RELaTED · REnewable Low TEmperature District

District heating (DH) systems are one of the most energy efficient heating systems in urban environments, with proven reliability within many decades already. DHs have traditionally been designed to be operated in a hierarchized way, with central energy production facilities delivering heat to a variety of distributed consumption locations.DHs are identified as key systems to achieve the de-carbonization of heating energy in European Cities. Renewable and waste heat sources are foreseen at the same time as de-carbonized heat sources and the way to guarantee competitive energy costs with limited influence of fossil fuel supply price volatility. To achieve this, conversion of DHs is needed regarding:- The reduction of their operation temperature to avoid current technical constraints in the integration of low-grade industrial heat sources,- The introduction of larger shares of renewable energy sources (RES) in the DH network.- The introduction of distributed heat sources (reject heat from cooling equipment...).- To guarantee economic viability with the trend of DH heat load reduction due to the evolution of the building stock toward NZEB (Near Zero Energy Buildings).RELaTED will provide an innovative concept of decentralized Ultra-Low Temperature (ULT) DH networks, which allow for the incorporation of low-grade heat sources with minimal constraints. Also, ULT DH reduce operational costs due to fewer heat losses, better energy performance of heat generation plants and extensive use of de-carbonized energy sources at low marginal costs.The RELaTED ULT DH concept will be demonstrated in four complementary operation environments (new and existing DH, locations, climatic conditions, dimension…) in Denmark, Estonia, Serbia and Spain.RELaTED approach will follow the strategy of the electrical smart grids, in which energy generation is decentralized and consumers evolve to prosumers (they consume and produce energy).