Ambient Temperature Variations Research Articles

AC Excitation to Mitigate Drift in AlGaN/GaN HEMT-Based Sensors

AlGaN/GaN high electron mobility transistor (HEMT) based sensors hold promise as small solid-state physical and chemical sensors because they can operate without a reference electrode and can be integrated into miniaturized sensor arrays. However, over extended time periods, low frequency noise causes anomalous variations (drift) in sensor signal, especially in liquid environments. These effects occur despite electromagnetic interference mitigation. To understand the low frequency noise, 1/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> noise measurements between 0.1 and 100 kHz were undertaken, in both air and water, under constant pH and normal laboratory pressure conditions. The 1/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γ</sup> noise for the device in water was larger in magnitude than in air, and estimates for the γ-parameter in air and water were approximately 1 and 1.5, respectively. The corner frequency was observed between 100 and 1000 Hz. Based on this analysis, AC excitation at 1 kHz was applied to the conduction channel to compare the sensor stability in de-ionized water with DC operation. In this controlled test, introduction of AC excitation resulted in a strong correlation of sensor signal with the ambient temperature variations over nearly 90 hours of testing (effectively acting as a temperature sensor with a high degree of stability) while operation in DC mode resulted in largely no correlation with temperature. This indicates that AC excitation above the corner frequency is a potentially effective method to mitigate long-term sensor instability, a critical limitation for any AlGaN/GaN transistor-based physical or chemical sensors in aqueous environments.

Combined effect of ambient temperature and solar radiation on maned sloths' behaviour and detectability

AbstractChanges in ambient temperature and solar radiation may affect sloths' metabolic rate and body temperature, with consequent changes in activities, postures and microhabitat selection. Although the separate effect of temperature and solar radiation on sloth's behaviour have been previously studied, the combined effect of these climatic factors on behavioural aspects of sloths has never been systematically evaluated in field conditions. Here we evaluated the influence of hourly ambient temperature variation on maned sloth (Bradypus torquatus) activities, postures and tree crown positions, under sunny and cloudy conditions; and tested if any of the animal posture and position increase their exposure to human detection. We performed 350 h of visual observation on eight maned sloths, equipped with radio‐backpacks, in northern Bahia, Brazil, recording their activities, and their resting postures and positions on tree crowns. We also recorded the time taken to visualize the sloths on 58 days to analyse if sloths' detection is affected by posture and position. Higher ambient temperature, within a range of 21–33°C, increased the sloths' activity levels in cloudy conditions but reduced their activity in sunny conditions. Increasing ambient temperature also reduced the frequency of huddled posture and increased the frequency of extended posture and permanence in the inner tree crown. Lastly, the postures and positions did not influence sloths' detectability. Thus, the direction of the temperature–activity relationship depends on climatic conditions (sunny/cloudy), and individuals rely on resting postures and positions to thermoregulate. The warmer and drier future climate, expected to occur in the northern Atlantic Forest, may impose change in the diurnal activity levels and postural pattern for this threatened species, leading maned sloths to reduce its activity on sunny and warmer days and adopting an extended posture.

Optimized Placement of Frost-Measuring Sensors in Heat Exchangers via Image Processing of Frost Formation Pattern.

Heat exchangers (HXs) play a critical role in maintaining human thermal comfort and ensuring product safety and quality in various industries. However, the formation of frost on HX surfaces during cooling operations can significantly impact their performance and energy efficiency. Traditional defrosting methods primarily rely on time-based control of heaters or HX operation, overlooking the actual frost formation pattern across the surface. This pattern is influenced by ambient air conditions (humidity and temperature) and surface temperature variations. To address this issue, frost formation sensors can be strategically placed within the HX. However, the non-uniform frost pattern poses challenges in sensor placement. This study proposes an optimized sensor placement approach using computer vision and image processing techniques to analyze the frost formation pattern. Through creating a frost formation map and evaluating various sensor locations, frost detection can be optimized to control defrosting operations with higher accuracy, thereby enhancing the thermal performance and energy efficiency of HXs. The results demonstrate the effectiveness of the proposed method in accurately detecting and monitoring frost formation, providing valuable insights for sensor placement optimization. This approach presents significant potential in enhancing the overall performance and sustainability of the operation of HXs.

