Transcritical CO₂ System Fits ‘Biodynamic’ German Farm Shop

A farm shop in Dottenfelderhof, southwest Germany, has chosen Teko’s ROXSTAsmart Integral, an integrated transcritical CO₂ (R744) refrigeration, air conditioning and heating solution, for a replacement building – and high-quality products.

The Dottenfelderhof farm shop has sold “biodynamic” food products – based on ethical, holistic and ecological farming practices – since 1968. Sustainability and environmental concerns were therefore a given when it came to choosing a new refrigeration system for its new building. The shop is located on an estate – where the food is grown – that can trace its roots to the year 976. 

“An ecological approach is completely embraced here, which fits perfectly with the current refrigerant situation, of course,” said Frank Redda, Managing Director of RS Kälte-Klima GmbH, which installed the system. “Right from the beginning, it was clear that only a holistic solution using the natural refrigerant CO₂ could be considered here.”

The new building feature an 800m² (8,611ft²) sales area, plus 700m² (7,535ft²) storage areas, offices, car park and social rooms. The shop receives around 400 customers a day, and the farm has 100 residents and 150 employees.

The estate produces fruits, vegetables, dairy products and baked goods. It keeps its own livestock on site, but also sells products from other biodynamic (Demeter certified) farmers in the area. The premises opened on May 28, 2020.

The refrigeration system is not the only sustainable solution on the estate. The new building is mainly made of wood, designed to meet low-energy standards, while the high quantity of glass in the walls and roof allow for plenty of natural light. Most of the electricity used comes from the farm’s own combined heat and power plant.

The total cost of the system has not been disclosed, but the Dottenfelderhof project has been partly subsidized by ecogreen Energie, a company specializing in energy efficiency projects. ecogreen provided funding for around 10% of the investment costs.

“Our aim is to provide companies with quick and easy access to funding,” said Marcel Riethmüller, Managing Director of ecogreen. “We were able to achieve this together with our partner companies [TEKO and RS Kälte-Klima] thanks to excellent cooperation.”

Why this solution?

As to why he, and his customer, chose a Teko solution for this project, Redda explained that his company has long experience working with Teko’s solutions, and cited the “simple handling, but extensive and sophisticated features,” of ROXSTAsmart as benefits.

Other deciding factors were the ability to ensure correct storage temperatures for the high-quality products, lowest possible dehumidification of goods, and “gentle” defrosting cycles for the cabinets. To achieve this, the farm shop chose the Frigolink control solution from German component maker Wurm Elektronische Systeme. The Frigolink also controls the heating, AC and ventilation.

“An important aspect is related to quality assurance requirements,” Redda explained. “Wurm Systems offers customized solutions for all areas of interest.”

The farm shop also opted for Wurm’s Frigodata XP analysis tool and FRIDA app. Using the FRIDA app, service technicians can operate the system via their smartphone or tablet. By means of internet-based and VPN-encrypted remote data transmission, appropriately authorized personnel have remote access to the system, enabling direct intervention without having to travel to the site.

The system is also equipped with Wurm’s Meteolink module, enabling anticipatory control of heating and AC for upcoming weather.

Commissioning of the system went as planned, and was completed in “just one day,” Redda said. “Since we already had good experiences with a comparable TEKO unit in another organic shop, we did not expect anything else.”

The ROXSTAsmart was installed indoors, in a central machine room, reducing noise levels. A buffer storage tank and feed pump for the cooling circuits is located in the same room.

22 cooling points

The new integrated system has a medium temperature capacity of 47kW (13.4TR), with 45kW (12.8TR) for air conditioning, and 70kW (238 KBTU/hr) for heating. It serves an area of 1,500m² (16,146ft²), and includes a total of 22 cooling points.

The system is equipped with Frascold compressors, a controlled suction-gas heat exchanger, and a combined gas cooler and heat pump evaporator with three EC fans from Whiteline. It also has 10 Whiteline R744 wedge coolers.

The combined gas cooler and heat pump evaporator has a bypass switch, to enable maximum heat recovery in the winter. The heat pump evaporator is also used if the outside temperature falls further below the set temperature, according to Teko’s website. With these measures, a total of 70kW of heating output is achieved.

An additional benefit of combining the gas cooler and heat pump evaporator is a reduced footprint and reduced noise. The noise emissions are only 30dB(A) at a distance of 10m (33ft). Waste heat from the gas cooler is also used to defrost the heat pump package “efficiently and economically, without additional electrical heating,” TEKO said.

The heat recovery system is able to provide 90 to 95% of the required heat output. In winter, when the recovered heat isn’t sufficient, an additional heat pump is switched on to cover the remaining 5-10%. Via an intermediate pumped circuit, the heating is transferred to a 500l (132gal) storage tank and distributed from there via ceiling air units to the required points in the store.

The temperature control is managed by hydraulic balancing of each heat exchanger, a fully automated process utilizing calculation algorithms. This building services system was provided by Kratschmayer Luft-Wärme-Klima GmbH.