"During the last 20 years the number of biomass district heating systems in Austria has been continuously growing. The combination of solar thermal technologies with combustion technologies for thermo-chemical conversion of woody biomass is one of the realized concepts to provide useful heat for space heating, domestic hot water preparation and process heat based on renewable energy resources. Several example projects of solar thermal supported biomass district heating systems in Austria have shown that a careful implementation of this concept to use the local solar energy potential and the regionally available solid biomass resources could be a successful approach. The present work will analyze in detail, if solar thermal technologies can be used in combination with an existing, biomass-fired district heating system to utilize the existent potential in the municipality of Moosburg with respect to technological, ecological and economic feasibility. The outcome of this analysis shall provide a basis for further decision regarding the application of solar thermal systems for useful heat generation. The selected methods of approach are an evaluation of the district heating system's current status, an analysis of the local solar potential and of the available regional woody biomass resources and the development of an appropriate system concept for later comparison. By modeling the expected heat demand of the investigated biomass district heating system a frame work for energetic analysis is established. A simulation program is applied to determine the energetic effects of a solar thermal system supporting a biomass district heating system with feed-in of solar heat. With the annuity method according to guideline VDI 2067 the economic assessment is carried out. Finally, the proposed solar-assisted biomass district heating application is compared to a reference system realized in Austria. This thesis shows that an assisting solar thermal plant will substitute a considerable share of district heat produced by boilers, if it is designed properly. The resulting fuel savings, cost savings, and emission savings are the positive effects, which influences the system's economic performance and its ecological sustainability. As worked out by this master thesis the boilers' mode of operation outside the heating season essentially impacts on the district heating plant's emission balance. With regard to negative consequences this work comes to the conclusion that due to high investment costs the economic feasibility of a solar-assisted biomass district Dipl. Ing. Martin DULLNIG iii heating system currently is hard to achieve. The decision pro or contra a solar thermal system supporting a district heating system finally depends on the plant owner's willingness to take a risk and on the support by public funding."