Plastics processors can cut energy costs without new machinery
Key Highlights
- U.S. plastics processors face less financial pressure to conserve energy because electricity represents a relatively small share of costs.
- Management attention, employee ideas, monitoring and energy targets can deliver an initial 10% energy-cost reduction.
- Maintenance measures such as fixing compressed-air leaks can provide additional savings without major capital expenditures.
- Primary machines, chillers and compressed air offer greater energy-saving opportunities than lighting in typical plastics plants.
By Bruce Geiselman
Plastics processors in the United States continue to lag much of the world in tackling energy conservation, according to Robin Kent, an international energy consultant and founder of Tangram Technology Ltd., Hitchin, England.
“I always call energy management the last great unexplored frontier of cost management,” Kent said.
U.S. plastics processors haven’t prioritized energy conservation because electricity remains a relatively small portion of total manufacturing costs in this country as compared with others. Kent estimates that electricity in the United States typically represents about 6 percent to 7 percent of a plastics processor's costs, compared with roughly 55 percent for raw materials, 20 percent for direct labor, and the remainder is spent on various overhead costs.
Low U.S. energy prices have historically made conservation a lower priority than other investments, Kent said. In countries where electricity is more expensive compared to other factors, processors have had a stronger financial incentive to eliminate energy waste.
Kent, who has traveled the world performing energy audits for clients, compared the difference in reaction to a compressed air leak between plant management in the United States and in China.
Kent said during a visit to a U.S. plastics processor, he might identify a compressed air leak, which costs a plant money in wasted energy, and find it still exists several years later. Meanwhile, in China, a team of workers would likely follow Kent around with tools so that they could fix the air leaks as soon as he identified them with a meter.
“It's a mindset thing which comes from the economics, and I don't think the economics are as pressing in the USA,” he said.
More efficient machinery isn’t necessarily the answer
Kent doesn’t automatically recommend that processors immediately replace old machinery, despite significant improvements over the past decade or more in energy efficiency by equipment manufacturers.
In most countries, businesses have a roughly three-year payback requirement for capital expenditure. At current U.K. electricity prices, newer equipment, like all-electric or servo-hydraulic injection molding machines (IMMs), can often meet that hurdle through energy savings alone.
In the United States, where there are lower energy costs, plastics processors typically want their capital expenditures to pay off in less than 18 months, meaning new equipment for the sake of energy savings alone would not meet their requirements.
New primary processing machines, like electric or servo-hydraulic IMMs, are significantly more energy efficient than older hydraulic machines. However, plastics processors are slow to invest in new equipment.
“The machine manufacturers have been doing some great stuff,” Kent said. “They're leading the way. It's the processors who aren't doing the replacement.”
When Kent visits a factory as an energy consultant, he aims to identify ways a processor can save 30 percent to 35 percent on their energy costs.
Generally, the cost savings break down to improvements in three areas.
The first 10 percent reduction can be accomplished through working with management to convince them to devote their attention to energy use, encourage employees to contribute ideas for eliminating energy waste, monitor energy use, and then establish targets for controlling energy use. These simple steps can be implemented in three to six months, Kent said.
“It’s about getting management to care,” he said. “If the managers go, ‘we care about this,’ it’s going to happen.”
Another 10 percent reduction can be achieved through maintenance, which includes eliminating compressed air leaks and checking chilled-water-flow temperatures. These are items that usually cost less than $1,000 to address and can be implemented in three to nine months, he said.
A final 10 percent reduction can be achieved through technology upgrades costing more than $1,000, such as installing variable-speed drives on processing equipment and eventually buying new, energy-efficient machinery. These improvements can take one to three years to adopt, he said.
“The technology of new machines is generally the lowest on our list because of the CapEx hurdles,” Kent said.
Don’t focus only on low-hanging fruit
One of the first energy conservation measures many plastics processors undertake is replacing older lighting with new energy-efficient LEDs.
While modern lighting can save some energy, lighting in a typical plastics plant represents only about 2 percent to 4 percent of electricity consumption, Kent said.
Larger savings can be found elsewhere. Primary machines account for about 66 percent of energy use, and chillers and compressed air represent about 12 percent each, he said. Kent focuses his energy surveys on making extruders, IMMs, blow molders, chillers, compressors and pumps run more efficiently, rather than treating lighting as a major energy-efficiency opportunity.
Measurement is critical; some can be done for free
Monitoring energy consumption allows plastics processors to see where and when they are using electricity, and to begin identifying sources of waste.
Plenty of companies sell energy monitors and software that can collect detailed usage data, identifying which machinery on the factory floor is consuming the most energy and possibly helping companies recognize ways to conserve.
However, not all energy monitoring has to cost additional money. Most utilities will provide industrial customers with electricity-use data in 15-minute or 30-minute intervals. Kent recommends that processors put that data into an Excel spreadsheet and graph their energy consumption patterns. Then, look for unusual patterns.
He said a plastics processor that failed to shut down its machinery over weekends when there was no production could consume nearly 80 percent of the energy the plant uses during the week while manufacturing. He compared that plant’s energy consumption to a similar facility that used very low levels of energy during weekend shutdowns.
“For a plastics processing site operating 24/5, the weekend shutdown load, as a percentage of the normal operating load, should be in the region of 5-10 percent,” Kent said.
Viewing an energy consumption graph might convince a company to make additional changes, including not starting equipment early each morning if production won’t begin for several hours.
Kent outlines his suggestions for plastics processors to reduce their energy consumption in two books: “Energy Management in Plastics Processing” and “Sustainability Management in Plastics Processing.” Both books are available through Amazon in the U.S.
About the Author
Bruce Geiselman
Lead Reporter
Senior Reporter Bruce Geiselman covers plastics processing technologies and end markets including automotive and packaging. He also writes features, including In Other Words and Problem Solved, for Plastics Machinery & Manufacturing and The Journal of Blow Molding. He has decades of experience in daily and magazine journalism, including eight years at PMM, and is the recipient of a Jesse H. Neal Award, among other recognitions.