Characterization of Heat Storage Materials with Neutron Scattering and Imaging Techniques

Abstract

Roughly, three-quarters of the energy produced in the world ends up as waste heat. However, the waste heat can be harvested, stored and reused using specially built heat storage reactors for high- or low-temperature applications. This thesis attempts to provide new insight into metal halide ammines as a potential heat storage system with a high energy efficiency. These materials undergo desorption and absorption of NH3-gas in a thermochemical reaction, which results in an uptake or release of heat, respectively. This work shows the study of the thermochemical heat storage reactor prototype with the metal halide ammine salt Sr(NH3)xCl2 for low-temperature applications below 100 °C. The changes in kinetics and chemical- and physical properties during NH3 cycling were characterized by neutron imaging and scattering techniques. A honeycomb-shaped heat exchanger within the reactor was optimized based on the results from the neutron imaging investigations. The mechanical stresses and heat transfer within the heat exchanger were studied in detail. Overall, this project demonstrates for the first time the possibility of applying neutron imaging and scattering techniques for analysis of thermochemical heat storage materials and systems.