Ambient Temperature Operation Research Articles

Liquid Polyether-Based Water Harvester for Near Ambient Temperature Operation via Hydrophilicity-Difference-Induced Water Transfer

Liquid Polyether-Based Water Harvester for Near Ambient Temperature Operation via Hydrophilicity-Difference-Induced Water Transfer

Heat management system design and implementation in a PEM water electrolyser

Green hydrogen has emerged as a real alternative for the decarbonization of industry, mainly Oil&Gas, ammonia and the transport sector. In addition, in situations of global crisis like the current one, it is a key tool to avoid being dependent on natural gas exported from other countries. That is why the European Union has set a production target of 10 million tons of green hydrogen per year by 2030. As recently as May 2022 the European Union signed a pact with European electrolyser manufacturers in order to reach this target as rapidly as possible. There are many ways of producing hydrogen, natural gas/coal reforming, biomass pyrolysis, but all of them involve the production or capture of carbon dioxide, in some way, water electrolysis being the most efficient way to obtain hydrogen without greenhouse gas emissions, in addition, water electrolysis has great synergies with renewable energies. This article is based on the study of the different parameters that affect the efficiency of the electrolysis process, focusing on the operating temperature control. A temperature management system has been proposed to maintain the stack at the desired operating point. The real electrical consumption data during the operation of an electrolyser under different ambient temperatures have been studied. Real evidence has been found regarding the relationship between external temperature and the efficiency of the electrolyser, leading to a more in-depth analysis to obtain efficiency correction curves based on the ambient operating temperature.

Nanoscale engineering of polypyrrole-silver oxide composites for rapid and ultrasensitive room temperature carbon monoxide detection

In this work, a silver oxide decorated Polypyrrole (Ag2O@Ppy) composites-based sensor was fabricated, for the first time, via a simple solution mixing method. Extensive materials characterization, via XRD, AFM, SEM, UV–vis, FTIR, and Raman spectroscopies, elucidated the tailored nanoarchitecture, unveiling Ag2O nanoparticle decoration homogenously encapsulating Ppy matrices. Systematic comparative gas sensing analysis demonstrated remarkably high sensitivity and selectivity towards CO versus other hazardous species (NH3, NO2, H2S, SO2). A superb 387% response at 300 ppm CO was achieved, significantly exceeding other gases. Remarkably, outstanding 156% response even at ultralow 10 ppm concentration reflected an exceptional limit of detection rivaling most sensors. Rapid, reversible response kinetics with 111 s reaction and 66 s recovery times arose from synergistic coupling between Ppy and Ag2O nanoparticles enabling expedited charge transfer. Excellent linearity spanned an ultrawide 10–600 ppm range. Unprecedented performance combined sensitivity, selectivity, speed, stability, and ambient temperature operation. The work unveils tremendously promising Ppy-Ag2O nanocomposites for next-generation chemiresistive CO monitoring critical for environmental safety and healthcare.

(Invited) Addressing Durability in Long-Life, Low-Power Fuel Cells

Fuel Cells’ scalability and energy density make them excellent candidates for different applications, especially difficult to electrify applications. Their design flexibility can also be applied to low power, long-life applications. LANL has constructed a unique design to provide continuous, low power (< 100 µW) for very long duration (multiple decades). This LANL system operates passively, without active control of cell parameters, such as temperature and humidity. In addition, the system does not require interventions like refueling or maintenance during its operational lifetime. While the application and operational conditions of the systems mentioned here differ greatly from those of light and heavy-duty vehicles (e.g. ambient temperature operation, passive water management, low current densities), many of the modes of degradation are similar, and listed below: Membrane thinningDegraded performance due to loss of electrochemical surface area (ECSA)Loss of water management due to changes in hydrophobicityIncreased cell resistance due to corrosion of cell components To better understand these degradation processes LANL has performed accelerated stress tests (ASTs) to induce and quantify the membrane thinning, loss of ECSA, hydrophobicity, and bipolar plate corrosion. Those ASTs include long term OCV holds with reactants present, high potential cycling (1-1.5 V) in flooded conditions, potential cycling to induce catalyst Ostwald ripening, and exposure of cell components to corrosive environments.

