Simulation software as a tool in the design of solar thermal

The government regulations for energy use in buildings will be tightened in the future. At the same time the interest in environmental classifications and certifications of buildings is increasing. This has meant a new situation for solar energy. The designs of solar heating systems are often based on experience and/or rules of thumb, rather than calculations and simulations. This thesis examines whether simulation tools, in this case Polysun, are useful in this work. This is done by designing a solar heating system for an energy efficient preschool. In the process, important parameters are identified and their impact has been investigated. The model is finally validated against a real system.The results show that a system designed with Polysun save SEK 400 000 while a system designed by the rules of thumb only saves SEK 300 000, over 33 years. As expected, the collector area and the collector efficiency have a major impact on solar heat exchange. It also turns out that the climate data and the loads, especially hot water loads, have a significant impact on the outcome. When the same system is simulated with two different climate files, the solar contribution differs 9 %. This, despite the fact that both are used frequently to represent a normal year in Stockholm.A comparison of flat-plate collectors and vacuum tubes show that the flat-plate collectors are advantageous in a system with smaller collector area, because of the lower price. In a system with bigger collector area, vacuum tubes may be preferable due to higher yield during spring and autumn.A validation of the model is done against measured data from a real system (measured by SP Technical Research Institute of Sweden, 2001). A comparison of the solar output from the simulations and the measurements show a low correlation. Differences are assumed to be due to the fact that climate data for normal years Stockholm 1986 is used. This means that no conclusions about the model can be drawn from this.Within the same project, simulations where carried out, also by SP. The models used were validated against the measured values and showed good correlation. The simulations which where then made, by SP, were performed with climate data for Stockholm in 1986. These results correlate well with the simulated values from Polysun. This implies that the model in Polysun can describe reality well