Dennree relies on ammonia chillers to cool organic food
Refrigeration technology keeps food fresh and preserves vitamins
Whole food specialist Dennree is a well-known wholesaler for organic food and natural cosmetics in central Europe. Founded in 1974, Dennree currently has a workforce of 5,500 employees. A few years ago, Dennree purchased a former warehouse from a discount food retailer in Töpen, Germany, and converted it into a four-bay hall with separate cooling sections. This is where eco-friendly GEA technology is used to refrigerate dairy and meat products, fruit and vegetables awaiting distribution to organic markets.
Sustainable and time flexible
Three new cold storage facilities built in the existing 21,000 sqm warehouse are used to store dairy products and fresh produce at 6°C, apples at 4°C, tomatoes and cucumbers at 10 to 12°C, bananas at 14.5°C and potatoes and root vegetables at 7°C in a light-free space. The fourth bay covering 4,000 sqm for meat and sausage products and the machine room were added to the existing building. Longevity along with high availability and maximum energy efficiency were top priorities for the warehouse project. These factors made flexible, energy-saving and eco-friendly refrigeration technology indispensable.
Cooling concept with natural refrigerants
Three identical GEA BluAstrum chillers are the key components of the new refrigeration system. These machines operate with ammonia, a natural, eco-friendly refrigerant (R717), and provide up to 2400 kW of cooling capacity for cold storage in the warehouse. The energy reaches the cold stores through a brine (Hycool) circuit. With a volume of 55m³, the brine mass serves as a temperature buffer that prevents frequent start-stop cycles of the compressors, which helps extend their life cycle. The flow temperature of the brine is -3°C; the return temperature +2°C. This maintains the stored food products, including fresh produce, at the ideal temperatures and keeps them fresh for a long time. A separate propane refrigeration system provides the necessary 2°C storage temperature in the attached cold storage unit.
Powerful and energy-efficient – mission accomplished!
The ammonia cold water generators have been in operation since spring 2014. They have proven themselves at peak loads and high outdoor temperatures above 30°C in summer, as well as in the partial load range, where they operate with maximum efficiency. At the desired evaporation temperature of -6°C, the energy efficiency ratio (EER) of GEA chilled water generators is very good at 4.8. In partial load operation, the coefficient of performance increases to more than 8.0, depending on the load. Flexible and energy-saving partial load operation is possible thanks to state-of-the-art frequency converters that enable the screw compressor speed to be adapted to prevailing requirements and reduce energy consumption to a minimum.
Overview of the cooling system in the converted warehouse:
- 3 GEA BluAstrum 1000R, (ESEER approx. 8.0)
- Refrigerant in chiller: ammonia (R717, GWP = 0, ODP = 0)*
- Cold transport in buildings via a 3,500m brine network
- 6 speed-controlled 30 kW brine pumps
- 56 coolers each with 4 to 80 kW cooling capacity
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