|Tristan Coffin | Director of Sustainability & Facilities
Whole Foods Market’s Northern California Division
This blog is based on the recent E360 Webinar, “Pioneering Natural Refrigerants: A Grocery Case Study.”
Those who follow commercial refrigeration trends in the U.S. are probably aware of Whole Foods Market’s exploration of natural refrigerants. If there’s one thing that drives our unique approach to sustainable refrigeration, it’s a willingness to deploy new system architectures, both in centralized and stand-alone applications. In a recent E360 Webinar, I had the opportunity to discuss these natural refrigerant strategies in greater detail, in particular the R-290/CO2 cascade architecture deployed in our Santa Clara location and the wider adoption of self-contained, R-290 cases.
With sustainability goals of reducing refrigerant charges and environmental impacts, improving energy efficiencies and lowering our total equivalent warming impact (TEWI), Whole Foods Market has embraced natural refrigerants in 25 stores — 15 of which utilize entirely all-natural refrigeration systems (like Santa Clara). Of course, every refrigeration decision is based on the imperative of maintaining operational uptime, regardless of the choice in refrigerant or architecture.
Santa Clara: R-290/CO2 cascade case study
Whole Foods Market Santa Clara is an example of where we deployed a first-of-its-kind system architecture to achieve an all-natural, sustainable refrigeration solution. The centralized system features a state-of-the art, R-290/ CO2 cascade architecture with seven sealed R-290 chillers located on the rooftop. These chillers are each charged with 30–40 pounds of R-290 and are responsible for cooling the high-temperature CO2. The CO2 portion of the system is located within the mechanical space of the store itself.
To ensure system safety and comply with local authorities having jurisdiction (AHJ), the system was designed with extensive safety measures. Venting considerations are especially important when dealing with R-290, which is classified as a flammable A3 refrigerant. In the event of a leak (or purposeful venting), the rooftop chillers are mounted on 8-inch stands and an open base frame construction to elevate them off the roof level and allow gas to safely disperse.
The system also utilizes other measures to ensure pressure safeguards in the R-290 chillers, including compressor de-energization, system bypass and relief valves. In this particular installation, a flare stack was added months after the installation was completed, per the request of the local AHJ. This tied the high-pressure relief to smoke and heat sensors below the roof deck. Any detection of fire triggers the automatic release and flare of the R-290 charge.
In addition, the R-290 chillers have built-in leak detection to comply with Section 606 of the California Fire Code, including a system shutdown mechanism. With all these safety measures in place, it’s important to note that there have been zero leaks of R-290 to date.
This R-290/CO2 cascade system represents the application of R-290 in larger-charge systems. Not only is it an example of a successful Significant New Alternatives Policy (SNAP) test market application, it serves as both a good case study for us and a proving ground for our industry.
Self-contained, R-290 cases
The Santa Clara store also features the use of R-290 in self-contained cases, now present in more than 100 Whole Foods stores. We find these cases to be both aligned with our sustainability goals while also offering many benefits, including: very low refrigerant charge, very low leak rates, merchandising flexibility, reduced installation and maintenance costs, and energy savings from 30–50 percent over industry baseline averages. And, compared to R-404A’s global warming potential (GWP) of 3,800, R-290 has a GWP of 3.
As Whole Foods Market continues to explore the use of natural refrigerants, we find ourselves focusing less on a ‘one size fits all’ approach to solve some of the challenges in refrigeration. Instead, we consider different climate zones and building types as key factors to deploying best-fit solutions, as we continue to forge a path in long term sustainability.