Operating Temperature Research Articles

High-Yield WS2 Synthesis through Sulfurization in Custom-Modified Atmospheric Pressure Chemical Vapor Deposition Reactor, Paving the Way for Selective NH3 Vapor Detection.

Nanostructured transition metal dichalcogenides have garnered significant research interest for physical and chemical sensing applications due to their unique crystal structure and large effective surface area. However, the high-yield synthesis of these materials on different substrates and in nanostructured films remains a challenge that hinders their real-world applications. In this work, we demonstrate the synthesis of two-dimensional (2D) tungsten disulfide (WS2) sheets on a hundred-milligram scale by sulfurization of tungsten trioxide (WO3) powder in an atmospheric pressure chemical vapor deposition reactor. The as-synthesized WS2 powders can be formulated into inks and deposited on a broad range of substrates using techniques like screen or inkjet printing, spin-coating, drop-casting, or airbrushing. Structural, morphological, and chemical composition analysis confirm the successful synthesis of edge-enriched WS2 sheets. The sensing performance of the WS2 films prepared with the synthesized 2D material was evaluated for ammonia (NH3) detection at different operating temperatures. The results reveal exceptional gas sensing responses, with the sensors showing a 100% response toward 5 ppm of NH3 at 150 °C. The sensor detection limit was experimentally verified to be below 1 ppm of NH3 at 150 °C. Selectivity tests demonstrated the high selectivity of the edge-enriched WS2 films toward NH3 in the presence of interfering gases like CO, benzene, H2, and NO2. Furthermore, the sensors displayed remarkable stability against high levels of humidity, with only a slight decrease in response from 100% in dry air to 93% in humid environments. Density functional theory and Bayesian optimization simulations were performed, and the theoretical results agree with the experimental findings, revealing that the interaction between gas molecules and WS2 is primarily based on physisorption.

Enhanced CO2 capture and reverse water gas shift reaction using CaO in NaCl-CaCl2 molten salt medium

This study introduces an Integrated Carbon Capture and Utilisation-Reverse Water Gas Shift (ICCU-RWGS) approach, a novel method for in situ CO2 adsorption and conversion, leveraging the synergistic effects of CaO within a NaCl-CaCl2 molten salt blend to enhance CO2 capture and conversion efficiency. Building upon this foundation, we optimize CaO concentration and operating temperature to maximize CO2 uptake and conversion performance. The research focuses on integrating CaO with a NaCl-CaCl2 molten salt blend (mass ratio 4:6) to improve CO2 sorption and conversion performance. Findings show significant enhancements in CO2 uptake and CO yield with the presence of molten salt compared to systems without it. The optimal operating temperature and CaO concentration are identified for maximum CO yield. Characterisation techniques like in-situ infrared spectroscopy, XRD, and SEM provide insights into the behavior of CaO in the molten salt, revealing the solubility of the partial carbonate formed from CO2 and CaO, dispersion of CaO particles, and their morphological characteristics. Overall, the study demonstrates the potential of CaO-molten salt integration in improving ICCU-RWGS process efficiency and contributes to the development of more effective and sustainable ICCU technologies.

Improved prediction of critical currents for multi-pancake coil across variable temperature regions

With the increasing performance of the second-generation high-temperature superconducting (2G-HTS) tapes, the technology of all-REBa2Cu3O7-δ (REBCO, RE: rare earth) superconducting magnets has developed rapidly. However, the 2G-HTS magnet with hybrid cryocoolers constantly adjusts its operating temperature according to the actual demands, which involves the critical current when the magnet crosses variable temperature regions. In this paper, a modified ideal model based on the homogenization model is proposed, which can predict the critical current of 2G-HTS magnets more consistently. The in-field properties of REBCO tapes in variable temperature regions were tested by the physical property measurement system. Furthermore, the improved model was combined with the in-field properties of REBCO tapes to obtain the critical currents of a 2G-HTS multi-pancake (MP) coil at 20 K, 30 K, 65 K, and 77 K. The critical current of a multi-pancake coil at 77 K was experimentally verified. The modified ideal model uses the actual current density, which results are closer to the experimental results with an agreement of 97.3%. This new method proposed in this work is significant in quickly predicting critical currents for 2G-HTS magnets across variable temperature regions.

