The concept of “green” is a hot topic in packaging today, with companies constantly striving to win plaudits for their newer, more eco-friendly packages. But green, or sustainable, concerns are impacting the production side of the packaging equation as well, most obviously in the area of energy efficiency.
Discussions of production line energy efficiency typically begin (but nowadays don’t end) with a look at motors, and with good reason. Armory Lovins, chairman and chief scientist of the Rocky Mountain Institute, a resource policy think tank based in Snowmass, Colo., states that nationwide, the energy consumption of industrial electric motors can be cut by 50 percent. Other estimates vary, but it is clear that this is an area rife with huge energy saving potential.
In the quest for dramatic energy savings, switching to energy-efficient electric motors is generally a good place to start. This may include high-end NEMA Premium efficiency motors that meet guidelines established by the National Electrical Manufacturers Association. Though these motors typically cost 10 percent to 15 percent more than other energy-efficient motors, they frequently yield a quick payback on the investment. But that is just a start, because energy-efficient motors are only a piece, albeit an important one, of the puzzle.
“Making sure motor power ratings have been closely matched to the load or application (often referred to as sizing) is another way to ensure a motor is being used efficiently,” notes Corey Morton, product manager for automation supplier B&R Industrial Automation Corp., of Roswell, Ga. That’s because motors run most efficiently when operated at around 75 percent of their full load rating.
“On new equipment, proper sizing may be relatively easy to implement,” observes Morton, “but often, for existing equipment, motor replacement may not be an option.” These cases are tailor-made for variable frequency drives (VFDs), with their ability to vary the motor’s energy output to match the load. Energy savings ranging from 3 percent up to a whopping 60 percent can result, depending on the application.
VFDs can pay off in other ways as well. “Starting an electric motor with full line voltage results in a large, inrush current that can be six to 10 times the motor’s full load current. For large-horsepower motors, this can be an enormous amount of current that may even result in momentary voltage sags on the facility’s distribution system,” says Morton. The result may be a large peak demand and inefficient operation of other equipment due to the momentary voltage sag. Depending on the company’s utility contract, it can also result in penalty pricing as well.
“A VFD can address both issues by slowly ramping the motor up to the desired speed,” continues Morton. “The starting current is reduced to levels required to accelerate the load to the desired speed, eliminating the voltage sags that would have resulted from the large inrush of current.”
More than motors
New motors or old motors, it’s a question of looking at the whole system, says Rich Mintz, national product manager for drives supplier SEW Eurodrive, of Lyman, S.C. “The goal is to get the most mechanical energy out of the least amount of electrical energy.”
The VFD can help in this regard. “The importance of the VFD is not just to limit the inrush of the motor. The most important thing to consider is that when a drive is employed, it provides the system with intelligence and flexibility.” He says that by providing the ability to control a motor’s starting, ramping, speed and other variables, it gives users the ability to manage energy consumption.
He cites for an example a plant with regenerative drives that return energy to the power system. Factor in drives with a control algorithm that monitors when other drives in a process or plant are starting or stopping, with some timed to operate only during periods of regeneration, resulting in a net power consumption of zero. “While a lot of applications can’t just sit around and wait to run, what about air compressors? Chillers? Pumps? Mixers, fillers or conveyors? Will a start delay of a few seconds or even minutes really make much difference in these applications?” Mintz asks. “And when they do operate, is it OK to extend the ramp and maybe operate at a lower ‘full speed?’ ”
Mintz challenges other engineers to look for applications such as these, pursuing what he calls a holistic approach to energy issues. He adds, “These are the best ways to save energy: slow start, slower operating speed, shut off when not in use. The intelligence of VFDs,” he observes, “makes such controls simple and inexpensive to implement.”
B&R’s Morton is one engineer who has accepted that challenge. He says that Energy Management Systems (EMS) are not only an effective way to reduce energy usage, but can also be used to manage demand charges. “Monitoring and control devices can be placed at power distribution points and at large loads,” he notes. “Staggering the start of large loads can be used to prevent peak demand charges. Equipment or systems that can be interrupted without disrupting production can also be used to limit demand through load-shedding schemes (shutting off loads to avoid peak demand charges).”
