Thermodynamic Evaluation of a Solar-Driven Adsorption Desalination Cooling Cycle

Abstract

The growth of the world population increases the demand for fresh water for human consumption, agriculture, and industrial production. Current sources and their respective procurement and treatment processes are insufficient to meet this growing demand and approximately 40% of the world's population is already somehow under water stress. Of all available water on the planet 97% is salinized and only 2-3% is available for human consumption, so desalination processes are presented as an alternative to be considered to mitigate the effects of water scarcity. Current commercially used desalination processes are energy intensive from 3.5 to 12 kwh/m3 of potable water produced in addition to potential environmental risk due to the discharge of brine laden with pre and post-treatment chemicals. In the evaluation of available technologies, thermal adsorption desalination (AD) processes are arousing growing interest due to their ability to cogenerate double distilled water and cooling effect with lower energy consumption and lower environmental impact. This paper presents a model based on the theoretical adsorption cycles and analyses the correlations between thermodynamic and operational parameters and their influence on system performance. The configuration of the system studied consists of a single bed reactor adsorption system using thermally activated silica gel (ads) through thermal energy from solar collectors. The performance indicator parameters used were specific drinking water production (kgh2o/kgads), (kJ/kg), and refrigeration effect (kJ/kg). With the simulation of the model the maximum values of water production per cycle 0.50 to 0.53 (kgh2o/kgads) were obtained with the inlet temperature of 80 to 95° C respectively and a cooling effect of 1,350 kJ/kg obtained at 90° C.