The company’s Southwater plant operates two independent compressed air networks at 7bar and 8.4bar with the principal input coming from an Atlas Copco ZR160VSDFF oil-free, water-cooled rotary screw compressor. Energy recovery is being utilised from this compressor for heating applications on site such as office heating, providing heat for the packing area and essential condensation protection inside the warehouse complex.
The compressor has an integral energy recovery capability that enables hot water to be taken from its outlet at temperatures of up to 85°C – a standard or retrofit option that is available on Atlas Copco water-cooled compressors in its ZR55-900 range – and the hot water returns at approximately 35°C in a closed loop. This usable heat is transferred to other site operations by means of plate heat exchangers and the whole network is controlled by the site’s building management system.
The use of the energy recovery from the compressor has meant that the demand on the gas-fired heating boiler has dropped dramatically, resulting in significant energy and cost savings. Ordinarily, the waste heat from the compressor operation would just be dissipated to the atmosphere and lost but, according to Dean Shackel, Facilities Manager at Sony DADC UK Limited, the energy recovery figures achieved are even better than those originally predicted during the project’s design phase and amount to an impressive 100-110kW on average from the ZR160VSDFF alone. Dean calculates that the total energy savings from the utilisation of the energy recovery feature of the ZR160VSDFF, as well as hot air usage from the outlet of two other Atlas Copco air-cooled compressors, comes to over 700,000kWh per year.
 
All of the available heat from the compressor is used during the winter months and this is where the maximum savings are made. Dean also suggests that the addition of the energy recovery in parallel with the boiler means that there is, in effect, a backup heating source: "Now we are out of the coldest period of the year we are using the recovered energy from the compressor for heating the building’s hot water supply, in addition to its space heating capability. This actually means that the gas boiler is currently not in use at all at the moment!"
As a result of Sony DADC UK Limited’s energy efficiency awareness and endeavours to reduce its plant’s carbon footprint using technology such as energy recovery, the company has recently won the 'The Green Award for the Use of Energy' at the Gatwick Diamond Business Awards.
As Sony DADC UK Limited’s experience demonstrates, with the majority of the electrical energy employed in compressed air production being converted into heat and traditionally lost, compressor energy recovery enables operators to make substantial reductions in their fuel consumption, particularly where there is a use for hot water.  Furthermore, it is possible to achieve indirect process savings by reducing the maintenance costs of associated equipment and, in specific applications, overall process efficiency can be increased.