Food manufacturer Poole’s Pies is looking forward to an 11 per cent cut in the cost of electricity following the installation of ABB drives within its refrigeration plant
Installation of ABB drives in the refrigeration plant at Poole Pies' Wigan facility is expected to bring an annual £6200 reduction in energy costs, giving a 2.3-year payback period for the project. Owned by David Whelan, founder of JJB Sports, the company employs 100 staff and can produce 200,000 meat pies a day, as well as 80,000 other puff pastry products.
Introduction of a new production line, complete with spiral freezer, designed for the manufacture of a variety of puff pastry products, prompted the company to look at improving its energy efficiency. For many companies in the food manufacturing sector, refrigeration can account for 70-80 per cent of the electricity bill, so any savings made in this area are likely to be significant.
Installed by Seward Refrigeration, the refrigeration system operates on pumped ammonia refrigerant at an operating temperature of -40degC. Seward chose ABB drives to run two of the major components in the refrigeration system; the condenser and the compressor.
For this system, the condenser is an evaporative type, its fan controlled by an ABB standard drive — variable speed operation of the fan gives significant reduction in power even for a small reduction in speed: for example, a ten per cent speed reduction gives 30 per cent less energy consumption.
A single 315kW screw compressor is used to provide refrigerant for the spiral freezer. Use of an ABB drive permits energy saving at part load conditions — the compressor can operate at speeds between 1500 and 3600rpm at 100 per cent slide valve position. With this mode of operation, the machine operates at optimum efficiency for any given speed.
The best of both worlds
“Although the full load efficiency of screw compressors is good, part load performance with slide valve control is generally poor," says Brian Seward of Seward Refrigeration. "With variable speed control of the compressor at Poole’s Pies we now have the best of both worlds: good efficiency at both part load and full load.”
Use of a low harmonic ABB industrial drive on the screw compressor minimises harmonic interference on the mains supply and avoids the use of complex solutions to ensure conformity with G5/4 requirements. Other advantages of the ABB drive include operation at unity power factor, allowing reactive power charges to be avoided. The standalone design of the drive gives it a small footprint, minimizing space requirements in the control room.
Since refrigeration systems typically run 24 hours, most fan and pump applications are potential candidates for AC drives, says ABB. Any refrigeration system with a wide variation in operating hours or with a heat load that is less than the peak load can benefit from an AC drive.
