| Energy and environment are the hottest topics of the world today. And with the emphasis of the energy saving and environment protect, the utilization technology of low-grade energy such as the solar energy and waste heat is focused widely. Low-grade thermal energy resource is very rich in our country while was also wasted a lot due to the lack of emphasis and low efficiency. To develop the high efficient low-grade thermal energy utilization technology is an urgent task in dealing with the energy crisis. But how to utilize the low-grade thermal energy is a huge technology problem such as the mismatching between the energy supply and need. So we analyze and research the combination technology of temperature-life and energy storage as follow:(1) Study on a low-grade thermal energy storage methodology based on thermochemical pressure-down desorption technology. Aiming at the difficulty in utilizing low-grade thermal energy, a new target-oriented desorption method was proposed to decrease the overall driving heat source temperature of thermochemical sorption system. Lower the regeneration temperature by lower the bundle pressure in desorption process through the adsorption of auxiliary reaction salt. MnCl2-expended carbon composite energy storage material is main reaction salt which filled in main reactor while the auxiliary reaction salt is NaBr-expended carbon composite energy storage material. The desorption temperature of MnCl2-expended carbon composite energy storage material is high so it’s difficult to be applied. Through the pressure-down sorption technology, low-grade thermal energy was stored and thermal grade was lifted. In the experimental study, when the output temperature of main reactor is 134℃,141℃,147℃, the capacity in energy storage process is 1528kJ,1357kJ,772kJ. The capacity in energy discharge process is 2020kJ,1806kJ,846kJ. The capacity in low temperature heat source is 6432kJ,6255kJ,6893kJ. So the efficiency of energy storage is 0.18,0.17,0.08 while the efficiency of exergy is 0.27,0.25,0.13.(2) Study on a low-grade thermal energy storage methodology based on thermochemical temperature-life adsorption technology. A temperature-lift method was proposed to increase the output temperature of thermochemical sorption system in using the single variation character between the balance temperature and pressure of thermochemical sorption. The temperature will rise by increasing the pressure. Through the thermochemical temperature-life adsorption technology, low-grade thermal energy was stored and thermal grade was lifted. In the experimental study, when the output temperature of main reactor is 40℃,50℃,60℃, the capacity in energy storage process is 2393kJ,1937kJ,964kJ. The capacity in energy discharge process is 2020kJ,1806kJ,846kJ. The capacity in low temperature heat source of liquid storage vessel is 4509kJ,3797kJ,3835kJ. So the efficiency of energy storage is 0.33,0.31,0.19 while the efficiency of exergy is 0.32,0.32,0.20.(3) Study on an integrated low-grade thermal energy storage methodology based on thermochemical pressure-down desorption process and temperature-life adsorption process. Aiming at lifting the grade of thermal energy, an integrated low-grade thermal energy storage cycle based on thermochemical pressure-down desorption process and temperature-life adsorption process was proposed. The cycle combined the advantage of pressure-down desorption process and temperature-life adsorption process while at the same time, overcome the weaknesses of them. There are two reactors and a liquid storage vessel in the experiment system. MnCl2-xpended carbon composite energy storage material is main reaction salt which filled in main reactor while the auxiliary reaction salt is NaBr-expended carbon composite energy storage material. The NH3 liquid was stored in liquid storage vessel. Firstly lower the driving heat source in using the pressure-down desorption technology in desorption energy storage process so that the low-grade heat will be transformed to chemical energy. Increase the grade of thermal energy by using the temperature-lift adsorption technology in adsorption process. Through the transformation process from chemical energy to heat energy, realize the high efficiency utilization of low-grade thermal energy. In the study, the capacity in energy storage process is 7165kJ. The capacity in energy discharge process is 5705kJ. The capacity in low temperature heat source of auxiliary reactor is 6489kJ, The capacity in low temperature heat source of liquid storage vessel is 5304kJ. So the efficiency of energy storage is 0.3 while the efficiency of exergy is 0.39.In the aspect of energy storage density, the density of most of the thermochemical sorption salt is higher than 800kJ/kg while at the same time, the density of sensible heat storage(20℃temperature’s difference) is around 20-80kJ/kg. The density of phase change energy storage is around 80-220kJ/kg. We could conclude the storage density of thermochemical sorption is much higher than sensible heat and phase change energy storage and has a bright future.In contrast with traditional energy storage technology, the thermochemical energy storage technology has the advantage in lifting the grade of thermal energy, adjusting the output temperature and high density. When storing the low-grade thermal energy high efficiently, it can also lift the grade of thermal energy. |
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