Search

Despite efforts to mitigate climate change, annual greenhouse gas emissions continue to rise, which may lead to the global warming of our planet. Buildings' thermal energy needs are inherently linked to climate conditions. Consequently, it is crucial to evaluate how climate change affects these energy demands. Despite extensive analysis, a comprehensive assessment involving a diverse range of building types has not been consistently conducted. The primary objective of this research is to perform a coherent evaluation of the influence of climate changes, construction element properties, and the Heating, Ventilation, and Air Conditioning (HVAC) system type of control on the energy requirements of six buildings (residential, services, and commercial). The buildings are considered to be located in a temperate Mediterranean climate. Our focus is on the year 2070, considering three distinct climatic scenarios: (i) maintaining the current climate without further changes, (ii) moderate climate changes, and (iii) extreme climate changes. The buildings are distributed across three different locations, each characterized by unique climatic conditions. Buildings' envelope features a traditional External Thermal Insulation Composite System (ETICS) and expanded polystyrene (EPS) serves as thermal insulation material. Two critical design factors are explored: EPS thickness ranging from 0 (no insulation) to 12 cm; and horizontal external fixed shading elements varying lengths from 0 (absence) to 150 cm. Six alternative setpoint ranges are assessed for the HVAC system control: three based on the Predicted Mean Vote (PMV) and three based on indoor air temperature (Tair). Results were obtained with a validated in-home software tool. They show that, even under extreme climate conditions, the application of thermal insulation remains energetically favorable; however, its relative importance diminishes as climate severity increases. Then, proper insulation design remains important for energy efficiency. The use of external shading elements for glazing (e.g., overhangs, louvers) proves beneficial in specific cases. As climate changes intensify, the significance of shading elements grows. Thus, strategic placement and design are necessary for good results. The HVAC system's energy consumption depends on the level of thermal comfort requirements, on the climate characteristics, and on the building's type of use. As climate change severity intensifies, energy demands for cooling increase, whereas energy needs for heating decrease. However, it is essential to recognize that the impact of climate changes on HVAC system energy consumption significantly depends on the type of building. [ABSTRACT FROM AUTHOR]

With half-cut photovoltaic (PV) modules being the dominant technology on the market, there is an increasing necessity for accurate modeling of this module type. Circuit simulators such as Simulink are widely used to study different topics regarding photovoltaics, often employing a solar cell block available from the Simcape library. The purpose of this work is to validate this model against measurements for a partially shaded half-cut PV module. Diverse shading scenarios are created by varying the number of shaded substrings, the number of shaded solar cells in the substring, and the shading level. For every shading scenario, the PV module's I-V curve is measured, along with in-plane irradiance, air temperature, and module temperature. A comprehensive evaluation of simulation accuracy is presented. The results confirm a high accuracy of the model with mean nRMSE values of 2.2% for I-V curves and 2.8% when P-V curves are considered. It is found that the simulation errors tend to increase when increasing the number of shaded substrings. At the same time, no obvious dependency of simulation accuracy on the shading level or the number of shaded solar cells in the substring is found. [ABSTRACT FROM AUTHOR]

The combined heating method of seat heating and air conditioning (A/C) was applied in the passenger compartment under different experiment conditions, using thermocouples to continuously measure the wall surfaces and air temperatures in the passenger compartment and the passengers' skin temperatures of 17 segments. Meanwhile, a subjective evaluation questionnaire survey was conducted using a nine-point evaluation scale on the local and overall thermal sensation and thermal comfort of the passengers, and the data from the questionnaire were analyzed with the ANOVA method. The results showed that the use of the heating pad directly affected the changes in human skin temperature, which in turn affected the local and overall thermal sensation and thermal comfort. For the two thermally stimulated segments of the back and under the thighs, the skin temperature of the back was higher than that of the thighs. Using the heating pad resulted in a rapid increase in the mean skin temperature in the early period of the experiment. Thermal sensation of the back and under-thighs shifted rapidly towards the hot zone in the first 10 min, and then settled around +3, with even more significant differences between the groups. Thermal sensations in non-thermally stimulated segments changed in relation to their position on the heating pad, with slower changes in those at the "distal" end of the body, the head and the feet. Continued use of the heating pads at lower ambient temperatures maintained overall thermal comfort at a neutral level in the range of 0–1, whereas at higher ambient temperatures there was a gradual deterioration of local and overall thermal comfort. [ABSTRACT FROM AUTHOR]

This research was carried out to compare selected forecasting methods, such as the following: Artificial Neural Networks (ANNs), Classification and Regression Trees (CARTs), Chi-squared Automatic Interaction Detector (CHAID), Fuzzy Logic Toolbox (FUZZY), Multivariant Adaptive Regression Splines (MARSs), Regression Trees (RTs), Rough Set Theory (RST), and Support Regression Trees (SRTs), in the context of determining the temperature of brine from vertical ground heat exchangers used by a heat pump heating system. The subject of the analysis was a public building located in Poland, in a temperate continental climate zone. The results of this study indicate that the models based on Rough Set Theory (RST) and Artificial Neural Networks (ANNs) achieved the highest accuracy in predicting brine temperature, with the choice of the preferred method depending on the input variables used for modeling. Using three independent variables (mean outdoor air temperature, month of the heating season, mean solar irradiance), Rough Set Theory (RST) was one of the best models, for which the evaluation rates were as follows: CV RMSE 21.6%, MAE 0.3 °C, MAPE 14.3%, MBE 3.1%, and R2 0.96. By including an additional variable (brine flow rate), Artificial Neural Networks (ANNs) achieved the most accurate predictions. They had the following evaluation rates: CV RMSE 4.6%, MAE 0.05 °C, MAPE 1.7%, MBE 0.4%, and R2 0.99. [ABSTRACT FROM AUTHOR]

