High Temperature Cycling Research Articles

Experimental Analysis of the R744/R404A Cascade Refrigeration System with Internal Heat Exchanger. Part 2: Exergy Characteristics

This paper examines the exergy efficiency and exergy destruction rate of the R744/R404A cascade refrigeration system (CRS) using an internal heat exchanger in supermarkets according to various conditions affecting the system. A refrigerant of a low-temperature cycle uses R744 and a refrigerant of a high-temperature cycle in the CRS uses R404A. Experiments were conducted by changing various conditions on the high- and low-temperature side, and exergy analysis was performed accordingly. The main results are summarized as follows: (1) the lower the total exergy destruction rate of the CRS, the higher the exergy efficiency of the system, and accordingly the coefficient of performance (COP) of the system is also improved. (2) In the CRS, since the optimum cascade evaporation temperature exists (about −16 °C), it can be said that the limit point, that is, the cascade evaporation temperature with the maximum COP of the system, is the optimum point at about −16 °C. Therefore, at this optimum point, the exergy destruction rate of the cascade heat exchanger becomes the minimum. In other words, it should be noted that when the cascade evaporation temperature is the optimum point, the exergy destruction rate of the R744 compressor and the cascade heat exchanger is minimal. The purpose of this study is to provide basic design data by analyzing the exergy characteristics according to various conditions on the high- and low-temperature side for optimal design of a CRS to which R744 is applied.

A Review on Recent Progress in the Integrated Green Hydrogen Production Processes

The thermochemical water-splitting method is a promising technology for efficiently converting renewable thermal energy sources into green hydrogen. This technique is primarily based on recirculating an active material, capable of experiencing multiple reduction-oxidation (redox) steps through an integrated cycle to convert water into separate streams of hydrogen and oxygen. The thermochemical cycles are divided into two main categories according to their operating temperatures, namely low-temperature cycles (<1100 °C) and high-temperature cycles (<1100 °C). The copper chlorine cycle offers relatively higher efficiency and lower costs for hydrogen production among the low-temperature processes. In contrast, the zinc oxide and ferrite cycles show great potential for developing large-scale high-temperature cycles. Although, several challenges, such as energy storage capacity, durability, cost-effectiveness, etc., should be addressed before scaling up these technologies into commercial plants for hydrogen production. This review critically examines various aspects of the most promising thermochemical water-splitting cycles, with a particular focus on their capabilities to produce green hydrogen with high performance, redox pairs stability, and the technology maturity and readiness for commercial use.

Performance Analysis of a Novel Cascade Vapor Compression System for Small-Scale Desalination and Cooling

Abstract The demand for improving living standards has led to increasing freshwater consumption and comfort cooling, requiring significant performance improvements. In this regard, a novel and efficient cascade refrigeration system (CRS) for simultaneous generation of considerable freshwater and cooling effect is proposed. The system does not require dedicated components for desalinating seawater because it is a by-product of the proposed CRS. Utilizing the cascade configuration enhances energy efficiency by lowering the compression work while improving energy recovery by utilizing the heat rejected from the condenser of low-temperature cycle to vaporize seawater for desalination in the evaporator of the high-temperature cycle of the proposed cascade system. A mathematical model of the innovative system based on thermodynamic and economic principles has been developed and utilized to predict the proposed system's thermal performance and cost-savings. A comprehensive analysis has been conducted to study the effect of multiple parameters such as the evaporator, condenser, and brine boiling temperatures. The main studied parameters were coefficient of performance (COP), gain output ratio (GOR), freshwater production, and total cost-savings. For a 10 tons of refrigeration (TR) unit, the freshwater production was between 56.11 and 73.36 kg/h, with cost-savings reaching 2226 US$/year. It was found that the freshwater production increased with condenser and brine boiling temperature but decreased with evaporator temperature. The COP improvement can be as much as 26% over the reference cooling system without desalination.

