## 5 Conclusions
Increasing the flow rate, final temperature, and PCM conductivity reduces the duration of the storage. It is noted that the conductivity of the nodule envelope, due to its low thickness, has a negligible influence on storage performance. If the PCM mass is the same in the storage tank, the smaller the nodules are, the larger the exchange surface between the PCM and the HTF, and the higher the heat transfers, with a consequent decrease in storage time. Finally, a parametric study of the tank dimensions shows that the results are independent of the tank geometry if the volume is the same. The next step of this project consists in increasing the size of the TES system and combining it with an existing industrial process. This will make the analyses of the performances of the installation possible, and determine whether the charge and discharge times are compatible. Then, an optimization study will be necessary to determine the ideal parameters of the storage facility, in order to achieve optimum performance via the targeted industrial process. Conceptualization, D.H. and J.-P.B. ; software, E.F.; investigation, D.H., S.R. and Y.L. ; resources, F.J.; writing--original draft preparation, D.H. and Y.L. ; writing--review and editing, E.F., F.J. and J.-P.B. ; supervision and funding acquisition, D.H. and J.-P.B. All authors have read and agreed to the published version of the manuscript. This research was funded by the ANR-SEED program of the French National Research Agency (project ANR-13-SEED-0007). The authors declare no conflict of interest. **Nomenclature**  
DSC & Differential scanning calorimetry  
HTF & Heat transfer fluid  
MSDS & Material safety data sheet  
PA & Palmitic acid  
PCM & Phase change material  
SA & Stearic acid  
TES & Thermal energy storage  
TG & Thermal gravimetric  
EU & European Union  
\(Cp\) or \(c\) & Specific heat  
D & Diameter  
M  
D1, D7, D14,  
D21 and D28  
Energy  
J or kWh  
\(h\) & Enthalpy or heat transfer coefficient  
J/kg or W/m\({}^{3}\)  
\(L\) & Latent heat  
J/g or kWh/m\({}^{3}\)  
\(m\) & Mass  
mg or kg  
\(\dot{m}\) & Mass or volume flow rate  
kg/s or L/h  
N & Number of experiments in Student's Law  
na & Non available  
\(Nu\) & Nusselt number  
\(Pr\) & Prandtl number  
\(r\) & Radius  
\(R\) & Thermal resistance  
K/W  
\(Re\) & Reynolds number  
\(S\) & Area  
\(\rm{m}^{2}\)  
\(\rm{St}_{N-1,\gamma}\) & Student's number  
\(T\) & Temperature  
\(V\) & Volume  
\(\gamma\) & Level of confidence in Student's Law  
\(\delta\) & Uncertainty in Student's Law  
\(\Delta\) & Variation between initial and final state  
\(\varphi\) & Heat transfer flux  
\(\lambda\) & Thermal conductivity  
\(\rm{W/m\cdot K}\)  
\(\rho\) & Density  
\(\eta\) & Efficiency  
\(\sigma\) & Standard deviation in Student's Law  
\(\tau_{95\%}\) & Storage responsiveness (time to reach 95% of the final  
storage capacity)  
Subscripts  
_cond_ & Conductive  
_conv_ & Convective  
_ext_ & External  
_HTF_ & Heat transfer fluid  
\(i\) & Initial  
\(\dot{m}\) & Inlet  
\(f\) & Final  
\(l\) & Liquid  
\(L\) & Latent  
\(m\) & Melting  
\(mp\) & Melting point  
_Nod_ & Nodule  
_out_ & Outlet  
_ref_ & Reference  
\(s\) & Solid  
\(S\) & Sensible  
_th_ & Thermal  
\(w\) & Wall