Inhaltsverzeichnis
WRGpot - Potential and concepts for waste water heat recovery in combination with solar collectors and heat pumps
The objective of the project is to find possibilities for the reduction of the heat demand for the hot water preparation of low energy and passive house buildings, in order to advance a further step into the direction of plus-energy buildings.
Titel und Synopse
Ziel des Projekts ist es, Möglichkeiten zur Reduktion des Energiebedarfs für die Warmwasserbereitung in Niedrigenergie- und Passivhäusern - auf dem Weg zum Plus-Energie-Haus - zu finden. Dabei kommt dem Verhältnis zwischen eingesparter Energie und Investitionskosten großes Augenmerk zu.
Project description / tasks
Status
ongoing
Summary
Starting point / motivation
In modern Low-Energy and Passive Houses, the energy demand for domestic hot water (DHW) is often higher than the energy demand for heating. Additionally higher temperatures are needed than for example for the flow temperature of a floor heating system. Thus, the relevance of the energy demand for DHW increases drastically with an increasing insulation standard of buildings. With regard to a development towards Plus-Energy-Buildings it is absolutely necessary to aim at a further development of more efficient concepts for the preparation, the storage and the distribution of DHW, as well as heat recovery from the wastewater.
A further motivation is the fact, that even in Low-Energy and Passive Houses a high effort is necessary in order to reach a high solar fraction of the heating demand (80-100%). Compared to the achievable energy savings, the expenditures for such solar thermal systems are very high, so that they can hardly be realized in an economic way. A significant reduction of the investment costs can only be reached, if the solar plant can cover 100% of the heat demand and thus an auxiliary system can be spared.
Contents and goals
In this project it is planned to analyse, whether the collector area, the buffer storage volume and the investment costs of such concepts can be significantly reduced by the following measures:
- If the set-temperature of the storage can not be reached directly by the solar collectors, a small heat pump heats the upper part of the buffer storage to the set-temperature while extracting the necessary heat from the bottom part of the storage (relatively low investment costs, as no ground collector or borehole is needed as a heat source for the heat pump).
- Wastewater heat recovery in a simple way (if possible no intermediate storage of the wastewater), for example via heat pipes directly into the lower part of the solar buffer storage.
- Optional: Photovoltaic-Panels charge electricity into the grid during summer as a compensation for the electricity consumed by the heat pump in winter.
The integration of the heat pump offers the advantage that relatively low temperatures can be reached in the bottom part of the buffer storage. This enables a high potential for the solar gains and for the wastewater heat recovery during the crucial season of the year. The space requirement and the investment costs of the heat pump and the wastewater recovery system should be relatively small in comparison to the savings that can be achieved due to the reduction of the collector area and the buffer storage volume.
Expected results / conclusions
- Investigation of the potential for waste water heat recovery in buildings concerning the temperature level and the quantity of the waste water by means of measurements in 3 buildings.
- Comparison of different concepts for waste water heat recovery in combination with a solar thermal system and a heat pump including a cost-benefit-analysis.
- Detailed analysis of two promising concepts by means of dynamic system simulations.
Project partners
Project management
Institute of Thermal Engineering, Graz University of Technology
Project or cooperation partner
- AEE INTEC - Institute for sustainable technologies
Contact address
Institute of Thermal Engineering, Graz University of Technology
Dr. Andreas Heinz
Inffeldgasse 25b
Tel.: +43 (316) 873 7313
E-Mail: andreas.heinz@tugraz.at
