Research carried out at the University of Kassel in Germany has shown that pneumatic actuators consume 10.3 times more energy than electromechanical actuators and 4.4 times more energy than hydraulic actuators. The research, which included the cost of implementing or retrofitting an existing system, did not take into account air leaks, which can add another 50% to energy bills.
This is borne out by our own experience in the UK at a margarine manufacturer which operates five 110kW compressors. The company concluded that one of the compressors was there purely to maintain air pressure because of all the leaks in the several kilometres of air-lines around its plant. Operating the 110kW compressor on electricity costing 10p/kWh for 24 hours a day, 365 days a year, meant that more than £95,000 was being wasted every year.
It is difficult to quantify the total equivalent hole diameter for the holes in an air-line because often you don’t know where they are. Diagnostics personnel have to carry listening devices to detect hisses in the pipework and establish where the leaks are in order to seal them. Because the temperature of the air-lines always fluctuates, condensation forms and leaks occur. You can never find all of these leaks and even if you do fix them, they come back somewhere else.
The German study estimated the total air leaks to be roughly equivalent to a 6mm diameter hole per km of pipework, costing £20,000 a year in wasted energy. Another study, conducted by University of Pittsburgh on continuous automotive welding guns, suggests that the energy cost of operating a servo-electric actuator is about a tenth of the cost of using pneumatic actuation – the equivalent of £470 instead of £4,700 a year.