Many studies have sought to overcome the two main limitations of the average method of ISO 9869-1—its long test duration and low accuracy. These studies reported that the reliability of the results is dependent on the temperature differences. This consensus was based on the results of studies that measured a few cases with specific temperature differences, and the convergence criteria utilized for the representative thermal transmittance (U-value) were rarely examined. This study analyzed the influence of the average temperature difference and test duration on the convergence characteristics and accuracy of U-value estimation using the average method. Data from a north-facing exterior wall with a theoretical U-value of 0.145 W/m2·K were measured between June 2022 and May 2023. The influences of different measurement conditions were analyzed for cases divided based on four measurement periods and 11 average air temperature differences. The findings show that an accurate U-value can be obtained from 7 days' worth of measurement data with an average temperature difference of 10 °C or higher and that the improvement in accuracy is minimal under stricter conditions. To achieve a convergence probability of over 90% for temperature differences of 10 °C or greater, the second and third criteria required measurement periods of 7 and 15 days respectively. [ABSTRACT FROM AUTHOR]

There have been fruitful publications on thermal comfort of urban residential buildings in China. However, there is a lack of reviews on this topic to perform a comprehensive analysis and find opportunities to meet occupants' thermal comfort needs while improving building energy efficiencies. This paper addresses this issue by presenting a systematic review on the advancements in research on thermal comfort in urban residential buildings in China. Firstly, two common thermal comfort research approaches, i.e., field studies and laboratory studies, are discussed. Secondly, eleven main thermal comfort evaluation indicators are summarized. Finally, this paper analyzes the thermal comfort survey data from different researchers, discusses the impacts of adaptive behaviors on human thermal comfort, and provides recommendations for future research on urban residential thermal comfort. It was found that people have higher and higher requirements for their indoor thermal environment as time goes by, especially in the winter; the thermoneutral temperature is higher in warmer climate regions in the summer but lower in the winter than in colder climate regions; the thermoneutral temperature tends to increase with the indoor air temperature due to an adaptation to the indoor thermal environment. The outcomes of this paper provide valuable information on thermal comfort behaviors of urban residents in different climate zones in China, which can serve as a resource for the academic community conducting future research on thermal comfort and assist policymakers in enhancing building energy efficiencies without compromising the occupants' comfort. [ABSTRACT FROM AUTHOR]

In order to explore the law of gas–solid countercurrent cooling heat transfer in a vertical sinter cooling furnace at a high temperature, based on the Euler model and the local non-thermodynamic equilibrium theory, an exergy efficiency model was built to evaluate the heat transfer process in the vertical sinter cooling furnace with different parameter changes. It was found that the inlet temperature of cooling air and sinter inlet temperature are the main factors affecting the temperature field and gas–solid heat transfer characteristics in the furnace. Under the conditions of each parameter, the cooling air temperature presents a radial "M" shape distribution. The axial cooling section is the most intense area of gas–solid heat transfer, and this part has the best heat transfer effect. When the inlet temperature of cooling air and the inlet temperature of sinter increase, the outlet temperature of sinter and the outlet temperature of cooling air increase. When the sinter equivalent diameter increases, the cooling air outlet temperature decreases gradually, while the sinter outlet temperature increases gradually. When the diameter and height of the cooling section increase, respectively, the outlet temperature of the sinter decreases and the outlet temperature of the cooling air increases. Based on dimensional analysis, the heat transfer correlation formula suitable for certain test conditions is obtained. [ABSTRACT FROM AUTHOR]

This paper experimentally analyses an indoor environment assessment of a large group of respondents regarding their subjective perception of overall comfort, indoor air quality and humidity. The questionnaire survey was applied as a testing method together with measurements of the physical parameters conducted with a microclimate meter. Two types of environment were analysed: educational rooms and the climate chamber. The comparative analysis of the sensations experienced within them indicates that they generate quite similar responses; however, some discrepancies have been identified. The overall comfort of the climate chamber was typically assessed as being higher than that of the educational rooms at the same air temperature. The most favourable air temperature in the climate chamber was ca. 20.7 °C, while in the educational rooms it was ca. 22.3 °C. The most preferable conditions in the climate chamber occurred at a thermal sensation vote of −0.4 ("pleasantly slightly cool"), while in the educational rooms it occurred at +0.2 ("neutral/pleasantly slightly warm"). Quite strong correlations between overall comfort and indoor air quality as well as between humidity assessment and humidity preference votes were observed, which did not seem to depend on the type of environment. These findings are important because results from the simulated conditions are often used in the analyses of actual living/working environments. [ABSTRACT FROM AUTHOR]

This paper presents an application of the Simulink stvmgain S-function for the thermal modelling of a building zone based on the resistance–capacitance scheme of EN ISO 13790. That model in the form of the state-space matrix with time-varying elements was used in simulations of a building with hourly and, suggested in that standard, daily averaged ventilation airflow in five European cities. The following two ventilation schedules were used: occupancy-based; and wind-dependent. Comparative simulations were conducted in EnergyPlus. In general, the results obtained for the annual heating and cooling demand were better for hourly than daily averaged ventilation with an error below 10%. However, in several cases of cooling, the error was above 30%. When considering hourly indoor air temperatures, the proposed method provided very good results with MAE of up to 0.52 °C and 0.46 °C, RMSE < 0.69 °C and 0.62 °C, and CV(RMSE) < 3.09% and 2.75% for the daily averaged and hourly ventilation flow, respectively. For wind-driven ventilation, the temperatures were as follows: MAE < 0.49 °C and 0.48 °C; RMSE < 0.69 °C and 0.68 °C; and CV(RMSE) < 3.01% and 2.97%. [ABSTRACT FROM AUTHOR]

