Ian S. McKay

DESIGN AND OPTIMIZATION OF HIGH PERFORMANCE ADSORPTION-BASED THERMAL BATTERY

Electric vehicle (EV) technology faces a substantial challenge in terms of driving range, especially when the vehicle’s climate control system relies entirely on the onboard electric battery. Therefore, we are developing an advanced adsorption-based thermal battery (ATB) capable of delivering both heating and cooling for electric vehicles with minimal use of the electric battery bank. While adsorption based climate control systems offer the advantage of direct usage of primary thermal energy sources for operation, they typically have low COP values, and are often bulky and heavy. A compact and lightweight ATB is necessary to replace existing climate control systems in EVs that use electric battery for operation. In this paper, we present a detailed computational analysis of adsorption kinetics taking place within an adsorption bed that is capable of delivering large cooling and heating capacities by making use of novel adsorbents. The overall design of the adsorption bed, which is a critical element in achieving a high performance thermal battery, is also discussed. To make performance predictions, we characterized the adsorbents to obtain their thermophysical and transport properties as well as adsorption characteristics. The model consequently incorporates these measured properties to predict the performance variation as a function of time. This work provides the critical parameters affecting heating and cooling rates, and identifies avenues for further improvement in the overall performance of the thermal battery. NOMENCLATURE

One-pot solvothermal synthesis of a well-ordered layered sodium aluminoalcoholate complex: a useful precursor for the preparation of porous Al2O3 particles

One-pot solvothermal synthesis of a robust tetranuclear sodium hexakis(glycolato)tris(methanolato)aluminate complex Na3[Al4(OCH3)3(OCH2CH2O)6] via a modified yet rigorous base-catalyzed transesterification mechanism is presented here. Single crystal X-ray diffraction (SCXRD) studies indicate that this unique Al complex contains three penta-coordinate Al3+ ions, each bound to two bidentate ethylene glycolate chelators and one monodentate methanolate ligand. The remaining fourth Al3+ ion is octahedrally coordinated to one oxygen atom from each of the six surrounding glycolate chelators, effectively stitching the three penta-coordinate Al moieties together into a novel tetranuclear Al complex. This aluminate complex is periodically self-assembled into well-ordered layers normal to the [110] axis with the intra-/inter-layer bindings involving extensive ionic bonds from the three charge-counterbalancing Na+ cations rather than the more typical hydrogen bonding interactions as a result of the fewer free hydroxyl groups present in its structure. It can also serve as a valuable precursor toward the facile synthesis of high-surface-area alumina powders using a very efficient rapid pyrolysis technique.

Pulsed Heat Transfer for Thermal Maximum Power Point Tracking

This paper presents a new method for enhancing thermal energy harvesting via pulsed heat transfer. By acting as a variable thermal resistance that theoretically generates no entropy, a pulsed thermal connection allows calibration of the effective thermal resistance of an energy harvesting system. By adjusting the frequency and duty cycle of the pulsed heat transfer, the method allows an energy harvester to be continuously optimized for a variable incident heat flux. In this paper, the analysis of a generalized model shows how the pulse strategy theoretically allows any heat engine-heat sink pair to work at the same power and efficiency as a 1:1 thermal resistance-matched engine-heat sink pair of equal or greater total thermal resistance. Experiments with a mechanical thermal switch validate this model, and show how the pulse strategy can improve the efficiency of a system with equal engine and heat sink thermal resistances by over 80% with no increase in the hot-side maximum temperature, although at reduced total power. At a 1:2 engine-sink resistance ratio, the improvement can simultaneously exceed 60% in power and 15% in efficiency. The thermal pulse strategy could be implemented to improve of a variety of systems that convert thermal energy, from waste heat harvesters to the radioisotope power systems on many spacecraft.Copyright

Experimental Characterization of Adsorption and Transport Properties for Advanced Thermo-Adsorptive Batteries

Thermal energy storage has received significant interest for delivering both heating and cooling in electric vehicles, to minimize the use of the on-board electric batteries for heating, ventilation and air-conditioning (HVAC). An advanced thermo-adsorptive battery (ATB) is currently being developed, to provide both heating and cooling for an electric vehicle. We present a detailed thermophysical and physicochemical characterization of adsorptive materials for the development of the ATB. We discuss the feasibility of using contemporary adsorptive materials, such as zeolite 13X, by carrying out a detailed experimental characterization. In this study, zeolite 13X is combined with aluminum hydroxide (Al(OH)3) as a binder to improve the thermal conductivity. We also investigate the effect of densification on the overall transport characteristics of the adsorbent-binder composite material. Accordingly, the effective thermal conductivity, surface area, adsorption capacity and surface chemistry were characterized using the laser flash technique, surface sorption analyzer, thermogravimetric analyzer, and x-ray scattering technique. Thermal conductivity predictions of both zeolite 13X and its combination with the binder were made with existing conductivity models. Thermal conductivity in excess of 0.4 W/mK was achieved with the addition of 6.4 wt.% of Al(OH)3. However, a 10.6 % decrease in adsorption capacity was also observed. The experimental characterization presented herein is an essential step towards the development of the proposed ATB for next-generation electric vehicles.Copyright