The Development of Mathematically Highly Condensed Computer Simulation Models

The cooperative work of the International Energy Agency (IEA) on evacuated collector systems (IEA Solar Heating & Cooling Programme, TASK VI: Performance of Solar Heating, Cooling, and Hot Water Systems Using Evacuated Collectors) covered both experimental and analytical activities on various active solar energy systems, ranging from small domestic hot water to large industrial process heat and district heating plants. During the investigations strong experimental evidence was found that universal system characteristics of the respective installations exist, which may be used for "simplified modelling". Thus investigations of these characteristics were performed with the objective to generate them by analytical approach. Originally only the so-called energy Input-/Output-Diagrams were considered, which connect the thermal output of the system with the daily or monthly incident radiation sum. However, in the course of the investigations it was shown that similar characteristics exist for various other values such as solar fraction, maximum temperature, auxiliary and parasitic energy, and others. It has been furthermore shown that for the ample determination of system characteristics complex and detailed models are needed. Thus the originally chosen term of "simplified" models was replaced by "mathematically condensed" ones, as those models condense the information to a few elementary equations. Most of the programmes which evolved from these investigations are user-friendly, offer a novel family of accurate and fast design methods, and provide a good understanding of complex systems. Two of these programmes (i. e. ISFH/chapter 7 and G/chapter 5) are available to the public and are used in practice for research and design purposes. Information on ordering these programmes is found in Chapter 3.