Motor Skills: How Georgia-Pacific is Testing Algorithms to Save Energy And Cut Emissions

March 2, 2020

min read

You cannot always see the engine room of the modern world, but you can certainly hear it whirring away in the background. Our homes, offices and factories are powered by a huge army of AC induction motors, from the handbag-sized motors in swimming pool pumps and air conditioning units, to the giant beasts of burden that drive massive conveyor belts on a production line.

Those billions of AC induction motors, which convert electrical energy into mechanical energy, burn through vast amounts of energy. In fact, they consume nearly 1 of every 2 kilowatt hours (45%) of the world’s power generation. In 2020 alone, motors are set to consume almost 12,000 terawatt hours of energy, which is enough to supply the United States for three whole years. These mind-boggling numbers explain why even a small improvement in the efficiency of AC induction motors will have a huge positive impact in the form of reduced energy consumption and related carbon emissions.

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Now imagine a double-digit efficiency boost across a whole fleet of massive motors, allowing an industrial giant to slash its electricity consumption, massively reduce emissions and still make the products we rely on every single day. That is exactly what is happening on Georgia-Pacific’s tissue production line. The Koch Industries-owned company is testing cutting-edge software that reduces the electricity consumption of a crucial hardworking machine by as much as one-third.

That is no small feat, given that motors can account for up to 80% of a large industrial company’s power consumption, according to Neil Singer, the president of Armonk, New York-based engineering firm AC Kinetics, which developed the software. Koch Industries is a key investor in AC Kinetics, but, perhaps more importantly, is also offering its facilities as a laboratory to refine and improve the technology in a real-world setting. 

First, a quick primer on the powerful motors that Georgia-Pacific uses on the production line of that personal hygiene staple, jumbo bath tissue. A pair of 75 horsepower motors propel the converting machine, the giant metal spools that unwind the tissue paper from a parent roll — a giant cylinder whose height and base stand taller than an adult human — and rewind the paper into a thinner log. Those slimmer logs are then slit into rolls of the final product: the compact, tightly wrapped rolls that you see in public restrooms.

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The converting process from parent roll to an everyday product like tissue paper is a bit like a swan swimming across a pond: Both look smooth and serene on the surface, but just out of sight, the webbed feet, or induction motors, are working overtime. Michael Younis, director of energy optimization for Georgia-Pacific’s consumer products business, explains that the converting process is a start-stop affair that requires the motors to continually ramp up and down in power.

That is because the winders, which start on a fresh log every minute, accelerate to a whirr, and then decelerate as the diameter of the smaller log grows. They stop completely to transfer to the next log, and then power up again. “Their speed and torque are constantly changing to maintain sheet speed,” added Singer. The converting machine’s two motors will perform this cycle nearly 1,200 times in one day, together consuming nearly 124 kilowatt hours of energy. 

The winding cycle’s peaks and troughs might be necessary to get the job done, but they take a toll on the motors’ efficiency, or how much electrical energy they convert into mechanical energy. Ramping any AC induction motor up and down, rather than running it at a constant speed, tends to increase the amount of wasted energy, which is lost to the noise you hear and heat you can feel. That is why AC induction motors usually have a rated efficiency of over 90%, but a much lower efficiency in practice, of around 60-70%. “You use the motor according to what the process requires, not the other way around,” says Singer. “For example, you only need high torque for part of the tissue winding cycle.”

He uses the analogy of a car engine to explain the efficiency conundrum. Theoretically, an engine should last decades, and achieve a top speed of 150 mph. But a driver is unlikely to be driving at a constant speed of 30 mph on a straight, flat highway in mild, unchanging weather. And the engine will swiftly burn out if the driver is holding the pedal to the metal. AC induction motors also fail when pushed to the limit. That is because motor insulation degrades faster at higher temperatures: The rule of thumb is a halving of life for every 15-20 °F increase over the rated ambient temperature of a motor, which is often 100 °F. The ACK motor control software has proven to significantly reduce motor operating temperature.

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In practice, the motors used for industrial applications, including the jumbo bath tissue production line, often seem too big for the job. The machine designers specify motors that will be lightly loaded to ensure reliability and longevity. Sometimes designers then attempt to squeeze maximum efficiency from the motors by running them in energy-saving modes. But there is a trade-off: Currently available energy-saving modes compromise the machine’s performance, especially its handling of the load and speed variations.

AC Kinetics’ software means that Georgia-Pacific does not need to sacrifice anything. The algorithm allows the company to boost the efficiency of the converting machine’s motors — thereby saving significant amounts of energy — without compromising on performance. “This technology gives you a way of having your cake and eating it too,” says Singer.

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The software is not installed on the motor itself, but on the motor drive, the hardware that regulates the power supply to the motor, configuring automatically for optimal operation. The drive is cyclically ratcheting power up and down so the winders can spool the paper at a constant speed of nearly 2,000 feet per minute. “It’s a bit like a car going between red lights,” says Singer.

These dynamic changes in load are a tough workout for the motor, and they cause fluctuations in rotor velocity. AC Kinetics’ software-enhanced “ACK drive” minimizes those fluctuations by analyzing mountains of real-time data about the voltage and current that flow to both the drive and the motor. The ACK drive optimizes the motor’s electrodynamics, allowing it to rev up and down with pinpoint precision, thereby boosting its efficiency. The motors consume less power throughout the cycle, especially at lower loads and speeds, with no impact on performance. “You’re using just the right amount of torque for the application,” says Singer.

In the trials on Georgia-Pacific’s powerful motors used on the production line of jumbo bath tissue, the ACK drive boosted the efficiency of motors in the machinery from 7.2% to 40% — the most recent tests showing a slash in overall power consumption by 31%. The software has the potential to squeeze extra efficiency from the tens of thousands of machines and motors on the Georgia-Pacific factory floor and across the wider Koch universe. It could prevent the emissions of millions of tons of carbon dioxide from power generation.

Singer is excited about the potential for his software, but he is also grateful to have found “the perfect proving ground” for his technology. “Koch Industries couldn’t have been any more supportive in terms of experimenting with this technology.”