Electricity savings of 15 000 a year
August 1st 2006

Nine ABB variable speed drives will be saving the National Marine Aquarium in Plymouth over 15 000 in electricity annually.One 11kW pump alone will save 2900 per year.The Aquarium features a 2.5 million litre seawater tank, which, at 10.5m, is Britain's biggest. Keeping the inhabitants of the tanks healthy involves constant pumping of water at the correct temperature, resulting in a substantial energy bill. John Selwood, engineering manager for the facility, says:"We needed to save energy, however we have nine pumps for the tanks that must be on all the time, with varying flow and pressure."

The constant operation means that reliability and accurate control are vital. Although the Aquarium's pumps were operated by an automatic control system using PLCs, flow and pressure were controlled provided by a manual throttle valve.This resulted in surplus energy as the pumps were running at 100% speed, with only a proportion of its output being used.

Selwood asked electrical contractor Drew & Co to investigate the pumping and heating systems and suggest ways to save energy. Its managing director, Andrew Botterill, says:"Because the pumping system provides essential life support to the fish in the tanks, it was essential that we install reliable control systems. ABB's drives give us the reliability we need."

Constant operation of the pumps meant that the installation of the drives had to be a hot changeover, with the minimum possible downtime of the pump. This was helped by the interchangeable keypads on the ABB drives.

Drew carried out an energy appraisal to determine where most of the energy was being used. Nine ABB variable speed drives were installed, ranging from 7.5 to 18.5kW. Single drives now control the duty and standby pumps sets, changing automatically to the duty pump as required. Pressure transducers in the pump output provide a feedback signal to the drive, allowing the throttle valves to be kept fully open, allowing the VSD to determine the correct pump speed for the desired flow rate.

Following installation, energy consumption figures were again monitored."Our initial assessment was that the client would save 14 000 on energy.Three months after the drives were installed we estimated that the aquarium would save even more 15 600," says Botterill.

The ABB drives were sourced from ABB Drives Alliance partner APDS."We aim to build a support mechanism for the client and APDS to help with ongoing maintenance," says Botterill.

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