Studying the Effect of Operating Conditions and NO2 Cathode Contamination on PEM Fuel Cells Using Distribution Function of Relaxation Times Analysis.

The effect of NO2, an air pollutant, on the durability of polymer electrolyte membrane fuel cells (PEMFCs) and the affected electrochemical processes in the PEMFC following the contamination were investigated. In-situElectrochemical Impedance Spectroscopy (EIS) measurements were conducted on PEMFCs under different operating conditions of temperature and relative humidity (RH). NO2 was introduced to the cathode inlet flow. Analyses of the EIS measurements were performed using a genetic algorithm called ISGP (Impedance Spectroscopy by Genetic Programming) to obtain the distribution function of relaxation times (DFRT, a.k.a. DRT) models. Utilizing ISGP enabled us to differentiate the various phenomena in PEMFC and study how they are affected by NO2 contamination. Moreover, the experiments demonstrate the effectiveness of the mitigation method to flush the PEMFC and regenerate its performance after being contaminated, particularly at low operating temperatures. Energy-dispersive X-ray spectroscopy (EDS) technique is performed on the contaminated PEMFC to detect the presence of any nitrogen components in the FC's gas diffusion layer and the catalyst layer post the mitigation step. Cyclic Voltammetry is also performed on the contaminated cell to determine the effect of the contamination on the electrochemically active surface area of the cathode by evaluating the double-layer capacitance.

Solid-State Rigid Polymer Composite Electrolytes with In-Situ Formed Nano-Crystalline Lithium Ion Pathways for Lithium-Metal Batteries.

Polymer-based solid-state electrolytes with excellent processability and flexibility are ideal candidates for commercialisation in lithium-metal batteries. However, the current polymer-based solid-state electrolytes still have many problems such as low ionic conductivity, limited Li+ transport number and high interfacial resistance with electrodes. To address the above challenges, a solid-state rigid polymer composite electrolyte with high ionic conductivity (2.8 mS cm−1) has been prepared based on the rigid polymer poly(2, 2′-disulfonyl-4, 4′-benzidine terephthalamide) (PBDT). Locally aligned PBDT-EMImN(CN)2 grains are interspersed with in-situ formed interconnected LiFSI to form the structure of the polymer composite electrolyte. The formation of defective LiFSI nanocrystals at grain boundaries inside the polymer electrolyte acts as additional conductive networks providing fast Li+ transportation (tLi+=0.59). The flexible region in the electrolyte gives excellent interfacial impedance (32.5 Ω cm2) with Li-metal electrode. The Li||Li batteries can be stably cycled for over 1000 cycles at 1 mA cm−2 (25°C). The assembled Li||LiFePO4 batteries exhibit excellent cycling and multiplication performance over a wide operating temperature (from -20 to 60°C). Moreover, this electrolyte material exhibits compatibility with high-voltage cathode LiNi0.6Mn0.2Co0.2O2 batteries. This electrolyte and design strategy is expected to inspire the realization of all-weather practical solid-state lithium-metal batteries.

The prediction of thermal sensation in building using support vector machine and extreme gradient boosting

The building has great potential for energy savings as one of the locations that humans often occupy. In addition to energy efficiency, humans must consider environmental sustainability and the comfort of the building's occupants. Conditioning of indoor air quality, including those related to thermal comfort, continues to be pursued to be more economical, one of which is to utilize the prediction of occupants' thermal sensations. The prediction results can be utilized to adjust room air conditions more economically. This paper proposes using extreme gradient boosting (XGBoost) and support vector machine (SVM) to predict the thermal sensation in the building. The built environment parameters are preprocessed, and the thermal sensation is predicted by intelligent systems. The ten variables that most influence the level of accuracy of this thermal sensation prediction system are thermal preference vote, indoor operative temperature, Griffith's neutral temperature, indoor globe temperature, mean radiant temperature, Indoor air temperature, predicted mean vote, and outdoor mean temperature. SVM with four features, XGBoost and XGBoost with hyperparameter tuning, achieve an accuracy of 99.45%, 97.81%, and 98.08%, respectively. Regarding computational complexity, training an SVM system with the same number of features requires a shorter time than XGBoost training. The same thing also happened with the test of the SVM system, which required a shorter time compared to the time for the examination of the XGBoost system.

