# Towards Improving the Durability and Overall Performance of PV-ETICS by Application of a PCM Layer
## 5 Conclusions  
The results of numerical analyses presented in the paper confirmed the risk of destructive overheating, which can appear on PV panels combined with external thermal insulation (PV-ETICS). Regardless of the location within Europe, the potential for electricity generation in the vertical configuration of PV panels is similar. Based on the initial analyses, it was revealed that, regardless of the building location, the temperature of PV elements exceeded 80 \({}^{\circ}\)C. Moreover, for some specific locations in the south of Europe, the overheating is much more serious, with temperature above 85 \({}^{\circ}\)C, which can cause faster degradation and decrease the overall performance of electricity production over time.  
For the improvement of system durability and to protect the panels against the ageing effect caused by temperatures above 85 \({}^{\circ}\)C, a modification of the system was proposed. The proposed idea was the thermal activation of the adjacent layer by phase change material application. A dynamic simulation with a coupled power and heat flow model, including latent heat storage, was used. The obtained results show that the amount of PCM that should be applied depends on the location and varies between 1.0 and 4.5 cm. These results seem to be reasonable considering the total weight of the system. On the other hand, the  
Figure 10: Comparison of the maximum values of the PV temperature in the case of PV-ETICS and En-ActivETICS.  
Figure 9: Calculated values of the t80 and degree hours (DH80) parameters for ETICS and PV-ETICS.  
proper design of the PCM layer regarding mechanical stability and thermal performance is a key issue for further investigation. Application of the encapsulated technology will increase the total thickness of the layer, resulting in significant overestimation.  
The final analyses for the case with the PCM layer applied in direct thermal contact with the PV panel (EN-ActivETICS) confirmed the correctness of the previous assessment. Due to the latent heat storage of solar energy in peak hours, the maximum temperature does not exceed 85 \({}^{\circ}\)C. This condition should lead to the safety and long-term usage of the photovoltaic system. On the other hand, it should be noted that the PCM layer can change its chemical properties over time. Moreover, the tightness of the cover layer is the weakest point of the system, and the risk of material leakage exists. Therefore, the overall thermal performance can change in time, and further full-scale and long-term measurements are necessary to confirm the overall performance of En-ActivETICS.  
Conceptualization, D.H., A.W.; methodology--heat transfer, D.H., A.W.; methodology--power flow, D.H., D.K.; numerical analyses, A.W.; formal analysis, D.H., A.W.; investigation, D.H., A.W., D.K., S.I., T.K., Z.S.; data curation, A.W.; writing--original draft preparation, D.H., A.W., D.K.; writing--review and editing, S.I., T.K., Z.S.; visualization, A.W.; supervision, D.H. All authors have read and agreed to the published version of the manuscript.  
This research was supported by the project En-ActivETICS: in a framework of M-ERA.NET by ETAG (grant No. 3-4/MOBERA1719029), NCBiR (grant No. M-ERA.NET2/2018/2/2019) and SAS (grant No. M-ERA.NET 2/2018/786/En-ActivETICS), by the Estonian Centre of Excellence ZEBE (grant TK146), by personal research funding (grant PRG483), and by Finest Twins project (grant No. 856602).  
Not applicable.  
The authors would like to thank [PERSON] from Sto Corp. for his valuable advice and support.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of the data; in the writing of the manuscript, or in the decision to publish the results.