates the positive outcome of collaborative working. By using the unique skills & disciplines of both organizations has allowed existing technologies to deliver a number of projects with innovation & exceeding the expectations of the client.”

“The packaged Pump as Turbine solution from KSB & May Gurney captures previously untapped free energy. The capital cost and associated payback period benefit of installing our solution is far greater than that of comparative traditional turbine solutions and other new alternative solutions being offered to the market”

“By listening to the needs and requirements of the market, KSB & May Gurney, will invest additional time and resources to develop the Pump as Turbine solution in line with the needs of our clients”

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