Modeling and Simulation of Phase Change Material Based Thermal Energy Accumulators in Small-Scale Solar Thermal Dryers

Abstract

AbstractSolar thermal energy is of intermittent and dynamic character and the necessity to use this energy during non-sunshine periods has led to the development of thermal energy accumulators. The need of compact solutions have prompted researchers towards using latent heat storage. Phase change materials as thermal energy storage are attractive because of their high storage density and characteristics to release thermal energy at constant temperature corresponding to the phase transition temperature. The chapter overviews the recent state-of-the-art small-scale solar thermal dryers integrated with phase change material as an energy accumulator. This is an intensive field of investigation for more than 30 years with importance for the agriculture and the food industry especially in hot climate. A variety of commercial small-scale solar dryers are offered as a low-cost, zero-energy solution for small farmers. And yet, there are no commercial systems using latent thermal storage because at the present level of development this unit will increase unacceptably the price of the system. The solution needs very simple design, accessible materials, and optimal conditions for operation.The aim of the present work is to make an overview of the methods for theoretical evaluation and prediction, which are used to design and assess this devices and to point out the most appropriate of them for this new solution. The models enable to distinguish the most cost- and energy-effective solar dryer systems with thermal storage among the great number of designs, devices, and materials. The resulting conclusions from the collected and compared information will serve as a base for a novel solution of a cost-effective thermal energy storage for a small-scale solar dryer, which will lead to improved efficiency of the drying process, due to controlled temperature and longer operational time. This information might serve also in the development of the wider field of thermal energy storage, which is an important part of the technologies of renewable and waste energy conversion.Key wordsComputational Fluid DynamicsEnergy efficiencyExergy efficiencyLatent heatPhase change materialSolar dryerThermal energy accumulator