Recently, data-based artificial intelligence technology has been developing dramatically, and we are considering how to model, predict, and control complex systems. Energy system modeling and control have been developed in conjunction with building technology. This study investigates the use of an artificial neural network (ANN) for predicting indoor air temperature in a test room with windows on an entire side. Multilayer perceptron (MLP) models were constructed and trained using time series data obtained at one-second intervals. Several subsampling time steps of 1 s, 60 s, 300 s, 600 s, 900 s, 1800 s, and 3600 s were performed by considering the actual operation control mode in which the time interval is important. The performance indices of the neural networks were evaluated using various error metrics. Successful results were obtained and analyzed based on them. It was found that as the multi-step time interval increases, performance degrades. For system control designs, a shorter prediction horizon is suggested due to the increase in computational time, for instance, the limited computing capacity in a microcontroller. The MLP structure proved useful for short-term prediction of indoor air temperature, particularly when control horizons are set below 100. Furthermore, highly reliable results were obtained at multi-step time intervals of 300 s or less. For the multivariate model, both calculation time and data dispersion increased, resulting in worsened performance compared to the univariate model. [ABSTRACT FROM AUTHOR]

High outdoor temperatures and thermal gains due to solar radiation, which penetrates the interior of buildings as the climate warms up, pose a major challenge to maintaining thermal comfort in passive sports facilities. Superbly insulated and airtight envelopes, specific microclimatic requirements and very high user activity can easily lead to overheating and thermal imbalance during summer. This paper focuses on the influence of the varying thermal capacity of external walls and night-time cooling on thermal comfort in a passive sports hall building. Based on experimental studies of the thermal conditions in the building, a model of it was created in Design Builder. Through simulation, the program initially analysed the thermal conditions that arise under different envelope assemblies. Two different ways of cooling the building at night were then analysed: mechanical and natural. The results presented showed that in a well-insulated sports hall with a large volume, the type of wall material alone had only a limited influence on thermal comfort in summer. In contrast, night-time cooling in integration with the accumulation of cold in the building's structural components had a significant impact on protection against overheating during the summer. The type of envelope material is even more important when night-time air exchange is high. Intensive natural ventilation is associated with the highest number of hours in the comfort range—28.1–32.4% more hours in relation to the variant without night ventilation. The use of mechanical ventilation, operating at night at maximum capacity, will result in an increase in the number of hours with air temperatures in the −0.5 < PMV < +0.5 range by only 14.1–21.3%. The high thermal mass of the envelope, combined with adequate ventilation, reduces the occurrence of very high indoor air temperatures, thus alleviating the nuisance of overheating. The maximum internal air temperature during the day is lower by 2.4–3.3 K, compared to the case when no night ventilation is used. Mechanical ventilation operating at its maximum capacity can reduce the maximum internal temperature by 1.2–1.6 K. [ABSTRACT FROM AUTHOR]

The combustion chamber operating pressure, air inlet temperature, and bio-fuel blending ratio are the key factors affecting the emissions of aero engines. Numerical simulations were used to investigate the emission patterns of CO, CO2, NO and carbon soot at the combustion chamber outlet at different temperatures, pressures and blending ratios. The results show that the emission patterns of CO, CO2, NO and carbon soot vary greatly. With increasing working pressure and inlet air temperature of the combustion chamber, the CO2 emissions initially increase rapidly. However, when the working pressure exceeds 0.7 MPa and the inlet air temperature exceeds 450 K, the growth rate of CO2 emissions slows down. On the other hand, CO emissions show a relatively steady increase, but when the working pressure exceeds 0.5 MPa and the inlet air temperature exceeds 550 K, the CO emissions increase rapidly. The CO emissions decrease uniformly with an increase in the blending ratio, whereas the CO2 emissions are not significantly affected by the blending ratio when the bioethanol/aviation fuel ratio is less than 30%. However, when the blending ratio exceeds 30%, the CO2 emissions gradually decrease with an increase in the blending ratio. With increasing pressure, the distribution of NO in the combustion chamber shifts backward gradually, and the NO generation is related to the working pressure in a power function. The NO generation increases rapidly with an increase in the inlet air temperature, but it tends to slow down when the temperature reaches 550 K. The NO generation increases exponentially with an increase in the blending ratio. As the inlet air temperature increases, the soot emissions increase exponentially. The soot is concentrated in the head of the combustion chamber, and the maximum generation gradually decreases. When the biofuel blending ratio is 20%, the soot emissions show a trend of slowing down and then rapidly decreasing. Overall, the soot generation decreases gradually with an increase in the biofuel blending ratio. [ABSTRACT FROM AUTHOR]

Over the past decade, the integration of desiccant technology with evaporative cooling methods has proven to be highly effective and efficient in providing comfortable indoor environments. The performance of desiccant-based direct evaporative cooling (DEC) systems is strongly influenced by environmental conditions, and their output behavior varies across multiple climatic zones. It is not easy to assess the system performance in numerous climatic zones as it is a time-consuming process. The current study focuses on determining the feasibility of a solid desiccant integrated with a direct evaporative cooler (SDI-DEC) for three different climatic zones of Pakistan: Lahore (hot and humid), Islamabad (hot and semi-humid) and Karachi (moderate and humid). To serve this purpose, a specially designed controlled climate chamber with an integrated air handling unit (AHU) was installed to create multiple environmental conditions artificially. It could also provide global climatic conditions under temperature and absolute humidity ranges of 10 °C to 50 °C and 10 g/kg to 20 g/kg, respectively. The weather conditions of the selected cities were artificially generated in the climate chamber. Based on different operating conditions, such as inlet air temperature, humidity and regeneration temperature, the performance of the system was estimated using performance indicators like COP, dehumidification effectiveness, solar fraction and supply air conditions. Results showed that the maximum temperature achieved from solar collectors was about 70 °C from collectors with an area of 9.5 m2. Moreover, the observations showed that when the regeneration temperature was increased from 60 °C to 80 °C, the COP of the system decreased about 41% in a moderate and humid climate, 28% in a hot and semi-humid environment and 23% in a hot and humid climate. The results revealed that an SDI-DEC system has the potential to overcome the humidity and cooling loads of the multiple climatic scenarios of Pakistan. [ABSTRACT FROM AUTHOR]

