Using a CO2 cooling system reduced this organic grocery store’s refrigerant use by 60% to 65% a year.


Arizona-based Sprouts Farmers Market is not only a leader in natural and organic foods, but the mid-sized regional grocery chain also is setting the industry benchmark for being an environmentally conscious neighbor and grocer. As part of that effort, Sprouts joined the EPA‘s GreenChill partnership in May 2010. Since then, eight Sprouts stores have earned GreenChill Store Awards.

In late 2010, Sprouts raised the bar again when it set out to meet the EPA‘s most stringent GreenChill standards with construction of its store in Thousand Oaks, CA. Sprouts tapped Hill Phoenix to design a system that not only would be environmentally friendly, but also energy efficient and cost effective to install and maintain.

“We challenged Hill Phoenix to come up with a design that would reduce our use of refrigerants by an amount that would allow us to meet GreenChill Platinum standards,” said Jerry Stutler, vice president, construction and facility engineering for Sprouts Farmers Market. “We felt that Hill Phoenix was more advanced in the engineering and manufacturing of CO2 systems than any other manufacturer in the market today.”

In April 2011, Hill Phoenix completed the installation of an innovative new refrigeration system that earned Sprouts one of only three GreenChill Platinum Awards in the nation.

THE CHALLENGE: REDUCE HFC EMISSIONS, CONTROL COST

“Before we got involved with GreenChill, we were averaging about 2,000 pounds of refrigerant in our systems. Then we reduced that by about 60% to 65% with our stores that are GreenChill Gold certified. This new CO2 design yields an even more significant reduction in HFCs,” Stutler said. “The main goal at Thousand Oaks was to reduce the risk of leaking harmful HFC into the atmosphere, and secondly, to reduce the cost of our initial refrigeration charge. And finally, we wanted to reduce our potential exposure to costly catastrophic leaks in our systems,” he added.

According to GreenChill, most of the 35,000-plus supermarkets in the United States use centralized direct expansion (DX) systems to chill their products. Typically, these refrigeration systems are charged with 3,000 to 4,000 pounds of refrigerant and can leak more than 20% of their charge each year.

GreenChill Platinum Award certification requires the use of only non-ozone depleting refrigerants. In addition, the store must achieve an average HFC refrigerant charge of no more than 0.5 pounds of refrigerant per 1,000 Btuh total evaporator cooling load and a storewide annual refrigerant emissions rate of no more than 5%. 

KEY CONDENSERS

In collaboration with Sprouts’ construction and facilities engineering team, Hill Phoenix designed and manufactured an innovative new answer featuring a full CO2 cascade system for both low-temperature and medium-temperature applications the Second Nature MT2LX.

The Hill Phoenix cascade systems consist of two independent refrigeration systems that share a common cascade heat exchanger. The upper-cascade system is a reduced charge HFC system that cools the CO2 in the lower-cascade. The HFC system rejects heat to ambient through the condenser, in this case an air-cooled, microchannel condenser.

“It was really important that we were able to utilize air cooled condensers. Nobody in the industry really thought that you could earn a Platinum Certification with air cooled condensers,” said Tom Kilroy, inside sales engineer with Hill Phoenix Systems division. “Otherwise, you would need a separate condensing loop, pumping station, and an expensive fluid cooler on the roof.”

The Second Nature MT2LX design combines two of Hill Phoenix’s systems into one energy-efficient, environmentally friendly, unified system that is designed, manufactured, and installed specifically to meet the GreenChill Platinum requirements that Sprouts set for its new Thousand Oaks store. The newly designed system consists of a low temperature CO2 cascade compressor system combined with a medium temperature CO2 secondary coolant system.

“Hill PHOENIX’s project with fellow GreenChill Partner Sprouts is a perfect example of what companies can do when they take the ‘GreenChill spirit’ and push the boundaries of the achievable,” said Keilly Witman, manager of EPA’s GreenChill Partnership. “This store represents many firsts: the first CO2 cascade system to achieve platinum; and the first platinum store west of the Mississippi.”

“It‘s tough to put a dollar value on the potential payback for this investment. If we had a catastrophic leak in our old system, we could have leaked 2,000 pounds of refrigerant. Multiply that by $10 per pound to recharge the system. With today‘s system, we only have the potential to leak 235 pounds of refrigerant,” said Stutler. “Certainly we‘re hoping to save money over the years, but how do you put a dollar amount on the value of being green, reducing your carbon footprint and improving the overall system performance?” ES