Lamé Resonator Integrated With Chevron-Shaped Thermal Actuators to Improve Motional Resistance and Temperature Stability

This paper presents a capacitive bulk mode resonator operating in Lamé mode, where the motional resistance and temperature stability are enhanced by implementing a set of chevron-shaped thermal actuators to reduce the transducer air gaps. The chevrons are heated using micro-heaters that are integrated on the actuator. The device is fabricated in the PiezoMUMPS standard microfabrication process by MEMSCAP. The measured resonant frequency for the fabricated device was observed to be 17.9 MHz. It has been experimentally shown that the transducer air gap can be reduced from 2.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu m$</tex-math> </inline-formula> to 0.5 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu m$</tex-math> </inline-formula> by applying a heater voltage of 2.7 V at atmospheric pressure. In the proposed resonator, the transmission loss can be reduced by 8.54 dB when the actuators are biased at 1.8 V in vacuum, as opposed to when the actuator is off. Under these conditions, the thermal actuators each consume 39 mA. In addition, the implemented thermal actuators can function as integrated heaters that increase the temperature of the suspended square structure to compensate for ambient temperature variations. As such, applying a voltage of 1.8 V in vacuum reduces the resonant frequency from 17.95 MHz to 17.91 MHz, while applying a voltage of 2.6 V at atmospheric pressure reduces the resonant frequency from 17.97 MHz to 17.86 MHz.2022-0188

Interfacial trap charge and self-heating effect based reliability analysis of a Dual-Drain Vertical Tunnel FET

This manuscript exclusively addresses the reliability concern of a double-drain vertical TFET (DD-VTFET) by analysing the influence of interface trap charges and variation in ambient temperature on various DC and analog/RF figure of merits. For detailed analysis, performance of the device is evaluated by considering different densities and polarities of trap charges existing at gate-oxide/channel interface. TCAD-based simulation results reveal that trap charges significantly alter the flat-band voltage, which further causes variation in the device performance. It is observed from the transfer characteristic curve that the leakage current is degraded from 10−18 to 10−13A/μm when a positive (donor) charge density of 1013 cm−2 is introduced at oxide/channel interface. However, cut-off frequency is found to be improved under the influence of donor traps, which is mainly attributed due to improvement in transconductance of the device. Moreover, simulation results indicate that DD-VTFET is immune to the negative (acceptor) traps in comparison with the positive traps. Furthermore, the analysis carried out for temperature affectability on the device performance suggests that, at higher ambient temperature, the off-state current degrades more in subthreshold region (at low gate bias) due to dominance of the Shockley-Read-Hall (SRH) and trap-assisted tunneling (TAT) mechanisms, which exponentially depend on the temperature. Therefore, the leakage current increases approximately by an order 7 when temperature is increased from 200 K to 400 K. Since band-to-band tunneling starts dominating over SRH and TAT in the super-threshold region (at high gate bias), the impact of temperature variation along with presence of the trap charges is found to be insignificant on the transfer characteristics.

Experimental Study of MICP-Solidified Calcareous Sand Based on Ambient Temperature Variation in the South China Sea

With the continuous advancement of the construction of the Hainan Free Trade Port and Island Reef Project, deploying Microbial Induced Calcium Carbonate Precipitation (MICP technology) for related research on the temperature range in this area would be of great significance. MICP technology is an innovative and sustainable new soil reinforcement technology that uses the metabolic activity of specific bacteria to produce calcium carbonate precipitation (CaCO3) to connect loose soil. A few previous studies reporting on the applications of MICP technology in different temperature environments drew different conclusions. Therefore, this study involved MICP sand column reinforcement tests at ambient temperatures of 20 °C, room temperature, 30 °C, and 40 °C. The reinforcement effect was evaluated using indicators such as CaCO3 generation rate, Ca2+ conversion rate, bacterial adhesion rate, water absorption rate, and unconfined compressive strength, providing a reference basis for the future applications of MICP technology to island and reef engineering construction. The results showed that, with an increase of temperature from 20 °C to 40 °C, the CaCO3 production rate, Ca2+ conversion rate, and unconfined compressive strength showed a trend of first increasing and then decreasing; the UCS was 548 KPa at 20 °C and 2276.67 KPa at 30 °C; the water absorption rate at 20 °C was 25.32, which decreased continuously with increasing temperature, and reached 21.49 at 40 °C; and the bacterial adhesion rate also continued to rise in the range of 20 °C to 40 °C, from 10.91 to 28.44. The increase in temperature had an impact on the physiological state of bacterial cells. A scanning electron microscope test shows that CaCO3 crystal forms generated under different temperature environments were different, and the CaCO3 mineral deposits generated during MICP reinforcement at 30 °C were denser. Fewer gaps were present between adjacent sand particles, and the bond was tight, which served better as a bridge. The strength of the solidified sample was also higher. The annual average temperature of the South China Sea is about 30 °C. The findings of this experiment provide feasibility and sustainable development for MICP project reinforcement in the South China Sea.

