# Dynamic Thermal Rating and Development of Renewable Energy Zones in Sicily
## 4 Methodology
### Application of Dynamic Thermal Rating to Sicilian Transmission Grid
#### 4.2.1 Climatic Study of Sicilian Municipalities for Dynamic Thermal Rating  
The aim of this part of the study was to classify Sicilian municipalities according to their potential for thermal exchange between the conductors and the surrounding environment, typical of the area in which the municipalities are located. The main variables influencing the thermal exchange between the overhead conductor and the surrounding environment are as follows [12]:  
* Wind speed;
* Average outdoor temperature. Therefore, through the online platform \"Servizio Informativo Agrometeorologico Siciliano\" (SIAS) [16], data were collected from about 40 SIAS meteorological stations evenly distributed over the Sicilian territory. The data collected from the SIAS meteorological stations consist of the following:  
* Daily average temperatures from 2018 to 2023;
* Daily average wind speeds from 2018 to 2023;
* Altitude above sea level for each station. These data were then summarized by calculation (using Excel) for each site:* Average monthly temperatures and wind speeds from 2018 to 2023;
* The average of the monthly average temperatures and wind speeds from 2018 to 2023. Since the meteorological stations are sufficiently evenly distributed over the territory, Sicily was divided into 36 micro-zones. The size of these micro-zones was based on the actual concentration of available meteorological stations. Therefore, some micro-zones have a larger area than others due to the lower availability of meteorological data to reference. Conversely, where the concentration of stations is higher, smaller micro-zones were identified. The places where the stations are located are hereafter referred to as \"source municipalities\". The monthly average outdoor temperature and the monthly average wind speed for all other municipalities are calculated based on the values from the source municipality of the same micro-zone. The following formula was used to calculate the monthly average outdoor temperature for each municipality \(\mathrm{T_{m}}\) [\({}^{\circ}\)C]:  
\[\mathrm{T_{m}}=\mathrm{T_{sm}}-(\mathrm{Z_{m}}-\mathrm{Z_{sm}})\times\delta [^{\circ}\mathrm{C}] \tag{2}\]  
where  
* \(\mathrm{T_{sm}}\) is the monthly average temperature of the source municipality [\({}^{\circ}\)C];
* \(\mathrm{Z_{m}}\) is the altitude of the municipality [m];
* \(\mathrm{Z_{sm}}\) is the altitude of the source municipality [m];
* \(\delta\) is the vertical temperature gradient [\({}^{\circ}\)C/m]. The determination of this formula and the vertical temperature gradient were taken from the current UNI10349 standard [17]. The altitudes of the stations were taken from the SIAS website [16], while the altitudes of all Sicilian municipalities were taken from [18]. To calculate the monthly average wind speed for each municipality \(\mathrm{V_{m}}\) [m/s], the following formula was used:  
\[\mathrm{V_{m}}=\mathrm{V_{sm}}\times\mathrm{C}\Big{[}\frac{\mathrm{m}}{\mathrm{ s}}\Big{]} \tag{3}\]  
where  
* \(\mathrm{V_{sm}}\) is the monthly average wind speed for the source municipality [m/s]
* \(\mathrm{C}\) is a dimensionless multiplicative coefficient. The multiplicative coefficient \(C\) has been used to account for variations in wind speed within the same micro-zone. In cases where a small part of the territory is characterized by high average slopes, the wind speed is usually less homogeneous. In order to improve the calculation of \(\mathrm{V_{sm}}\), a multiplicative coefficient was proposed, which can take the following values:  
\[\mathrm{if}\ |\mathrm{Z_{m}}-\mathrm{Z_{sm}}|\leq 250\ [\mathrm{m}]\ \mathrm{ then}\ \mathrm{C}=1 \tag{4}\]  
\[\mathrm{if}\ \mathrm{Z_{m}}-\mathrm{Z_{sm}}\geq 250\ [\mathrm{m}]\ \mathrm{ then}\ \mathrm{C}=0.9 \tag{5}\]  
\[\mathrm{if}\ \mathrm{Z_{ms}}-\mathrm{Z_{m}}\geq 250\ [\mathrm{m}]\ \mathrm{ then}\ \mathrm{C}=1.1 \tag{6}\]  
These values effectively simulate the real conditions, as they have been obtained after sample checks of the actual wind speed distribution in high-slope areas in Sicily.