The installation of a new ammonia refrigeration system featuring a low harmonic, industrial drive within the 315kW screw compressor and variable speed operation of the condenser fan, will allow a UK puff pastry producer to realise an 11% reduction in its refrigeration energy costs.

With refrigeration accounting for about 70-80% of the electricity bill of companies in the food manufacturing sector, UK Poole’s Pies was prompted to pay specific attention to this aspect on the occasion of installing a new production line, complete with spiral freezer, designed for the manufacture of a variety of puff pastry products.

Energy saving features of the ammonia system

A refrigeration system operating on pumped ammonia refrigerant at an operating temperature of -40°C was installed by Seward Refrigeration. The system features:

• A low harmonic, industrial drive within the 315 kW screw compressor: A single 315kW screw compressor used to provide refrigerant for the spiral freezer. The use of a 315kW low harmonic, industrial drive within the 315kW screw compressor that provides refrigerant to the spiral freezer that has been supplied by ABB, permits energy savings at partial load conditions. The screw compressor can operate at speeds between 1500 and 3600 rpm at 100% slide valve position. With this mode of operation, the machine operates at optimum efficiency for any given speed. “With variable speed control of the compressor at Poole’s Pies, we now have the best of both worlds: good efficiency at both partial load and full load,” says Brian Seward of Seward Refrigeration.

• Variable speed operation of the condenser fan: The condenser is an evaporative type with the fan controlled by a 15kW standard drive also supplied by ABB. Variable speed operation of the fan gives significant reduction in power even for a small reduction in speed. For example, a 10% speed reduction gives 30% less energy consumption.

11% electricity cost savings

Poole’s Pies can produce 200,000 meat pies a day, as well as 80,000 other puff pastry products. With the installation of the new system, the puff pastry producer expects to realise electricity cost savings of 11%, which translate to about £6,200 savings per year. This means that the payback period for the project is only 2.3 years.