3D imaging reveals apical stem cell responses to ambient temperature

Plant growth is driven by apical meristems at the shoot and root growth points, which comprise continuously active stem cell populations. While many of the key factors involved in homeostasis of the shoot apical meristem (SAM) have been extensively studied under artificial constant growth conditions, only little is known how variations in the environment affect the underlying regulatory network. To shed light on the responses of the SAM to ambient temperature, we combined 3D live imaging of fluorescent reporter lines that allowed us to monitor the activity of two key regulators of stem cell homeostasis in the SAM namely CLAVATA3 (CLV3) and WUSCHEL (WUS), with computational image analysis to derive morphological and cellular parameters of the SAM. Whereas CLV3 expression marks the stem cell population, WUS promoter activity is confined to the organizing center (OC), the niche cells adjacent to the stem cells, hence allowing us to record on the two central cell populations of the SAM. Applying an integrated computational analysis of our data we found that variations in ambient temperature not only led to specific changes in spatial expression patterns of key regulators of SAM homeostasis, but also correlated with modifications in overall cellular organization and shoot meristem morphology.

Sensorless temperature control of household refrigerators based on the electric current of the compressor

The present study is aimed at putting forward a novel temperature controller (including software and hardware) for a fan-and-damper refrigerator considering the electric current drawn by the single-speed compressor as the process variable. The control algorithm consists in a dynamic reference modification of a PI controller, together with a set of empirical conjectures. In addition, a purpose-built electronic board was designed and prototyped. All experiments were performed in-house with the refrigerator placed in a climate chamber. The refrigerator was tested at two different surrounding air temperatures (16 and 25 °C) under pulldown, defrost recovery, and variable ambient temperature regimes. It was noted that the proposed controller was able to maintain the refrigerator temperature within ±1 °C tolerance bounds – figures like those obtained for the baseline thermistor-based temperature controller – albeit being less costly.

Long-term ultrasonic monitoring of concrete affected by alkali-silica reaction

This article presents continuous monitoring results of alkali-silica reaction (ASR) development in concrete specimens for over 400 days using ultrasonic testing and expansion measurements. Eight concrete specimens with nonreactive aggregate (Control), reactive coarse aggregate, and reactive fine aggregates were cast with two reinforced confinement conditions. The specimens were conditioned in an environmental chamber with high temperature and humidity (38°C and 90% relative humidity) to accelerate the ASR development. A multichannel ultrasonic monitoring system was developed to collect ultrasonic signals automatically, and the expansions in three directions were measured periodically. Results showed that the relative velocity change could detect the ASR initiation in all reactive specimens and show a correlation with expansion in the early stage. However, these correlations are inconsistent for different ASR specimens, and the velocity change becomes less sensitive to ASR damage in the late stage (after 300 days). Irrecoverable velocity drop was observed during every chamber shutdown period, especially in specimens with higher levels of ASR damage. This phenomenon suggests that the nonlinear ultrasonic response caused by the ambient temperature variation may indicate the ASR damage.

Tropical super flies: Integrating Cas9 into Drosophila ananassae and its phenotypic effects

Ectotherms such as insects are animals whose body temperature largely depends on ambient temperature and temperature variations provide a selection pressure affecting the geographical distribution of these species. However, over the course of evolution, some insect species managed to colonize environments characterized by various temperature ranges. Therefore, insects provide an excellent study system to investigate the basis of adaptation to temperature changes and extremes. We are generally using the vinegar fly Drosophila ananassae as a model system to investigate the genetic basis of cold tolerance. This species has expanded from its tropical ancestral range to more temperate regions resulting in a cosmopolitan, domestic distribution. Previously, we identified candidate genes significantly associated with cold tolerance in this species. We now established molecular genetic tools to assess the function of these genes. Using CRISPR/Cas9 methodology for genome editing and the PiggyBac system, the Cas9 enzyme was successfully integrated into the genome of three fly strains with different levels of cold tolerance. We further report on preliminary findings that the Cas9 integration itself did not have a consistent effect on tolerance to cold. In conclusion, we offer with our study the molecular tools that allow studying stress-related candidate genes in D. ananassae in the future. In addition, we point out and provide guidance on the challenges that come with genome editing in a non-model species.

