Danfoss heat recovery unit can reduce heating costs and CO2 emissions

Using waste heat from its refrigeration system, a busy Danish supermarket reduced its annual heating bill by 89.7 percent and its CO2 footprint by 6.7 tonnes per year.

Instead of simply letting the heat dissipate, as most supermarkets still do, a Danfoss Heat Recovery Unit (HRU) recycles it to heat the store’s 1,900 m2 and provide plenty of hot tap water all year. According to store manager Morten Birkebaek, the best part is that none of his 55 employees noticed anything during installation or the first year of operation.

The challenge: Recycle waste heat from a CO₂refrigeration system without interfering with operations 

Everyone who has ever been near the business end of a refrigerator or air conditioner knows that keeping things cool generates heat. The amount of waste heat in a home is minimal. In a modern supermarket with aisles full of refrigerators and freezers, the heat is significant – enough to heat the entire supermarket and its hot water if properly recycled.According to Morten Birkebæk, store manager at MENY’s Fredericia supermarket in Denmark, making better use of waste heat was a winwin. “As a merchant responsible for the store’s bottom line, I’m, of course, interested in cutting unnecessary costs wherever possible,” he explains. “But if we can reduce our carbon footprint simultaneously and do it all in a hassle-free way for our customers and employees, then count me in.”

The solution: Turnkey installation of a Danfoss Heat Recovery Unit 

The business case for reusing heat from the store’s CO2 refrigeration system was obvious. “The calculations were straightforward,” Birkebaek recalls. “We knew how many kWh we needed to heat the store and provide hot water, and we knew how much we were paying the district heating company for that energy.” Danfoss and the installer, Dansk Varmegenvinding, proposed a turnkey solution that included everything: hardware, connections, installation, and a service agreement. We calculated the payback period for the investment with their assistance, which was favourable. My only concern was that the heat recovery unit’s installation and operation did not complicate my employees’ lives.”

The result: Annual energy savings of 89.7 percent and a CO2 reduction of 6.7 tons: all with no operational disruptions 

Birkebaek can now see exactly how much energy, money, and CO2 the store has saved after a full year of operation. MENY in Fredericia reduced its energy consumption by 135 MWh in total during the first year, with 56 MWh coming directly from the Danfoss Heat Recovery Unit (HRU) and 79 mWh coming from a year-long Danfoss EnergyTrim contract. Furthermore, the store reduced its carbon footprint by 6.7 tonnes CO2 , equivalent to driving worldwide.  

“There were no big surprises in energy savings”, he says. “We are very close to the savings the installer and Danfoss calculated in their proposal. We saved more in Year 1 than we thought we would. That we could also save so much, CO₂ is a plus.”

What surprised Birkebæk was how simple the installation and operation of the new heat recovery unit had been. “None of my 55 employees noticed anything. The installer came and set up the heat recovery unit and made sure it was running optimally, and it has ever since. We have all the hot water for cleaning and restrooms and all the heat we need year-round.”

According to the installer, Peter Thomsen, Manager at Dansk Varmegenvinding, MENY’s experience is an excellent example of what many supermarkets can expect. “We’ve installed 50 heat recovery units with an average payback period of 2.4 years. For this project, we proposed a heat recovery unit that best matched the store’s size and refrigeration system from the 83 versions available from Danfoss. While the MENY results are typical, it’s important to note that all installations vary in site size, electrical wiring, and piping. It’s also critical that the CO₂ refrigeration system works as energy and produces sufficient heat.”

In addition to the heat recovery unit’s installation’s simplicity, Birkebæk had one other surprise. In the middle of the first winter of operation, he received an unannounced visit from the district heating company that provided the store with heat. “They were sure that the meter that measures the district heating water flow was broken because they couldn’t see that we were drawing many kWh from the system. We could assure them that everything was working just fine.”