Applying chemical heat storage to saving exhaust gas energy in diesel engines: Principle, design and experiment

Abstract

Abstract Thermal energy storage has become more and more important to improving the overall efficiency of energy systems by utilising the wasted energy. This study was aimed to develop a chemical heat storage (CHS) system using magnesium hydroxide (Mg(OH)2) and its dehydration and hydration reactions to recover the thermal energy wasted by the exhaust gases in internal combustion (IC) engines. Experiments were conducted on a Diesel engine (D1146TI) to estimate the percentage of exhaust gas energy stored by CHS technology in the heat storage process. In this process, at 80% engine load, 61.4% of chemical material reacted and 5.05% heat energy of exhaust gas was stored in an hour. The percentage of the stored exhaust gas energy decreased with the engine loads. In the heat output process, in one of the proposed applications, the engine intake air was heated with the stored energy by hydrating MgO when the temperature of the inner wall of the reactor (T6) increased from 45 °C to 86.4 °C. The experimental results show that at the ambient temperature 23 °C, the intake air can be heated to the temperature 5.7 °C-17.3 °C higher than the ambient temperature. The applications of CHS to heating the engine, lubricant or batteries in hybrid vehicles are proposed.