Microclimate Analysis of Outdoor Showcases in Tropical Climate—Two Case Studies in Al Ain, Abu Dhabi, United Arab Emirates

Abstract

Al Ain, near Abu Dhabi, United Arab Emirates, is characterized by hot desert climate with high temperatures, aridity, and almost no rain. Several truncated earthen walls were discovered at the historic house of Sheikh Mohammed Bin Khalifa, a component of the World Heritage Cultural Sites. These remains are preserved in situ, outdoors, protected in glass showcases for public display. As this situation is not documented in the literature, the local Authority has requested to study the showcase environment to optimize conservation. The solar radiation and the projected shades have been modeled over one year; the temperature and humidity inside and outside the showcases, as well as the moisture content, have been measured to assess the potential preservation risks. The paper presents the results, i.e., the direct solar radiation generates extreme conditions of greenhouse effect with extremely high temperatures and forces evaporation from the remains. During the night, the excess moisture condenses on the inner surface of the glass panes, forming large drops that affect viewing and are dangerous for conservation. The repetition of evaporation–condensation cycles accumulates soluble salts on the remains. The paper discusses mitigation strategies (e.g., shading, ventilation, and cooling, to reduce the greenhouse effect) to improve conservation and fruition.

Preventing Glass Misting in Indoor Showcases with Burial Remains at Al Ain, UAE

“…If one excludes the formation of large drops that grow and fall on the remains, as observed in the outdoor showcases [14], the simple glass misting penalizes the exhibition, but not necessarily the conservation. To this aim, the relative humidity in the showcases and the differences between the mixing ratios in the showcase and the room are more relevant.…”

“…For the external conditions, a pair of combined sensors (T E |RH E ), including air temperature (T E ) and relative humidity (RH E ), has been installed outdoors, protected with a standard multiplate solar shield (for details see [14]).…”

“…The two showcases located outdoors lie in extreme conditions, and in particular, the greenhouse effect generated by the strong solar radiation of the Tropic of Cancer. They have been studied and presented in another paper [14]. The result was that the strong solar radiation hitting the glass panes generates a greenhouse effect and the showcases reach very high temperatures, e.g., 80 • C. During the day, the extreme heat forces moisture to evaporate from the remains; during the nocturnal cooling, the moisture in the air reaches saturation and condenses on the inside surface of the glass panes, forming large drops that hide the view, and fall onto the earthen remains.…”