Energy recovery

18 June 2014

Automotive textile manufacturer Autofil Worldwide has achieved average cost savings of £37,000 a year and reduced annual CO2 emissions by 260,000 tonnes since adopting Atlas Copco’s energy recovery technology.

The primary manufacturing operations at Autofil’s 10,000sq m UK plant require a substantial volume of compressed air, which is supplied via an Atlas Copco system. The system is controlled by an ES 360 optimiser, and comprises 12 compressors, including three GA 160+ units and a GA 250 compressor connected to a stand-alone ER-S5 energy recovery unit.

As well as the considerable demand for compressed air on site, the dyeing processing has an equally large requirement for process hot water. A 50,000 litre tank stores water for several dyeing process operations in the factory and the by-product heat from the GA 250 compressor is used to pre-heat this water to around 50°C, rather than relying on additional gas power to heat it at point of use.

This is made possible by the ER-S5 energy recovery unit, whereby hot oil from the compressor’s air end is diverted through a stainless steel plate heat exchanger. Heat from the oil is transferred to cool water on the opposite side of the exchanger, producing a continuous flow of hot water from the ER outlet.

The water circuit between the tank and ER unit takes cooler water and replaces it with the heated water. After a few hours, this circuit reaches its optimum inlet/outlet temperature: inlet water from the top of the tank to the ER at ±30°C; outlet water fed back from the ER to the bottom of the tank at ±55°C, achieving a temperature rise of 25°C.

Based on the compressor running for 8424 hours per year, the combination of the GA 250 and ER-S5 unit is recovering more than 1.4 million KWh of energy a year.

Commenting on this substantial reduction in his company’s carbon footprint, Steve Charlton, Autofil’s engineering and IT manager, said: "We are an energy conscious company and constantly strive for improved efficiency and energy saving solutions in the way we run our operations. Atlas Copco’s Compressor Technique Service team have been able to provide sustainable energy-saving solutions over recent years to help us reduce our compressed air energy consumption, notably the introduction of their ES 360 optimiser controller which matches supply to demand, allowing us a 360 degree visualisation of the compressed air installation in terms of pressure, supply and demand. Now, we have added an energy recovery unit to further optimise the installation.”

By recovering this heat for another practical purpose, the potential for savings is obvious. To provide evidence of this, inlet/outlet temperatures from the ER-S5 are continuously monitored via the temperature sensors provided and can be visualised in a number ways − on the compressor controller and on Autofil’s ES360 optimiser controller, which allows for trend readings and can be continuously monitored via the company’s BMS. 

With Atlas Copco SMARTLINK-Energy, the values can be monitored at any time anywhere via the SMARTLINK website. These monitoring and display solutions allow the creation of reports, essential for ISO auditing requirements, as well as for internal management and performance systems.