Preparation of unidirectional porous AlN ceramics via the combination of freeze casting and combustion synthesis

• Unidirectional porous AlN ceramics (UP-AlNs) were successfully fabricated. • The combination of freeze casting and combustion synthesis is economical. • The diluent content and solid loading affected the microstructure and open porosity. • The UP-AlNs exhibited anisotropic thermal conductivity and compressive strength. • The UP-AlNs have promising application prospects as catalyst supporters or filters. Unidirectional porous AlN ceramics (UP-AlNs) have attracted great attention for their wide applications in catalyst supports, filters and composite reinforcements. However, traditional fabrication processes usually require high temperature and long production cycle. Herein, UP-AlNs were successfully fabricated via the combination of tertiary butyl alcohol (TBA)-based freeze casting and combustion synthesis route using Al and AlN powders as raw materials. The microstructure, open porosity, thermal conductivity and compressive strength of UP-AlNs can be manipulated by synergistically regulating the AlN diluent content and Al/AlN solid loading of the freezing slurries. The optimal UP-AlNs exhibited controllable structure wavelength ( λ ) and open porosity in a wide range of 21.1-47.1 μm and 54.2%-86.0%, respectively. In addition, the corresponding products also possessed anisotropic thermal conductivity and compressive strength. This novel route for the fabrication of UP-AlNs has the advantages of low cost, energy-saving and high efficiency, which shows significant promise for industrial applications.

Performance of liquid crystalline polyester composite burn-in board connectors under cyclic high-temperature condition

The performances of connectors for burn-in tests made of various glass fibre/liquid crystalline polyester composites were analysed using mechanical testing and finite element analyses. Three different composites (E6006L, E6007LHF, and E6808UHF) were evaluated, containing one of two fibre types (chopped or milled) at different contents by weight. Material characterisations of the composites were accomplished by static tensile and fatigue testing under three temperature conditions (23 °C, 160 °C, and 220 °C). The tensile strength, failure strain, and S–N curves of the materials were identified and applied in finite element analyses of the connector structure. The structural integrity of each connector subjected to cyclic high temperature condition was then evaluated using stress and fatigue analyses, and the fatigue life was calculated according to material. Finally, the 40 wt% milled glass fibre/liquid crystalline polyester composite was identified as the most appropriate material for the burn-in test board connector structure.

Electrochemical and thermal characteristics of aging lithium-ion cells after long-term cycling at abusive-temperature environments

This work prepares five kinds of cell samples, i.e. the fresh cell, the cell degrades to 90% SOH (state of health) after high-temperature cycling, the cell degrades to 80% SOH after high-temperature cycling, the cell degrades to 90% SOH after low-temperature cycling and the cell degrades to 80% SOH after low-temperature cycling to reveal the electrochemical and thermal characteristics of the aging cells induced by abusive-temperature cycling. The cells under abusive-temperature environments show severe degradation behaviors over cycling, which may be mainly attributed to lithium inventory loss, anode material loss and electrode interface deterioration. Besides that, abusive-temperature cycling affects the thermal stability of positive electrode materials and single cells, and this is related with environmental temperatures. By comparison to the fresh cell, the thermal stability of the positive electrode materials and single cells after high-temperature cycling is improved, which is different from that of the low-temperature cycled ones who illustrate deteriorated thermal safety at elevated temperatures. Therefore, the thermal risk of aging cells after long-term low-temperature cycling is worthy of more concern, the according monitor and/or management of these cells during operation, transportation, storage and recycle, etc. should be valued.

Genetic selection modulates feeding behavior of group-housed pigs exposed to daily cyclic high ambient temperatures.

This study was conducted to evaluate the effect of genetic selection (Lines A and B; Line A pigs have a greater proportion of Pietrain genes than those from Line B and therefore, selected for improved lean tissue accretion) on the feeding behavior of group-housed pigs exposed to daily cyclic high ambient temperatures. Feeding behavior of 78 barrows housed together in a single room was recorded in real time by five automatic feeders. The feeders registered each visit of each pig (day, hour, min, and second) and the amount of feed requested. Daily cyclic high ambient temperature was induced exposing pigs at 22°C from 18.00 to 10.00 h and 30°C from 10.01 to 17.59 h. From this temperature variation, day-period was divided into: 22°C(06-10h), from 6.00 to 10.00 h; 30°C(10-18h), from 10.01 to 17.59 h; and 22°C(18-06h), from 18.00 to 5.59 h. Meal criteria was estimated based on the probability of animals starting a new feeding event within the next minute since the last visit (Pstart). After defining the meal criteria, the number of meals (n), feed intake rate (g/min), feed intake (g/meal), feeder occupancy (min/meal), and interval between meals (min) of each animal were calculated. Greatest probability of starting to feed was observed at 22°C(06-10h), followed by 30°C(10-18h) and then 22°C(18-06h). Regardless of time period, pigs from line A had greater feed intake rate and lower feed intake, feed occupancy per meal and probability of starting a meal when compared with line B pigs. Only line A pigs had greater feed intake and feeder occupancy per meal at 22°C(18-06h) than remainder of the day. This indicates that pig feeding pattern is strongly related to the circadian rhythm. However, the genetic selection for improved lean tissue accretion may modulate pigs feeding behavior under daily cyclic high ambient temperatures.