People tend to spend considerable amounts of time in buildings; thus the issue of providing proper indoor environmental quality is of significant importance. This paper experimentally analyses the subjective sensations of the occupants of intelligent and traditional buildings with the focus on possible differences between these two types of buildings. The study is based on a large database of 1302 questionnaires collected in 92 rooms where simultaneous measurements of the indoor environment physical parameters (air and globe temperature, relative humidity, carbon dioxide concentration, and illuminance) were carried out. Their impact on the subjective assessment of the indoor environment has been presented and analysed. The results show that the occupants seemed to be more favourable towards the indoor conditions in the intelligent building; however, the differences in comparison to the traditional buildings were not considerable. Similarly, self-reported productivity proved to be higher in the intelligent building, while the optimal range of air temperature, which ensured highest productivity, was 22–25 °C. Moreover, a strong correlation between the occupants' overall comfort and their perception of the air quality has been found. [ABSTRACT FROM AUTHOR]

A field survey of indoor environmental measurements and questionnaires on thermal sensation, overall comfort, and behaviors was conducted in four office buildings in Japan by visiting each office every month over a duration of more than a year during the coronavirus disease 2019 (COVID-19) pandemic. The indoor environment was measured concurrently. We obtained 1047 votes from office workers in their 20s to 60s. The regression and Griffiths' methods were used to calculate the indoor comfort temperature. A logistic regression analysis was used to develop the occupant behavior model. Over 70% of the occupants found the indoor environment comfortable at a mean comfort temperature of 23.2 to 25.9 °C. Gender differences were observed in thermal sensation and overall comfort, but a gender difference was observed only in the cooling mode for the indoor comfort temperature. An adaptive model was developed for the office buildings in Nagasaki city to predict the indoor comfort temperature from the outdoor air temperature. The proportions of heating, cooling, and fan usage can be predicted from the outdoor air temperature using a logistic regression analysis. The adaptive model and occupant behavior model are useful for the indoor temperature control of the existing buildings and thermal simulation of the new building design. [ABSTRACT FROM AUTHOR]

The standard for ergonomics of the thermal environment provides information on the calculation of optimal thermal comfort. Operative temperature (OT) is one of the essential elements of thermal comfort and is a function of air temperature, mean radiant temperature (MRT), and air velocity. This paper investigates the impact of diverse influences on MRT in an office room based on occupant position and posture (seated and standing). A comparative simulation study of the varied thermal transmittance (U-value) of the only external wall with a window in an office room depending on the wide-ranging outdoor temperature is conducted in the MATLAB tool Simulink. The air temperature and air velocity are assumed according to the standards, and the MRT is simulated. The angle factors, U-value of walls/windows, occupant position, occupant posture, and outdoor temperature are the critical parameters that affect MRT. The results show varied responses from MRT for each of the five outdoor temperature scenarios simulated for three types of exterior walls. Seated occupants have equal MRT, whereas standing occupants have minor discrepancies when exposed to a window at the same distance in all outdoor scenarios. When the placement of occupants is not equally exposed to the window, the seated occupants have a higher MRT difference than the standing occupants. [ABSTRACT FROM AUTHOR]

A novel robust finite time disturbance observer (RFTDO) based on an independent output-finite time composite control (FTCC) scheme is proposed for an air conditioning-system temperature and humidity regulation. The variable air volume (VAV) of the system is represented by two first-order mathematical models for the temperature and humidity dynamics. In the temperature loop dynamics, a RFTDO temperature (RFTDO-T) and an FTCC temperature (FTCC-T) are designed to estimate and reject the lumped disturbances of the temperature subsystem. In the humidity loop, a robust output of the FTCC humidity (FTCC-H) and RFTDO humidity (RFTDO-H) are also designed to estimate and reject the lumped disturbances of the humidity subsystem. Based on Lyapunov theory, the stability proof of the two closed-loop controllers and observers is presented. Comparative simulations are carried out to confirm that the proposed controller outperforms conventional methods and offers greater accuracy of temperature, humidity, and carbon dioxide concentration, having superior regulation performance in terms of a rapid finite time convergence, an outstanding disturbance rejection property, and better energy consumption. In addition to presenting the comparative simulation results from the control applications on the VAV system, the quantitative values are provided to further confirm the superiority of the proposed controller. In particular, the proposed method exhibits the shortest settling time of, respectively, 15 and 40 min to reach the expected temperature and humidity, whereas other comparative controllers require a longer time to settle down. [ABSTRACT FROM AUTHOR]

