Characterization of thermal performance, flux transmission performance and optical properties of MAX phase materials under concentrated solar irradiation

The correct specification of glazings for façades can reduce the energy consumption in buildings. The heat exchange occurs through transparent surfaces and radiation reaches the building as light and heat. Therefore, glazings significantly contribute to the heat transfer between outdoor and indoor spaces and act directly on daylighting and thermal comfort. This paper reports on the spectrophotometric characterization of glazings transmittance for the study of components of a modular façade system and its suitability for the climate of Portugal (temperate climate). The study focused on results of spectrophotometric measurements of optical properties, specifically the transmittance of some types of glazings (solar control, self-cleaning, low-e, float, and extra-clear) and two types of double glazings. The results show the percentage of transmission to ultraviolet, visible, and near-infrared regions and its importance, which enabled the analysis of the glazing efficiency regarding daylighting and the correlation to thermal performance. Subsidies and indications for the specification and adequate uses of transparent surfaces have been presented and complemented the datasheets available from the manufactures.

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Comparison of ISS–CATS and CALIPSO–CALIOP Characterization of High Clouds in the Tropics

Remote Sensing ◽

10.3390/rs12233946 ◽

2020 ◽

Vol 12 (23) ◽

pp. 3946

Author(s):

Pasquale Sellitto ◽

Silvia Bucci ◽

Bernard Legras

Keyword(s):

Optical Properties ◽

Space Station ◽

Satellite Observation ◽

Observation Data ◽

Upper Troposphere ◽

Cloud Properties ◽

Synchronous Orbit ◽

The Tropics ◽

High Clouds

Clouds in the tropics have an important role in the energy budget, atmospheric circulation, humidity, and composition of the tropical-to-global upper-troposphere–lower-stratosphere. Due to its non-sun-synchronous orbit, the Cloud–Aerosol Transport System (CATS) onboard the International Space Station (ISS) provided novel information on clouds from space in terms of overpass time in the period of 2015–2017. In this paper, we provide a seasonally resolved comparison of CATS characterization of high clouds (between 13 and 18 km altitude) in the tropics with well-established CALIPSO (Cloud–Aerosol Lidar and Infrared Pathfinder Satellite Observation) data, both in terms of clouds’ occurrence and cloud optical properties (optical depth). Despite the fact that cloud statistics for CATS and CALIOP are generated using intrinsically different local overpass times, the characterization of high clouds occurrence and optical properties in the tropics with the two instruments is very similar. Observations from CATS underestimate clouds occurrence (up to 80%, at 18 km) and overestimate the occurrence of very thick clouds (up to 100% for optically very thick clouds, at 18 km) at higher altitudes. Thus, the description of stratospheric overshoots with CATS and CALIOP might be different. While this study hints at the consistency of CATS and CALIOP clouds characterizaton, the small differences highlighted in this work should be taken into account when using CATS for estimating cloud properties and their variability in the tropics.

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