Highly stable operation of LiCoO2 at cut-off ≥ 4.6 V enabled by synergistic structural and interfacial manipulation

Elevating the charge cut-off voltage is the most effective approach for boosting the energy density of LiCoO2 (LCO), which however is hindered by accelerated structural devastation and interfacial degradation at high voltages, e.g. ≥ 4.6 V vs. Li/Li+. In this work, we propose a synergistic strategy by designing a Mg doped and Se coated LCO (LCO-Mg@Se). The strong Mg-O bond greatly stabilizes the layered structure of LCO, to alleviate the lattice parameter variation during deep delithiation. Se surface treatment, acting as an artificial CEI layer, interacts with O2−: 2p during deep stage of charge, effectively weakening the Co: 3d-t2g – O2−: 2p hybridization. Moreover, the Se coating layer could inhibit the parasitic side reactions and refrains the electrolyte corrosion toward the electrolyte-cathode interface, further mitigating the phase transformation to disordered rock salt phase at LCO particle surface and reducing the generation of resistive byproducts. These cooperative efforts enable the substantially enhanced high-voltage electrochemical performance of LCO-Mg@Se, achieving 147 mAh g−1 after 1000 cycles (72.9% retention) at charge cut-off 4.6 V and 148 mAh g−1 after 400 cycles at charge cut-off 4.65 V. The high-temperature cycling performance and thermal stability are greatly enhanced as well. This bifunctional structure/interface engineering approach provides scalable design ideas for developing cathode materials for high energy density batteries.

Energy and exergy analysis of NH3/CO2 cascade refrigeration system with subcooling in the low-temperature cycle based on an auxiliary loop of NH3 refrigerants

This paper proposes a NH3/CO2 cascade refrigeration system that sets an auxiliary refrigeration loop in the high-temperature cycle to increase the subcooling degree in the low-temperature cycle (CRSS). Based on the basic principles of thermodynamics, a mathematical model is established and theoretical simulation is carried out to obtain the influence of key parameters on the cycle performance. Compared with the conventional cascade refrigeration system (CCRS), the conclusions find that there exists an optimal condensation temperature of low-temperature cycle (TMC.opt) to maximize COP. The maximum COP of CRSS is 4.58% higher than that of CCRS when the subcooling degree is 10 °C. The maximum exergy efficiency is 0.391, increasing by 4.40%. With the increase of the subcooling degree, both the COP and the TMC.opt of CRSS increase. When the subcooling degree increases from 5 °C to 15 °C, the performance increment increases from 2.73% to 6.00%. When the evaporation temperature of the system changes, both the COP and exergy efficiency decreases slightly and it is found that the performance is better when the evaporation temperature is lower when condensation temperature is kept constant. Besides, the discharge temperature of the NH3 compressor in CRSS can be reduced by 9.9 °C when the evaporation temperature is −30 °C.

A Simulation Research on NH3/CO2 Cascade Refrigeration System Based on Theoretical Model

The rapid development of the refrigeration industry has benefited production and life, and has also brought irreversible negative impacts on the current environment. Finding environment friendly, energy-saving, stable, and new-type alternative refrigerants has become a common concern and research hot spot of researchers and the refrigeration industry around the world. In this article, a NH₃/CO₂ cascade refrigeration system model is established. CO₂ is used as the refrigerant in the low temperature cycle, NH₃ is used as the refrigerant in the high temperature cycle, and the condensing evaporator is used to couple the heat exchange between the high and low temperature circuits. Based on the first law of thermodynamics and the second law of thermodynamics, the author carries out the energy analysis and exergy analysis of the cascade system. Applying MATLAB software to establish the simulation calculation of NH₃/CO₂ cascade cycle. Through simulation, the author explores the effects of low temperature cycle CO₂ evaporation temperature and high temperature cycle NH₃ condensation temperature cycle parameters on the system cycle performance and system exergy efficiency. This paper provides a certain theoretical basis for improving the design of system structure and the system performance coefficient through simulation calculation.

