| Solar energy with its rich resources, clean environmental protection, has got more and more attention of people from all over the world, There are many researchers studying the use of solar energy, including solar air conditioning system with lithium bromide solution, meets the requirement of energy conservation and environmental protection. But due to the solar energy is intermittent, to make full use of solar energy with cooling requirements at night, it should set up energy storage devices on the basis of the original refrigeration unit to improve the utilization efficiency of solar air conditioning unit.Three-phase solution energy storage is a new type of energy storage system, belonging to one kind of thermochemical energy storage technology. Using a variety of low and medium grade energy as heat source, the refrigerant water of the absorption refrigerating agent evaporates in the process of energy storage, then refrigerant vapor is cooled and liquefacted, accumulated in the water storage tank, and the dilute solution is concentrated and crystallizated in the process. At night when there are cooling requirements, strong solution absorbs the stored refrigerant, so as to realize refrigeration. Due to the presence of crystallization, the system has been further improved the energy storage density, and due to it can use a variety of low grade energy as a drive source of heat, including solar energy, so the energy sources are wide and high availability. The three-phase refers to the solution, crystal and steam respectively, there have been scholars at home and abroad beginning to study three-phase energy storage system and has made certain progress.This paper is studied based on the new type of three-phase energy storage system that has put forward using the lithium bromide water working as medium. The properties of lithium bromide aqueous solution were studied, especially the enthalpy, entropy and the key parameters of crystallization temperature that influencing system performance. By looking for a large number of literature getting the relation between the three parameters and the solution temperature and concentration, to simulate calculation on the computer conveniently. On the basis of this, efficiency the performance of the system was studied, including energy analysis, exergy analysis and entropy production analysis, in other words 3E analysis. System will be divided into four modules, mathematics and physics models were builded respectively, using MATLAB software programming for simulation. By calculating exergy loss of the main parts to get the exergy efficiency, in addition to the entropy production and the energy efficiency. And the areas of larger exergy loss and entropy production were also found, which laid a foundation for system optimization. Otherwise, the factors that affect the system performance were analyzed, including heat source water temperature and flow rate, cooling water temperature and flow rate in the absorber, evaporation temperature and condensation temperature. By analyzing the influence of different factors on the performance of the system, the method of the optimization of system design was found, providing a theoretical basis for experimental prototype design of three-phase energy storage system. |
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