HYDROGEN GAS RECOVERY THROUGH THE PERMEATION MEMBRANE BASED BIMETALLIC PALLADIUM ALLOY

Generally, the H2 gas produced from the industrial processes is not in a pure state but is mixed with other compounds. For example, the off-gas produced in the oil refinery process still contains CH4, H2, and other gases. Thus, the process of separating as well as recovering the valuable H2 gas from other gas compounds is of essential process. Currently, the H2 separation process is being developed with relatively low costs with good efficiency, namely using the permeation membranes separation process, in which the compounds with high permeability tends to be more easily separated. Here we report the hydrogen recovery process from the mixed H2/N2 off-gas contains 61 % hydrogen and 39% balancing nitrogen, by using the bimetallic Pd-Ag membrane, where the effect of the gas feed pressure (1 and 2 bar) and operating temperature (373.15, 423.15, 473.15, and 523.15, 573.15 K) on the resulting permeate flux is comprehensively studied. We found that the flux and permeability increased with the increase in the gas feed pressure and temperature. Under the same gas temperature of 373.15 K, the permeation flux at the 2 bar gas feed pressure was found to be 2.047 mol.s-1.m-2, which was 166% greater than that of 1 bar pressure, i.e. 1.204 mol.s-1.m-2. Meanwhile, under the same gas feed pressure of 2 bar, the permeation flux at the operating temperature of 573.15 K was found to be 2.103 mol.s-1.m-2, which is 104,9% greater than that of 373.15 K operating temperature, i.e. 2.047 mol.s-1.m-2. These findings suggest the breakthrough advantages of the Pd-Ag alloy membrane for its high hydrogen permeability at low pressure.

Studying the Gas Sensitivity and Magnetic Properties of Magnesium Ferrite Prepared by the Sol-Gel Route

Nickel-doped manganese–magnesium ferrite (NixMn0.25-xMg0.75Fe2O4) was prepared using the auto-combustion method. X-ray diffraction patterns showed a single ferrite spinel phase in all the prepared samples. The crystallite size ranged from 24.30 to 28.32 nm, increasing with increasing the Ni content. The porous structure of all the samples was verified with a scanning electron microscope. FE-SEM images were used to confirm the production of spherical or semi-spherical nanoparticles with little change in particle size distribution. The study revealed that the nanoparticles were small enough to behave superparamagnetically. According to the magnetic tests conducted with the VSM at room temperature, the hysteresis loop region is practically non-existent, indicating typical soft magnetic materials. In addition, the conductance responses of the magnesium ferrite nanocomposite were measured by exposing it to the oxidizing gas (NO2) at different operating temperatures. The results showed that the sensor with the nano ferrite sample of (x = 0.20) has a good sensitivity of 707.22% as well as response and recovery times.

Study on Thermal and Luminescence Properties of YAG:Ce Ceramics Excited by High‐Power Fiber Laser with the Condition of a Water‐Cooling Package

A high‐power white laser source is prepared by using a 455 nm blue laser to excite YAG:Ce ceramics. To achieve high‐power output, a water‐cooling device is used to reduce the operating temperature of ceramics. The luminescence properties of laser‐excited phosphor ceramics are studied under different blue excitation power and different irradiation time. The experimental results show that the luminous flux of phosphor ceramics excited by the blue laser increases linearly with the increase of blue laser power, depending on the heat dissipation of the water‐cooling device. When the blue laser power increases to 73.1 W, the phosphor ceramics do not reach the luminescence saturation state. The luminous flux of phosphor ceramics excited by 73.1 W blue laser is stable within 60 min. The maximum luminous flux is 8094 lm, and the maximum working temperature of the ceramics is 110 °C. The experimental results show that water‐cooling packages are an effective means to realize high‐power white laser sources.

