Austrian national project

The national project at Institute of Thermal Engineering of the Graz University of Technology is dedicated to the development of an integrated heat pump in the capacity range of 3-5 kW, preferentially using a natural refrigerant, e.g. CO₂ (R744) or propane (R290). The project comprises

• the system assessment of 3 possible system layouts
• the cycle analysis to identify the best of 3 refrigerants for the chosen system layout
• the construction of a prototype and lab-testing
• detailed simulations of the chosen system and its dynamic interaction with the heating system and the building (dynamic simulations in TRNSYS).

The system and cycle analysis resulted in a prototype concept for a CO₂-B/W heat pump. The system incorporates a horizontal ground collector, the CO₂ heat pump and a buffer storage, which is connected to a low temperature space heating emission system and a plate heat exchanger for instantaneous DHW preparation. The heat pump concept has a bi-partite gas cooler, by which space heating energy can be produced in the lower part (temperature level about 35°C) and DHW energy can be reheated in the upper part to the temperature level of the DHW of about 55°C. This configuration also enables a simultaneous space heating and DHW operation. Moreover, a passive and active cooling function can be realised by an external hydraulic. Also a simultaneous active cooling and DHW operation is possible. Results of the project are described in detail in the final report on prototype systems . The system concept is depicted in (Fig. 1).

Fig.1   Concept of the Austrian prototype 5 kW CO₂-B/W heat pump (source: Heinz and Rieberer, 2010)

The Austrian Institute of Technolgy AIT (formerly arsenal research) joined the Austrian team in 2008 for field monitoring of combined operating heat pump systems for space heating and DHW. 9 systems have been field monitored. Moreover, two ground-coupled compact units with horizontal collector for the functions space heating, DHW, ventilation and passive ground cooling have been in field monitoring for one year. Summarising results on the field tests are documented in the final report on field monitoring and as Best Practice sheets.

Activities are supported by the Austrian heat pump associations LGWA and BWP concerning the market survey and the heat pump statistics.