In the three stores where Metro Wumart China is running a transcritical CO2 system, the energy performance of the systems is “on target,” with one “far better than others,” said Alan Lin, the retailer’s Head of Facility Management, adding, “The operation is smooth and safe.”

However, Metro Wumart – which has since October 2019 been 20% owned by German retailer Metro AG and 80% owned by Chinese retailer Wumart – has no plans currently to install transcritical systems at other stores,” Lin said.

Original owner Metro AG  installed the first transcritical system at a new store in Beijing in January 2018, and then two others at existing stores in Beijing and Chongqing in June 2019. The two Beijing transcritical systems employ parallel compression while the Chongqing system uses an ejector; both the parallel compression and ejector technologies are thought to be firsts for China.

Metro Wumart’s Chongqing store is located in the Nan’an district and originally opened in 2001. The store’s sales area is 8,597m2 (92,537ft2) The store’s transcritical CO2 system, provided by Carrier, replaced an existing R22 system. “Due to the high temperature of Chongqing in the summer, we chose to use the ejector system as a solution for this store,” said Metro AG in 2019. Energy savings compared to the previous system were estimated to be 25%. Emissions were expected to be reduced by around 917 metric tons of CO2e per year.

The Chongqing store’s system has a low-temperature cooling capacity of around 140kW (39.8TR) and a medium-temperature cooling capacity of around 350kW (99.5TR). The CO2 gas coolers and evaporators are from Güntner, the controls from Danfoss and the refrigerated cabinets from Haier Carrier, which also handled installation. In addition, the CO2 system employs heat reclaim to provide hot water.

Second parallel compression store

Metro Wumart’s second Beijing store with transcritical CO2 refrigeration, called the Beijing Shilihe store, opened in 2006. The two-story building has a sales area of 6,587m2 (70,902ft2). The store’s transcritical CO2 system, provided by Italian refrigeration supplier Crea, also replaced an existing R22 system.

The system, which employs parallel compression, was estimated to save 25% in energy consumption. Emissions were expected to be reduced by 830 metric tons of CO2e per year.

The system has a total low-temperature cooling capacity of around 100kW (28.4TR) and a medium-temperature cooling capacity of around 130kW (37TR). In addition, the system provides around 220kW (62.6TR) of high temperature cooling for a prep room and sales area.

The CO2 gas coolers are from Modine, evaporators from Güntner, controls from Carel, and refrigerated cabinets from Panasonic. Shanghai-based installation contractor Shanghai Qingneng Cool Chain Equipment & Engineering, which partners with Crea, handled installation.

SCM Frigo installed the transcritical CO2 system in Metro Wumart’s first transcritical store in Beijing, also a first for SCM Frigo in China. The system comprises two indoor racks, both with parallel compression and two remote air-cooled gas coolers. Refrigerating capacities are approximately 275kW (78.2TR) for medium temperature and 93kW (26.4TR) for low temperature.

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