Dimensioning of Solar Thermal Systems for Multi-Family Buildings in Lithuania: an Optimisation Study

Small-scale solar thermal domestic hot water (DHW) systems in Lithuania can produce up to 523 kWh per year per one square meter of solar collector area. It is therefore one of the most common solar thermal applications in the country with the expected payback period of approximately 10 years. However, the number of solar water heating systems (SWH) installed in the renovated multi-family buildings is quite limited. On the other hand, the potential of integrating solar thermal systems in these buildings is much higher as DHW usage during the day is more uniform in multi-family buildings compared to the single- family houses. This aspect brings out a higher solar energy share without adding additional volume to the hot water storage tank. Simplified optimization tools for solar collector area selection, volume selection for the accumulation tank, installation costs and payback period estimation are required for promoting SWH systems for DHW production in multi-family buildings.This paper deals with DHW consumption analysis in multi-family buildings in Lithuania as well as modelling of solar thermal systems to produce a tool for decision makers for preliminary analysis of SWH systems integration in renovated multi-family buildings. The main target group for the tool developed are multi-family buildings connected to district heating network. Simulation software "T*SOL 5.0 Pro" was used for SWH systems performance evaluation as well as financial analysis of SWH system alternatives