Together with an evaluation of the outcome of this project, a special aspect is the comparison of centralized and decentralized solar domestic hot water systems for terraced houses. Alongside the classical, self-sufficient ‘one-family house’ type of hot water central heating system, exists the possibility to connect the solar units of terraced houses together and to collect the heat in a central tank. The hot water is then directed to each individual house via a simple network of pipes. The production and distribution of heat for the heating system is also done via the central network.

The objective of the project, i. e. whether centralized systems for the combined supply of several houses with a solar collector area of 20-60 m2 can be an appropriate alternative to standard solar systems for each individual house was thoroughly investigated. The project offered optimal conditions for this investigation, as both system types were put directly

alongside each other so that both would be used under the same conditions (weather, orientation, demands made on the system).

2 Method

In addition to the technical and primary energy assessment of the systems with the help of a comprehensive measurement program and parallel computer simulation tests, a further important criterion of a hot water system, i. e. the economic implications involved, were also investigated. Not simply the initial investment, but the annual total costs with regard to the investment made, as well as the running costs incurred, were taken into account. As an alternative to the centralized freshwater storage system as used in Gelsenkirchen, the performance of other centralized systems on the market were also simulated, not just from the point of view of energy efficiency but in terms of economy. The simulation program used was MATLAB-Simulink®-Toolbox”CARNOT”/1/, a program specially developed by the Solar Institute Julich for researching conventional heating units and likewise innovative thermal solar systems. The results were generalised in order to be applicable to other solar settlements. However, the presence of influences which are not directly quantifiable should also be taken into account.

3 Results

As a result of the project, a research paper entitled „Advice on the Planning of Solar Hot Water Systems in Housing Settlements" was produced /2/. Following on from this, the most important findings both from the real-life comparisons made in Gelsenkirchen as well as the continuing generalized research done on the basis of computer simulations and economic analyses, were documented as a guideline for general use.