DATE: Thursday, July 29, 2021
TIME: 10 - 12 pm
ADVISOR(S): Dr. Hongyan Ma
DISSERTATION TITLE: EXPERIMENTAL AND NUMERICAL STUDIES OF NOVEL THERMAL ENERGY STORAGE MATERIALS FOR APPLICATIONS IN CONCRETE AND ENERGY STORAGE SYSTEMS
For the sake of energy saving and green energy deployment, thermal energy storage (TES) - in view of supplementing energy consumption of buildings and improving demand flexibility and overall resilience of grid - is desired. In this study, several types of novel thermal energy storage (TES) materials and composites are explored, and a series of numerical simulation models and experimental protocols are developed to evaluate the potentials of these materials to be applied in concrete, pavement, and thermal energy storage systems.
TES materials studied include phase change material (PCM) and thermochemical material (TCM). The first two type of novel TES materials/composites are at the micro-scale, which use micro diatomite (DE) and cenosphere (Ceno) as carriers of PCM (i.e., n-octadecane), respectively. Both DE-PCM composite (30wt% PCM, latent heat of 68 J/g) and CenoPCM composite (46wt%, latent heat of 109 J/g) have been proved to have pozzolanic reactivity, which prevents leakage of PCM and maintains the mechanical properties of the functional construction materials incorporated with PCM. The third type of novel TES material is at the macro-scale, utilizing lightweight sand (LWS) and lightweight coarse aggregate as carriers to load PCM. Mortar prepared with PCM loaded LWS has comparable compressive strength to that of reference mortar using normal rive sand and 63% smaller autogenous shrinkage, along with an abatement of apparent hydration heat as well as a delay of peak temperature. The last two types of novel TES materials are solid-solid PCM (SSPCM, i.e., PEG-PMDI-Graphite composite) and TCM (i.e., struvite-K). Their phase change mechanisms/properties and thermal stabilities/reliabilities are revealed. The results suggest high potentials of them in specific TES applications.
The above multi-scale TES materials and composites can be used independently or in combination, according to application scenarios. To evaluate performance of TES materials in various scenarios, numerical simulation frameworks and experimental protocols have been developed and implemented. Three representative scenarios (i.e., thermal cracking control for concrete, thermal curling mitigation for pavement, and TES enhancement for geothermal energy storage systems) have been selected for study in this dissertation. The studies presented in this thesis show that TES materials (i.e., PCMs and TCMs) are technically feasible in mitigating thermal degradations of concrete and enhancing efficiencies of TES systems. They have promising marketability upon they can be economically available.