In the present research, the energy flow of electric vehicle batteries under different environmental temperatures was experimentally examined in a climate chamber. The energy flow characteristics, energy loss conditions, and the critical components' operating conditions and working efficiency under different environmental temperatures were comparatively analyzed. The test results show that the environmental temperature has a profound impact on an electric vehicle's performance and the critical components' working conditions. The driving mileage of the tested vehicle at −7 °C, 23 °C, and 35 °C was found to be 162.89 km, 256.09 km, and 198.69 km, respectively. The environmental temperature does not have much effect on the loss of the motor and motor control unit under driving conditions, and the proportion of those at different temperatures is in all cases about 18%. The battery-recycled energy at 23 °C under braking conditions is much higher than that at −7 °C and 35 °C, leading to a longer driving range. The power battery pack thermal transfer loss at −7 °C is much greater than that at 23 °C and 35 °C due to the low charging and discharging efficiency and the high energy consumption required to warm up the battery at a low environmental temperature. The compressor energy consumption accounts for a large proportion in both braking and driving conditions at 35 °C, and the proportions are 15.25% and 12.41%, respectively. The battery state-of-charge drops the fastest at −7 °C, followed by 35 °C, due to the differences in the power demands of air conditioning, warm air positive temperature coefficient (PTC), and battery PTC in high- and low-temperature environments. The working condition of the front motor under driving conditions at 35 °C is the most severe and leads to the lowest working efficiency. [ABSTRACT FROM AUTHOR]

This work aims to assess the effect of the operating parameters of the gasifying agent preheating temperature and equivalence ratio (ER) on the conversion of sewage sludge (SS) to syngas through gasification and combined heat and power (CHP) generation. A novel gasification model was simulated in Aspen Plus to represent a fixed-bed updraft gasifier to generate syngas from SS through an equilibrium approach restricted by temperature. The novelty of this work is that the model was developed by applying the gasifying agent preheating temperature as an operating variable instead of the gasification temperature. It was calibrated by using a set of experimental values and then validated by comparing the numerical results with the experimental outcomes related to nine different operating conditions of air preheating temperatures and ER. A good agreement between the simulation and experimental results was observed. The optimum gasification process parameters of the air preheating temperature and ER were predicted to be 150 °C and 0.2, respectively. The CHP generation potentiality of SS was assessed to be 2.54 kW/kg SS as dry solids (DS), of which 0.81 kW was electrical and the remainder was thermal power. The conversion of SS to CHP through the proposed treatment can reduce 0.59 kg CO₂/kg SS as DS emissions compared with that of natural gas combustion to generate a similar quantity of energy. [ABSTRACT FROM AUTHOR]

Infrared thermography is a predictive maintenance tool used in substations to identify a disturbance in electrical equipment that could lead to poor operation and potential failure in the future. According to Joule's law, the temperature of electrical equipment is proportional to the current flowing through it. Other external factors, such as solar incidence, air humidity, wind speed, and air temperature, can interfere with its operating temperatures. Based on this premise, this article aims to analyze the influence of atmospheric and load conditions on the operational cycle of thermography-monitored equipment in order to describe the operating temperature of the object using only external data and to show the impacts of external influences on the final temperature reached by the object. Five multivariate time series regression models were developed to describe the maximum equipment temperature. The final model achieved the best fit between the measured and model temperature based on the Akaike information criterion (AIC) metric, where all external variables were used to compose the model. The proposed model shows the impacts of each external factor on equipment temperature and could be used to create a predictive maintenance strategy for power substations to avoid failure. [ABSTRACT FROM AUTHOR]

Improvement of the energy efficiency of buildings contributes to energy savings. It is obvious that thermal modernization of a building reduces the demand for energy needed to heat it. The energy demand itself also depends significantly on the temperature maintained inside the building. The article proposes a methodology for determining the economic and ecological benefits of thermal insulation of a building and the optimal thickness of thermal insulation depending on the pre-set temperature. The analysis includes various types of heat sources and materials used for thermal insulation. A range of pre-set air temperature values in residential premises from 17 °C to 26 °C was analysed. Determining the optimal thickness of the external walls, in accordance with the preferences of building users, even at the level of designing the thermal insulation of the building, is of significant importance for economic and ecological benefits. The optimum thickness of thermal insulation in the case of the ecological assessment was much higher in each variant than in the case of the economic assessment. [ABSTRACT FROM AUTHOR]

Airborne dust and dust storms are natural disasters that transport dust over long distances from the source basin, sometimes reaching hundreds of kilometers. Today, Iraq is a basin that produces dust storms that strike all neighboring countries such as Iran, Kuwait and Saudi Arabia. These storms affect the productivity and capacity of the photovoltaic modules and reduce the amount of electricity that is generated clearly. Airborne dust reduces the intensity of solar radiation by scattering and absorbing it. In addition, the dust accumulated on the photovoltaic modules causes a deterioration in their productivity. In this study, an extensive review of wind movement and its sources, especially those that hit the city of Baghdad, the capital of Iraq, was conducted. Practical experiments were also carried out during a storm to measure important variables that had not been measured practically before at this site. The experimental tests were carried out starting from 1 April 2022 and continued until 12 April. Within this period, a dust storm occurred that lasted for three consecutive days that was considered one of the most severe storms that the city of Baghdad had experienced in the last few years. Practical measurements showed a deterioration in the solar radiation intensity by up to 54.5% compared to previous days. The air temperature during the storm decreased by 21.09% compared to the days before the storm. From the measurements of ultrafine aerosol particles PM1 and PM2.5, there was a significant increase of 569.9% and 441% compared to the days before the storm, respectively. Additionally, the measurements showed an increase of 217.22% and 319.21% in PM10 and total suspended particles, respectively. Indoor performance experiments showed a deterioration of current, voltage, power and electrical efficiency by 32.28%, 14.45%, 38.52% and 65.58%, respectively, due to dust accumulated during the storm days compared to the previous days. In the outdoor experiments, the rates of deterioration of current, voltage, power and electrical efficiency were greater, reaching 60.24%, 30.7%, 62.3% and 82.93%, respectively, during the storm days compared to the days before it. During a storm, cleaning the panels is futile due to the high concentration of dust in the air, especially by water. However, the photovoltaic modules can be dry cleaned with bristle brushes after the storm has subsided. [ABSTRACT FROM AUTHOR]

