Integration of Local Renewable Energy Sources for the enhancement of existing DH systems

European Directive 2012/27 suggests that an efficient district heating must include massive use of CHP and RES, and even more important, that comparison among different heat production solutions should consider also fuel extraction, conversion and transport. Under this perspective, both solar radiation and wood biomass as local energy sources can become interesting solutions to increase the share of renewable energy production in existing DH systems. These two renewable sources are analysed in this paper with different solutions. The first solution studied in the article is the direct heat production through water-cooled solar collectors. Wood biomass use has the capability of producing heat at proper temperature and provides increased availability, reliability and flexibility with respect to solar energy. For this reason, the heat production through a wood biomass fired plant based on ORC has been analysed as a second alternative. The third solution considers the parallel use of these two local sources, as an improvement with respect to the single systems, through the installation of a biomass dryer that is supplied by air-cooled solar collectors. The results of this analysis point up the benefits that can be reached through the integration of DH systems with local renewable energy. In particular, the biomass solar dryer appears the most interesting solution, thanks to the share of energy that is supplied by the external air for drying the biomass.