Effects of Porous Graphene on LiOH Based Composite Materials for Low Temperature Thermochemical Heat Storage

Thermochemical heat storage material inorganic hydrate LiOH is selected as a promising candidate material for storing low-temperature heat energy because of its high energy density(1440 kJ/kg)and mild reaction process.However,the low hydration rate of LiOH limits the performance of low temperature thermochemical heat storage system as well as the thermal conductivity.In this study,porous-graphene/LiOH composite thermochemical heat storage materials with strong water sorption property and higher thermal conductivity were synthesized by hydrothermal process.The experimental results show that the hydration rate of the composites was greatly improved.The heat storage density of the composite materials was increased by 47%(from 661 kJ/kg to 974 kJ/kg).By combing the porous graphene,the thermal conductivity of composites with different contents were highly increased by 21.1%to 78.7%,but the increase of heat storage density is opposite to that of thermal conductivity.The development of high-performance materials for thermochemical heat storage should consider the relationship between the heat storage density and thermal conductivity of the material,and the thermal conductivity of the supporter needs to be further improved.

Carbonation Reaction of Lithium Hydroxide during Low Temperature Thermal Energy Storage Process

In order to apply lithium hydroxide(LiOH)as a low temperature chemical heat storage material,the carbonation reaction of LiOH and the prevention method are focused in this research.The carbonation of raw LiOH at storage and hydration condition is experimentally investigated.The results show that the carbonation reaction of LiOH with carbon dioxide(CO_(2))is confirmed during the hydration reaction.The carbonation of LiOH can be easily carried out with CO_(2) at room temperature and humidity.LiOH can be carbonated at a humidity range of 10%to 20%,a normal humidity region that air can easily be reached.Furthermore,the carbonation reaction rate has not nearly affected by the increase of reaction temperature.An improved storage method by storing LiOH at a low humidity less than 1.0%can be effectively prevented the carbonation of LiOH.The hydration reaction ratio of LiOH at the improved storage method shows a better result compared to the ordinary storage method.Therefore,the humidity should be carefully controlled during the storage of LiOH before hydration and dehydration reaction when apply LiOH as a low heat chemical storage material.