Ammonia (NH3) has been receiving the attention of researchers as an alternative promising green fuel to replace fossil sources for energy production. However, the high NOx emissions are one of the drawbacks and restrictions of using NH3 on a broad scale. The current study investigates NO production/consumption for a 70/30 (vol%) NH3/H2 mixture using kinetic reaction mechanism concepts to shed light on the essential reaction routes that promote/inhibit NO formation. Sixty-seven kinetic reaction mechanisms from the literature have been investigated and compared with recently reported measurements at a wide range of equivalence ratios (ϕ) (0.6–1.4), atmospheric pressure and temperature conditions. Both numerical simulations and experimental measurements used the same combustion reactor configuration (premixed stabilized stagnation flame). To highlight the best kinetic model for the predicting of the NO experimental measurements of NO, a symmetric mean absolute percentage error (SMAPE) has been determined as a preliminary estimation by comparing both numerical and experimental measurements. The results found that the kinetic reaction mechanism of Glarborg showed an accurate prediction with a minor error percentage of 2% at all lean and stoichiometric conditions. Meanwhile, the kinetic model of Wang accurately predicted the experimental data with 0% error at ϕ = 1.2 and underestimated the mole fraction of NO at 1.4 ϕ with an error of 10%. The sensitivity analysis and rate of production/consumption of NO mole fractions analysis have also been implemented to highlight the most important reactions that promote/inhibit NO formation. At lean and stoichiometric conditions, Glarborg kinetic model shows that the kinetic reactions of HNO + H ⇌ NO + H2, HNO + O ⇌ NO + OH, and NH + O ⇌ NO + H are the most important reaction routes with considerable effect on NO formation for 70/30 (vol%) NH3/H2 mixture. In contrast, the reactions of NH2 + NO ⇌ N2 + H2O, NH2 + NO ⇌ NNH + OH, NH + NO ⇌ N2O + H, and N + NO ⇌ N2 + O significantly consume NO to N2, NNH, and N2O. Further, Wang's mechanism illustrated the dominant effect of each HNO + H ⇌ NO + H2, N + OH ⇌ NO + H, NH + O ⇌ NO + H in NO formation and NH + NO ⇌ N2O + H, NH2 + NO ⇌ NNH + OH, and NH2 + NO ⇌ N2 + H2O in the consumption of NO mole fractions. [ABSTRACT FROM AUTHOR]

Upgrades in building energy efficiency codes led to differences between buildings designed according to outdated codes and those with most recent requirements. In this context, our study investigates the influence of external wall thermal transmittance, thermal inertia, and orientation on energy demand (heating, cooling) and occupant thermal comfort. Simulation models of an office building were designed, varying (i) the thermal transmittance values (0.20 and 0.60 W/(m2K)), (ii) the room orientation (four cardinal directions), and (iii) the wall thermal inertia (approximately 60 kJ/(m2K) for low and 340 kJ/(m2K) for high thermal inertia. The energy demand for heating and cooling seasons was calculated for Ljubljana using EnergyPlus 9.0.0 software. The reduction of the external wall thermal transmittance value from 0.6 W/(m2K) to 0.2 W/(m2K) contributes to significant energy savings (63% for heating and 37% for cooling). Thermal inertia showed considerable potential for energy savings, especially in the cooling season (20% and 13%, depending on the external wall insulation level). In addition, the orientation proved to have a notable impact on heating and cooling demand, however not as pronounced as thermal inertia (up to 7% total energy demand). Comparison of the thermal comfort results showed that when internal air temperatures are identically controlled in all the rooms (i.e., internal air temperature is not an influencing factor), the external wall thermal transmittance, thermal inertia, and room orientation show negligible influence on the average occupant thermal comfort. The simultaneous achievement of thermally comfortable conditions in the working environment and low energy use can only be achieved by simultaneously considering the U-value and thermal inertia. [ABSTRACT FROM AUTHOR]

The automation strategies currently used in HVAC systems do not control the system temperature variables (supplied air, chilled, and condensation water temperatures) in an optimized way. Normally, these temperatures are fixed in design conditions, or vary according to the weather conditions. However, studies demonstrate that adequate control of these three temperatures can provide significant reductions in the energy consumption of the air conditioner system. Therefore, this work analyzes the benefits of individualized and integrated automation of these three variable temperatures in different tropical and subtropical weather conditions through computer simulation for a typical commercial building. The results of integrated automation show savings in consumption between 5.03% and 19.68% compared to a fixed control, and between 3.22% and 8.21% compared to a weather-based control alone, showing that the integrated strategies are better than both models adopted as market benchmarks. [ABSTRACT FROM AUTHOR]

Agrivoltaics (APV), the co-location of agriculture and photovoltaics (PV), addresses an inherent competition for land usage. Taking the same dual-use concept to the urban landscape, rooftop APV can provide locally grown food in areas of need while providing distributed energy generation. In this multi-year investigation, different APV plots in northern Colorado, USA, were studied for crop metrics, light transmission, air temperature, soil/substrate temperature and moisture. Crops were grown under different solar panel types including opaque silicon and opaque and semi-transparent (ST) thin-film CdTe technologies. Growth conditions were characterized showing generally improved conditions and moderated temperatures under the panels. The ST-CdTe panels had increased photosynthetically active radiation (PAR) compared to both opaque panel types without a significant corresponding increase in temperature. [ABSTRACT FROM AUTHOR]

