## 3 Laboratory Analyses  
The laboratory methodology proposed by [PERSON] _et al._[16] to select a suitable PCM for a TES application is used. In previous studies, the selection of a PCM was based only on the phase change thermal range, the enthalpy and the specific heat. In this new methodology, a combination of thermal stability, health hazard and cycling stability is presented to complement previous analyses. Differential scanning calorimeter (DSC) analyses were carried out to measure the phase change thermal range and the enthalpy of fusion along the range of temperatures in which the experimentation at pilot plant was performed. The equipment used to carry out the analysis was a DSC-822e commercialized by Mettler Toledo (Greifensee, Switzerland). A dynamic method analysis based on earlier studies [17] was performed. A sample of 12.8 mg sealed in a 40 \(\mu\)L aluminium crucible was heated under an inert atmosphere of N\({}_{2}\) up from 20 \({}^{\circ}\)C to 75 \({}^{\circ}\)C at a heating rate of 0.5 \({}^{\circ}\)C/min and cooled back at the same range of temperatures and heating rate. The results obtained are compared and discussed against the ones provided by the manufacturer. The thermal stability of the paraffin is analyzed using a thermogravimetric analysis (TGA). It measures weight changes in a material as function of temperature (or time) under a controlled atmosphere. The TGA was performed with a Simultaneous SDTQ600 from TA Instruments (New Castle, PA, USA) under nitrogen flow. The heating rate applied was 10 \({}^{\circ}\)C/min between 25 \({}^{\circ}\)C and 600 \({}^{\circ}\)C to a 30 mg sample size. \begin{table}
\begin{tabular}{c c c} \hline
**Properties** & **Units** & **Values** \\ \hline Melting area & (\({}^{\circ}\)C) & 53–59 \\ \hline Congealing area & (\({}^{\circ}\)C) & 59–53 \\ \hline Heat storage capacity \(\pm\) 7.5\% (combination of latent and sensible heat in a temperature range of 50 \({}^{\circ}\)C to 65 \({}^{\circ}\)C) & (J\(\cdot\) kg\({}^{-1}\)) & 160 \\ \cline{2-3} \cline{2-3} Specific heat capacity & (J\(\cdot\) kg\(\cdot\) K \({}^{-1}\)) & 2 \\ \hline Density solid (at 15 \({}^{\circ}\)C) & (kg\(\cdot\) L\({}^{-1}\)) & 0.88 \\ \hline Density liquid (at 80 \({}^{\circ}\)C) & (kg\(\cdot\) L\({}^{-1}\)) & 0.77 \\ \hline Heat conductivity (solid and liquid) & (W\(\cdot\) (m\(\cdot\) K)\({}^{-1}\)) & 0.2 \\ \hline Volume expansion & (\%) & 12.5 \\ \hline Flash point (PCM) & (\({}^{\circ}\)C) & \textgreater{}200 \\ \hline Max. operation temperature & (\({}^{\circ}\)C) & 80 \\ \hline \end{tabular}
\end{table} 
Table 1: Thermo-physical properties of RT58 according to the manufacturer. The cycling stability was analyzed to detect possible changes in the thermo-physical properties of the material along a certain amount of freezing/melting cycles. In the present study, the studied thermo-physical properties studied were the latent heat and the melting temperature. First, a cycling test (1200 cycles) was performed using a thermal cycler from Termocilador GENE Q Hangzhou BioerTechnology (Hangzhou, China). Three samples have been gathered each time after 500, 1000, and 1200 samples from an Eppendorf. The temperature program for one cycle was 1.5 min at 45 \({}^{\circ}\)C and 1.5 min at 70 \({}^{\circ}\)C to ensure full solidification and full melting during the cycle. The applied heating rate is the fastest: around 20 \({}^{\circ}\)C/min. Second, an evaluation of the cycled samples was performed using the same apparatus and methodology used for the DSC analysis. Finally, the infrared (FT-IR) spectroscopy was carried out to study the chemical stability of the material after a certain amount of cycles. Its working principle is based on the measurement of the molecules bonds vibration under infrared light. FT-IR spectroscopy was performed using a Spectrum Two from Perkin Elmer (Waltham, MA, USA) and supported by a Dynascan interferometer (Perkin Elmer, Waltham, MA, USA) and OpticsGuard (Perkin Elmer, Waltham, MA, USA).