Forooza Samadi, assistant director of the Alabama Industrial Training and Assessment Center and assistant professor of mechanical engineering at the University of Alabama in Tuscaloosa, recently studied ways factories could cut costs and carbon emissions. She was coauthor on the paper, “Strategic Evaluation of Sustainable Practices for HVAC Systems in Small- and Medium-Sized U.S. Manufacturers,” published in the ASME Journal of Engineering for Sustainable Buildings and Cities in August 2024. Here, she described some of her findings.
Industries are so varied that their energy usage and carbon emissions tend to be difficult to reduce. Can you put some of this into context for us?
Industries range widely, from food processing and pharmaceutical to lumber mills or advanced semiconductor fabrication. Each of them has unique energy needs and challenges, and the energy usage patterns may even vary for one industry depending on the climate zone. Even for one plant, there may be different patterns depending on production lines with different customer demands. There isn't a way to make one rule that can be applied to all of them, and some of them are really challenging to electrify or decarbonize. But sometimes a small change in, say, HVAC or the compressed air system or motors can yield substantial benefit and cut energy use by 10 to 15 percent.
I was surprised when I found out about the considerable effect of HVAC usage on the total energy consumption of industries. It's higher than 40 percent. Sometimes there are specific needs, such as maintaining part of the plant at a specific temperature or humidity, for, say, food industries or even for workers’ comfort or safety. But there are many cases where some improvement can be applied. Naturally, when you walk through a plant, you see big machines, motors, air compressors, but not necessarily HVAC units.
What are the most common kinds of recommendations provided by industrial training and assessment centers, and do manufacturers actually adopt them when they're when they are given those recommendations?
Industrial training and assessment centers try not to recommend anything that interferes with the operations. Our common recommendations are on comprehensive systems: HVAC systems, chillers, motors, renewable energy sources. Compressed air pressure and leak reduction are the two most common recommendations on compressed air systems, as compressed air is expensive to produce. Applying recommendations in those systems is easy, and the savings can be significant.
For example, regarding pressure systems in the 100 psi range, every 2 psi reduction in discharge pressure results in 1 percent reduction in energy consumption. Many facilities really don't need pressures higher than 95 or 100 psi. However, they are reluctant about applying the recommendation because of the potential complaints from the workers. So we encourage them to reduce the pressure step by step, 1 to 2 psi each time and stop it whenever they receive negative feedback. Even with a 1 or 2 psi reduction, you can get some savings and the payback is immediate, because it's just one person changing the set point.
The other thing is paying attention to the age of HVAC units. There is a graph in our paper that shows how HVAC units degrade; After 20 years, they need to be changed because the coefficient of performance drops considerably.
There's a considerable expense in buying a whole new HVAC system. Is there some barrier to that for small and medium manufacturers?
Yes, they prefer to focus on the production needs and customer needs. So yeah, sometimes that is not feasible to apply these recommendations. But while the implementation cost may be high, there is usually a good payback.
There are lots of potential changes manufacturers could make. If every factory owner made their equipment as efficient as possible, how much of a difference would it make?
The difference is huge. The numbers I have are based on the industrial training assessment centers website and come from energy assessments performed on more than 20,000 small and medium sized manufacturing facilities. The data shows a substantial potential for reducing energy consumption, resulting in the annual energy cost savings of around $700 million per year and more than 8 million metric tons of reduction in carbon dioxide emissions per year. All these improvements applied to HVAC systems.
Jeffrey Winters is editor in chief of Mechanical Engineering magazine.
