Scott Institute for Energy Innovation

Redox heat engines for fuels and cooling

November 29, 2017

9:00 a.m. - 10:00 a.m. ET

Scott Hall 5201, Marquis Conference Room


Arun Majumdar
Founding Director of the Advanced Research Projects Agency-Energy (ARPA-E)
Co-Director of the Precourt Institute for Energy
Jay Precourt Professor
Stanford University

Abstract

The science and engineering of heat engines have largely focused on energy conversion between heat and mechanical or electrical work. This talk will present two types of heat engines for work based on redox reactions.

First is the continuous electrochemical heat engine (CEHE) that leverages the advances in flow batteries for direct heat to electrochemical work. Using stacks of electrochemical cells driving flowing electrolytes in symmetric redox reactions at different temperatures, we demonstrate two continuous electrochemical heat engines that operate at 10–50ºC and at 500–900 ºC, respectively. Simulations suggest system efficiencies over 30% of the Carnot limit and areal power densities competitive with solid-state thermoelectrics at maximum power. The key advantage is the ability to fully decouple entropy conversion, thermal transport, and electrical transport.

Hydrogen produced by splitting water is one of the most fundamental reactions in energy research. We report the development of a new class of materials – entropy stabilized oxides (ESOs) – that harnesses the large entropy change during a solid-solid phase transition to thermochemically split water and produce H2 at temperatures below 1000 oC. This is a significant breakthrough over previously reported ones at 1500 oC, because it enables compatibility with the infrastructure of the existing chemical industry.

Despite the preliminary success, there are numerous unanswered questions with regards to the thermodynamics, kinetics and chemistry of these redox reactions using ESOs. Deeper understanding will not only allow the possibility of further temperature reduction but also sufficiently high kinetics to make this approach industrially relevant. This approach has the potential to open new options for low-cost low-carbon H2 production as well as other important redox reactions, such as reduction of CO2.​

Bio

Dr. Majumdar's research in the past has involved the science and engineering of nanoscale materials and devices, especially in the areas of energy conversion, transport and storage as well as biomolecular analysis. His current research focuses on using electrochemical reactions for thermal energy conversion, thermochemical redox reactions, understanding the limits of heat transport in nanostructured materials and a new effort to re-engineer the electricity grid. Learn more.

Majumdar’s Distinguished Lecture to follow at 12:00 p.m. Note that his lecture at noon is sold out. Coffee will be provided.

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