Best practices
Hot Ice Weiz
The project is focused on the use of latent heat with two ice storages and heat pumps in combination with unglazed solar collectors and a PV system. It is designed as a pilot project for local heat supply.
The construction of the MFH (multi-family home) which is located at Bärentalweg 6 in A-8160 Weiz was finished in April 2015. The building is a wood frame construction which accommodates ten different apartments on three floors. The total area adds up to 1477 m², whereof an area of 957m² is heated.
It fulfils the passive house standard and has a calculated heat demand of 9.91 kWh/(m²a).
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Lessons learned
- Use of innovative heat source – ice storage connected with solar thermal absorbers works very well for multi -family buildings with very low energy demand (passive house standard).
- Comprehensive concept including PV modules lets increase the energetic independence of the buildings.
- Quality of the system’s control is crucial.
- Compared to design data increased heat demand due to increased room temperature & DHW consumption
Key facts
| Building | Heat pump and source | |||
| Location | Weiz, Austria | Number of HP | 2 | |
| Construction | 2015 | Installed power | 6 kW + 10kW | |
| Heat distribution | underfloor heating | Operation mode | monoenergetic | |
| Heated area | 957 m² living | Heat source | ice storage + solar | |
| Level of insulation | very good | |||
| Heating system | Domestic hot water | |||
| Heat demand | Type of system | central | ||
| Heating temperature | 35 °C | Max. temperature | 60 °C | |
| Circulation system | yes | |||
| Other information | ||||
| Electric energy consumption 2016 | 16850 kWh | |||
| Investments costs | unknown | |||
| PV installation | yes | |||
Description of the technical concept
The heat provided from the solar collector can either be delivered to the ice storage via a heat exchanger or to the heat pumps. The heat pumps lift the heat to the desired temperature level. (Remark: Up to now, it is not possible to use heat from the solar collector directly to heat the DHW or the SH storage.)
Depending on the current heating requirement, one or two heat pumps are in operation. They always work in one mode (DHW or SH storage, with priority on DHW) and ensure that the temperature in the storages remains within the desired range. If both heat sources (solar collector & ice storage) are not sufficient, it is possible to heat the two storages with auxiliary heaters (electrical heating rods).
During summer, this system can also be used for cooling. For this purpose, the ice storage is used directly as heat sink (“cold source”) for “passive cooling”, so that no chiller (reversible heat pump) is needed.