Preparation and characterization of corundum ceramics doped with Fe2O3 and TiO2 for high temperature thermal storage

High-temperature thermal storage materials have received urgent attention for efficient thermal transfer in solar thermal power generation. Corundum ceramics doped with Fe2O3 and TiO2 were prepared via a pressureless sintering. A Fe2O3–TiO2 system with different Fe2O3/TiO2 ratios was applied to corundum ceramics. Phase composition, microstructural evolution, sintering properties, high temperature resistance and thermophysical properties were evaluated. The results indicated that Fe2O3 and TiO2 rendered the grains highly active and enhanced the bonding between grains due to existing stably in the lattice of corundum. In addition, decrease in the Fe2O3/TiO2 ratio led to a new phase of FeAlTiO5, which refined the grains. These effects gave the samples good sintering properties and thermal shock resistance, but the thermal expansion coefficient mismatch between FeAlTiO5 and corundum deteriorated the high-temperature (1300 °C) stability. Formula C1 (Fe2O3/TiO2 ratio of 9:1) sintered at 1600 °C had the optimum comprehensive properties, possessing a bending strength loss rate of 1.54% after 30 cycles of thermal shock (1100 °C-room temperature, air cooling) and a constant strength retention rate of approximately 71.34% after 90 h high-temperature cycle. The corresponding thermal conductivity and specific heat capacity were 18.81 W/(m·K) and 1.02 J/(g·K) at 25 °C, which was suitable as a high-temperature thermal storage material.

Effects of temperature and thermal cycles on the mechanical properties of expanded polystyrene foam

Understanding the effects of high temperature and thermal cycles on the mechanical properties of expanded polystyrene (EPS) foam is critical for its use in sandwich panels. This paper presents an experimental investigation of these effects in typical environmental conditions that exist in construction applications. A total of 117 small specimens were cut from metal-faced sandwich panels with EPS core and were exposed to different numbers of thermal cycles and/or sustained high temperatures. The specimens were then loaded under compression, tension, and four-point bending for evaluating the degradation of the mechanical properties of the foam. The thermal cycles reflect typical surface temperature during daily summer conditions, with a period of 24 h each and with a temperature varying between 24°C to 80°C. The results show that the modulus of elasticity of EPS foam in compression reduced by about 38% after exposure to thermal cycles for 45 days, whereas the tensile and shear moduli reduced by about 5.7% and 13.8%, respectively. Exposure to sustained high temperature after thermal cycles led to larger degradation of the elastic and shear moduli in the range of 38%–50%. These degradations can lead to early failures in applications that rely on the EPS foam as a structural component like in insulating sandwich panels.

High-temperature behaviour of basalt fibre reinforced concrete made with recycled aggregates from earthquake waste

Sustainable construction promotes the use of recycled aggregates from the demolition of either old concrete structures or earthquake-damaged structures. This construction approach has a positive impact on concrete production by reducing the consumption of natural resources. In this context, the current paper focuses on the two aspects, both related to the concrete made with recycled aggregates processed from earthquake-waste and reinforced with short (chopped) basalt fibres, i.e. (1) the residual strength of such the material after a high-temperature cycle (up to 700 °C); and (2) the mechanical behaviour of the material as a part of a confined square specimen structure after a thermal cycle and then wrapped with a carbon fibre reinforced polymer (CFRP) sheet. The effects of basalt fibres on the mechanical behaviour are investigated by testing ordinary concrete (no recycled aggregates) and the concrete with 50% and 100% replacement ratios of recycled aggregates, in all cases before and after a thermal cycle. The results show that using basalt fibres significantly improves the concrete mechanical performance not only at room temperature but also after a thermal cycle, even for a small fibre content (less than 4 kg/m3). Also, the CFRP sheet significantly enhances the load-carrying capacity of the concrete specimen after subjected to a high temperature. In addition, a design-oriented model is formulated to evaluate the load-bearing capacity of CFRP-wrapped specimens with the temperature effect.

