Analysis of solar thermal systems and future development possibilities in Lithuania

  • Rokas Valančius
  • Andrius Jurelionis
  • Juozas Vaičiūnas
  • Eugenijus Perednis
  • Vykintas Šuksteris
Keywords: solar collectors, solar thermal systems, domestic hot water, energy prices, simulation and monitoring, payback time


Solar thermal systems with a total solar panel area varying from 2 to 204 m2 have been installed in Lithuania for over 20 years. The reviewed solar thermal domestic hot water systems in Lithuania produce up to 528 kWh per year per one square meter of solar collector absorber area. However, the  performance of these systems varies depending on the type of energy users, equipment and design of the  systems, as well as their maintenance. The  aim of this paper was to analyse solar thermal systems from the perspective of energy production and economic benefit as well as to outline the differences of their actual performance compared to the  numerical simulation results. A number of different solar thermal systems in Lithuania were selected for the analysis varying both in equipment used (flat type solar collectors, evacuated tube collectors) and type of energy user (domestic hot water heating, swimming pool, district heating). The  simulation software Polysun 8.1 was used for evaluation of solar thermal system performance, as well as financial analysis of alternatives of these systems. The results of the analysis showed that in the analysed cases the gap between measured and modelled data of heat energy produced by solar thermal systems was up to approximately 11%. The calculation of internal rate of return showed that a grant is required in most cases for solar thermal projects to be fully profitable.