# Experimental Investigation and Optimization of a Glazed Transpired Solar Collector
## 3 Conclusions  
The main objective of this work was to optimize the design of a glazed transpired solar collector (GTC) and to assess its potential in reducing the energy consumption of buildings when it is integrated in ventilation systems. The investigations were entirely based on experimental studies. The experimental tests indicated that the GTC design \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Hour/Configuration** & **Without/With** & **Without/With** & **Without/With** & **Without/With** & **Without/With** \\
**(Day) Ventilation** & **GTC** & **GTC** & **GTC** (21 April & **GTC** (18 May 2021) \\
**Load (W)** & **(15 April 2021)** & **(16 April 2021)** & **(2021)** & **(2021)** \\ \hline
8 & 354/304 & 374/306 & 265/236 & 133/104 \\
9 & 328/265 & 296/94 & 190/24 & 53/- \\
10 & 306/231 & 229/- & 128/- & -/- \\
11 & 243/116 & 198/- & 101/- & -/- \\
12 & 166/- & 106/- & 24/- & -/- \\
13 & 118/- & 106/- & 60/- & -/- \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Experimental building ventilation load without/with GTC. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Hour/Configuration** & **Without/With** & **Without/With** & **Without/With** & **Without/With** \\
**(Day) Temperature (\({}^{\circ}\)C)** & **GTC** & **GTC** & **GTC** (21 April 2021)** & **GTC** (18 May 2021) \\ \hline
8 & 73.9/4. & 6.5/9.3 & 11/12.2 & 16.5/17.7 \\
9 & 8.4/11 & 9.7/18.1 & 14.1/21.0 & 19.8/23.9 \\
10 & 9.3/12.4 & 12.5/27.0 & 16.7/26.8 & 22.2/30.2 \\
11 & 11.9/17.2 & 13.8/28.1 & 17.8/28.9 & 23.9/34.5 \\
12 & 15.1/25 & 17.6/35.6 & 21.0/35.5 & 25.3/37.0 \\
13 & 17.1/30.7 & 17.6/33.7 & 19.5/30.3 & 26.6/37.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 9: Ventilation (supply) air temperature without/with GTC. with 30 mm between the absorber and the glass layer leads to enhanced heat transfer effectiveness and overall efficiency regardless of airflow rates. This configuration of the GTC prototype was installed within the facade of a full-scale experimental building. The results, based on long-term analysis, showed that the energy consumption for heating and ventilation was substantially reduced in the case of the building with the GTC compared to the configuration without the GTC. The savings in terms of ventilation load can reach 90%, depending on solar radiation. Moreover, the ventilation load reductions can be up to 25% even under unfavorable weather conditions (reduced solar radiation intensity and low outside temperature). These data confirm the significant capacity of GTCs to contribute to the overall energy performance of buildings, especially in cold and windy climates. This is all the more important as the recent coronavirus pandemic led to higher demands concerning the minimum rates of outdoor air ventilation in buildings. In this context, solar air-heating applications, especially those based on GTCs which can be wider and less restricted by climate conditions, represent proper solutions to minimize this increased energy demand of ventilation. However, the technology based on solar air collectors (including GTCs), despite some progress, remains underutilized compared to its huge potential. Consequently, further analyses should be performed, together with numerical modeling, to continuously improve the efficiency of this equipment and its integration within the facades of buildings and ventilation systems. As a result, this study should be further considered to investigate innovative designs of GTCs (e.g., with embodied phase-changing materials) under different climate scenarios and various thermal inertia characteristics of buildings. Conceptualization, C.I.T. and C.S. ; methodology, C.I.T., C.S. and F.B. ; validation, C.I.T. and F.B. ; formal analysis, C.I.T. and C.S. ; investigation, C.S. and C.C. ; data curation, C.S. and C.C. ; writing--original draft preparation, C.I.T.; writing--review and editing, C.I.T. and C.C. ; visualization, C.I.T.; supervision, C.I.T.; project administration, C.C. ; funding acquisition, C.C. All authors have read and agreed to the published version of the manuscript.