The carbon footprint of an air compressor

Airpower UK Ltd was recently asked to look at an installation of a standard rotary screw compressor.

The compressor model was an Ingersoll Rand SSR ML15 - Capacity at 7.5 bar 88 cfm.

It was reported that the compressor was only running on-load for 18% of the time. We were asked to look at the electrical and environmental costs of having an oversized machine running in this way.

The following calculations are based around the proposal to install a variable speed drive compressor. The main advantage of a VSD compressor is it removes the waste lost in offload running. For more info see our page on energy saving compressors.

Calculations as follows:-

80 run hours per week x approx 50 weeks per year = 4000 hours/year

4000 x 82% unload time = 3280 hours where the machine is running but not producing air.

Note the 82% unload figure may not be accurate. This assumes that the compressor never actually shuts down, however most rotary screw compressors including the Ingersoll Rand SSR ML range will close down after a set period of time usually 2-5 minutes if no air is required. For example on a lunch break etc. assuming there are no leaks in the system the compressor should shut down and motor stop.

3280 x 9.35 KW Off load power consumption = 30668 kWh

30668 x £0.08 electrical cost = £2453.44

E.On recently published their carbon intensity figures: http://www.eon-uk.com/about/2898.aspx
In the creation of 1 kWh 0.7Kgs of CO2 is produced.

From this we can calculate the amount of carbon dioxide created by the waste of 30668 kWh of electricity.

30668 x 0.7 = 21467.6 Kgs

Over 21 tonnes of CO2.

Such wastage is so common in our industry and this case study highlights the exceptional environmental and financial cost of running non-efficient equipment.

Airpower UK Ltd are specialists in air energy research. We genuinely do care about the environment and are willing to work with clients to bring carbon emissions down. We offer free advice and in many cases we can provide air energy audits free of charge, click here for further information.