German food wholesale specialist METRO AG is one of the leading users of natural refrigerants in the world, with about 100 stores running transcritical CO2 systems. One of those transcritical CO2 stores, located in St. Pölten, lower Austria, has the further distinction of being METROs first “net-zero” store, with a goal of using only renewable energy created on site with a 6,000m2 (64,583ft2) photovoltaic system on the roof.
Opened in 2017, the 12,700m2 (136,702ft2) St. Pölten store is part of the company’s ambitious plan to reduce its CO2 emissions by 50% in 2030 as compared to 2011 levels. As the store’s energy profile is refined, it will be used as a model for optimizing efficiency in new stores, especially in Europe.
“New [METRO] stores opening today have to be much more competitive in terms of energy demand to reach our 2030 targets,” explained Olaf Schulze, Director Energy Management at METRO AG, during ATMOsphere Europe in Warsaw, Poland, on October 16.
St. Pölten is designed to realize a 60% reduction in energy demand as compared to the METRO worldwide average. Because of the time needed to optimize systems and the extreme temperatures of the past two summers, this figure hasn’t been realized yet, but Schulze said the store is well on track to achieving the designed efficiencies.
Already the store is being recognized. In 2018, it received the German EHI Energy Management Award for its dramatic energy reduction. It has also achieved “outstanding” certification from BREEAM, an evaluation system for the ecological and socio-cultural sustain- ability of buildings.
Efficient Transcritical System
The St. Pölten store is equipped with a transcritical CO2 booster system supplied by German OEM Teko, with a number of features designed to boost efficiency. Andreas Meier, Managing Director for Teko, was also at ATMOsphere Europe to present alongside Schulze on the particulars of the refrigeration system his company supplied.
The refrigeration rack offers 290kW (82.5TR) on the medium-temperature side and 93kW (26.4TR) on the low-temperature side, as well as full heat recovery (160kW/45.5TR) used to heat domestic hot water in the building. It also includes an Evalift suction heat-exchanger system to improve system efficiency, as well as parallel compression. Most of the building is cooled by natural ventilation, with 12kW (3.4TR) of air conditioning for the sales area also being supplied by the refrigeration rack.
Thanks to these features, the St. Pölten store’s transcritical system is 20% more efficient than a standard transcritical CO2 system, said Schulze. He expects the return of investment in the premium paid over a standard system to be less than five years.
Other energy-saving initiatives include capturing and using rainwater; using glass fronts to capitalize on natural light; adding doors to the cooling cabinets; and using “smart cooling” techniques to make sure products are kept at the right temperature and energy isn’t wasted.
This article originally appeared in the November-December 2019 issue of Accelerate Magazine.