Microstructure and wear resistance of cold sprayed CoCrFeNi HEA coatings: Influence of powder particle size and spraying temperature

This study focuses on the successful fabrication of three distinct types of CoCrFeNi high entropy alloy (HEA) coatings through cold spray (CS) technology, with an emphasis on analyzing the impact of varying crucial CS parameters (spraying temperature and the range of powder particle size), on the coating's microstructure and tribological properties. Contrasted with conventional thermal spraying techniques, lower operational temperature in CS safeguards the materials from undergoing oxidation or phase transitions that are typically induced by high-temperature conditions. Additionally, the high-velocity impact of particles onto the substrate within CS process triggers plastic deformation, resulting in the creation of coatings that are characterized by heightened hardness, and greater density. Such coatings exhibit significantly enhanced performance and durability. The cocktail effect observed in CoCrFeNi HEA is reflected in a suite of exceptional properties that markedly surpass those exhibited by traditional alloys. Chiefly, this phenomenon is manifested through the alloy's exceptionally high hardness and dense structure, positioning CoCrFeNi HEA as a promising candidate for applications in high-wear scenarios. Experimental outcomes indicate that when smaller powder particles and higher spraying temperatures are employed, the porosity of CSed CoCrFeNi HEA coatings was observed to decrease by nearly an order of magnitude, concomitant with a 22.46% enhancement in microhardness. This improvement in microhardness translates into a significant reduction of over 72% in the wear rate, underscoring the positive correlation between enhanced microstructural integrity and wear resistance properties. By meticulously tuning spraying temperature and powder particle size, the resulting microstructure can be rendered increasingly dense and refined.

Calcium Manganite Based Materials for Thermochemical Energy Storage in High Temperature Solar Thermal Plants: Materials Screening

The urgent need for sustainable energy supply requires maximum exploitation of renewable energy sources. The latter, being of intermittent nature, need to be coupled with efficient energy storage. Solar-thermal power-plants are inherently compatible with thermal storage, which is a cost-efficient method of storing energy for later use but the field is currently dominated by sensible heat molten salts used as heat storage media but with a maximum operating temperature of about 560oC. Certain ceramic materials, able to induce reversible reduction-oxidation reactions under air flow, are promising alternatives to molten salts because they can withstand much higher temperatures (>1000oC) and thus can be integrated with high-efficiency air-Brayton thermodynamic cycles. At the same time the chemical energy stored/released during such reduction-oxidation reactions can boost energy storage density by up to 10 times cf. sensible only concepts. In this framework, Ca-Mn-based perovskite compositions were demonstrated to function effectively as energy storage materials. The current work offers insights on material synthesis parameters to achieve relatively high purity Ca-Mn-based compositions and subsequently optimize their redox performance in the course of a preliminary 5-cycle campaign. Moreover, the occurring structural transitions and their corresponding heat effects are also discussed and elaborated upon. This study is the first step towards the, currently in progress, process of synthesising – at multi kg scale – and shaping these compositions into extruded honeycomb-like monolithic structures for subsequent future application in lab- and pilot-scale high temperature thermochemical energy storage systems.

Doubling Power Conversion Efficiency of Si Solar Cells.

Improving solar cells' power conversion efficiency (PCE) is crucial to further the deployment of renewable electricity. In addition, solar cells cannot function at exceedingly low temperatures owing to the carrier freeze-out phenomenon. This report demonstrates that through temperature regulation, the PCE of monocrystalline single-junction silicon solar cells can be doubled to 50-60% under monochromatic lasers and the full spectrum of AM 1.5 light at low temperatures of 30-50 K by inhibiting the lattice atoms' thermal oscillations for suppressing thermal loss, an inherent feature of monocrystalline Si cells. Moreover, the light penetration, determined by its wavelength, plays a critical role in alleviating the carrier freeze-out effect and broadening the operational temperature range of silicon cells to temperatures as low as 10 K. Understanding these new observations opens tremendous opportunities for designing solar cells with even higher PCE to provide efficient and powerful energy sources for cryogenic devices and outer and deep space explorations.

