# Experimental Investigation and Optimization of a Glazed Transpired Solar Collector
The results revealed that the TSC average efficiency is 65% for wind velocities below 2 m/s but the TSC average efficiency decreases below 25% for wind velocities above 7 m/s. These results have been confirmed by computational fluid dynamics simulations dealing with TSCs: a wind velocity between 0.5 and 2 m/s would not have such a great impact on the TSCs' heat transfer effectiveness, but for wind velocities exceeding these values, the TSCs' efficiency would considerably decrease [31]. Furthermore, [PERSON] et al. [32] thoroughly studied the degradation over time due to meteorological factors (e.g., acid and neutral rain) of aluminum absorber elements in the case of TSCs. Their results showed that the degradations of absorber optical properties (e.g., emittance) are important if the TSCs are exposed to rain with a pH exceeding 3.5-4.5. Therefore, this type of solar air collector is not recommended to be used in such operating conditions. Inaddition, the facade of the building could be degraded due to water infiltration through the perforations of the absorber. In order to cope with these problems related to weather conditions (wind, rain, and snow), the TSCs can be provided with a layer of glass applied to the surface of the absorber plate. This type of solar air collector is known as \"Glazed Transpired Solar Collector\"--GTC. Comparisons carried out between TSCs and GTCs highlighted better performances for GTCs, particularly for applications in cold climates: the annual solar fraction for air-heating systems based on GTCs is nearly nine times higher than that based on unglazed transpired collectors (TSCs) in the severe cold climate region of China [33]; the thermal performance and economic characteristics of GTCs with a perforated corrugated plate are superior in comparison with other types of TSCs in rural areas of cold regions [34]; the heat loss of GTCs can be reduced up to 40% compared to TSCs in the case of powerful wind and cold zones [35]; and GTCs could also lead to improved indoor environments [36]. Despite these significant accomplishments, GTC design optimization is essential to keep on improving the heat exchange rate. For instance, [PERSON] and [PERSON] [37] proposed an air layer of 40 to 50 mm between the absorber plate and the cover glazing in order to minimize both shading and heat losses through convection. [PERSON] et al. [38] have analyzed the thermal performance of glazed solar air collectors without/with phase change material (an absorber plate of simple sheet metal/an absorber plate containing nine aluminum containers filled with paraffin) under real climatic conditions. They concluded that the configuration with thermal storage integrated in the absorber led to better efficiency and higher stability of the collector outlet air temperature. In addition, there are many studies focusing on the optimization of the GTC absorber. Three types of GTC absorber were considered for comparison by [PERSON] and [PERSON] [39] over a wide range of operating and design conditions: flat plate, finned plate, and v-corrugated plate. Their data showed that the v-corrugated absorber was the most efficient while the flat absorber was the least efficient, regardless of configuration (single pass or double pass). [PERSON] et al. [40,41] also compared two configurations of an absorber made of copper: double-pass finned plate and double-pass v-corrugated plate. The results confirmed, based both on theoretical and experimental analyses, that the GTC with the v-corrugated plate was roughly 10-14% more efficient. [PERSON] et al. [42] found that longitudinal fins attached behind the GTC absorber plate improved the heat exchange, with the efficiency being increased by 5-7.5% (depending on the airflow rate) for the configuration with fins compared to that without fins. [PERSON] et al. [43] investigated the possibility to enhance the GTC efficiency by using an absorber made of aluminum cans. The best efficiency was achieved for the configuration with the aluminum cans positioned in a zigzag pattern on the absorber.