A synergistic approach to enhance sensitivity and selectivity of room temperature operable ammonia gas sensor with humidity assistance using RGO/WO3 nanocomposite

In this study, the fabrication of an ultrahigh selective NH3 gas sensor based on RGO/WO3 nanocomposite has been proposed. The hydrothermal method was employed to synthesize the RGO/WO3 nanocomposite. The formation of RGO/WO3 nanocomposite and the elemental composition, structure and morphology of the as-synthesized materials were confirmed through an array of analytical techniques, including XRD, Raman, FT-IR, XPS and TEM. For gas sensing applications, pure RGO and RGO/WO3 have effectively spin-coated onto the interdigitated electrodes (IDE’s) based on fluorine doped tin oxide (FTO) respectively, and their sensitivity towards NH3 was tested. Gas sensing characteristics of prepared materials were analyzed at room temperature (25 °C) under different relative humidity (RH) levels. The developed RGO/WO3 sensor was subjected to different NH3 concentrations, demonstrating a high sensing response of 89% towards 500 ppm NH3 under 11%–97%–11% RH conditions. Notably, the sensor exhibited rapid response and recovery times with an average response time of 92 s and recovery time of 26 s when exposed to 500 ppm NH3 under the specified RH conditions. To gauge the material selectivity, the prepared nanocomposite was exposed to a range of volatile organic compounds and the results showcased the sensor’s remarkable selectivity and sensitivity specifically toward NH3 vapor. This superior performance can be attributed to the abundant active sites and the excellent electron transport properties inherent to the RGO component. Importantly, the RGO/WO3 sensor displayed high reproducibility and consistent responses, with minimal degradation (1.98% degradation) over 30 d at 11%–97%–11% RH. Furthermore, we examined the sensor’s response with varying levels of relative humidity to assess its potential for real-world applications. The sensor exhibited extremely low power consumption, outperforming a commercially available metal oxide sensor while operating at ambient temperature. The robust performance of RGO/WO3 coupled with low power requirements and ambient temperature operation, positions it as a promising candidate for next-generation gas sensing technologies.

Design of novel thermal management system for Li-ion battery module using metal matrix based passive cooling method

Reliable, efficient and safe energy storage is important for electric vehicles and renewable energy storage of power grid. Lithium-ion battery is preferred as energy storage device due to its higher energy density, low self-discharge and longer cycle life. Lithium-ion cells generate heat during high discharge rates and harsh ambient temperature operation, which raises cell temperature and impacts its performance. Therefore, an efficient thermal management system (TMS) is necessary to alleviate thermal issues during charge/discharge process. A combination of phase change material (PCM) with high conductive plate metal matrix is proposed to eliminate the limitation on the heat transfer characteristics of air-cooled systems. To analyze the thermal and electrochemical behavior of a Lithium-ion cell, a detailed CFD simulation with empirical NTGK electro-chemical model is used. The model is first validated with available experimental data and the analysis is then extended to predict thermal response of individual cell of 3s3p module under natural convection boundary conditions. Poor heat transfer capability associated with natural convection at elevated temperature and discharge rate causes the cell maximum temperature (Tmax) and uniformity (ΔT) to be higher than acceptable values of 45 °C and 3 °C respectively. A thermal management system based on passive cooling using PCM is proposed and analyzed using CFD model by first validating the PCM melting behavior under uniform heating. The model is then extended to analyze the impact of PCM on cell temperature rise at different discharge rates of 8 A - 25 A (≈1C - 3.2C) and various operating temperatures of 25°C to 35°C. Low thermal conductivity of PCM limits heat dissipation which leads to higher temperature gradient. A novel TMS based on plate metal matrix structure enclosing PCM is proposed to enhance heat conduction across PCM and increase heat dissipation to maintain battery module under safe operating temperature limits. This approach has brought down the module maximum temperature to 44.1 °C and temperature difference to 1.6 °C during operation at 25 A (3.2C) and 35 °C. Hence, PCM with high latent heat and low thermal conductivity could be used with high conductivity plate metal matrix to improve cell performance by keeping the cell temperature at required range.

