ROXSTAsmart integral at Dottenfelderhof – Sustainable CO₂ refrigeration for organic farming
For the new Dottenfelderhof farm shop, ROXSTA smart integral delivers an efficient CO₂ system for cooling, heating and climate control – combined with Wurm technology and funding support: sustainable, quiet and powerful.
Just 25 km from our headquarters in Altenstadt, on the outskirts of Bad Vilbel, lies Dottenfelderhof – a historic cultural landmark. First recorded in 976 as a monastic estate, it has been farmed since 1968 by the Dottenfelderhof cooperative using biodynamic Demeter principles.
From monastery estate to regional organic supplier
The evolution of Dottenfelderhof
Today, the farm operates on many levels: diverse agriculture, fruit and vegetable cultivation, livestock, an agricultural school, research, marketing, and a wide range of events. In the farm dairy, milk is crafted into award-winning cheeses and dairy products. Grain from the fields is baked into a variety of breads and pastries in the wood-fired bakery in the monastery garden. Together with freshly harvested fruit and vegetables, a wide organic range, and products from other regional Demeter farmers, these goods are sold in the farm shop and at local markets.
Farm sales are a cornerstone of Dottenfelderhof’s success. It began in 1973 with milk and bread sold from a converted cellar. Soon, garden and field produce were added. As the product range steadily expanded, more space was needed. In the 1980s, the community transformed a former cowshed into a farm shop and relocated part of the assortment into a separate store on the grounds. As the variety of goods continued to grow, it quickly became clear that another move would be unavoidable.
After years of planning, the development plan was finalized in early 2019. Things then moved quickly – on May 28, 2020, the new farm shop opened its doors. The sales area nearly doubled to almost 800 square meters, complemented by another 700 square meters for cold storage, warehouses, offices, staff rooms, and parking for market vehicles. The building was constructed right in front of the farm’s entrance, so the nearly 400 daily customers no longer need to drive onto the farm itself – with its narrow lanes once crowded with pedestrians, bicycles, strollers, cars, and delivery vehicles. Instead, they can park conveniently in the spacious lot at the new shop.
“The situation has been untangled,” says Peter Hollerbach, head of the farm shop. “Separating farming and retail is a real benefit, not least for the 100 residents of the farm and about 150 employees. Integrating storage and cooling facilities has also streamlined operations. With the new building, there’s no need for interim storage scattered across the farm – products go directly to counters, displays and shelves, or can be loaded straight into our market vehicles.”
The new building was designed not only to improve product presentation and streamline operations – ecological considerations were at the heart of the plan. Constructed primarily from wood, it meets low-energy building standards. Generous glass walls and skylights flood the space with natural light, greatly reducing the need for artificial lighting. Much of the electricity is supplied by the farm’s own combined heat and power plant, while waste heat from the refrigeration system is harnessed for climate control and hot water.
Comprehensive CO₂ refrigeration solution
ROXSTAsmart integral replaces outdated decentralized systems
The refrigeration installation was carried out by RS Kälte-Klima GmbH in Sulzbach/Saar. Managing Director Frank Redda explains: “We were delighted to take on the Dottenfelderhof project! Sustainability is a core value here – perfectly aligned with today’s refrigerant challenges. The farm is a pioneer in efficiency and environmental responsibility. From the outset, it was clear that only a holistic solution with natural CO₂ would be the right fit. We’ve been working closely with TEKO for many years, so we chose the ROXSTAsmart integral – a series-built all-in-one system for cooling, heating and air conditioning. TEKO designed the unit to be easy to handle while offering a wide range of sophisticated functions, which our service technicians quickly confirmed on site. Commissioning was seamless and completed within a single day. Having already had excellent results with a comparable TEKO system in another organic market, we weren’t expecting anything less.”
The old farm shop had been cooled by multiple stand-alone units installed at different locations around the premises. With the new building, ROXSTAsmart integral was installed indoors in a central machine room – drastically reducing noise levels. The buffer tank and circulation pumps for the various heating and cooling circuits are also housed there.
The lovingly crafted products of the organic farm demand the highest standards in refrigeration and control technology. Storage conditions must never compromise quality.