Numerical modeling of alkali metal heat pipes

Heat pipe cooled reactors passively transfer heat from the core to the energy conversion system through alkali metal heat pipes. Further studies of the heat transfer characteristics of alkali metal heat pipes are needed to develop heat pipe cooled reactors. This work used a two-dimensional heat and mass transfer model of an alkali metal heat pipe. The flow field was validated against CFD predictions which showed that the model has less than 10 % errors in the velocity distribution and less than 5 % errors in the pressure distribution. A comparison of the predictions with experimental data in the literature indicated that the predicted wall temperature error was within 30 °C. This model was then used to analyze four factors that affect heat transfer in sodium heat pipes. The simulations show that higher heat fluxes shorten the startup time by approximately 70 % but significantly increase the operating temperature. The heat flux distribution significantly affects the evaporator temperature distribution. The heat transfer boundary condition on the condenser’s outer surface mainly affects the operating temperature and startup time. Increasing the heat pipe length-to-diameter ratio with a fixed heat flux increases the operating temperature with the increase proportional to the heat flux. This model provides accurate simulations of sodium heat pipes for various heat transfer boundary conditions. The simulations provide a reference for the selection of working conditions for heat pipe operation instability experiments.

Properties of foam concrete containing phase change material impregnated pumice

Energy consumption rises as a result of numerous electrical devices used to maintain thermal comfort of interior building areas. Using building materials with low thermal conductivity and density as well as an effective thermal energy storage plan can help to mitigate this. In order to enhance thermal performance of building, phase change material (PCM) was incorporated to foam concrete mixture in this study. Capric acid (CA)-palmitic acid (PA) eutectic mixture was prepared and impregnated with pumice (50 % by weight), a light and porous material. DSC results indicated that pumice/CA-PA composite exhibited a melting temperature of 22.84˚C and a freezing temperature of 20.85˚C, with corresponding enthalpy values for melting and freezing determined to be 85.4 J/g and 85.1 J/g, respectively. TGA analyses demonstrated that operational temperature of pumice/CA-PA composite was significantly below its thermal degradation temperature (194˚C). The prepared pumice/CA-PA composites were replaced with silica aggregate at different rates and incorporated in foam concrete mixture. Porosity and water absorption values rose as pumice/PCM content increased, yet there was a 7.2–41.1 % drop in dry unit weight when compared to reference. Compressive strength also showed a linear decrease and the lowest compressive strength value was recorded as 4.71 MPa in the presence of 40 % pumice/PCM. Thermal conductivity dropped from 0.487 W/mK to 0.167 W/mK, suggesting that foam concrete samples that were produced are all suitable as insulation materials. In peak solar radiation hours, PCM-impregnated pumice foam concrete (PFC) provided about 11.8 % and 8.72 % surface and room center temperatures compared to that of the reference in maximum case. PFC with PCM provided 6.54 % warmer surface temperature in cold weather. PFC-PCM can provide a cooler indoor temperature during peak temperature hours. Therefore, it may have a great potential to decrease the cooling load of a building.

Completely sealed direct carbon solid oxide fuel cell with in situ steam-carbon gasification reaction