A Chemical Synthesis of CdSnO 3 Nanoparticles and their Performance in Hydrogen Sensing

Abstract: CdSnO3 nanoparticles were successfully synthesized without any templates by simple co-precipitation synthesis route. Further characterized by using X-ray diffraction (XRD) measurements, field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectroscopy and their hydrogen sensing properties were investigated. The CdSnO3 nanoparticles exhibited outstanding gas sensing characteristics such as, higher gas response, extremely rapid response, fast recovery, excellent repeatability, good selectivity and at ambient operating temperature (~ 30C). Furthermore, the CdSnO3 nanoparticles can detect up to 5 ppm for hydrogen with reasonable sensitivity at an ambient operating temperature.

Capability demonstration of a 3D CdZnTe detector on a high-altitude balloon flight

In collaboration between the University of Michigan and Los Alamos National Laboratory, a 3D position-sensing CdZnTe (CZT) detector prototype was built and integrated into a high-altitude balloon platform to evaluate its performance in a space-like mixed-radiation environment. The detector prototype, Orion Eagle, was designed to operate in near-vacuum environments without any temperature regulation. Orion Eagle was hand-launched from NASA’s Columbia Scientific Balloon Facility (CSBF) at Fort Sumner, NM on September 26, 2021, and successfully operated throughout a 9-hour flight, which reached 38.5 km in altitude. The flight met its objectives, successfully detecting atmospheric gamma rays and galactic cosmic rays, and raising the Technical Readiness Level from 4 to 6 for large-volume 3D CZT detector technology for space applications. Ionization tracks produced by charged particles create spatial signatures in the detector that are distinguishable from discrete gamma-ray interactions. Therefore, the 3D position-sensing capabilities using pixelated electrodes on a CZT detector can help enable discrimination of background charged particles from gamma-ray events without an anticoincidence shield. The potential for background rejection capability, ambient-temperature operation, gamma-ray coded-aperture and Compton imaging, and near High Purity Germanium (HPGe) energy resolution motivate the use of large-volume 3D CZT imaging spectrometers in future space missions.

Support Pore Structure and Composition Strongly Influence the Direct Air Capture of CO2 on Supported Amines.

A variety of amine-impregnated porous solid sorbents for direct air capture (DAC) of CO2 have been developed, yet the effect of amine-solid support interactions on the CO2 adsorption behavior is still poorly understood. When tetraethylenepentamine (TEPA) is impregnated on two different supports, commercial γ-Al2O3 and MIL-101(Cr), they show different trends in CO2 sorption when the temperature (-20 to 25 °C) and humidity (0-70% RH) of the simulated air stream are varied. In situ IR spectroscopy is used to probe the mechanism of CO2 sorption on the two supported amine materials, with weak chemisorption (formation of carbamic acid) being the dominant pathway over MIL-101(Cr)-supported TEPA and strong chemisorption (formation of carbamate) occurring over γ-Al2O3-supported TEPA. Formation of both carbamic acid and carbamate species is enhanced over the supported TEPA materials under humid conditions, with the most significant enhancement observed at -20 °C. However, while equilibrium H2O sorption is high at cold temperatures (e.g., -20 °C), the effect of humidity on a practical cyclic DAC process is expected to be minimal due to slow H2O uptake kinetics. This work suggests that the CO2 capture mechanisms of impregnated amines can be controlled by adjusting the degree of amine-solid support interaction and that H2O adsorption behavior is strongly affected by the properties of the support materials. Thus, proper selection of solid support materials for amine impregnation will be important for achieving optimized DAC performance under varied deployment conditions, such as cold (e.g., -20 °C) or ambient temperature (e.g., 25 °C) operations.

Enhanced heat transfer performance of a new horizontal buried tube heat exchanger

To reduce the land area of horizontal buried tube heat exchanger, a finned strengthened heat exchanger was designed, and shallow geothermal utilization system model was established. The effects of fin shape and arrangement, soil type, ambient temperature and intermittent operation on the system?s heat transfer performance were investigated. The soil utilization area of the heat exchanger is increased, and the heat exchange performance of the system is enhanced by adding fins on the smooth tube. The optimal shape of the fins is rectangular, and the optimal fin lay-out is horizontal. When the soil property is clay, the heat transfer is the smallest, and the heat transfer performance is improved compared with the smooth tube. Intermittent operation not only improves the heat exchange, but also enhances the effect of adding fins to improve the heat exchange performance of the system. Compared with the original smooth tube, the soil utilization range is increased by 20%, and the heat exchange is increased by 42%.