The need to reduce energy consumption in greenhouse production has grown. Thermal heating demand alone accounts for 80% of conventional greenhouse energy consumption; this significantly reduces production profit. Since microclimate affects crop metabolic processes and output, it is essential to monitor and control it to achieve both quantity and quality production with minimum energy consumption for maximum profit. The Internet of Things (IoT) is an evolving technology for monitoring and controlling environments that have recently been adopted to boost greenhouse efficiency in many applications by integrating hardware and software solutions; therefore, its adoption is thus critical in enabling greenhouse energy consumption minimisation. The first objective of this study is to improve and validate a greenhouse dynamic air temperature model required to simulate or predict indoor temperature. To achieve the first objective, therefore, an existing model was enhanced and a closed loop test experimental data from the IoT cloud-based control system platform deployed in the prototype greenhouse built in Cranfield University was used to validate the model using an optimisation-based model fitting approach. The second goal is to control the greenhouse air temperature in simulation using relatively simple PI and on-off control strategies to maintain the grower's desired setpoint irrespective of the inevitable disturbances and to verify the potential of the controllers in minimising the total energy input to the greenhouse. For the second objective, the simulation results showed that the two controllers maintained the desired setpoint; however, the on-off strategy retained a sustainable oscillation, and the tuned PI effectively maintained the desired temperature, although the average energy used by the controllers is the same. [ABSTRACT FROM AUTHOR]

To minimize the impact of snowfall and ice formation on safety of transportation, salt is sprinkled on the asphalt every winter. However, the use of salt has economical as well as ecological disadvantages. To resolve these problems, road heating systems are used in the northern regions of Europe and America. Despite their widespread usage, considerable potential of the operational optimization is evident. The current systems are controlled under predefined weather conditions such as start of operation at 5 °C air temperature, even when snowfall is absent. Consequently, loss of energy input to heat the system is caused. To avoid unnecessary financial and energetic expense, this study presents CFD-based performance investigation as a basis for a novel predictive controller to increase the operational efficiency of hydronic road heating systems (HRS). The simulation model was developed based on a real operational HRS located in Ingolstadt and composed of bridges and ramps for a total surface of 1989 m2. Climate data of the years 2019–2020 from local weather stations were implemented in the simulation model for performance prediction on extreme climate conditions. This investigation identified that up to 70% of operational hours in terms of energy input can be saved by using a hypothetical predictive controller, thus making the HRS a more economically efficient and environmentally attractive alternate to conventional de-icing techniques. [ABSTRACT FROM AUTHOR]

This paper presents the thermal calculations of an air-finned heat exchanger working at temperatures above zero degrees and their verification through testing on a real device. Then, on the basis of the calculations, the influence of evaporation temperature on the drying rate of the constant speed of air flowing through the exchanger was analysed. A quantitative analysis of the effect of the temperature difference between the air being dried and the evaporator on the acceleration of the process was performed. For the analysed case, the same water mass (condensate) can be obtained for an evaporation temperature of 0 °C almost four times faster than for 10 °C. To compare temperature cases, the SMER (specific moisture evaporation ratio) was calculated, which allowed the systems to be compared in terms of energy consumption. The theoretical analysis showed that by reducing the boiling point by 10 degrees, we could increase the SMER from 0.51 kg h 2 0 / kWh to 2.18 kg h 2 0 / kWh . After receiving the experimental results and including the efficiency of the system, these values were, respectively, 0.44 ± 0.01 kg h 2 0 / kWh and 1.91 ± 0.06 kg h 2 0 / kWh . [ABSTRACT FROM AUTHOR]

The effects of cold surface temperature, wet air state (temperature and humidity) and original drop size on frost dendrites growth of two neighboring separate frozen water drops of same size under natural convection conditions were investigated by quantitative measurement. It was determined that for different cold plate surface temperature conditions, i.e., the ordinary-low temperature and the cryogenic temperature range, the frost formation mechanism is different. Under the conditions that the air temperature is not too high and absolute humidity is not too excessive, the influence of frozen water drop size on the longest dendrite of frost crystals becomes more and more obvious with the decrease in cold plate temperature. The changes in air temperature and relative humidity both change air absolute humidity, so they have similar effects on the growth of dendrites. However, the effect of wet air state on the growth of frost dendrites is not monotonous, which needs to be considered comprehensively in combination with heat and mass transfer and the existence of heavy phase layer. The thickness of 'the initial continuous frost layer' was measured and it was disclosed that the initial frost layer thickness is 1.7–3.0 times that of the height of the frozen water drop diameter. This value may be possibly used as initial frost layer thickness in heat and mass transfer-based frost layer growth prediction models, at least for ordinary-low temperature conditions. [ABSTRACT FROM AUTHOR]

Students require a comfortable thermal environment for better academic learning and health in general. In Nepal, the majority of school buildings are constructed using local materials, but little consideration is provided to the thermal environment required for comfort. Therefore, this study demonstrates the advantages of using passive design measures through a simulation that can be used either in the early stages or as a retrofit to determine how the building performs in terms of comfort and the thermal environment. First, the thermal environment of school buildings and thermal comfort of students were evaluated through field surveys. Subsequently, a simulation was performed to investigate the operative temperatures in the classroom of a school building in Kathmandu. DesignBuilder software was used to create the base model and the simulated operative temperature was validated using the measured globe temperature. Subsequently, passive strategies, such as natural ventilation, insulation, and thermal mass, were applied and analysed. The field survey showed that the indoor globe and outdoor air temperatures were correlated, and the students perceived a hotter environment and preferred a cooler environment. Within this context, the average comfort temperature was 26.9 °C. The simulation results showed that the operative temperature was reduced to below 27 °C with a maximum reduction of 3.3 °C due to the integrated design impact, which is within the comfortable limit required during school hours. This study helps to design Nepalese school buildings in a better way by considering passive design strategies during architectural design to make classrooms more thermally comfortable. [ABSTRACT FROM AUTHOR]