Maintaining the correct storage temperature, minimizing product dehydration, and ensuring gentle defrost cycles for refrigerated cabinets are all crucial. These requirements are met with FRIGOLINK from our partner Wurm Elektronische Systeme in Remscheid. That’s why even the smallest cooling points have been equipped with this solution. In total, the project includes 22 refrigerated units, all managed by FRIGOLINK – with energy efficiency as another key focus.
The building systems are seamlessly integrated as well. Heating, air conditioning, and ventilation are also controlled via Wurm technology. When systems interact this closely to ensure every project requirement is met, we call them “integral systems.”
“Another important aspect is quality assurance,” explains Frank Redda. “Wurm provides tailored solutions for every requirement. At Dottenfelderhof, we rely on the proven analysis tool Frigodata XP and the FRIDA app. With FRIDA, service technicians can operate the system directly via smartphone or tablet. Secure, VPN-encrypted remote data transfer enables authorized personnel to access the system anytime – allowing immediate action without the need for on-site travel.”
The waste heat from the refrigeration system is used to heat and cool the market, offices, staff rooms and storage areas – covering 90–95% of the required heating demand. The remaining 5–10% is supplied by a heat pump. Through an intermediate circuit with a pump, heat and cooling energy flow into a 500-liter buffer tank and are then distributed throughout the market via ceiling-mounted air units. Thanks to GTM’s innovative building technology, this process is remarkably simple. The system performs the hydraulic balancing of individual heat exchangers automatically using advanced algorithms, ensuring precise and highly efficient temperature control. The building technology concept was planned and implemented by Kratschmayer Luft-Wärme-Klima GmbH from Waldenburg.
The integrated WHITELINE gas cooler also functions as a heat pump evaporator. In winter, when outdoor temperatures drop, a bypass allows full use of waste heat. If the temperature falls further, the heat pump evaporator steps in. This setup delivers a total heating capacity of 70 kW. By combining both units, the required footprint is reduced, and noise emissions remain very low at just 30 dB(A) measured 10 meters away. In addition, waste heat from the gas cooler defrosts the heat pump package efficiently and economically – without the need for extra electric heating.
In summer, the same piping system circulates chilled water to the ceiling units, keeping the market at a comfortable temperature.
The refrigeration system is also equipped with Wurm’s METEOLINK module, which enables predictive regulation of heating and cooling. This significantly enhances both operational reliability and comfort.
Energy efficiency with funding support
Dottenfelderhof benefits from financial incentives for CO₂ technology
When it comes to energy efficiency funding, ecogreen Energie is the go-to partner. With more than 10 years of experience, their experts help companies secure financial support for energy-saving projects. Dottenfelderhof is another success story realized in collaboration with ecogreen, RS Kälte-Klima and TEKO. The project demonstrates how farm shops can take advantage of funding opportunities to offset the additional costs of high-efficiency refrigeration technology. In this case, around 10% of the investment costs were subsidized.
Marcel Riethmüller, Managing Director of ecogreen, explains: “Our goal is to give companies quick and easy access to funding programs. Together with our partner companies, we achieved this here through excellent teamwork.”
Key facts & figures
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Total area: approx. 1,500 m²
- Refrigeration units: 22 in total
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8 refrigerated counters (butchery / bakery)
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9 cold rooms (dairy / fruit & vegetables / cheese / meat)
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1 fresh meat preparation area
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4 wall-mounted refrigerated cabinets (dairy / meat)
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ROXSTAsmart integral
Integrated system for cooling, heating & air conditioning
- Refrigerant: R 744 (CO₂)
- Medium temperature cooling:
- 3 x Frascold compressors (1 with frequency inverter)
- 47 kW (t0 -5 / tGC out 38 °C)
- Heating: 70 kW (tWater in/out 25/40 °C)
- Air conditioning: 45 kW (t0 2 / tGC out 38 °C)
Regelung
Wurm Control electronics FRIGOLINK – HCO₂
Special features
- COOL₂HEATbasic heat recovery incl. loading pump
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Controlled suction gas heat exchanger for NK, HP and AC
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WHITELINE gas cooler / heat pump evaporator combination unit with 3 EC fans: 310 kW (tLE 35 °C / tGC out 37 °C)
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10 x WHITELINE CO₂ flat evaporators
Image credits: RS Kälte-Klima / jannasfotografie / Bernd Liebermann