The dual-mode sensing of pressure and temperature based on multilayer structured flexible sensors for intelligent monitoring of human physiological information

Flexible multifunctional sensor with excellent performance via unsophisticated fabrication method is imperatively anticipated for the development of smart human health monitoring systems and wearable electronic devices. Here, we report a multilayer dual-mode flexible sensor (DMFS) by integrating different sensing layers on the two sides of a flexible dielectric substrate for sensing pressure and temperature. The introduction of elastic nanofiber skeleton structure and internal “sea urchin” like conductive materials is the top priority for the DMFS to have excellent sensing performance and durability. As a result, the fabricated DMFS ultimately shows excellent pressure sensitivity of 111.96 kPa−1 within a wide sensing range up to 70 kPa. In the case of temperature stimulus, the DMFS accomplishes a high, linear response to the ambient temperature variation within the range from 20 °C to 50 °C, while maintaining high stability and durability after long-term bending cycles. In addition, DMFS reveals its great potential for non-contact dynamic temperature measurement by being integrated into an intelligent temperature monitoring system. Most importantly, a novel smart human health-monitoring system, which attributes to the coordination and common work of multiple DMFS, has been developed and realizes simultaneous detection of multiple physiological signals of human beings in real-time.

All fiber Mach–Zehnder interferometer for simultaneous measurement of temperature and refractive index

An all fiber Mach–Zehnder interferometric (MZI) sensor for measuring temperature and refractive index (RI) is proposed and experimentally demonstrated. The proposed sensor is fabricated with a coreless–few mode–coreless fiber structure. Variations in ambient temperature and RI cause changes in phase differences between the fundamental mode and the higher-order modes, leading to shifts in interference spectrum. The two resonance dips shifts within the wavelength spectrum are used to investigate the temperature and RI characteristics of the sensor. Experimental results show that the two dips have different responses to temperature and RI, indicating that the sensor can realize simultaneous measurement of temperature and RI; the maximum sensing sensitivities are 0.0739 nm/°C and −25.29 nm/RIU, respectively. The proposed sensor has potential applications in physical, biological, and chemical sensing owing to its low cost, good linearity, and simple fabrication.

Hybrid optimization algorithm for thermal displacement compensation of computer numerical control machine tool using regression analysis and fuzzy inference.

During the machining process, the computer numerical control machine is susceptible to variations in ambient temperature, cutting heat, and friction within the transmission parts, which generate different heat sources. These heat sources affect the machine structure in different ways, causing deformation of the machine and displacement of the tooltip and workpiece position, ultimately resulting in deviations in machining accuracy. The amount of thermal drift depends on several factors, including the material of the machine components, the cutting conditions, the duration of the machining process, and the environment. This study proposes a hybrid optimization algorithm to optimize the thermal variables of computer numerical control machine tool spindles. The proposed approach combines regression analysis and fuzzy inference to model the thermal behavior of the spindle. Spindle speed and 16 temperature measurement points distributed on the machine are input factors, while the spindle's axial thermal error is considered an output factor. This study develops a regression equation for each speed to account for the different temperature rise slopes and spindle thermal variations at different speeds. The experimental results show that the hybrid thermal displacement compensation framework proposed in this study effectively reduces the thermal displacement error caused by spindle temperature variation. Furthermore, the study finds that the model can be adapted to significant variations in environmental conditions by limiting the machining speed range, which significantly reduces the amount of data needed for model adaptation and shortens the adaptation time of the thermal displacement compensation model. As a result, this framework can indirectly improve product yield. The effects observed in this study are remarkable.

Bimetal Temperature-Compensated Ramsey Cavity for Atomic Fountain Frequency Standards

A typical Ramsey cavity, commonly used in atomic fountain frequency standards (AFFSs) for microwave interrogation, is sensitive to ambient temperature variation. Then, it becomes one of the main limiting factors for the AFFSs operating in a narrow operating-temperature range and a temperature-well-controlled environment up to now. In this article, a new design of bimetal temperature-compensated Ramsey cavity (BTCRC) based on the thermal expansion self-compensating mechanism is presented and experimentally demonstrated. This cavity is a typical TE011-mode cylindrical microwave resonator with a titanium tube and two oxygen-free copper (OFC) caps. The resonance frequency (RF) of the cavity can be immune to temperature variations if the dimensions of the tube and caps are properly designed. To validate this self-compensating mechanism, a BTCRC resonating at the Rb clock frequency with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> -factor of about 17000 is constructed. And its RF thermal coefficient is measured to be 0.73 kHz/°C, which is about 150 times superior to −115.9 kHz/°C of a typical OFC Rb cavity in the temperature range of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$22.48~^{\circ }\text{C}$ </tex-math></inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$37.48~^{\circ }\text{C}$ </tex-math></inline-formula> . During the operation of AFFSs, this BTCRC ensures that the microwave field amplitude inside the cavity, which dictates the transition probability and thus the contrast of the Ramsey fringes, will be stable in time. In addition, the potential temperature variation-induced frequency shifts due to cavity pulling are significantly minimized.

