Thermal Energy Storage - Design and Control

The energy transition to non-fossil energy sources and carriers calls for a massive expansion of renewable energy sources such as photovoltaic (PV) systems or wind turbines. These systems provide electrical energy in a highly intermittent fashion. This is challenging both in terms of the grid balance (matching of supply and demand) and in terms of power peaks, especially during the day, when the solar irradiation is most intense. An obvious solution to this challenge is the introduction of energy storage systems. There are several possibilities for short-term energy storage systems. They differ in terms of energy storage density, round-trip efficiencies, power-to-capacity ratio, and cost. In this thesis, we focus on thermal energy storage. In this process, excess electrical energy is converted into heat, which is then stored. When electricity demand arises, the stored heat is converted back into electrical energy. Typically, such a conversion chain incurs significant losses. However, a new concept applies the well-known thermodynamic cycle from gas turbines to a piston-based engine, achieving a round-trip efficiency of over 70%. This efficiency is comparable to that of battery solutions and is outstanding for thermal storage systems. This concept is made possible by fully variable valve actuation developed by etavalve.

The energy transition to non-fossil energy sources and carriers calls for a massive expansion of renewable energy sources such as photovoltaic (PV) systems or wind turbines. These systems provide electrical energy in a highly intermittent fashion. This is challenging both in terms of the grid balance (matching of supply and demand) and in terms of power peaks, especially during the day, when the solar irradiation is most intense. An obvious solution to this challenge is the introduction of energy storage systems.
There are several possibilities for short-term energy storage systems. They differ in terms of energy storage density, round-trip efficiencies, power-to-capacity ratio, and cost.
In this thesis, we focus on thermal energy storage. In this process, excess electrical energy is converted into heat, which is then stored. When electricity demand arises, the stored heat is converted back into electrical energy. Typically, such a conversion chain incurs significant losses. However, a new concept applies the well-known thermodynamic cycle from gas turbines to a piston-based engine, achieving a round-trip efficiency of over 70%. This efficiency is comparable to that of battery solutions and is outstanding for thermal storage systems. This concept is made possible by fully variable valve actuation developed by etavalve.

The aim is to find an optimal design and controller of such a thermal energy storage system as described above. The system shall be setup in simulation and optimal designs shall be evaluated for different use cases using the optimization framework DEnOBS from the IDSC. The ultimate goal is to evaluate the economic potential of such an energy storage system in various environments and configurations.

The aim is to find an optimal design and controller of such a thermal energy storage system as
described above. The system shall be setup in simulation and optimal designs shall be
evaluated for different use cases using the optimization framework DEnOBS from the IDSC.
The ultimate goal is to evaluate the economic potential of such an energy storage system in
various environments and configurations.

Dr. Theo Auckenthaler, ML H40, 071 511 61 99, tauckenth@ethz.ch; Dr. Andyn Omanovic, etavalve, ML H40, 079 524 39 89, andyn.omanovic@etavalve.com

Dr. Theo Auckenthaler, ML H40, 071 511 61 99, tauckenth@ethz.ch;
Dr. Andyn Omanovic, etavalve, ML H40, 079 524 39 89, andyn.omanovic@etavalve.com