“We follow only one road: we are installing natural refrigerants in all countries where it is technically possible,” said Olaf Schulze, director (Energy and Management) of METRO AG. “Therefore, we invite our international partners, from the suppliers, from the industry, to follow us, to support us and challenge us, in order to bring the new technology to the market,” he said, emphasising the Düsseldorf-based retailer’s goal to forge partnerships all over the world.
Clear commitment to natural refrigerants
Present in 2,000 locations and 29 countries, METRO has been recognised globally as an environmental leader with Schulze overseeing the company’s switch from f-gases to natural refrigerants. Under his leadership the company has equipped 39 stores with CO2 transcritical systems and 47 stores with CO2 subcritical systems. In 2016, it plans to equip 53 additional stores with natural refrigerants.
“We have a clear internal commitment,” Schulze explained. “In all of our existing and new stores, where it’s technically possible, we will only install natural refrigerants. We started this process in 2008 and have clear planning until 2030.”
By 2025, Schulze estimates that METRO will have stopped using f-gases in around 90% of its stores. According to him, the company is on track to open, on average, 50 natural refrigerant stores every year, globally. In China, METRO plans to equip 12 stores in 2016.
With refrigeration responsible for more than 20% of the company’s greenhouse gas emissions, METRO was eager to find a way to reduce this negative environmental impact. Its climate strategy, published in 2011, aims to reduce the group’s carbon impact by 20% by 2020. During the COP21 climate conference in Paris, METRO’s targets were adjusted, with plans to reduce the company’s carbon impact by 50% by 2030.
At an estimated €800 million, METRO’s F-Gas Exit Programme (introduced in July 2013) ranks among the METRO Group’s biggest investment plans.
Reducing total cost of ownership with heat reclaim
Ian Crookston, manager for energy management at Sobeys, a Canadian grocery retailer, explained that in the case of CO2, using heat reclaim, parallel compression, ejectors or three-level systems are some of the possibilities at hand to reduce total costs. Sobeys started installing CO2 transcritical systems in 2009, and is now using CO2 transcritical centralised booster system with heat reclaim.
“CO2 as a natural refrigerant has a number of thermodynamic advantages over typical synthetic refrigerants,” explained Crookston. “The system’s heat reclaim can be used for the HVAC purposes (heating, ventilating and air conditioning), and for heating domestic hot water, of which large quantities are required for cleaning in-store food production equipment.”
Crookston said Sobeys took advantage of CO2’s gliding temperature and high efficiencies to heat water up to 85 degrees Celsius before blending with cold water to ensure a final outlet temperature of 45 degrees Celsius.
Heat reclaim attractive with CO2 systems
In a CO2 transcritical booster system, there is no correlation between low temperature compressor power and outdoor ambient temperature. However, there is a strong correlation between outdoor ambient temperature and the power consumed by the medium temperature compressor. When outdoor ambient temperature rises, the coefficient of performance drops. “For a given outdoor ambient temperature, the discharge temperature of the high pressure compressor increases, and is higher for a CO2 system than a system running a synthetic refrigerant. This is one of the reasons why heat reclaim is so attractive with CO2 systems,” Crookston explained.
He added that in order make a data-driven decision on heat reclaim, the end user needs to take into account a number of things, such as heating requirements, legal requirements, regional costs and component efficiencies. “If waste heat is available, [using it] makes sense. If it’s not available, we must make the decision on relative costs,” he concluded.
Depending on relative energy costs, Crookston presented the company’s energy savings in different regions. Where waste was available, the annual net savings were positive (Ontario: CAN$ 1,870, Nova Scotia: CAN$ 4,937, and British Columbia: CAN$ 2,348).
“CO2 technology is rapidly evolving, and many new improvements continue to come to market. These are exciting times to be in the refrigeration [business].”