Design of a Flexible Thin-Film Encapsulant with Sandwich Structures of Perhydropolysilazane Layers.

Perovskite solar cells (PSCs) have attracted considerable attention due to their excellent photovoltaic properties, but stability issues have prevented their widespread application. PSCs must be protected by encapsulation to extend their lifetime. Here, we show that perhydropolysilazane (PHPS)-based multilayered encapsulation improves the lifetime of PSCs. The PSCs were encapsulated by converting PHPS into silica under vacuum ultraviolet (UV) irradiation. The PHPS-based multilayer encapsulation method achieved a sandwich structure of PHPS/poly(ethylene terephthalate) (PET)/PHPS with a water vapor transmission rate (WVTR) of 0.92 × 10-3 gm-2 d-1 (at 37.8 °C and 100% relative humidity). We then performed a reservoir test of the encapsulated PSCs to confirm the moisture stability of the encapsulation based on PHPS/PET/PHPS barrier films. The cell lifetime remained stable even after 1000 h of ambient-temperature operation. Finally, we analyzed the mechanical flexibility of the PHPS/PET/PHPS multibarrier through bending tests. The multibarrier exhibited high mechanical stability with no large increase in WVTR after bending.

A multifaceted screening of applied voltages for electro-assisted anaerobic digestion of blackwater: Significance of temperature, hydrolysis/acidogenesis, electrode corrosion, and energy efficiencies

A microbial electrolysis cell-assisted anaerobic digester (MEC-AD) was operated with vacuum toilet blackwater at different applied voltages (0–1.6 V) at room temperature (R20). A parallel MEC-AD was operated at 35 °C (R35) to provide a kinetics index at mesophilic temperature. Both reactors failed at 1.6 V due to the alkaline pH created by anodic corrosion. In R20, the best performance was observed at 1.2 V, with methane yield, COD removal, hydrolysis and acidogenesis efficiency increased by 59.9%, 27.0%, 52.0%, and 44.9%, respectively, compared to those of 0 V. Enrichment of hydrolytic and syntrophic bacteria (e.g., Clostridium, Bacteroidales, Sedimentibacter, Syntrophomonas) and increased abundance of genes encoding complex organics (e.g., proteins, carbohydrates, lipids) metabolism in R20 at 1.2 V corresponded to the enhanced hydrolysis/acidogenesis processes. R20 at 1.2 V generated 1.16 times more net energy than R35 at the optimum voltage for methane yield (0.8 V), indicating ambient temperature operation of MEC-AD systems would be a more sustainable strategy.

Quaternary Ammonium Ion-Tethered (Ambient-Temperature) HDDA Reactions.

The hexadehydro-Diels-Alder (HDDA) reaction converts a 1,3-diyne bearing a tethered alkyne (the diynophile) into bicyclic benzyne intermediates upon thermal activation. With only a few exceptions, this unimolecular cycloisomerization requires, depending on the nature of the atoms connecting the diyne and diynophile, reaction temperatures of ca. 80-130 °C to achieve a convenient half-life (e.g., 1-10 h) for the reaction. In this report, we divulge a new variant of the HDDA process in which the tether contains a central, quaternized nitrogen atom. This construct significantly lowers the activation barrier for the HDDA cycloisomerization to the benzyne. Moreover, many of the ammonium ion-based, alkyne-containing substrates can be spontaneously assembled, cyclized to benzyne, and trapped in a single-vessel, ambient-temperature operation. DFT calculations provide insights into the origin of the enhanced rate of benzyne formation.

Poly(ionic liquid)-functionalized graphene oxide towards ambient temperature operation of all-solid-state PEO-based polymer electrolyte lithium metal batteries

