SUBJECT: Ph.D. Dissertation Defense
BY: Aravindh Rajan
TIME: Tuesday, November 23, 2021, 9:00 a.m.
PLACE: Virtual, Virtual
TITLE: Conceptualization, Thermodynamics, Kinetics, and Prototyping of Continuous Electrochemical Refrigeration
COMMITTEE: Dr. Shannon Yee, Chair (ME)
Dr. Matthew McDowell (ME)
Dr. Marta Hatzell (ME)
Dr. Seung-Woo Lee (ME)
Dr. Nian Liu (ChBE)


The rise of the average global temperature and, thus, global cooling demand is expected to be accompanied by record high sales of refrigeration and air-conditioning units. The state of the art in modern refrigeration and heat pumping is based on the vapor compression cycle. The refrigerants used in these units have a global warming potential (GWP) 1-4 orders of magnitude larger than that of carbon dioxide. Therefore, it is imperative to develop a zero-GWP refrigeration technology that can meet the cooling load demand at cost competitive efficiencies. Drawing inspiration from the vast recent progress made in flow batteries, I propose an electrochemical refrigerator. I will first introduce how electrochemistry may ne used to generate heat absorption. I will then discuss how continuous electrochemical refrigeration can be achieved in two incarnations: the Brayton and Stirling electrochemical refrigeration cycles (BECR and SECR). Then I present theoretical analyses for both these cycles, revealing the key thermodynamic, kinetic, and operational parameters using low order models, and introducing dimensionless figures-of-merits whenever possible to guide future research. I will then describe the key material properties and tradeoffs that must be considered when trying to screen/engineer new half-cell reactions that could be used in said electrochemical refrigerator. Then, I will review the setup and performance of the BECR proof-of-concept which achieves a peak COP of ~8, and a peak cooling load of ~1 W. Finally, I introduce the concept of Electrochemically Assisted Advective Cooling (EAAC), a cooling scheme that has the potential to provide higher cooling heat fluxes. I will finish by discussing the setup, performance, and limitations of the EAAC scheme.