Extension of Germany’s Largest Solar District Heating System with Seasonal Thermal Energy Storage
Abstract
This publication introduces several measures to extend and optimize Germany’s largest solar district heating system with seasonal thermal energy storage, located in southern Germany in the city Crailsheim. The aim of the extension is to achieve a solar fraction above 50 % in order to reduce CO2 emissions and to demonstrate the functional and economic attractiveness of solar district heating systems with seasonal thermal energy storage. The investigated measures comprise different concepts for the extension of the solar thermal collector area with high-efficiency flat-plate collectors and the extension of the borehole thermal energy store, which serves as seasonal thermal energy store in the system. As an alternative, the installation of an overground hot water thermal energy store is considered to increase the heat storage capacity. Other measures are the installation of a second heat pump as well as the reduction of the return flow temperature of the district heating grid. Further, combinations of the above mentioned measures are investigated. The effects of the specific measures are quantified by means of annual system simulations with the transient simulation software TRNSYS 17.