đź“ŤFreiburg im Breisgau, Germany
Picture: Gebäudeforum Klimaneutral
As part of the SanBest research initiative, a comprehensive modernization of the heat supply system was implemented in a multi-building residential complex located in the Mooswald district of Freiburg im Breisgau, Germany. The project, titled “Wärmepumpe im Contractingmodell”, serves as a demonstrator site under the name “Freiburg Seepark.” The ensemble consists of two multi-family buildings (11 and 15 dwellings), two terraced housing rows (5 houses each), and two semi-detached houses, totaling approximately 40 residential units and a heated area of 3,432 m². Originally constructed in 2002, the buildings were served by a shared heating central unit utilizing an earlier-generation groundwater heat pump system. Due to poor performance and the unavailability of spare parts for the original heat pump system, a new system was commissioned and implemented under a contracting model. The previous system achieved a seasonal performance factor (JAZ) of only ~1.9 and relied heavily on an electric resistance heater for domestic hot water production, leading to high electricity costs. The new heat pump installation aimed to increase system efficiency, operational reliability, and compatibility with long-term contracting frameworks by offering guaranteed minimum seasonal performance figures (JAZ of 4.0 for space heating and 2.5 for hot water)
Key facts
| Building | Heat Pump and Source | ||
| Location | Freiburg im Breisgau, Germany | Number of HP | 2 |
| Construction | 2002 | Operation mode | Monoenergetic |
| Heated area | 3430 m² | Heat source | Groundwater |
| No. of apartments | 40 | Type of system | Central |
| Level of insulation | Very good | ||
| Heating sytem | Domestic Hot Water | ||
| Heating temperature | 146 °C | Max. temperature | 75°C |
| Installed power | 146 kW | Installed power | 77 kW |
| Other information | |||
| Storage tank | 2x 900L | Coefficient of Performance (average yearly) | 2,5 |
| HP Only / Hyrbid | HP only |
Description of the technical concept
The heating system at Freiburg Seepark uses two groundwater-source heat pumps to provide space heating and hot water for approximately 40 residential units. Heat is drawn from a groundwater well, where stable underground temperatures enable efficient energy extraction. The water passes through heat exchangers and is then returned to the ground via a reinjection well. The system includes two Waterkotte heat pumps: a low-temperature unit (146 kW) for underfloor space heating and a high-temperature unit (77 kW) for domestic hot water. Each uses scroll compressors with two-step modulation (50%/100%) for efficient load matching. Heat is distributed from a central plant room to the apartments via insulated pipes. A legionella filter allows lower hot water circulation temperatures, improving energy efficiency. The system is monoenergetic, fossil-free, and designed to fully meet heating demands year-round with seasonal performance factors (JAZ) of 4.0 (heating) and 2.5 (hot water).
Case study delivered by: Gebäudeforum Klimaneutral