The chemical looping heat pump (CLHP) is a promising electrochemical heat pump technology due to high system efficiency, scalability, and use of low-to-zero Global Warming Potential (GWP) fluids. However, similar to other emerging HVAC&R technologies, there is a lack of direct comparison and discussion of economics between CLHPs and conventional vapor compression (VC) heat pumps. In this work, a generalized modeling framework to estimate the levelized cost of energy (LCOE) for space conditioning applications is used to assess the early-stage economic feasibility of CLHP. The LCOE consists of two components: levelized operating expenditures and levelized capital expenditures. These clarify the influence of key factors such as annual cooling and heating delivered and price of electricity. The simulations show that the LCOE of CLHP could be less than that of VC in the case of unit utilization of >30,000 kWht yr(-1), operating current density of >0.4 A cm(-2), and 30% performance improvements. This is despite the projected capital cost of CLHP is nearly 1.6 times higher than that of VC system.

All datasets reported in the paper and all original code are deposited in this repository.

Air conditioning, space heating, and refrigeration account for nearly 40% of the primary energy use in the U.S. residential and commercial buildings. To reduce energy consumption, the development of highly efficient heat pumping technologies will play an indispensable role. The chemical looping heat pump (CLHP) system has shown 20% to 30% performance improvements relative to current vapor compression technologies. However, the results were mostly based on a simplified form of thermodynamic models, which necessitates experimental investigations and a deep understanding of the behavior of a non-ideal CLHP cycle. In this study, electrochemical cell materials and system performance of the CLHP cycle were evaluated based on the combination of component models and experimental results. The overpotential of the electrochemical cell was analyzed and coupled with a cycle model to understand the non-ideal behaviors of the cooling mode and the performance of the CLHP system. Lastly, the result of this study was compared with the previous analysis to discuss the impact of chemical kinetics on the CLHP cycle.

Selecting appropriate working fluids is important for improving the technology readiness level of electrochemical heat pumps (EHP), which is a promising emerging technology for space conditioning and thermal management applications. The major contribution of this paper is to develop and evaluate key metrics to identify electrochemically active working fluids based on heat pump cycle requirements. The key metrics include the possibility of phase change after a chemical reaction, reversible cell voltage and power consumption, cooling and heating capacity, and environmental and safety aspects. Such metrics are applied to conduct fluid screening to assess their suitability. Isopropanol/acetone showed the highest potential to deliver efficient cooling and heating when applied to an EHP system; the use of ethanol/acetaldehyde and methanol/formaldehyde would easily enable electrochemical fluid condensation over a wide range of operating temperatures. Although the approach is demonstrated for selected organic fluids, the screening framework can be readily employed for other chemical compounds expanding the design space of electrochemical heat pumps.

Air conditioning, space heating, and refrigeration account for approximately 40% of electricity usage in the U.S. residential and commercial building sector. Therefore, the develop-ment of more energy efficient heat pump technologies remains an ongoing pursuit with widespread practical implications. Electro-chemical looping heat pump (ELHP) technology has emerged as an attractive alternative to conventional vapor compression systems (VCS), theoretically promising significant improvements in both performance and energy consumption. However, efficient ELHPs require selective facilitation of redox reactions that interconvert working fluids with minimal energy input. In this work, we report on the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mediated oxidation of isopropanol (IPA) to acetone as a promising system for ELHP. We characterized the performance of seven different TEMPO derivatives for mediated electrocatalytic IPA to acetone conversion. 4-Methoxy-TEMPO emerged as the most promising candidate which selectively oxidized IPA to acetone in basic pH as confirmed via electrochemical methods and 13C NMR. Coupling experimental results with DigiElch simulations helped in characterizing the rate constant for the reaction as 6 M-1 s-1 and a turnover frequency of 3.1 s-1 at pH 10. Bulk electrolysis measurements followed by 13C NMR highlighted the selectivity of the catalyst (similar to 100%), even at IPA concentrations as high as 0.5 M IPA, making them ideal for use in practical ELHP. This work introduces a methodology to identify suitable catalysts for efficient ELHP and other bulk conversion methods based on concepts of highly selective mediated electrocatalysis.

The Heating, Ventilation, Air Conditioning, and Refrigeration (HVAC&R) industry has heavily relied on vapor compression cycles since the early part of the 20th century. However, due to environmental concerns and advances in both material and thermal sciences, non-vapor compression technologies have gained attention as potential alternatives to conventional HVAC&R systems. Non-vapor compression technologies also termed not-in-kind technologies, include solid-state refrigeration technologies, thermally-driven cycles, gaseous cycles, chemical heat pumping, membrane heat pumping technologies, and desiccant systems among others. In 2014, the U.S. Department of Energy's Building Technology Office (BTO) released a report that compared several non-vapor compression technologies and quantified the potential energy savings. Since then, other researchers have reviewed not-in-kind technologies and compared them with vapor compression systems. However, no direct comparison with the current state-of-the-art equipment and forthcoming standards is available in the literature. To this end, this paper addresses three major aspects: (i) assessing the current state-of-the-art to identify key advancements in conventional and novel HVAC&R technologies; (ii) defining suitable figures-of-merit to compare the different technologies from a thermodynamic standpoint as well as technology readiness; (iii) creating a roadmap for the development of novel HVAC& R technologies.

A unitized regenerative fuel cell (URFC), an electrochemical device operated in both water electrolysis (WE) and fuel cell (FC) modes, is a promising technology in interconverting renewable electricity and chemical fuels within a compact system. However, Proton-exchange membrane-based URFCs usually employ a significant amount of precious metal catalysts, e.g., up to 4 mg((Pt+IrO2)) cm(-2), to achieve high efficiency in round-trip operations. Here, we present a PEM-URFC electrode that uses only 0.8 mg((Pt+Ir)) cm(-2) without compromising the performance of URFC. IrO2-shells (70 nm) layered upon hemispherical Pt particles (Pt@IrO2) are formed using sequential electrodeposition over Ti-felt electrodes. A 100 % improvement in WE compared to performance without Pt supports and superior mass activity (44 A mg(Ir)(-1) at 2 V-cell) with an insignificant degradation rate of 155 mu V h(-1) at 0.4 A cm(-2) are demonstrated. In addition, high round-trip efficiency of 49 % at 0.4 A cm(-2) in URFC is achieved.