Once upon a time, it was hard to get plastics processors to give more than lip service to the idea of conserving energy in their plants. I think it’s safe to say that those times are gone for good. It’s still true that energy cost represents only 4% to 5% of total processing costs, but the possible savings from good energy management are in the region of 30% of current energy costs for most plastics plants—and that goes straight to the bottom line. About two-thirds of those savings can be achieved by no-cost or low-cost actions. For example, one-third of the savings can be achieved through management actions—i.e., monitoring and targeting energy usage, creating management controls, raising employee awareness, and setting appropriate policies. Another third of the savings can be achieved through maintenance actions—simple quick-fix actions such as controlling the use of utilities. The final third is achieved through capital investment in energy savings—and the average payback for such investments is around six to nine months.
Don’t take my word for it. These are some conclusions of a fascinating and highly readable book just published by Plastics Information Direct in the U.K. (www.pidbooks.com). Energy Management in Plastics Processing: Strategies, targets, techniques and tools (265 pages soft cover, $160 plus shipping) was written by Dr. Robin Kent of Tangram Technology Ltd., British consulting engineers for plastics processing. This book really gets down to details on what to do and how to do it if you really want to find out where the energy goes in your plant and eliminate waste. It’s full of guidelines, charts, graphs, and practical tips on every aspect of energy use and plastics processing (even mold design):
- Don’t rush to turn down the lights or heat—as Dr. Kent’s chart here shows, lighting, heating, and office use of energy account for only about 8% of the total.
- Learn the difference between the base load and the process load (fixed vs. variable load) of energy use in your plant. The base load should be 10% to 40% of the average total load. That’s dead weight, unrelated to productive output, but fortunately it is fairly easy to trim, Kent says.
- Learn about power factor, maximum demand, and available capacity—and how each one affects your electrical bill.
- Learn about motor management—there are probably lots of small motors in your plant that are eating you alive.
- Reducing the cost of compressed air is one of your biggest opportunities. The real cost of compressed air is more than 10 times the equivalent quantity of electricity. Vacuum ain’t free either.
- Get out there and start measuring! As Dr. Kent writes, “If it cannot be measured it cannot be controlled. If it is not being measured then it is not being controlled.”