Northumbrian Water to save £100,000 energy costs with ABB drives 15 August 2011
Northumbrian Water says it will save more than £100,000 a year on pump running costs, following a project with ABB Drives Alliance partner, Quantum Controls, to install ABB low voltage ac drives on its anaerobic digester.
Ian Clark of Northumbrian Water explains that the utility was experiencing a problem with pumps on its three digester tanks at the Bran Sands sewage treatment works on Teesside.
Each digester tank had two 90kW star-delta controlled pumps with no speed control. When run at full speed, the pumps caused foaming of the liquid in the tanks, making it difficult to control digestion and to measure sludge levels.
However, as well as processing the sewage sludge, the digesters also produce methane, which is supplied to engines that contribute up to 4MW of power – and the foaming was also interfering with methane production.
Quantum Controls fitted two low-voltage ac drives to one of the digester tanks, and demonstrated that, as well as reducing motor speeds from 1,500 to 900rpm to avoid foaming, the approach reduced motor energy consumption so cut costs.
Quantum Controls calculated that the overall saving would be £107,000, giving a payback of three months, and cutting Northumbrian's CO2 footprint by more than 700 tonnes per year, giving an additional saving of £8,600 under the current UK carbon tax credits scheme.
This brings total savings up to £115,000, with a return on investment of 92 days.
"This project was a good example of the partnership that exists between NWL and one of our preferred suppliers," comments Clarke.
"We gave Quantum the basic specification and they supplied the equipment to suit. Due to our limited on-site resources, they also installed and commissioned alongside NWL technicians."
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