Ben Green, resident expert on sustainable packaging at vendor Siemens Energy & Automation Inc., Alpharetta, Ga., favors a holistic approach to energy issues, though at Siemens, it’s included under the heading of Optimized Packaging Line methodology. It’s a concept that the company highlighted at the Anuga FoodTec show in Cologne, Germany, last March, one that focuses on products that combine operational and energy efficiency, plus energy management.
“The push for this has really been from the end-users, from what I’ve seen. End-users are demanding machines that use less energy, that have far less downtime, and that deliver more throughput for the amount of energy they are putting into it.” Siemens, says Green, has been active in addressing these issues at the original equipment manufacturer (OEM) level, working with them to see how different designs can impact the amount of energy being used. “The idea is to get more bang for your energy buck,” he reiterates.
The design issues he alludes to involve more than just old motor vs. new motor decisions, even when focusing strictly on energy efficiency. “Some of the machines on a typical packaging line are old machines that have one big induction motor along with a lot of gearing, belts, pulleys, chains, and so on, and over time those things wear and get less efficient.” Green points out how inefficiencies in the motor, gear box and other components have a cumulative effect, resulting in a system that is less efficient than its components. “You will be pulling in more electricity to produce the same number of parts because of the efficiency losses in the mechanical system.”
Mike Wagner, packaging segment business manager, OEM business solutions, for automation supplier Rockwell Automation Inc., Milwaukee, concurs. While noting that discussion of energy efficiency issues often focuses on motors, Wagner says, “I think, for the most part, if there are significant gains to be had in terms of efficiency, I would typically look at the gear box and geartrain mechanisms.”
And it’s not simply older machines that manifest energy-sucking mechanical inefficiencies in these areas. Relentless cost pressures are impacting OEM design decisions. “The trend in the market is to go with lower-cost equipment, so what we’re seeing is some substitution from the higher-cost precision gear box to a lower-cost gear box. There’s a short-term gain in terms of cost, but it can impact efficiency. Using low-cost, low-efficiency gear boxes, you can lose 10 percent to 15 percent efficiency.” He’s talking specifically about mechanical efficiency, but of course, there’s a concomitant loss of energy efficiency.
Control systems can be an energy drain as well, particularly for high-speed machines or machines with complex motion-control systems, if the control isn’t fast and robust enough for the application. “Latencies introduced by the control system can negatively impact machine throughput or performance,” notes B&R’s Morton. “This may result in longer production cycles to produce a given amount of product, leading to increased energy costs due to longer operating schedules.”
Another overlooked energy hog: “Air,” says Rockwell’s Wagner. “You can walk into the typical plant during shutdown and hear the air leaking. That means the compressors are going to work harder, using more energy. So air consumption should be one of the leading energy efficiency targets.”
The U.S. Department of Energy seems to agree with him. It estimates that optimizing compressed air systems by installing variable speed drives, along with preventive maintenance to detect and fix air leaks, can improve the energy efficiency of those systems by 20 percent to 50 percent.
Additionally, Wagner recommends considering getting rid of compressed air altogether where feasible. “Look at electronic actuation, linear motors, they can replace many air cylinders that are in the field today. That gives you a more expensive solution up front, but one that yields significant long-term savings.”
Bill Schiel, industry solutions manager for energy at manufacturing software supplier Wonderware, in Houston, also looks at packaging industry energy efficiency issues through a wide lens. In his case, it’s the methodology of Overall Equipment Effectiveness (OEE). This measure of manufacturing effectiveness employs the formula OEE = Availability x Performance x Quality. Availability is uptime as a percentage of time scheduled for work, Performance is the speed at which work is done as a percentage of designed speed, and Quality is the percentage of good units out of the total number of units produced.
“Basically, a packaging line, whether it has efficient motors or not, is running most efficiently when it is making the correct product at the correct rate and it’s not being wasteful. Anything less than that and you are wasting energy, along with materials and labor.” Schiel says. “OEE allows you to detect when these things are occurring, which is the key so you can take some corrective action.”
Schiel’s colleague, Maryanne Steidinger, Wonderware’s product manager, MES & EMI, stresses that this requires real-time monitoring and reporting capability. “The food and beverage industry have the highest degree of need right now for these kinds of systems,” she adds. “Because energy is so expensive now, and their business environment so competitive, they really need to be able to home in on the resources they are using.”
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