High temperature electrical insulation and adhesion of nanocrystalline YSZ/Al2O3 composite film for thin-film thermocouples on Ni-based superalloy substrates

Electrical insulation and adhesion are two vital aspects for the integrated thin film sensors with Ni-based superalloy substrates. In this paper, nanocrystalline yttria-stabilized zirconia/alumina (YSZ/Al2O3) composite film was fabricated on Ni-based superalloy substrate by reactive magnetron sputtering. The X-ray diffraction and scanning electron microscope results show that tetragonal zirconia (t-ZrO2) nanocrystalline is homogeneously dispersed in the amorphous Al2O3 matrix. The crystal size of the t-ZrO2 nanocrystalline is well maintained with the temperature up to 1000 °C. The resistivity of the film is about 108 Ω·cm at 1000 °C, which is three orders of magnitude higher than that of the pure Al2O3 film. Furthermore, this YSZ/Al2O3 film demonstrates superior toughness and adhesion with the Ni-based superalloy substrate even after undergoing high-temperature cycles. Finally, a S-type thin-film thermocouple was fabricated on the YSZ/Al2O3 film shows good stability, repeatability, and linearity in multiple thermal cycling tests up to 900 °C exceeded 48 h.

Cathode-anode reaction products interplay enabling high performance of LiNi0.8Co0.1Mn0.1O2/artificial graphite pouch batteries at elevated temperature

LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode coupling with artificial graphite (AG) is a promising tendency for high-energy-density batteries. However, realization of long-term lifespan under current realistic conditions remains a “Gordian knot” for large-scale commercialization-oriented realm owing to the aggressive and highly reactive Ni 4+ sites on the delithiated cathodes and electrolyte exhaustion. Vinylene carbonate (VC) is commonly employed as the additive for graphite anode in carbonate electrolytes. However, VC has limited protection ability for NCM811/AG, especially for high-temperature cycling, showing conspicuous gas generation and large interfacial resistance. Herein, advanced carbonate-based electrolytes containing vinylene carbonate (VC) and phosphate compounds like triallyl phosphate (TPPC2) and tripropargyl phosphate (TPPC3) as electrolyte additives are reported to improve the performance of NCM811/AG pouch cells at elevated temperature. Theoretical calculations and comprehensive characterizations reveal that these two electrolytes well regulate the electrodes interface with more robust and homogenous films. Moreover, the TPPC2 and TPPC3 additives exhibit stronger tendency to eliminate the corrosive active oxygen ( 1 O 2 ) released from NCM811. These merits mitigate the electrolyte decomposition, decrease the gas generation, inhibit the dissolution of transition metals from cathode, and protect the structure stability of NCM811. Such outstanding electrochemical performance reveals promising prospects in the commercialized application of NCM811/AG batteries. ● Advanced carbonate electrolyte is prepared with VC and unsaturated phosphate. ● VC and unsaturated phosphate are beneficial for generating polymer-rich CEI. ● Capacity retention of NCM811/AG cells is 90.5% after 500 cycles at 1.0 C and 55 °C. ● DEMS is used to investigate gas evolution from a new perspective.

Influence of the LiFePO4/C coating on the electrochemical performance of Nickel-rich cathode for lithium-ion batteries

LiFePO4/C (LFP/C)-coated LiNi0.8Co0.1Mn0.1(NCM811) was prepared by a simple ball milling method (400 rpm for 4 h), and the influence of different coating amounts of LFP/C on the electrochemical performance of NCM811 was studied in detail. When the LFP/C coating amount was 1 wt%, the material maintained good electrochemical cycling stability and rate performance. The capacity retention of NCM811 @ 1LFP/C after 300 cycles was 61.6% at 25 ℃, which was significantly better than the corresponding value of 48.63% of NCM811. Simultaneously, the high temperature (55 ℃) and high pressure (2.8–4.5 V) cycling stability performance of NCM811 @ 1LFP/C was also better than for uncoated materials. The EIS results showed that the 1LFP/C modification effectively reduced RSEI (from 46.37 to 32.13 Ω) and Rct (from 155.9 to 113.5 Ω), which was beneficial for the interface charge transfer of electrons and Li+ ions, consistent with the CV analysis. The XRD, XPS, and FESEM results indicated that the coating layer suppressed the changes in the NCM811 particle macro-volume and reduced the side reactions, improving the electrochemical performance of Nickel-rich layered materials.