Experimental Study of Thermal Resistance Values of Natural Fiber Insulating Materials under Different Mean Temperatures

The purpose of this paper is to experimentally study the thermal resistance (RSI value) of building insulation materials made mainly from natural fiber. Natural fibrous materials or renewable resources and their reinforcement composites are currently being used in building and construction as a potential solution to significantly reduce thermal load and energy consumption. The RSI value is used in describing the thermal efficiency of insulating material and in an analysis of heat transfer through the structural components of a building (such as walls, roofs, and windows) under steady-state conditions. In this study, the thermal resistance values of several samples made from coir fiber, rice straw fiber, energy reed fiber, and coconut wood were calculated from the thermal conductivity which was measured at mean temperature of 20°C, using the heat flow apparatus. The lowest RSI value was recorded in the phenol-formaldehyde polymer composites reinforced by rice straw fiber (0.115 m2·K·W-1) and coir fiber (0.128 m2·K·W-1) due to the relative thinness of the tested samples (8 and 12 mm). However, these samples can be used as an additional layer in multi-layered assemblies because of their low thermal conductivity value. The highest RSI value was reported on the binderless coir fiber panel (0.909 m2·K·W-1) at the thickness of 50 mm. Another investigation examined the relationship between RSI value and mean temperature to observe the influence of variations of ambient temperature on the heat resistivity of building insulation materials. Practical data showed the decreased linear proportion between thermal resistance and specific mean temperatures increased from 0 to 40°C. It is apparent that an increase in the interior and exterior temperature of a building significantly influences the thermal resistance of its insulation materials. Based on the experimental study, once the thermal conductivity coefficient of each sample was determined, the calculated RSI value was a valuable parameter to evaluate the thermal resistant effectiveness of a multi-layered installation, which allows us to investigate practically the effect of the thickness of additional layers from different insulating materials used in building envelopes.

Urban form features determine spatio-temporal variation of ambient temperature: A comparative study of three European cities

Driven by ongoing urbanization and accelerated global warming, urban heat stress develops into a major threat for a large part of the world population. While the literature is clear about the relevance of urban form in modifying urban heat, the spatially explicit context of heat modifications by the built environment is insufficiently explored across cities.Here we develop a consistent methodology based on a machine learning model to determine the predictive features of urban form that shape urban ambient temperature (AT) under different urban and climate conditions. For this, we combine urban climate data at 100 m resolution from the UrbClim model with urban form features computed from different open datasets. We exemplify our innovation by evaluating summer daytime and nighttime temperature variation within three European cities that are representative of distinct geographies and climates: Berlin, Zürich, and Sevilla. Mean AT at dense urban spots was higher by 3 °C (on average) during summer compared to sub-urban sites across all cities. We find that urban form features explain around 2/3 of within-city temperature variations. Vegetation cover and water bodies are most significant in explaining spatial temperature patterns during the daytime, while the impervious land cover is most critical at nighttime. Cooling effect of water areas can accumulate to −1.5 °C, while heating effects of roads can induce +0.5 °C during daytime. The magnitude of effects varies across cities, primarily based on the climate type, altitude, and dominant land-cover. However, further testing should be conducted to develop a better understanding of impact variations. The findings of this research will provide urban planners and policymakers with crucial insights towards heat mitigation and sustainable urban developments through region-tailored modifications and replacement of land-cover.

Variable ambient temperature promotes song learning and production in zebra finches.

Current climate change is leading to increasingly unpredictable environmental conditions and is imposing new challenges to wildlife. For example, ambient conditions fluctuating during critical developmental periods could potentially impair the development of cognitive systems and may therefore have a long-term influence on an individual's life. We studied the impact of temperature variability on zebra finch cognition, focusing on song learning and song quality (N = 76 males). We used a 2 × 2 factorial experiment with two temperature conditions (stable and variable). Half of the juveniles were cross-fostered at hatching to create a mismatch between pre- and posthatching conditions, the latter matching this species' critical period for song learning. We found that temperature variability did not affect repertoire size, syllable consistency, or the proportion of syllables copied from a tutor. However, birds that experienced variable temperatures in their posthatching environment were more likely to sing during recordings. In addition, birds that experienced variable prenatal conditions had higher learning accuracy than birds in stable prenatal environments. These findings are the first documented evidence that variable ambient temperatures can influence song learning in zebra finches. Moreover, they indicate that temperature variability can act as a form of environmental enrichment with net positive effects on cognition.

