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ENERGY EFFICIENCY: What you Measure Matters

Feb. 1, 2022
Only measuring incremental efficiency gain in motors fails to consider the power consumption of the overall system. The conversation needs to broaden for a complete approach.

By Benjamin Hinds, VP of Product Management, ABB Motors, Global NEMA Division

When shopping for a refrigerator, air conditioner or other appliance, most consumers understand the meaning of the government-backed Energy Star rating, sort of like they do the MPG rating on a vehicle. And they can do the math: a dryer with a 95 rating uses less energy than a dryer with an 87 rating. But does it really?

The Problem with the Standards

With the authority of Congress, the Department of Energy (DOE) establishes minimum energy efficiency standards on many products, including electric motors used in homes and businesses. The goal of those efficiency standards is the conservation of energy and the economic justification. For regulators, one of the easiest things to measure is the motor’s efficiency, but it might be time for Congress to consider another measure.

Incremental efficiency gains are the focus of the DOE’s efficiency standards. Regulating efficiency advances sustainability objectives, supports yearly cost savings for customers and may accelerate the return on investment for the motor or product containing a motor like an HVAC system. The standards have the added benefit of increasing consumer confidence in the products.

While consumers may find the energy efficiency rating comforting, there is an inherent shortcoming in measuring only one metric, like efficiency, because there is a big difference between energy efficiency and energy consumption. Yet, few in Washington seem to be aware of the difference. Industry needs to help move the conversation from measuring and regulating efficiency in motors to measuring and regulating overall system energy consumption; what we measure matters.

Federal mandates aiming to conserve energy by increasing the efficiency of induction motors fail in many ways. Only measuring an incremental efficiency gain in motors amounts to tunnel vision by failing to consider the measurement of power consumption of an overall system.

The Law of Diminishing Returns

Induction motors, covered under the current federal regulations, have improved efficiency enough over the past 150 years that they are now at the point of diminishing returns. To get a small efficiency gain to meet new regulatory requirements, manufacturers may have to implement changes that offset the efficiency gain by adding cost, weight and potentially size to the motor. It’s like adding a meter of length to a vehicle to meet a federal requirement for a safer car. The car is safer, but due to the extra length you must park in the street, so getting into and out of the car is less safe. The same essentially happens if an end user has to re-engineer a process to fit a higher-efficiency motor with more weight, larger size or a longer frame to scrape out a tiny efficiency gain.

Improved Technology

Additionally, motor technology continues to outpace regulations. While the DOE evaluates efficiency standards every six years, the focus on increasing minimum efficiencies of induction motors ignores more current motor technologies available. Recent technology advancements include permanent magnet or synchronous motor technology usage, enabling a motor to remain in the same frame size with improved efficiency. It is important to realize increased motor efficiency is not the main benefit. Instead, it is a reduction in total energy consumption, and in newer technologies, energy consumption has far more impact than efficiency due to how they operate.  For example, take the use of synchronous motor technology: instead of running less efficiently at partial load, the technology only uses the power that is necessary, and it generates less heat. The outcome: the motor uses less power overall.

Incorporating high-efficiency modern technology motors (which operate on or incorporate variable frequency drives or VFDs) will greatly improve power consumption, especially in applications that run at partial loads, with valves, or dampers most of the time such as fans and pumps. Significant power consumption savings are possible because the motor’s speed can be adjusted, along with the fan or pump output, to the current need of the application. According to a recent study, in all applications and subsectors, improved load control, either through installation of VFDs or adoption of advanced technologies, offers the greatest energy saving opportunities (3x-4x vs. improved motor efficiency).1   One might compare it to adaptive cruise control in newer passenger vehicles. The ability to adapt to the needs of the overall system reduces energy consumption and demonstrates the importance of looking beyond efficiency to the overall system power consumption.

Measuring Overall Power Consumption

You can save money and energy by increasing the efficiency of one component of a system – for example, the motor. But what about the energy you are consuming overall? Do you know where in your system lacks efficiency? The DOE has worked with the fan and pump industries to establish index metrics that look at total system efficiency. This begs teh question of federal regulators: are there greater energy gains that can be captured by taking the focus off measuring a small incremental gain in motor efficiency?

The answer is, most likely, yes. If you have an efficient motor running an inefficient pumping system, power is wasted because it requires more energy for the motor to run the inefficient pumping system. Conversely, an efficient pump system lowers the horsepower demand which consumes even less energy.

Bottom Line: Another Measurement Needed

When we look at the diminishing returns available on induction motor efficiency and pair those with new motor technology, we find ourselves at a regulatory crossroad. Industry needs to drive the conversation in Washington around the issue of updating the regulations to consider a more complete approach. We need to ask regulators if it is worth trying to squeeze out tiny gains in induction motor efficiency at the possible expense of increasing overall power consumption. Clearly, this isn’t to say that the components used should not have efficiency standards. But as shown above, one efficient component paired with an inefficient system does not equal a net gain and may, in fact, consume more energy overall.

So, what’s the answer? Mandating a system approach that looks at different measures, including overall power consumption, might be the solution. But moving regulators in the direction of a system approach could be challenging. This approach requires cooperation between Congress, the DOE, manufacturers, and individual and corporate consumers.

The evidence shows that when looking at sustainability and energy savings, mandates to squeeze more efficiency out of already efficient motors are probably not the answer. Keep the Energy Star, sure, but the industry is overdue for a conversation with regulators about widening the lens to capture a bigger picture.

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1. Lawrence Berkeley National Laboratory, U.S. industrial and commercial motor system market assessment report, Volume 1: characteristics of the installed base, January 2021, Page 9, permalink: https://escholarship.org/uc/item/16x3d348

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