Energy savings at UK’s South Staffs Water

2013-03-22 - The world’s first IE4 synchronous reluctance motor and drive package (SynRM) from ABB has replaced an induction motor-based variable-speed drive package at South Staffordshire Water in the UK, resulting in an additional 6 percent energy saving.

By ABB Communications

Keith Marshall, Supply Director, South Staffordshire Water PLC
The South Staffordshire Water company replaced a 20-year old, 115 kilowatt (kW) IE2 induction motor and drive system, which had already maximized the process energy savings opportunities at the pump house, with a new synchronous reluctance motor and drive system, providing even greater efficiency and reliability, with lower heat losses, less noise and reduced maintenance costs.

The system is used to control a single vertical shaft driven borehole pump at the Somerford pumping station, which extracts 2.5 million liters of water each day to serve the local community.

“While being one of the most efficient companies in the industry, our electricity bill is more than £9 million (approx. $13.4 million) per year and rising through increases in wholesale energy prices,” explains Keith Marshall, Supply Director at South Staffs Water. “Pumping water accounts for some 90 percent of this spend as we have one of the highest pumping heads of any UK water utility because of the deep boreholes and hilly terrain within our area of supply. A 6 percent reduction on one pump in a system that was already very efficient is massive news for us.”

The success of this trial has brought forward South Staffs Water Investment Programme so that benefits can be gained sooner.

“If we had chosen an older motor and drive combination elsewhere on the plant we believe the energy savings could easily reach 10 to 15 percent,” explains Glen Hickman from Sentridge Control, the company responsible for the design and commissioning of the installation.

Part of the benefit of the SynRM design at South Staffs Water has been a 58 percent reduction in frame temperature compared to the induction motor.

“This means that in the summer, using SynRM across more sites we can dramatically reduce the need for forced ventilation,” says Marshall. “As the rotor has effectively no losses this lowers the bearing temperature, which means we can either choose to extend the period between greasing or increase the bearing life expectancy, both of which will help reduce our maintenance costs.”

Another benefit has been a 75 percent reduction in audible noise: down from 78 dBA to 72.3 dBA when running at 1,450 rpm.

“This is great news for our neighbors and employees,” says Marshall. “Not necessarily at the Somerford pumping station, which is remote, but at booster stations closer to residential areas.”

The SynRM motor is specifically designed to work with variable torque loads controlled by variable-speed drives, which means they are ideally suited to the variable-speed demands of pumps and fans.

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