Adsorption Machine & Desiccant Wheel based SOLAR COOLING in a Second Law perspective

Abstract

This thesis work is intended to investigate energy and exergy performance of a low power prototype solar air conditioning system based on sorption materials. Its performance is analyzed in the light of both the First and Second Law of Thermodynamics and compared with conventional HVAC systems as well as with a further solar cooling technology based on desiccant wheels (Solar DEC). The adsorption machine based solar cooling plant was thoroughly designed and its thermal performance analysed in several operating conditions and then optimized according to a First Law and Second Law approach. The sensitivity theory was also applied in order to investigate the system response to deviations of some state variables from their nominal values. In this context a number of sensitivity coefficients were determined in relation to the most relevant design parameters. That provided useful information for control strategies in dynamic regime and hints for systems design and optimization. A general model was also developed and implemented in a computer code for the determination of the thermophysical properties of humid air streams when leaving a desiccant wheel, based on the Jurinak Method. An important outcome of this research work is that solar energy, with its relatively low energy potential -when made available by a low-to-medium temperature collector, such as with adsorption machines or desiccant wheels-, is a more appropriate energy source to air-conditioning than conventional systems, from a true thermodynamic point of view. In this sense its technology should be developed and its use should be encouraged.