Advanced Storage Concepts for Solar Combisystems

H. Druck, W. Heidemann, H. Mtiller-Steinhagen

Universitat Stuttgart, Institut fur Thermodynamik und Warmetechnik (ITW) Pfaffenwaldring 6, D-70550 Stuttgart Tel.: 0711/685-3536, Fax: 0711/685-3503

email: drueck@itw. uni-stuttgart. de, Internet: http://www. itw. uni-stuttgart. de

Using a typical single family house in Germany as an example, the influence of the solar collector area and the store volume on the energy savings is determined by means of numerical system simulations. Based on these results it is outlined how the system performance can be increased by using advanced storage concepts.

In particular the following storage concepts are investigated:

• hot water stores with improved thermal insulation (e. g. with vacuum insulation)

• stores using phase change materials (latent heat stores)

• thermochemical energy stores (e. g. based on sorption)

In addition to the primary energy savings that can be achieved with the different heat storage technologies and system concepts, the resulting solar thermal heat prices and the energy payback times are discussed.

1 Introduction

Thermal solar systems for domestic hot water preparation and space heating, so-called solar combisystems, are already introduced to the market, and their market share is increasing continuously. Today standardised solar combisystems consist of a solar collector with an area between 10 m2 to 20 m2 and a hot water storage tank with a volume in the range of 0.7 — 1.5 m3. If such systems are installed in a „typical" middle European single family house, they can save approximately 20 — 30 % of the primary energy required for domestic hot water preparation and space heating. In order to increase the energy savings, larger collector areas and/or store volumes are required.