Direct carbon solid oxide fuel cells (DC-SOFCs) offer the potential for clean and efficient conversion of chemical energy in carbon fuels into electricity. However, the reverse Boudouard gasification of carbon requires a high operating temperature (≥800 °C), which hinders the development of DC-SOFCs. We present a completely sealed DC-SOFC with in situ steam-carbon gasification. The cells have a symmetrical cell structure (Ag–Ce0.8Gd0.2O1.9/La0.9Sr0.1Ga0.8Mg0.2O3−δ/Ag–Ce0.8Gd0.2O1.9) and are loaded with K-loaded activated carbon fuel. Ca(OH)2 and Li4SiO4 are loaded into the anode chamber as the steam feedstock and CO2 sorbent, respectively. Completely sealed DC-SOFCs with Ca(OH)2–C of 0 %, 5 %, 10 %, 15 %, and 20 % have been tested at 700 °C. Compared with a cell with a conventional structure and a completely sealed cell without Ca(OH)2 loading, the electrochemical performances of all the completely sealed cells with Ca(OH)2 loading are significantly enhanced. The cell with Ca(OH)2 to C of 15 % obtained the highest maximum power density of 75 mW cm−2, which is approximately two-fold that of the conventional DC-SOFC. The mechanism for improving the performance of the cell is the introduction of steam. This study offers a new method to develop high-performance DC-SOFCs and reduce their operating temperatures.

Red-to-ultraviolet light chargeable Sm2+-activated deep-red persistent phosphor for simultaneous bioimaging and bio-temperature sensing

Persistent phosphor-based bio-applications do not need real-time photo-excitation and do not suffer from disturbance of stray excitation light, auto-fluorescence of the measured substance and heat produced by excitation. However, the persistent phosphors that well match the optical biological windows are deficient. Here, we report for the first-time divalent samarium (Sm2+) activated persistent phosphor with dual-functionality for simultaneous bioimaging and bio-temperature sensing. The persistent phosphor is Sm2+ and Nd3+codoped SrAl2Si2O8 that can be photo-charged in 250–660 nm and shows deep-red persistent luminescence (PersL) originated from both the 4f55d1 → 4f6 and 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions that well match the first optical biological window. The intense PersL output shows the effective operation temperature range of 240–340 K, covering the physiological temperature range of 298–325 K. It is found that quantum tunneling dominates both the visible light including red light charging process and PersL generating process. The temperature dependent PersL intensity ratio of the thermally coupled 4f55d1 → 4f6 emission band and the 5D0 → 7FJ emission lines is studied and a maximum relative sensitivity of 4.81 % K−1 at 200 K and 2.17–1.82 % K−1 in the physiological temperature range are achieved. The dual-functionality of SrAl2Si2O8:1 %Sm2+,1 %Nd3+ for simultaneous bioimaging and bio-temperature sensing is demonstrated. Our findings open up new scenarios for multifunctional applications of Sm2+.

Microclimate and Thermal Refuge Influences on Sage-Grouse Brood Habitat Selection

Wildlife space use is driven by three primary mechanisms, predator avoidance, foraging, and thermoregulation. The latter has largely been overlooked in wildlife research. Understanding how habitat use is influenced by thermoregulatory properties is a critical component to depicting species’ ecology. Galliformes’ (i.e., ground nesting birds with precocial young) ecology is predisposed to thermal extremes, where newly hatched chicks are unable to thermoregulate <14 d post-hatch, and have limited capabilities until >21 d post-hatch. We examined greater sage-grouse (Centrocercus urophasianus) brood rearing habitats and provide the first evaluation as to how microscale thermal environments influenced habitat selection. We monitored 24 broods, collected 82,929 black bulb temperature measurements from thermal arrays (n = 256) comprised of stainless steel black bulbs (i.e., surrogate for operative temperature) to compare brood morning (i.e., foraging, n = 78), afternoon (i.e., loafing, n = 82) and associated random locations (n = 96) between early (≤21 d post-hatch) and late (>21 d post-hatch) brood-rearing. We measured vegetation at all locations to disentangle relationships between cover and thermoregulatory metrics. We found that microclimates at all foraging locations heated more rapidly than either their loafing or random locations. Alternatively, loafing locations moderated ambient temperature more effectively than foraging locations but were similar to random locations. Broods were using loafing sites that both increased their ability to avoid predators (i.e., increased shrub structure) and buffered ambient temperature better than their foraging locations. Interestingly, random afternoon locations tended to lack concealment from predators, despite these locations showing improved thermal buffering compared to foraging locations. However, early brood-rearing habitats appeared to moderate ambient temperatures more effectively than late. Our results suggested that managing vegetation for structural heterogeneity will afford a diversity of thermal refuge for greater sage-grouse broods during this critical life history stage.

