## 2 Technical Solution
### Definition of Scenarios
#### 2.2.2 Enhanced Configuration with Solid Particles: Scenario III  
Despite its advantages, CSP remains more expensive than alternatives such as wind or PV technologies. To enhance its competitiveness, increasing operating temperatures in the power cycle is estimated to reduce costs by improving conversion efficiency and increasing energy storage densities. For instance, this could lead to a reduction in the size of the solar field, which can account for up to 50% of the total plant cost [13].  
To address these challenges, the use of DPS has been identified as a viable alternative. Key features of solid particles include the following [20]:  
* The ability to function as both a heat absorber and a thermal energy storage medium.
* Low heat transfer medium (HTM) costs.
* High stability at elevated temperatures.  
Due to these advantages, solid particles were considered to replace molten salts in the previously described power plant in Scenario I. For this study, an upflow receiver featuring a fluidized bed circulating through tubes was selected, generating a dense suspension of particles. This choice is justified for several reasons:  
* The gas-solid fluidized bed technology has been extensively used in industries such as chemical, petrochemical, metallurgical, and coal-based power generation, making it a mature technology [41].
* Fluidization enables the gas-solid mixture to behave like a gas, facilitating its transport and allowing particles to be easily separated from the gas. This process is particularly advantageous for energy storage, as it allows for the use of hot particles with high density [13].
* In comparison with other energy storage alternatives under investigation, this technology has been demonstrated in several large-scale projects, reaching capacities in the megawatt range [21], such as the experimental study conducted in France [42].  
To enable comparison, Scenario III adopts the same primary characteristics outlined in Table 2, except for those exclusive to this scenario, such as the receiver power, the thermal storage mass, and the annual electricity production.  
For this study, silicon carbide particles were selected. This choice is based on their size and density characteristics, which facilitate fluidization, as they belong to Group A of the Geldart scale [43]. Additionally, due to their ceramic nature, these particles can withstand temperatures up to 1000 \({}^{\circ}\)C, with the primary limitation being the material of the absorber tubes. Being chemically inert and non-explosive, they eliminate the challenges associated with solidification and the need for electric tracing, as is the case with molten salts. The main properties of these particles are summarized in Table 5.  
\begin{table}
\begin{tabular}{c c} \hline
**Area** & **Typical Efficiencies (\%)** \\ \hline Receiver & 87–90 [35; 36] \\ Steam generator & 80–90 [37; 38] \\ Power block & 41.20 [35] \\ Storage & 97–99 [39; 40] \\ \hline \end{tabular}
\end{table}
Table 4: Typical efficiencies in Scenario I.  
In this case, higher operating temperatures allow the adoption of a power block configuration typical of advanced supercritical fossil power plants, thereby increasing the power block efficiency [13]. A summary of the main conditions of the different states of this power block configuration is presented in Table 6.  
Similarly to the previous case, Table 7 presents the typical efficiencies for each section of the power plant in Scenario III, as reported in the literature. These efficiencies will be subsequently used in Section 3 for the plant simulation.