Solar cooling with aluminium pillared clays

Aluminium modified clays were prepared, characterised and tested for their potential application as solar coolers of roof surfaces. The water adsorption isotherm of the samples with restored cation exchange capacity was of hydrophilic type II, indicating multilayer adsorption with large heat of adsorption and pore condensation of water vapour at the pressures of the proposed application. In addition, high moisture adsorption capacity (more than 0.1 g of moisture per g of material at 60–70% of relative humidity) and fast kinetics for night sorption (comparable to silica gel) were determined for the freeze-dried pillared sample. In cyclic experiments with low irradiation during the day and night relative humidity of 55%, the maximum temperature inside the pillared montmorillonite was 6.5 °C lower than the corresponding temperature inside a typical soil sample. The primary mechanism for the reduced temperature elevation at aluminium modified clays was evaporative cooling and desorption with minor influence of solar reflection. These results indicate the suitability of aluminium pillared clays for lowering the roof surface temperatures.

Roof solar cooling with aluminium pillared montmorillonite.Figure optionsDownload as PowerPoint slideHighlights
► Aluminium pillared clays are hydrophilic with a type II sorption isotherm.
► High moisture sorption capacities and fast kinetics are observed.
► Night moisture sorption and day solar desorption cools the materials surface.
► Pillared clays have a significant potential for solar cooling applications.