# Techno-Economic Analysis of a Solar Thermal Plant for Large-Scale Water Pasteurization
## 5 Conclusions  
A techno-economic analysis of a solar thermal plant for water pasteurization has been presented. The effectiveness of different thermal treatments was first evaluated experimentally, and one has been chosen as a test case for the development of a lumped-component model of the whole plant. The model has been shown to correctly guarantee the target treatment conditions, and then used to evaluate the performance of the plant in different configurations. The optimal plant configuration from a techno-economic perspective has been assessed on the basis of two design variables, namely the solar multiple and the thermal energy storage duration. The most advantageous configuration has been obtained using a solar multiple between 0.75 and 2.75, according to the size of the plant, and a TES duration equal to 12 h. The unit cost of water treatment ranges from \(\approx\)32 EUR-cents m\({}^{-3}\) for a 50 L s\({}^{-1}\) facility, to \(\approx\)25 EUR-cents m\({}^{-3}\) for a 500 L s\({}^{-1}\) one. Based on the reported analysis, it can be concluded that: (i) an increase of the thermal energy storage duration generally leads to reduction of costs; (ii) the optimal solar multiple depends on the considered scenario; (iii) the economic optimization model is very sensitive to the capital expenses. Indeed, the solar field represents the higher contribution to the capital cost; therefore, in perspective, the opportunity to access to the fiscal advantages for energy reclassification operations may be interesting to reduce the overall expenses. Starting from these latter general rules obtained for the four analysed cases, further up-scaling can be considered to assess the validity of these model predictions to even larger plant layouts. Finally, other solar technologies may be also considered for the solar field; it would be indeed interesting to analyse the exploitation of, e.g., concentrated solar power. In addition, other renewable sources of heat or waste-heat recovery from industrial processes may be investigated to power the water treatment line [55; 56; 23]. Conceptualization E.C., P.A. ; methodology P.A. ; software A.B. ; validation M.M., L.B. ; formal analysis M.M., L.B. ; investigation A.B., F.B. ; resources F.B. ; data curation M.F. ; writing--original draft preparation A.B. ; writing--review and editing M.F. M.M., L.B. ; visualization A.B. ; supervision M.F., E.C., P.A., L.M. ; project administration L.M. ; funding acquisition E.C., L.M. All authors have read and agreed to the published version of the manuscript. The activity has been financially funded by Societa Metropolitana Acque Torino (SMAT) S.p.A.. M.M. and M.F. acknowledge funding from the Clean Water Center at Politecnico di Torino. Figure 7: Unit cost of water pasteurization as a function of the solar multiple for (**a**) different capacities of the plant (20 years lifetime) and (**b**) different expected lifetime of the plant (250 L s\({}^{-1}\)). All these calculations consider 12 h of thermal energy storage duration. **Acknowledgments:** The authors acknowledge [PERSON] for her help during the experiments. The authors are grateful with [PERSON], [PERSON] and [PERSON] for helpful discussions. **Conflicts of Interest:** The authors declare no conflict of interest.