A MENY supermarket in Fredericia, Denmark, has reduced its annual heating bill by 89.7% and its carbon emissions by 6.7 metric tons of CO2e through the recovery of waste heat from its CO2 (R744) refrigeration system with the help of a Danfoss Heat Recovery Unit (HRU). 

The supermarket uses the excess heat for space heating and hot water production.

During the first year of operation, the HRU provided 82% of the supermarket’s heating requirements, with additional heat coming from the district heating network during cold months, according to a presentation by Danfoss at the ATMO World Summit on March 30. The 24-hour online conference was organized by ATMOsphere (formerly shecco), publisher of R744.com.

Prior to installing the HRU, the 1,900m2 (20,450ft2) supermarket used 150MWh (42,640TRh) of heat a year. After working with Danfoss to optimize its heating system, the store’s heating demand was reduced by 79MWh (22,463TRh), and the installation of the HRU reduced it by a further 56MWh (15,923TRh).

“There were no big surprises in terms of energy savings,” said Morten Birkebæk, store manager at MENY’s Fredericia supermarket. “We are very close to the savings that the installer and Danfoss calculated in their proposal. In fact, we saved more in year one than we thought we would. That we could also save so much CO2₂e is really a plus.”

This HRU is one of 115 that Danfoss has installed across Europe, 93 of which are located in Denmark. Others can be found in Finland, Germany, Lithuania, Norway, Germany, and Sweden and Finland.

Danfoss’s Heat Recovery Unit

“In the past, heat recovery in the supermarket was not common,” said Dawid Lawreszuk, Project Manager of the HRU at Danfoss. “All heat generated by the cooling pack was dissipated to the atmosphere, at the same time heat was needed for space heating or domestic hot water preparation.”

According to Lawreszuk, some solutions existed, but there was little consistency in construction and installation, which lead to inefficiencies. However, Danfoss’s HRU “resolves all of those issues,” he stated during the ATMO World Summit session.

The HRU is a prefabricated solution that is easy to install, and standardizes heat recovery across a supermarket’s network of properties, according to Lawreszuk’s presentation. It can collect all available heat from a supermarket’s refrigeration system, and it allows for surplus heat to be sold to the district heating network.

There are six standard layouts based on the size and needs of the supermarket. Danfoss’s HRU portfolio can cover heating demand from 22kW (6.3TR) to 540kW (154TR), with possible heat recovery between 100kW (28TR) and 400kW (114TR). 

Danfoss presentation at ATMO World Summit

For stores up to 1,500m2 (16,145ft2), Danfoss recommends its one-tank system solution. For medium and large stores, it recommends its two-tank system solution to allow for more heat storage. Both solutions can have direct or indirect connection to external heat sources, and the two-tank system solution offers additional options to allow for heat resale.

According to Lawreszuk, achieving the best results requires the heating system to be optimized first, and for the correct design parameters to be chosen. The latter can be done using Danfoss’s CoolSelector2 software.

The maximum payback period of the company’s HRU is 24 months, but when surplus heat is sold to the district heating utility, costs can be recouped after 18 months. Over the course of 10 years, the HRU can generate around €62,000 ($66,473) in savings if the primary heat source is district heating. An additional €23,000 ($24,659) can be made with heat resale. 

Heat Recovery with alternative refrigerants

While Danfoss’s HRU is designed to recover waste heat from CO2 (R744) refrigeration systems, it can also work with systems that use other refrigerants, like ammonia/NH3 (R717), according to Mark Sever, Global Application Expert Food Retail at Danfoss. This would simply require a different plate heat exchanger.

“We saved more in year one than we thought we would.”

Morten Birkebæk, MENY

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