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Electricity generation from variable renewable energies is expected to dominate the future energy supply in many countries, which will lead to an increased demand for flexibility options. Carnot batteries offer the technical prerequisites for meeting this flexibility demand and are relatively easy to scale. This paper investigates the future economic potential for Carnot batteries by coupling the energy systems optimization model REMix and the agent-based electricity market model AMIRIS. While REMix evaluates the least-cost infrastructure configuration of the energy system and the role of Carnot batteries in it, AMIRIS focuses on the corresponding profitability of these storage systems. The modelling chain is applied in a case study of a zero-emission energy system in Central Europa for the year 2050. To provide guidance for a promising technology development, a parameter scan for costs and efficiencies of Carnot batteries is performed for this system. We find that from an energy system design perspective the availability of a low-cost storage medium is a key driver for the usage of Carnot batteries. In addition, the combination of Carnot batteries with wind energy provides benefits due to the possibility of longer storage durations compared to electrochemical battery systems. Depending on the system's design, their specific role in the energy system, and bidding strategy, Carnot battery operators achieve positive annual gross profits on electricity markets when fully exploiting their substantial market power. We conclude that the development potential of Carnot batteries must be leveraged to make them competitive with other storage technologies on a broader scale. Additionally, our research highlights the crucial role of the chosen strategy for the Carnot battery. This becomes increasingly important when the installed storage capacity and power constitute larger shares of the overall energy system.

The goal of European energy policy is to become climate neutral. The long-term energy strategies of various European countries include additional targets such as diversification of energy sources, maintenance of security of supply and reduction of import dependency. When optimizing energy systems, these strategic policy targets are often only considered in a rudimentary way and thus, an understanding of the corresponding interdependencies is lacking. Moreover, hydrogen is considered as a key component of a fully-decarbonized energy system, but its particular role in the power sector is still unclear due to low round-trip efficiencies.