The role of thermal energy storages in future smart energy systems

This paper conducts an in-depth energy systems analysis on the role of thermal energy storages in Denmark's transition to a fully decarbonized Smart Energy System. Using the EnergyPLAN software and national-scale energy system scenarios, the research examines how the use and impact of thermal energy storages evolves during this transition. Findings indicate that thermal energy storages play an important role in minimizing fuel consumption, curtailing losses, and in improving the overall energy-efficiency and balance of supply and demand. Initially, it primarily lowers fossil fuel use, potentially by 3 TWh per year. As renewable energy increases in the system, its main focus shifts towards reducing excess electricity via power-to-heat and conserving biomass, cutting up to 1 TWh of excess electricity annually through added flexibility. Variable system costs potentially decrease by 17–67 million EUR yearly, though economic feasibility depends on the phase of the transition when investment costs are included. In a future smart- and fully decarbonized system, the economic feasibility is heavily affected by energy prices along with other heat- and storage alternatives and flexible consumption. This leads to the novel understanding that the role of thermal energy storage changes along with the transition of the energy system.