Senior Mechanical Engineer at Target, Erich Schwab, stated in the webinar that all of Target’s new stores will default to a hybrid cascade HFC/CO2 direct expansion (DX) system designs and that there will be at least two CO2 stores constructed in 2016. The company chose the hybrid as its standard” refrigeration system, which is designed to stay below transcritical threshold.
Target’s 5 natural refrigerant installations
Both pumped and DX systems have been tested at Target for over four years. Target’s first natural refrigerant store in St. Paul, Minnesota used pumped CO2. Learnings were applied to the second store in San Clemente, California, which trialed a DX CO2 system. The third hybrid store opened in Conyers, Georgia, aimed to test the performance of CO2 in southern climates; the fourth was built in Los Angeles in a smaller urban-format store; and the fifth, installed in March 2013 in Columbia, Missouri, was a replica of the Conyers design.
We believe that advancing CO2 technologies in supermarket refrigeration systems is absolutely viable. Which is why Target is changing its prototype for new stores from R404A to hybrid CO2 solutions,” said Schwab.
CO2: Target’s refrigerant of choice
Target’s experience with CO2 has proven to be an interesting journey,” Schwab notes. “Transcritical was considered, but non-standard construction and complex systems led to a different outcome and an energy penalty in warm locations when operating in the transcritical. A hybrid R134a/CO2 DX is the optimal solution for Target.”
The criteria of evaluation for what the best design was for Target moving forward was the total cost of ownership including: capital investment, energy use, uptime, maintenance/ repair costs, and overall carbon impact. To make CO2 a viable solution for Target, performance had to improve in 4 out of 5 of these categories.
I’m happy to report that Target has seen significant improvement in one of our focus areas, specifically energy,” said Schwab.
Energy usage for the hybrid CO2 DX systems installed in Conyers, compared to the first St. Paul installation using R404A on the high side, saw a reduction of nearly 10%. “On a percentage bases we expect a 65% reduction in total carbon impact with hybrid systems (due to lower HFCs and energy savings),” said Schwab.
Schwab anticipates costs to decrease in the future as these systems gain acceptance and noted that Target estimated at last year’s ATMOsphere America 2014 conference that hybrid systems account for an annual energy savings of 2000 USD.
Next steps: ‘Looking at ways to decrease GWP through all-natural solution’
We’re (Target) looking at ways to decrease GWP through an all natural solution using ammonia on the high-side,” said Schwab. “We’re very interested in some of the things going on in the industry right now with regards to that. We’re also continuing to monitor industry advancement with regards to CO2 transcritical in Europe and also looking at a R290 self- contained case solution for possible use in distributing systems.”
Tips for successfully running a CO2 refrigeration system:
- Make sure your service channel is capable of supporting low moisture and high purity CO2
- Store a charge on-site
- Store unique components on-site
- Administer preventative maintenance
Target’s Pfresh Supermarkets
During 2009, a new store prototype was developed for general merchandise stores. These stores, dubbed PFresh, include an array of perishable and frozen foods, meat, and dairy.
MORE INFORMATION
Source
GreenChill Webinar: Experiences with CO2 Cascade System Design
