The fundamentals of energy-efficient manufacturing

When one speaks of “energy-efficient manufacturing,” it is about a slightly different kind of “green” than that touted by the retail giant Wal-Mart. To be a Wal-Mart supplier, a company must measure its greenhouse-gas emissions, solid-waste production, and water consumption, then sum this data into a so-called “sustainability index.”

But in the manufacturing realm, energy efficiency mostly comes down to the manufacturing processes themselves. It seems that few, if any, manufacturers require suppliers to prove they are energy efficient. That said, more and more companies are jumping on the energy-efficiency bandwagon. The “green” they are after is a better bottom line. Using less energy lets plants rely less on the utility grid, and, therefore, cut costs and be more competitive.
A pledge of enery efficiency among manufacturers might become commonplace thanks to a voluntary agency called the U.S. Council for Energy Efficient Manufacturing (U.S. CEEM). U.S. CEEM wants to help U.S. industry become more energy efficient. Members include U.S. manufacturers such as 3M, Alcoa, Ford Motor Co., and Toyota, as well as agencies such as the Alliance to Save Energy, the American National Standards Institute, the U.S. Dept. of Energy, and the U.S. Environmental Protection Agency’s Energy Star for Industry program.

A manufacturing “energy quotient”?

Thomas Kiser of energy consultant PSI Energy Solutions, Fremont, Ohio comments that, “It’s easy for manufacturing engineers to use scare tactics and say, ‘What if an energy-efficiency strategy causes me to make bad products?’ Many manufacturing engineers lack courage because their leadership does not give them the blessing to become more efficient.”

But how does a company decide whether or not it is efficient enough? “PSI helps manufacturers in their energy-efficiency endeavors by establishing what I call the ‘energy quotient’ for all their manufacturing processes of interest, whether they be stamping, metal handling, or injection molding — even the paint shop, or a conveyor line making potato chips,” says Kiser. “Most companies know how much energy they have purchased to get things done. All they need to do is look at their utility bills. But few manufacturers really know how many BTUs their assembly line or canning line needs. This is where establishing the energy quotient comes into play.”

PSI starts by measuring every process of interest gauge the energy it consumes. This entails the sub-metering of devices that use energy such as actuators, conveyor lines, electric motors, and compressors. And sub-meters themselves aren’t just read-outs attached to power lines. They include infrared guns, temperature sensors that can look through a device like an X-ray machines, current transducers which can measure electricity without invading wires, and gas meters. The results break down energy use by process. The so-called Kiser energy quotient (whether good or bad) is expressed as

[EN] / [EP]

where EN = energy needed, and EP = energy purchased. It can be seen that Kiser’s energy-efficient approach belies the traditional assumption that a company needs all the energy it has purchased (where the energy quotient would be 1/1). In fact, there are practices that can cut a company’s reliance on the grid. So the quest for energy efficiency becomes a quest for a higher energy quotient, which is a more concrete goal.

For example, a process with an energy quotient of 1/10 means that for every unit (BTU) of energy really needed, a company has, in fact paid for 10. A lot of the energy has gone to waste. The quotient 0.1 is rather pitiful, says Kiser. He says a good goal to shoot for is an overall energy quotient of 3/1. This boils down to only purchasing one unit of energy from a utility for every three units of energy needed.

After establishing a quotient and sub-metering appropriate processes, next comes quantification of output. “Say an assembly line was set-up to do 60 widgets, (or F-150s, or rubber tires. It doesn’t matter.) per hour,” says Kiser. “At the end of the day, the object is to count the production throughput, whether by piece or by weight, to compute the energy per piece. Say, for example, a company manufactures potato chips. Further suppose last month, it used electric and natural gas at the rate of $1,000/week per 1,000 lbs of potato chips. But next month, it is still paying $1,000/week but only will make 800 lbs of chips. This tips-off managers that the amount of energy used in a particular line is going up.”

Part and parcel with the endeavor to become more energy efficient is the need to meter all the energy a plant recovers. This is the rejection energy a plant recycles to another system somewhere in the facility.

“For example, say a plant uses a lot of electricity in its motors on the factory floor,” says Kiser. “Some of the electricity used turns into heat and is lost. An answer might be to put in water-cooled motors to use the rejection heat to make hot water for another system. So a process that was, say, 50% efficient is now 70% efficient and going up. The plant no longer must get hot water from a gas-fired boiler.”

