Novel, low cost CaCl2 based desiccants for solar crop drying applications

A review on the use of calcium chloride in applied thermal engineering

“…The main drawback is the need to cool the absorber and to heat regenerator for appropriate operating conditions. In Kenya, a solar desiccant dryer based using clay-calcium chloride based solid desiccant and devoted to crop dying applications has been theoretically and experimentally investigated for years [6,96,97]. The purpose of the suggested dryer is an efficient drying of crops (maize in the studied case) in order to avoid fungal growth and aflatoxin production in crops by significantly extending the drying process during night-time, thus impacting rural communities health and reducing post-harvest crop losses due to contaminations, using local materials [6].…”

“…When solar supply is not available, inlet and exit windows are closed and air is circulated by a photovoltaic powered fan between the desiccant bed and the maize (the photovoltaic cells run on a battery). This application resulted in the continuous drying of fresh maize from 38 wt% to 15 wt% within 24 h [6,96]. The precise composition of the desiccant mixture in the prototype was not given but later reports from the team give some indications [96].…”

“…This application resulted in the continuous drying of fresh maize from 38 wt% to 15 wt% within 24 h [6,96]. The precise composition of the desiccant mixture in the prototype was not given but later reports from the team give some indications [96]. Indeed, three types of desiccant have been reported by the authors and said to have been used in the prototype: Type 1: bentonite (60 wt%), CaCl 2 (10 wt%), vermiculite (20 wt%) and cement (10 wt%) Type 2: bentonite (65 wt%), CaCl 2 (5 wt%), vermiculite (20 wt%) and cement (10 wt%) Type 3: kaolinite (65 wt%), CaCl 2 (5 wt%), vermiculite (20 wt%) and cement (10 wt%) All these clay-CaCl 2 desiccants show higher moisture sorption than commercial silica gel (between 30 and 45 wt% compared to 27 wt% for the investigated silica gel) [96].…”

“…The precise composition of the desiccant mixture in the prototype was not given but later reports from the team give some indications [96]. Indeed, three types of desiccant have been reported by the authors and said to have been used in the prototype: Type 1: bentonite (60 wt%), CaCl 2 (10 wt%), vermiculite (20 wt%) and cement (10 wt%) Type 2: bentonite (65 wt%), CaCl 2 (5 wt%), vermiculite (20 wt%) and cement (10 wt%) Type 3: kaolinite (65 wt%), CaCl 2 (5 wt%), vermiculite (20 wt%) and cement (10 wt%) All these clay-CaCl 2 desiccants show higher moisture sorption than commercial silica gel (between 30 and 45 wt% compared to 27 wt% for the investigated silica gel) [96]. The authors also report that the desiccant type 1 within Kenya's tropical climate can be used for at least one year without any substantial loss in moisture sorption performance; the estimated cost of these desiccants are the ninth of the cost of commercial silica gel [96].…”

Solar-Energy Drying Systems

“…The cost of desiccant materials is high causing the final product cost to be high. Hence, low cost desiccants (Thoruwa et al, 2000) particularly suitable for tropical countries are identified as bentonite-calcium chloride and kaolonite-calcium chloride. Yet another type is the one with thermal storage (sensible) to take care of intermittent incoming solar radiation.…”