This book presents peer-reviewed papers based on the oral and poster presentations during the 5th International Conference on Renewable Energy Sources, which was held from June 20 to 22, 2018 in Krynica, Poland. The scope of the conference included a wide range of topics in renewable energy technology, with a major focus on biomass, solar energy and geothermal energy, but also extending to heat pumps, fuel cells, wind energy, energy storage, and the modelling and optimization of renewable energy systems. This edition of the conference had a special focus on the role of renewable energy in the reduction of air pollution in the Eastern European region. Traditionally this conference is a unique occasion for gathering Polish and international researchers’ perspectives on renewable energy sources, and furthermore of balancing them against governmental policy considerations. Accordingly, the conference offered also panels to discuss best practices and solutions with local entrepreneurs and federal government bodies. The meeting attracts not only scientist but also industry representatives as well as local and federal government personnel. In 2018, the conference was organized by the University of Agriculture in Krakow in cooperation with AGH University of Science and Technology (Krakow), University of Žilina, Silesian University of Technology, International Commission of Agricultural and Biosystems Engineering (CIGR) and Polish Society of Agricultural Engineering. Honorary auspices were given by the Ministry of Science and Higher Education Republic of Poland, Rector of the University of Agriculture in Krakow and Rector of the AGH University of Science and Technology.