# A Novel Hybrid CSP-PV Power Plant Based on Brayton Supercritical CO\({}_{2}\) Thermal Machines
## 4 Discussion and Conclusions
However, the injection during radiation hours lacks rotational inertia in the conventional scheme. In the latter scenario, where full storage is required, the novel scheme injects 13.8% more electricity into the grid than the conventional one, with both injections having rotational inertia. In this case, the use of electrical resistors instead of a heat pump results in higher irreversibilities, which reduces the recovered power. In terms of costs, the preliminary estimation of the LCOE has been based on an assumption of 6 equivalent hours of operation each day throughout the year, resulting in a total production of 12 h, equivalent to 50% of the capacity factor. The obtained LCOE (USD 171/MWh) is lower than the current CSP technology with a 45% capacity factor [40]. In [22], Generation 3 technology is examined, based on S-CO2 with turbine inlet temperature up to 800 \({}^{\circ}\)C of, ternary salts, a 38% capacity factor, and central tower receivers. The resulting LCOE for this technology is USD 238/MWh. This demonstrates the significant cost advantage of the heat pump system, which replaces the expensive heliostat solar field with a combination of a PV plant and a parabolic trough collector field. Figure 8 provides a detailed breakdown of the costs associated with this novel system. It reveals that more than half of the total cost is attributed to the PCHE and turbomachines. This fact suggests that there is potential for cost reduction, particularly in these components. Notably, a cost reduction is expected as the S-CO2 technology deploys, because these components, especially the heat engine compressors, are currently in the first steps of the learning curve. If we consider the same energy production of 600 MWh per day, but with a 100 MW capacity PV plant and 6 h of battery storage, the LCOE would be lower than USD 140/MWh (assuming a battery cost of USD 250/kWh [41] and total battery replacement over the lifespan of the project). However, it is important to acknowledge that this battery system presents two significant drawbacks. Firstly, it requires a substantial amount of critical raw materials. Secondly, it results in the loss of rotational inertia, necessitating additional controls to manage grid frequency. In contrast, the proposed system injects electricity into the grid through a synchronous generator in the heat engine, without relying on critical raw materials for its storage components. Figure 8: Cost breakdown of the novel hybrid CSP-PV plant. Although the proposed system has not been able to beat the cost of a PV with battery storage, it exhibits several operational and construction advantages. In conclusion, this proposed system effectively reduces the LCOE compared with both current CSP power plants. Additionally, it enhances the performance of current hybrid CSP-PV power plants, especially in terms of long-duration energy storage capabilities. The preliminary LCOE estimation conducted in this study should be further refined in future works through annual simulations, including off-design responses of the entire system. While the current state of the art has been considered wherever possible (such as PTC and molten salts), the potential for evaluating advanced subsystems remains open for future exploration. Similarly, different S-CO2 layouts could be analysed, alongside current steam Rankine power cycles used in CSP, thereby establishing a comprehensive roadmap towards achieving the final hybrid configuration. Conceptualization, J.I.L., A.M.-C. and E.A. ; Formal analysis, E.A. and M.J.M. ; Funding acquisition, E.A. ; Investigation, J.I.L. and A.C.; Methodology, E.A., M.J.M. and A.C.; Project administration, J.I.L. and E.A. ; Resources, E.A. ; Software, A.C.; Supervision, J.I.L. ; Validation, J.I.L., A.C. and J.R.P.-D.; Visualization, J.R.P.-D.; Writing--original draft, J.I.L. and A.M.-C.; Writing--review & editing, E.A., A.C. and J.R.P.-D. All authors have read and agreed to the published version of the manuscript.