Date of Award

Summer 2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Micro and Nanoscale Systems

First Advisor

Leland W. Weiss

Abstract

An approach to recover and store waste heat is presented in this dissertation. The waste heat is the energy that is rejected to the environment without being put to practical use and it is a result of both equipment inefficiency and thermodynamic limitation on the equipment and the process. In a typical Otto cycle, for instance, out of the total energy consumed by the system, only one-third of the energy is converted into useful work and the rest is discharged in the environment as waste heat [1]. For a spark ignition, a 1.4 liters internal combustion engine with the thermal efficiency of 15% to 32%, 1.7 kW to 45 kW of energy is wasted through coolant in the radiator and 4.6 kW to 120 kW of energy is wasted by the exhaust gas [1, 2]. Similar to the case of industry, 20% to 50% of the total energy consumed during an industrial process is rejected as waste heat [3]. These losses could be minimized either by improving the efficiency of the system itself or via the installation of a secondary waste heat recovery system. The recovery system uses the losses to generate mechanical or electrical work to enhance the efficiency of the primary system [4]. In addition to thermal recovery, thermal storage can play an important role in thermal energy scavenging and efficiency. The thermal storage technique is well established in a solar power plant where the excess heat and/or the captured heat itself is stored temporarily in a thermal storage device. The thermal energy storage (TES) process is then reversed, allowing the stored heat to be made available to a boiler at the periods of higher energy demand. Such notion of heat recovery and heat storage via the utilization of microdevice and phase change material based TES is presented in this dissertation.

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