Hot and cold

Keeping the store at the optimal temperature is a seemingly never-ending battle for grocers. Cus­tomers, lights and the motors powering the cases, ovens and other equipment generate heat, while open refrigerated cases and the opening of freezer doors cool things down.

If not managed correctly, the HVAC system can be a major drain on the energy budget and not so much of a draw for shoppers. No grocer wants people scurrying past the freezer cases because they are too chilly or skipping the pet aisle because they’re wilting from the heat.

With fewer new stores being built, grocers are focusing on upgrading the equipment in existing stores to be more efficient, according to industry observers. Grocers are upgrading some of the components of their HVAC systems with more efficient drives in some instances or installing more automated controls to keep the store climate comfortable while keeping tabs on costs.

Phoenix-based Sprouts Farmers Market, for example, has equipped each store with variable speed drives on air handlers that include condensers and energy management systems on all the HVAC and refrigeration systems. This is part of the retailer’s participation in the U.S. Environmental Protection Agency’s GreenChill Advanced Refrigeration Partnership.

“In grocery, the HVAC system is a major expense in terms of energy costs and maintenance, along with lighting and refrigeration,” says Bill Conrad, account manager for Minneapolis-based Xcel Energy, an energy provider that operates in Colorado, Michigan, Minnesota, New Mexico, North Dakota, South Dakota, Texas and Wisconsin.

While some newer stores are making modifications to moderate store temperatures—such as putting doors on refrigerated cases—it is more difficult to retrofit existing stores. “It is very expensive to take 40 feet of open cases and put doors on them and the payback could take a long time,” Conrad says. “Then there is the challenge of convincing the marketers that the doors you’re putting on the cases to save on heating costs won’t impact sales.”

He says that grocers are implementing new technologies such as variable speed drives and automated controls to make their HVAC systems more efficient. “While it is easier to build energy efficient systems when you’re building from the ground up, energy management systems are helping grocers make the most of the systems in existing stores,” he says. “Automated temperature controls, for example, can help grocers gain efficiencies by adjusting the temperatures during unoccupied times.”

Kathy Loftus, global leader, sustainable engineering, maintenance and energy management for Austin, Texas-based Whole Foods, says it is important to regularly evaluate HVAC and other systems to ensure optimal performance. The retailer works with equipment manufacturers, energy provider Xcel Energy and other sources to identify areas of potential savings.

“For example, submetering on our energy systems helps us to pinpoint where things may not be working as efficiently as they could be,” she says. “We’ve also become more aggressive on our temperature and humidity setpoints and we’ve installed air circulating devices that help us save on heating and cooling.”

Loftus notes that many supermarkets have relied on air-cooled rooftops systems for heating and air conditioning, which may not always be the best approach unless they have highest Seasonal Energy Efficiency Ratings.

Even then, it’s important to take advantage of water-cooled chillers and combined heating and power systems that reclaim waste heat for absorption chillers for mechanical sub-cooling,” she says. “We’ve combined some of our cooling and refrigeration equipment to improve efficiency.”

It is important for engineers, manufacturers, retailers and energy suppliers to work together to brainstorm and perform field tests to gain efficiencies, she says. “Working together to address big energy and building issues is important and the U.S. Department of Energy’s Retail Energy Alliance is a valuable resource,” Loftus says. “Another big key to this is the support of utilities. Without the support of the utility providers, the payback [for energy-efficient systems] may be longer than some retailers can handle.”
 

VARYING THE SPEED
Most HVAC systems are designed to withstand the demands of heating the store on the coldest days and keeping things cool during a heat wave. But since extreme temperatures are not the norm, variable speed drives are helping to keep operating costs down when demand is not at peak.

“Most air handlers are designed to meet the needs of the most extreme temperatures, but they can operate at less than 100% capacity on the other days of the year,” says Ivan Spronk, product line manager for AC drives at Schneider Electric, based in Palatine, Ill. “If your store is in Miami, you will be pushing the cooling system at maximum on the ten hottest days of the year, and if your store is in New York, you max out your heating capacity on the ten coldest days of the year, but there are a lot of days in between.”