Endowing polyethylene oxide (PEO)-based electrolyte with low crystallinity and high efficient Li+ transport channels is urgently required for next generation all-solid-state lithium metal batteries (LMBs). Herein, a new type of oxyethyl containing poly(ionic liquid) modified graphene oxide nanoparticles (ox-PIL@GO) is coincidentally proposed for preparing PEO based organic–inorganic composite electrolyte membranes (CPEs). Both experimental and DFT simulation results indicate that the dissociation of the LiTFSI is significantly enhanced by the anticipated electrostatic interaction between imidazolium cation and TFSI- anions in CPEs. In addition, the formed electrostatic interaction can also inhibit the movement of TFSI-, giving rise to the increased lithium transference number of 0.61 from 0.21 for the neat PEO/LiTFSI electrolyte. Furthermore, the ion–dipole interaction between imidazolium cation and PEO chain largely reduces the crystallinity of PEO and the ionic conductivity of 1.01 × 10-4 S cm−1 at 40 °C is successfully obtained. As a result, the ox-PIL@GO incorporated PEO electrolyte enables the Li||Li symmetric cell with long-term, square-wave galvanostatic cycling test of 800 h at current density of 0.1 mA cm−2 at 50 °C and the solid-state LiFePO4|CPE|Li battery with high discharge specific capacity of 116 mAh g−1 at 40 °C at 1C for 300 cycles.

Poly(Ionic Liquid)-Functionalized Graphene Oxide Towards Ambient Temperature Operation of All-Solid-State Peo-Based Polymer Electrolyte Lithium Metal Batteries

Poly(Ionic Liquid)-Functionalized Graphene Oxide Towards Ambient Temperature Operation of All-Solid-State Peo-Based Polymer Electrolyte Lithium Metal Batteries

Enhanced Heat Transfer Performance of a New Horizontal Buried Tube Heat Exchanger

Horizontal buried heat exchangers cost less than vertical buried heat exchangers, but they need more land area. In order to reduce the required land area of horizontal buried tube heat exchanger, a finned strengthened heat exchanger pipe was designed to enhance the heat transfer performance, and a three-dimensional research model of shallow geothermal utilization system was established in Chengdu area . In this paper, the optimal shape and arrangement of fins are investigated, and the effects of inlet velocity, soil type, ambient temperature and intermittent operation on the enhanced heat transfer performance are studied. The results show that the enhanced heat transfer performance of rectangular fins is the best in the case of horizontal arrangement. The working fluid flow rate should not exceed 0.3m/s.Soil type has a great influence on heat transfer performance. The heat transfer of rock and soil is the largest, the heat transfer of clay is the smallest, but the strengthening effect of clay is the best. The longer the system runs, the obvious the influence of ambient temperature is, and the heat transfer efficiency increases by about 4% when the ambient temperature drops by 5K.

Evaluation of solar panel cooling systems using anodized heat sink equipped with thermoelectric module through the parameters of temperature, power and efficiency

• Increasing the surface temperature of solar panels reduces their efficiency and performance. • For every degree increase in ambient temperature, PV panel’s efficiency decreases by 0.5%. • The system's performance in two cooling modes of using a thermoelectric module and natural cooling of the system was compared with free convection. • Use of thermoelectric module with heater could increase the efficiency and power of solar panels by an average of 10.50% and 10.50%, respectively. Today, the importance and usefulness of renewable energies is known to everyone. One of the most widely used renewable energies is solar energy. A challenge in the production of electricity from the solar energy is an increase in the surface temperature of solar cells caused by ambient temperature and operating temperature, which reduces the efficiency and performance of solar photovoltaic systems. For every degree increase in ambient temperature, PV panel’s efficiency decreases by 0.5%. The system developed in this research consists of two main parts: solar panel and cooling units. The system's performance in two cooling modes of using a thermoelectric module and natural cooling of the system was compared with free convection. The results showed that the use of thermoelectric module with heater could increase the efficiency and power of solar panels by an average of 10.50% and 10.50%, respectively. The temperature of the solar panel during the test time was on average about 10.04 °C lower than normal operating conditions. The results of this study showed that the industrial design of solar panels with a system to reduce excess heat from solar radiation – can be useful and effective in increasing overall efficiency through reducing excess heat and increasing efficiency of the panels.

Electronic and Simple Oscillatory Conduction in Ferrite Gas Sensors: Gas-Sensing Mechanisms, Long-Term Gas Monitoring, Heat Transfer, and Other Anomalies.

