Four Institutes will work together on different tasks of the project. The results will be exchanged as often as necessary to get a better overview on certain aspects of large thermal solar combi-systems. The partners and their tasks are listed below.

SWT — Solar & Warmetechnik Stuttgart together with ZfS — Rationelle Energietechnik GmbH:

1. Selection of six existing combi-systems, equipping them with measurement instrumentation, measuring and analysing them in detail over a period of two years.

2. Check for defects of the system after a short measurement period, which have to be eliminated before further measurements.

3. Analysis of the operating behaviour of the system and single components. Outlining the advantages and disadvantages of the different systems.

4. Building up simulation models of the systems for analysis of the existing technique as well as development of improved systems by variation of parameters.

5. Calculate the economic efficiency of simulated improvements.

6. Implement economically efficient improvements in the existing system, further measurements.

7. Develop a guideline for planning and dimensioning of this system technology

ISFH — Institut fur Solarenergieforschung GmbH Hameln/Emmerthal:

1. Analysis of the stagnation effects of three large collector fields on a test bench as well as measurement of the stagnation in one existing system over two summers. Therefore detailed measurement of temperature, pressure and degradation of the solar fluid is planned.

2. Analysis of how the collector fields are deflated and recharged (during/after stagnation).

3. Investigation of two flat-plate and one vacuum-tube collector fields based on the results above.

4. Recommendations on how to reduce stagnation in the system based on the measurements and the results of the partners.

5. Investigation of these recommendations in real operating behaviour.

Fraunhofer-Institut fur Solare Energiesysteme, ISE, Freiburg:

1. Evaluation of the stagnation of collector fields by analysing the detailed performance during stagnation of a single collector.

2. Measurement of draining and steam power of single solar collectors under consideration of different absorber pipings.

3. Simulation of the stagnation behaviour of a single collector based on the measurements. Afterwards simulation of large collector field.

4. Simulation of the effect of a fluid-air-heat exchanger to transfer heat to the environment in case of stagnation.

5. Recommendation on how to reduce stagnation in collector fields based on the measurement results and collector simulation.

6. Analysis of the degradation of the solar circuit heat transfer fluid.

7. Publication of the results of all partners on a web page and in a work shop. (http://www. Solarkombianlagen-XL. info)

2. References

[1] Styri-Hipp, G.; Kerskes, H.; Druck, H., Bachmann, S.: Kombianlagen Abschlussbericht des Projektes „Testverfahren fur Solaranlagen zur kombinierten Brauchwassererwarmung und Raumheizung (Kombianlagen)", DFS, Freiburg, 12/2001

[2] Peuser, F. A.; Remmers, K.-H.; Schnauss, M.: Langzeiterfahrung Solarthermie — Wegweiser fur das erfolgreiche Planen und Bauen von Solaranlagen; Solarpraxis Supernova AG, Berlin, 2001, ISBN 3-934595-07-3 (English version: Solar Thermal Systems, Solarpraxis Berlin 2002, ISBN 1-902916-39-5)

[3] VDI 6002-1: Solar heating for domestic water — General principles, system technology and use in residential buildings (will be published in July 2004)

[4] TRNSYS Version 15.0 — User Manual. Solar Energy Laboratory, University of Wisconsin, Madison und Transsolar, Stuttgart.

3. Acknowledgement

This project is supported by the German Federal Ministry for the Environment (Bundesministerium fur Umwelt, Naturschutz und Reaktorsicherheit; Forderkennzeichen 0329268A-C). The authors gratefully acknowledge this support and carry the full responsibility for the content of this paper.

The Central Solar Heating Plant with Aquifer Thermal Energy Store in Rostock — Results after four years of operation

Thomas Schmidt1), Hans Muller-Steinhagen1)2)3)

1 Solar — und Warmetechnik Stuttgart (SWT),

A Research Institute within the Steinbeis-Foundation,

Pfaffenwaldring 10, 70550 Stuttgart, Germany,

Tel. +49-(0)711-685-3299, Fax: +49-(0)711-685-3242,

Internet: www. swt-stuttgart. de. Email: schmidt@swt-stuttgart. de

2) Institute for Thermodynamics and Thermal Engineering (ITW), University of Stuttgart

3) Institute of Technical Thermodynamics (ITT), German Aerospace Center

In Rostock the first German central solar heating plant with an aquifer thermal energy store (ATES) went into operation in 2000. The system supplies a multifamily house with a heated area of 7000 m2 in 108 apartments with heat for space heating and domestic hot water preparation. On the roof of the building 980 m2 of solar collectors are mounted. The ATES operates with one doublet of wells and is located below the building. The store works as a seasonal heat store to overcome the gap between high amount of solar energy in summer and highest heat demand of residential buildings in winter. The solar system was designed to cover half of the yearly heat demand for space heating and domestic hot water preparation by solar energy. This target could be reached in 2003 with a solar fraction of 49 %.

The plant is one out of eight demonstration plants that have been built within the German research programme “Solarthermie-2000” in the last eight years /1/. The supplied multifamily house, see Figure 1, was built in 1999 by the house building company WIRO, Wohnen in Rostock Wohnungsgesellschaft mbH, who still owns and operates the building. The main part of the heat supply system was designed by Geothermie Neubrandenburg GmbH (GTN). The project is evaluated by SWT, ITW and GTN for the part of the ATES. The paper gives a detailed description of the system and presents the main results from four years of operation.