Another example might be that of a digester, a septic tank with bugs in it. “The bugs eat the waste coming off the tons of potato peelings (used to make potato chips) that are dumped into the sewer,” says Kiser. “The digester turns all that food into natural gas, which is recovered and put into an engine that makes electricity for another area of the plant.”

Kiser explains that the last step to an energy-efficient manufacturing approach is to archive all the metered data. “This lets companies summarize their daily logs, enabling real-time awareness of whether they are, indeed, running more energy efficiently,” he says.

PSI puts its money where its mouth is. The firm has entered into long-term contracts with companies such as Ford, which has created accountability between PSI (the third party) and the plant, every day for 10 years. Should the efficiency in an area fall, PSI writes Ford a check. But when performance exceeds the goal, the companies split the profit 50-50.

Energy-efficient manufacturing, early-on

Surprisingly, some companies have had energy-efficiency programs for years. For example 3M, St. Paul, Minn., a member of U.S. CEEM, has had a program since 1973. “We have had a corporate energy leader each of those years and presently have a corporate goal to improve energy efficiency by 25% over a 10-year period,” says company Corporate Energy Manager Steve Schultz. “That 10-year period will end in 2015, and presently we are ahead of schedule. We have established this goal for a couple of reasons. One is that the use of less energy lets us purchase less energy, and that helps us reduce our costs. The other is that energy efficiency is good for the environment. Continually working to improve efficiency reduces our dependence on natural resources.”

According to Schultz, the 3M company culture supports the effort. “Our top-level leadership has recognized for a long time that energy-efficient manufacturing is important. Many years ago there were corporate goals for energy efficiency, which aligned with other company manufacturing productivity goals. That continues today.”

One way 3M makes its plants more energy efficient is by replacing old equipment that uses a lot of energy with newer, updated equipment. “We are doing this on a case-by-case basis, where we have out-of-date equipment and can justify the expense,” says Schultz. “Often, these kinds of improvements go hand-in-hand with other process improvements or upgrades.”

3M also stations teams on each of its sites that try to improve the efficiency of the plant. “For example, in some instances, we create a lot of heat in ovens that cure materials,” says Schultz. “We recover the heat to create steam. The steam is used to further heat the oven for the manufacturing process. Thus, the exhaust from the oven is not simply emitted into the atmosphere.”
Schultz also explains that at a high level, 3M tracks the energy (BTUs) it uses at each of the facilities worldwide. It measures the productivity from company facilities monthly and tracks the BTUs per unit of product produced.

“As the company grows, it is likely we will continue to need more energy,” says Schultz. “But we will waste less energy and improve our productivity by the targeted percentage.”

The Energy Star program administered by the EPA is one of the programs in which 3M participates. “A lot of people are not aware that Energy Star does more than supply labels for appliances and the like,” says Schultz. It has a program for industry called Energy Star for Industry, which shows manufacturers of any size how to better manage their energy use. You don’t have to be a big corporation to be a part of the program or to benefit from its resources. Another resource is the Dept. of Energy and its program, now called Better Buildings.

The well-known Leadership in Energy and Environmental Design (LEED) certification is more of a certification for a building. It is sponsored by the U.S. Green Building Council and would apply nicely to an office building.
The Energy Star for Industry program recognizes participants in its program annually. 3M has received the Sustained Excellence award for eight years in a row, a record for any manufacturer.

Making energy-efficient machines

Although some manufacturing plants don’t necessarily focus strategically on improving their energy efficiency, they still might earn more profit by using machines that are more energy efficient.

For example Cincinnati Inc. in Harrison, Ohio, says the company focuses on building energy-efficient lasers. “Users get more out of a given quantity of electricity, says Richard Neff, Market Development Manager. The machines are called fiber lasers, a new technology. A fiber laser is one in which the beam is actually generated in an optical fiber doped with rare-earth elements such as erbium, ytterbium, or neodymium. They use less energy than CO₂ or YAG lasers and also cut faster. Neff says companies use one-sixth the amount of electricity to make a part.

The company has also made efforts to use less electricity than normal. For example, it has installed high efficiency florescent lighting in the shop. When someone is not in an area of the shop, the lights turn off. “That technology pays for itself fairly quickly,” says Neff.