Look to Set Points to Boost Efficiency

In a large facility, it goes without saying that increasing overall efficiency will save large amounts of money every year in operating cost. But that savings is often dependant on implementing, and following up on, several best practices in myriad different places throughout a system.

When margins are tight, there are many ways to increase overall efficiency, reaping energy gains without a capitol investment.

To figure out how to implement an energy savings plan without an investment, that will result in a meaningful impact on the bottom line, Keith Nienhaus, project manager at Hixon Architecture, Engineering, Interiors, recommends starting small: by taking a close look at system set points to find sustainable ways to get more out of your energy dollars.

Nienhaus’ recommendations, which are outlined below, were given during a recent webinar hosted by Food Engineering Magazine, entitled “Saving Energy Without a Capitol Investment.”

In any facility, energy comes in various forms and is used at different quantities, so the first step in finding potential savings is to figure out where any excess energy is being used.

According to a Hixon poll, the areas of steam process and refrigeration were the top areas where energy conservation opportunities were the greatest.

Within these areas, Nienhaus said, managers should prioritize the evaluation of set points, or system operating points, with the goal of identifying the minimum thresholds required for different utility systems, and running them no higher than absolutely necessary.

For compressed air, said Nienhaus, “the rule of thumb is that each two PSI reductions are going to give you about a one percent increase in your system efficiency.”

In the case of a steam system, in a dairy facility for example, that small savings can add up. Nienhaus cited one such facility that reduced steam system pressure by 20 PSI to save over $30,000 in one year, just by changing system set points.

For a refrigeration system, paying close attention to condensing temperature can lead to the biggest payoffs. The rule of thumb here is that decreasing ammonia refrigeration system condensing temperature by just one degree Fahrenheit, results in a one percent efficiency gain, said Nienhaus.

However, “if you’re trying to lower your condensing temperature and you can’t get it any lower than it already is, that could be due to a number of things.”

In that case, looking deeper may reveal other reasons for an inability to lower condensing temperature. “Maybe you have non-condensables in the system, scaling on your condenser coils, or a fan or pump that’s not operating and you didn’t realize it,” he said.

If non-condensables are found, that’s something that can easily be taken care of with an auto purger, a piece of equipment which is often overlooked.

“If you don’t have an auto purger, we strongly recommend adding one, and if you do, make sure it’s functioning,” said Nienhaus. “They tend to be one of those items that sits on a wall and everyone assumes it’s doing what supposed to do, but oftentimes we’ll be in a facility and we’ll take a look at it and see it hasn’t been functioning in years, so if you’ve got it, make sure it’s working.”

Another important refrigeration system operating point that deserves special attention is suction temperature. Raising the suction temperature just one degree Fahrenheit will yield a two percent increase in system efficiency, said Nienhaus.

He added that facilities should look at smart ways to accomplish that goal, for instance, by varying temperature according to off-production times.

“Even if you can’t raise that suction temperature year round due to the product you’re handling, you have non-production times – say weekend evenings or even holidays – that can be valuable windows for savings.”

In fact, any non-production times represent opportunities to raise the suction temperature and earn energy savings until a facility gets back into production. Here, “a refrigeration system can be a big energy hog, so again, that little percentage can add up to some big money.”

Nienhaus also pointed to hot water temperature and room air temperature as areas where monitoring set points can pay off.

“Again, with your hot water system, you should run it as low as possible,” he said, adding that although temperature thresholds are typically driven by sanitation requirements, facilities often run hotter than necessary.

And when it comes to cooling, “don’t keep rooms any colder than they need to be,” he said. “Typically process and production requirements drive temperature requirements, especially for rooms like freezers, coolers and production spaces. If you take a hard look at those room temperatures, you may find you can run at a slightly higher temperature than you have been for years, so take a hard look at those room temperatures.”

“Just because something has been running a certain way for years, that’s no reason not to question it,” he said. “Don’t let complacency stop you from looking for some easy energy savings.”