Impedance investigation of the high temperature performance of the solid-electrolyte-interface of a wide temperature electrolyte

The high temperature cycling performance of a wide temperature electrolyte and the solid electrolyte interphase (SEI) along the cycling were investigated using a three-electrode pouch cell. The electrolyte developed in our lab demonstrated outstanding low temperature performance. The electrolyte was found to have a good and stable cycling performance at a high temperature in comparison with a state-of-the-art baseline electrolyte. Electrochemical impedance spectroscopy (EIS) was conducted on the anode, the cathode and the full cell independently with a reference embedded pouch cell. The distribution of relaxation times (DRT) transformation was calculated from the EIS spectrum. An equivalent circuit model was used to fit the anode EIS data and the electrochemical process on the anode was revealed. We concluded that a denser SEI layer was built on the anode of the improved electrolyte.

The impact of sulfate- and sulfide-bearing sand on delayed ettringite formation

With the increase of aggregate quarrying to meet the growing need for concrete construction comes a risk associated with new aggregate sources, which may not have uniform compositions and contain potentially harmful substances, such as sulfate and sulfide. To provide insights into the impact of sulfate- and sulfide-bearing sand on susceptibility to delayed ettringite formation (DEF), this study measures the evolution of expansion, acoustic nonlinearity (representing microscale damage), and dynamic elastic modulus of mortars prepared with varying cement compositions and exposed to an early-age high-temperature curing cycle. Samples containing sulfate- and sulfide-bearing sand show substantially higher initial levels of damage, with expansion starting at earlier ages than control samples. Damage in mortars using this sand can be attributed to accelerated decomposition of alkali-feldspar, microcracking due to relative thermal deformation between phases, early release of alkali that increases the amount of sulfate in the pore solution, and release of sulfate ions from aggregates.

Analyzing the dual-loop organic rankine cycle for waste heat recovery of container vessel

Increasing the efficiency of ships via waste heat recovery systems is one of the most effective methods to minimize emissions from ships, especially carbon dioxide emissions. The organic rankine cycle is a promising system. The purpose of this study is to analyze the dual-loop organic rankine cycle system using jacket cooling water, exhaust gas and scavenge air. Two model is designed to analyze the waste heat recovery system for the different main engine load. In the first model, while the exhaust gas is used as the heat source in the high temperature cycle, jacket cooling water and high temperature loop waste heat are used as heat sources in low temperature cycle. Scavenge air and exhaust gas and jacket cooling water are used as heat sources in the second model. Different working fluid combinations that have been familiar from literature and their alternatives are analyzed in two models and the net power output by using thermodynamics, reduction in carbon dioxide and fuel consumption are calculated. In low engine load, since the temperature range of scavenge air is low the second model is suitable for high main engine load. Results show that with the second model when benzene-R245fa(1,1,1,3,3-pentafluoropropane) combination is used as working fluid, 3373 kW net power can be produced, 13588,3 tonnes/year Carbon dioxide emissions can be reduced. However, since benzene is a flammable fluid, it is not recommended for use in the ship. Instead of benzene, R1233zd(E) (trans-1-chloro-3,3,3-trifluoro-1-propene) is more suitable for high temperature source.

A Nonaqueous Redox Flow Battery Operating over an 80 Degrees Celsius Temperature Range

Multi-redox electrolytes with redox potentials were evaluated in redox flow cells at -40, 25, 40 ºC and Cells operated at -40 ℃ were assembled with premixed electrolytes and a non-selective separator due to high impedance of the anion-selective membrane at -40 ºC. After 100 cycles at that temperature, cells were raised to room temperature and cycled, then to 40 ºC. This low temperature cell cycled stably though at room temperature for 9 cycles, despite an increase in capacity, the cell cycled with lower efficiency, which is presumably due to faster crossover at the higher temperature. Unlike room temperature cycling, the cell did not retain high capacity at 40 ºC. Active material decomposition is a plausible reason for lower capacity at elevated temperature. After the high temperature cycling, the cell was cycled for 9 cycles at room temperature to see if the capacity recovered, but the capacity remained similar as -40 and 40 ºC cycling with fading observed at this temperature. Post-cycling cyclic voltammetry shows some formation of byproducts in the high potential region, although their identity is unknown. This marks the first time that non-aqueous redox flow cells have been cycled at such low temperatures and over such a wide temperature range. Figure 1