Enhancing concentrated photovoltaic power generation efficiency and stability through liquid air energy storage and cooling utilization

Amid escalating climate concerns, particularly global warming, there is a significant shift towards renewable energy sources. Concentrated Photovoltaics (CPV) are at the forefront of this transition due to their high efficiency and clean energy generation capabilities. However, CPV cell stability and reliability are compromised by high operating temperatures, necessitating effective cooling solutions. This study proposes a novel coupled Concentrated Photovoltaic System (CPVS) and Liquid Air Energy Storage (LAES) to enhance CPV power generation efficiency and mitigate the challenges of high cell temperatures and grid integration. The research introduces an innovative process employing the cell liquefaction cycle for LAES, utilizing surplus cooling capacity to maintain CPV cells at optimal temperatures. A comprehensive thermodynamic analysis optimizes the coupled system’s operation and evaluates its economic benefits. The integrated system improves generation efficiency and economic viability of CPVS, resulting in a 24.41 % increase in photovoltaic module efficiency and a 2.03 % increase in overall rated power output. This leads to a 56.59 % increase in annual revenue for a 50 MW CPVS. Importantly, the findings demonstrate that integrating LAES with CPVS not only enhances solar energy utilization and economic benefits but also significantly contributes to the sustainability of clean, low-carbon energy systems, inspiring a greener future.

Predictive modelling of cooling consumption in nursing homes using artificial neural networks: Implications for energy efficiency and thermal comfort

The growing need for cooling within the built environment, propelled by climate change and the expansion of nursing homes due to the increase in life expectancy, highlights the urgency of implementing energy-efficient strategies in buildings occupied by older populations. As of today, there remains a need for comprehensive research into the influence of indoor and outdoor conditions, building, operational, and occupant characteristics, on energy consumption specifically for nursing homes. This study develops a systemic artificial neural network-based model with a multi-layer perceptron architecture to assess HVAC energy implications during the cooling season for older populations. Using monitored data from eight nursing homes, the model includes cooling area, construction age, outdoor and indoor temperatures, and outdoor relative humidity as inputs, and cooling consumption as the output. Results show excellent predictive capability (R2=0.95), with mean error of −0.5 kWh, root mean squared error of 13.7 kWh, mean absolute error of 10.2 kWh, and relative error of 0.051. These outcomes are better compared to linear models (R2≈0.65) under the same data set. Adjusting operative temperatures adaptively can significantly enhance resident comfort and achieve up to 23.4 % energy savings, particularly in hotter, drier climates. These findings are of paramount importance for effective energy management in buildings.

Multi-objective optimization of lithium-ion battery designs considering the dilemma between energy density and rate capability

Electrified transportation requires batteries with high energy density and high-rate capability for both charging and discharging. Li-ion batteries (LiBs) face a dilemma: increasing areal capacity and reducing electrode porosity to boost energy density often reduces rate capability due to a longer and more tortuous ion transfer path. Tailoring cell design parameters to balance these metrics is essential but challenging. Here, we present a multi-objective optimization framework targeting energy density, fast charging, high-rate discharging, and lifespan simultaneously. Four cell parameters—cathode areal capacity, N-P ratio, cathode porosity, and anode porosity—along with operating temperature, are selected as design variables. A physics-based pseudo-2D model, validated against experimental data, generates data to train the surrogate model, which is combined with the NSGA-II algorithm for rapid optimization. Three different objective calculation methods are compared to identify the maximum sum of energy densities, lowest polarization, and most balanced performance, respectively. Cell design parameters are optimized at different temperatures using the most balanced optimization method. Results demonstrate that elevating cell operating temperature achieves high-rate capability while maintaining high energy density, mitigating the energy-power trade-off and broadening battery design parameter ranges.