A variable speed drive is “more intelligent than an on/off switch,” he says. The speed of the motor is automatically adjusted to meet demand, he explains.

While running the HVAC system at full capacity only when needed saves on energy, there is also less wear and tear on the system. “There are a lot of other benefits to variable speed drive solutions, including prolonging the life of the equipment and reducing the noise levels in the store,” says Hua Zhang, HVAC segment manager for Schneider Electric.

Spronk says as retailers add smaller formats, HVAC systems are being adjusted to meet changing needs. “If you look at the typical store today, it is not a big supercenter with rooftop units,” he says. “What we’re seeing is more corner-store type stores with 75,000 square feet to 100,000 square feet, and the HVAC needs of stores that size are quite different.” 

The expansion of prepared foods in some stores is also resulting in changes to the design of HVAC systems. “Retailers are putting more cooking and baking equipment in the stores as they offer more prepared foods, and this has an impact on the HVAC system as the more equipment you put in the store the more heat that is generated.”

HVAC systems are also being designed with the climate of the region in mind, he says. “If you have a store in the South, obviously the system is more focused on cooling than heating and adjustments can be made to optimize the system based on the location,” he says. “It is no longer a one-size-fits-all approach.”

While HVAC equipment is becoming more energy efficient, there are still problems that can crop up to cause the system to sap more resources. For that reason, retailers are beginning to tap into energy management systems to monitor the performance of their HVAC systems.

“We’re seeing grocers become very focused on using facility management systems to be able to more efficiently manage their costs from an enterprise perspective, and HVAC systems are certainly a part of that trend,” says Matt Lauck, director of marketing for St. Louis-based Emerson Climate Technologies’ retail solutions division.

“Retailers want to examine trends in maintenance, energy usage and temperature maintenance, among other issues,” he says. “Once they gain greater visibility into the performance of their HVAC and other systems, they can become more proactive in how they manage these systems.”

While he says that equipment in new stores is generally more efficient, the HVAC systems have to be fine-tuned to handle the increased amount of cooking equipment and temperature-controlled cases, among other things. “While the equipment is more efficient in new construction overall, there is more of it and there are more products and customers, which all have an impact on the HVAC system.”

RECLAIMING HEAT
Since so much heat is generated by in-store equipment, it makes sense to try to capture and re-use it.

The Q-Pump, a non-reversing heat pump from Germantown, Wis.-based Desert Aire, can heat outdoor winter air without the need for auxiliary heat, according to company officials. “It is another piece of equipment in our arsenal that enables us to extract the energy of the refrigeration on the heat side for a more efficient way of doing heat reclamation,” says Dusty Jackson, national accounts manager for supermarkets.

Humidity control is another factor in maintaining the proper store temperature, Jackson says. He says Desert Aire’s TotalAire MSP series uses energy-efficient dehumidification technologies to provide the make-up air and moisture control required in supermarkets. “Too much or too little moisture in the store throws everything off, making the equipment run inefficiently and potentially making it uncomfortable for shoppers.”

Supermarkets and equipment manufacturers have also been working on more efficient systems for mixing the air in the store.

“We’re evaluating ways to provide a better air mix,” says Scott Jack, vice president of Henderson Engineers, Inc., based in Lenexa, Kan. The company has worked with a number of grocers and retailers, include Hy-Vee, Wild Oats, Price Chopper and Wal-Mart. “As we all know, hot air rises and the cooler air stays around the floor.”

REDUCING REFRIGERANT
Retailers and manufacturers are also exploring ways to reduce the amount of refrigerant in cooling systems. “There has been a big push to try to use water as a means of heat rejection,” Jack says.

Because HVAC systems are so critical to store operations, he suggests that retailers establish a test site when they make any modifications.

“The grocery store has to be a temperature-neutral place, or shoppers won’t stick around,” he says. “Grocers have to evaluate the trends in making these systems more efficient versus the costs and the impact on the overall shopping experience.”  

This entry was posted in Equipment, Design & Operations. Bookmark the permalink.