The early detection and warning of the presence of hazardous gases have been well studied. We present a study that focuses on some fundamental properties of gas sensors for liquefied petroleum gas (LPG) using spinel nanoferrites, namely, CoSm0.1Fe1.9O4, CoCe0.1Fe1.9O4, MgCe0.1Fe1.9O4, and MgFe2O4. A highly sensitive and selective response of 846.34 at 225 °C toward 10,000 ppm concentration of LPG was recorded. Other flammable gases tested were hydrogen, methane, propane, and butane. Electronic conduction of LPG sensors near saturation showed simple electrical oscillations that can be attributed to the self-dissociation of water molecules physically adsorbed on the surface of the chemisorbed oxygen species due to proton transfer. The oscillatory behaviors follow fluctuations in the operating temperature attributed to heat transfer between the physisorbed water molecules and the hot sensor surface. This depends on the LPG concentration because higher LPG concentration gives rise to greater heat transfer from the sensors. The adsorption and desorption of these water molecule multilayers take a few hundreds of seconds at low concentrations, while the adsorption formation process takes longer at higher concentrations. Other parameters such as LPG exposure time, bias voltage, relative humidity, ambient conditions, operating temperatures, and temperature of the gas not only affect electrical oscillations and thermal fluctuations but also switch the dominant charge carriers from p- to n-type or vice versa. The type of sensor surface, either p- or n-type, did not appear to affect the oscillatory behavior, while the exposure time, short or long, determined the appearance and further behavior of the oscillations. The long-time exposure to 10,000 ppm concentration resulted in the resistance gradually decreasing due to the lack of oxygen supply, while at 5000 ppm, this was constant, stable, and oscillated indefinitely. Changing the dry air to argon gas as a carrier and for dilution of the hazardous gas prevented the electrical oscillations and thermal fluctuations and significantly lowered the response values. Both the inert ambient (argon gas) and changing operating temperature flipped the dominant charge carriers of these sensors. The concentration of these chemisorbed oxygen species governs the charge space and depletion layers. In addition, the spinel nanoferrites used contained higher oxygen vacancies than the lattice oxygen and chemisorbed oxygen. When using dry air, the oscillations were observed at 3000 ppm concentration, while using argon gas, they were observed at 7000 ppm concentration. The room-temperature LPG responses were about 35 and 80 under 45% relative humidity using dry air and argon gas, respectively. These room-temperature measurements showed electrical oscillations but did not show any thermal fluctuations or heat transfer phenomena. This study presents a deeper insight into the fundamentals of gas-sensing mechanisms and energy costs involved.

A MEMS Turbopump for High Temperature Rankine Micro Heat Engines—Part I: Design and Fabrication

We report the design and microfabrication of a MEMS turbopump with thermal insulation, as the core component of a steam power plant-on-a-chip for waste heat recovery based on the Rankine thermodynamic cycle. Based on a first-generation microturbopump for ambient temperature operation, this second-generation device introduces materials for thermal insulation and design improvements to the rotordynamic components for operation at high temperatures. Thermal management is required to prevent water boiling in the pump and vapor from condensing in the turbine, bearings and seals. The device is a five-wafer stack that encloses a 4-mm diameter rotor disk with microturbine blades on one side and a viscous micropump on the other. This second-generation microturbopump implements unique thermal insulation strategies to isolate the pump from the surrounding hot flows. An out-off-plane thick molded glass embedded into the rotor prevents heat conduction from the turbine to the pump. In addition, an in-plane thick array of oxidized trenches prevents heat conduction from the thrust bearing region to the pump. The assembled microturbopump is fabricated and tested, resulting in the first MEMS turbopump demonstrated at high temperature. Design and fabrication are covered herein, whereas experimental demonstration and characterization are presented in Part II of this two-part paper. [2020-0050]

Study of thickness and temperature dependence on the performance of SnS based solar cell by SCAPS-1D

Photovoltaic characteristics of solar cell devices based on SnS, a promising material for solar cell applications, were analyzed in this paper by using Solar Cell Capacitance Simulator software (SCAPS). The device structure used for the simulation was glass/ITO/ZnO/CdS/SnS/metal contact where SnS was used as an absorber layer, CdS as a window layer, ZnO as a buffer layer. Simulation was carried out by varying different solar cell parameters, such as thicknesses of absorber as well as window layer and the ambient operating temperature. It is found that with the increase in thickness the efficiency increases up to a certain limit and then it saturates whereas with the increase in ambient operation temperature the efficiency decreases due to the drop in Vocfor the simulated solar cell device.