Due to the ever increasing share of renewable energy sources in the energy mix, large scale energy storage systems are considered essential to ensure security of supply in energy systems. Most renewable energy sources like wind and solar are intermittent by nature. Flexible, economic and efficient electrical energy storage systems are thus needed to shift large quantities of energy (MWh) from peak-production to peak-demand.
In recent years, Carnot batteries have been introduced as a novel grid-scale electrical energy storage to address this challenge. The storage concept involves three steps. First, electrical energy is converted into heat using a heat pump or joule heater. Secondly, the heat is stored. Finally, a heat engine technology is used to covert the heat back to electricity when needed.
Recently, different possible configurations for Carnot batteries have been proposed. Several alternatives for power-to-heat conversion, storage of thermal energy and heat-to-power conversion have been considered. These studies are typically limited to a steady-state performance evaluation. However, to assess the potential impact of this technology on the future electrical grid a better understanding of the dynamics of the system and interaction between the different subsystems is needed.
The goal of this master’s thesis is to study the impact of design choices for the heat pump components on the overall behavior of the Carnot battery. Therefore, a thermodynamic model of a Carnot battery will be developed. This model will be developed in the software environment Dymola (Modelica), which can perform detailed transient simulations of the total system. This thesis will focus primarily on the heat pump subsystem. Different component selection choices and the heat pump lay-out will be evaluated in order to optimize the behavior of a large scale heat pump (MW-scale) to fit in a Carnot battery.