Electrothermal Analyses of Bandpass NGD RLC-Network Topologies

This paper develops an original study of temperature effect on the unfamiliar bandpass (BP) negative group delay (NGD) lumped passive circuits. The paper presents the first study of electrothermal analysis of electronic circuits classified as BP-NGD topologies. The considered BP-NGD passive cells are mainly constituted by RLC-resonant networks. The equivalence between two basic BP-NGD topologies constituted by RLC-series and RLC-parallel networks is elaborated via the voltage transfer function (VTF) analogy. Then, the theoretical demonstrations are introduced to define the main specifications as the NGD center frequency, NGD value, attenuation and NGD bandwidth. The electrothermal innovative study is developed based on the temperature coefficient resistor (TCR) of elements constituting the BP-NGD circuits. With proofs of concept of RLC-series and RLC-parallel circuits operating with -500 ns NGD value at 13.56 MHz, calculated and simulated results showing are in excellent agreement. The sensitivity analyses of BP-NGD specifications in function of ambient temperature variation from 0°C to 100°C are investigated. The BP-NGD response variations versus frequency and temperature are characterized with thermo-frequency cartographies and discussed.

State of charge estimation of ternary lithium-ion batteries at variable ambient temperatures

Among the factors that affect lithium-ion batteries, ambient temperature has a great influence on the charge and discharge rate, general battery performance, and storage capacity of the battery, hence accurate state of charge (SOC) estimation over a wide range of temperatures is essential and necessary. In this paper, a Second-order Thevenin equivalent circuit model is established with ambient temperature compensation over varying ambient temperature conditions. An improved Fixed Range Forgetting Factor-Adaptive Extended Kalman Filtering (FRFF-AEKF) algorithm with the Saga-Husa Adaptive filter (SHAF) is proposed for the accurate estimation of SOC at variable ambient temperature. The temperatures −10°C, 10 °C, 25 °C, and 40 °C are set to depict low, normal, and high ambient temperatures in which lithium-ion batteries in electric vehicles (EVs) and most electronic devices usually operate. Tests conducted include the hybrid pulse power characterization (HPPC) for obtaining data required for parameterization, and for SOC estimation and verification, the Beijing Bus Dynamic stress (BBDST). The object of the tests was a ternary lithium-ion battery representing those used in electric vehicles (EVs). To improve adaptability, reduced noise, and achieve faster convergence with increased accuracy, the range of forgetting factor is fixed between a variable range of 0.997–1. To verify the performance of the proposed algorithm under varying conditions and different ambient temperatures, the SOC estimation result was compared with that of the adaptive extended Kalman filtering (AEKF) algorithm. The results show that the proposed improved algorithm implemented with the established Second-order Thevenin equivalent model has a 1.1 % better estimation accuracy compared to the results of the AEKF algorithm. This confirms that the proposed method can achieve accurate SOC estimation and is adaptive to variable ambient temperatures.

Performance evaluation of a hybrid thermoelectric generator and flat plate solar collector system in a semi-arid climate

This study investigates the performance of a hybrid system that combined thermoelectric generators (TEG) with a solar flat plate collector system (SFPC) to turn more renewable energy into useable energy under normal operating and environmental conditions. A multi-month case study was first time conducted to explore the performance of SFPC with and without TEGs under the cold climatic conditions of Abha, Saudi Arabia. The result demonstrates that the heat losses from the rear surface of the SFPC's absorber plate were effectively utilized by TEGs, thereby decreasing overall heat losses and increasing the SFPC's overall thermal efficiency. Further, it was found that adding TEGs at the rear surface of SFPC's absorber plate improves thermal efficiency and exergy efficiency by 8.4% and 1.3%, respectively. The hybrid TEG-SPFC system can turn waste heat into useable electricity, with a peak power output of 2.2 W at midday. Maximum power was generated around midday, when the temperature differential between the upper and lower layers of TEGs was greatest. In addition, it was noticed that the thermal efficiency of the SFPC diminishes when the inlet water temperature rises. A hybrid TEG-SFPC system's exergy efficiency depends on ambient temperature variation and solar irradiance.