## 6 Identification of MS-Driven Processes of Renewable Gas Production  
In CSP plants for electricity generation, direct solar irradiance is reflected, concentrated, and converted into high-temperature heat. The thermal energy is then converted to electricity through the use of thermodynamic cycles: in most plants nowadays, solar energy is transferred to an HTF that feeds a steam generator integrated into a Rankine cycle, similar to conventional thermal power plants. The intermediate step of heat generation not only allows for the production of electricity but also feeds heat-demanding processes, for industrial and civil uses, and facilitates schedule electricity generation through technologically mature TES systems, with to the aim of dispatchable generation, which, to date, cannot be pursued through other renewable energy technologies [145]. For this purpose, MS technologies are suitable for use in CSP plants in combination with TES, since MSs can be used both as a heat transfer fluid and as a storage medium. Although RESs are some of the most interesting and promising solutions for the transition to sustainable energy systems in the future, their main problem is their intermittent nature and fluctuations in their production, which makes it difficult to control and schedule them. Hence, the use of TES increases reliability and facilitates the integration of RESs, allowing for electricity and/or heat release whenever necessary to solve the demand-supply problem and to match peak demands. Therefore, MSs can act as an interface for the constant supply of renewable (high-temperature) heat from multiple sources to industrial processes. In particular, Figure 12 shows a conceptual diagram of the integration of an RES and an MS-TES system to provide heat and power to processes for hydrogen and syngas production, as presented in Section 3. The following are brief assessments of the feasibility of MS-driven processes for gas production, giving attention to the heat supply. Further details are reported in Tables 6 and 7. **Solid oxide steam electrolysis**: Heat is required almost exclusively for this process of steam generation (\(\sim\)1 atm and \(\sim\)100 \({}^{\circ}\)C). The electrolysis process itself is carried out in close-to-adiabatic conditions (thermoneutral potential), and the reactants are pre-heated mostly with heat recovered from the products. Co-electrolysis of H\({}_{2}\)O and CO\({}_{2}\) may also be carried out with SOECs, which leads to the production of syngas. Quaternary MS mixtures can be used to supply heat for steam generation. **Molten carbonate steam electrolysis**: Heat is required almost exclusively for this process of steam generation (-1 atm and -100 \({}^{\circ}\)C). The electrolysis process itself is carried out in close-to-adiabatic conditions (thermoneutral potential), and the reactants are pre-heated mostly with heat recovered from the products. CO\({}_{2}\) must be fed to the electrolyzer but, overall, is not produced/consumed in the process. CO\({}_{2}\) separation and recirculation may be included to produce H\({}_{2}\) and O\({}_{2}\). Alternatively, outlet H\({}_{2}\)/CO\({}_{2}\) mixtures can be fed to other synthetic fuel production processes (e.g., methanol, methane, etc.). Quaternary MS mixtures can be used to supply heat for steam generation. **Sulfur-family cycles**: The highest-temperature step of these cycles (SO\({}_{3}\) decomposition) requires heat at 800-900 \({}^{\circ}\)C and cannot be served by current commercial MS mixtures. Direct irradiation is currently used to solarize this step. Chloride salts could be considered in the future. Solar salt and other lower-freezing commercial mixtures can be used to supply heat to other process steps, namely, sulfuric acid concentration and SA vaporization and decomposition. Further integration points may be available for specific cycles of this family. **Sulphur-iodine cycle**: All information related to sulfur-family cycles can be applied.