A suitable indoor climate positively affects the lifespan of historical building structures. The path to an agreeable climate begins with monitoring current conditions. Considerable attention is given to monitoring the indoor climate of historical buildings. The motivation for monitoring air temperature and surface temperatures, relative air humidity or airflow can be, for example, the installation of heating, the occurrence of biotic damage, and others. Through the analysis of the most frequently used keywords, a strong connection was found, for example, between thermal comfort and the church. This review also summarises the various reasons for conducting microclimate monitoring studies in historical religious buildings on the European continent. It is supplemented with an evaluation of the monitoring methodology from the chosen period of the year point of view, the measured parameters, and the length of the interval between the recordings of quantities. It was found that in more than one-third of the cases, the recording time was less than or equal to 15 min, but mostly less than or equal to 1 h. Quite often, monitoring results are used to calibrate a simulation model describing the hydrothermal behaviour of a historical object under various operation alternatives (e.g., influence of ventilation, climate change, occupancy, etc.). This way, it is possible to test various intelligent systems in the virtual world without much risk before they are used in an actual building application. [ABSTRACT FROM AUTHOR]

The effect of supersonic air temperature on the mixing characteristics of liquid hydrocarbon fuel injected into three different supersonic airflows elevated in three steps from 373 K to 673 K was investigated numerically. Compressible Reynolds-averaged Navier–Stokes (RANS) equations were solved together with species conservation equation using ANSYS Fluent for two-phase flow simulations including fuel droplet breakup and evaporation. The turbulence model needed to close the RANS equations used the Shear Stress Transport (SST) k-ω model. The Eulerian–Lagrangian model was employed to track fuel droplets in mainstream air, and the Kelvin–Helmholtz and Rayleigh–Taylor (KH-RT) models were used to simulate the droplet breakup process. Numerical solutions were validated using experimental data. The higher the air temperature, the stronger the streamwise vortices downstream of the pylon. When the air temperature was 373 K, the liquid fuel hardly evaporated, but as the air temperature increased, and the mass fraction of the vaporized fuel and the mixing efficiency increased linearly downstream of the pylon. At air temperatures of 523 K and 673 K, the mixing efficiencies were 10% and 51% at the combustor outlet, respectively. The total pressure loss decreased slightly due to droplet evaporation as the temperature increased from 373 K to 673 K. [ABSTRACT FROM AUTHOR]

The temperature difference between day and night in a solar greenhouse is large. Heat in a greenhouse is typically in excess during the day while the temperature is low and the humidity is high at night. This study designs and tests an active heat storage and release air-source heat-pump system with a thermally insulated water tank as the energy storage body. By comparing air temperature and humidity in a test greenhouse with a control greenhouse in typical weather conditions, the power consumption and performance of the system are evaluated. The results show that compared with the control greenhouse, the average daytime temperature of the test greenhouse is lowered by about 3 °C during the operation of the system in typical weather conditions. At night, the average temperature is increased by about 4 °C, and the relative humidity is decreased by about 20%. When optimized, the maximum coefficient of performance (COP) of the system can reach 4.32 in heat storage mode. The nighttime heat release from the energy storage tank accounts for 26.9% to 51.2% of the nighttime energy consumption, and the energy utilization efficiency is 59.6% to 497.0%. This study provides a new way to control environmental parameters in solar greenhouses. [ABSTRACT FROM AUTHOR]

Liquid hydrogen has been studied for use in vehicles. However, during the charging process, liquid hydrogen is lost as gas. Therefore, it is necessary to estimate and reduce this loss and simulate the charging process. In this study, the initial charging process of a vehicle liquid hydrogen tank under room temperature and atmospheric pressure conditions was numerically investigated. A transient thermal-fluid simulation with a phase-change model was performed to analyze variations in the volume, pressure, mass flow rate, and temperature. The results showed that the process could be divided into three stages. In the first stage, liquid hydrogen was actively vaporized at the inner wall surface of the storage tank. The pressure increased rapidly, and liquid droplets were discharged into the vent pipe during the second stage. In the third stage, the mass flow rates of liquid and hydrogen gas at the outlet showed significant fluctuations, owing to complex momentum generated by the evaporation and charging flow. The temperatures of the inner and outer walls, and insulation layer, decreased significantly slower than that of the gas region because of its high heat capacity and insulation effect. The optimal structure should be further studied because the vortex, stagnation, and non-uniform cooling of the wall occurred near the inlet and outlet pipes. [ABSTRACT FROM AUTHOR]

This work aims to assess the impacts of climate change on photovoltaic (PV) electricity in two Italian cities, with different latitudes and Köppen–Geiger climate classifications. This was undertaken using the recent EURO-CORDEX set of high-resolution climate projections and PV power generation models, implemented on TRNSYS software. Data for two variables (surface air temperature and solar radiation) were analysed over a long period from 1971 to 2100. For future periods, two of the Representative Concentration Pathway scenarios (RCP4.5 and RCP8.5) used in the Intergovernmental Panel on Climate Change Fifth Assessment Report were considered. In both RCP scenarios and both locations, it is estimated that the yearly PV energy produced in the future period will not undergo significant variations on average given that the rate of decrease is foreseen almost constant; instead, a slight reduction in the PV energy was detected in the past period. It can be concluded that the PV market in Italy will grow in the next years considering that the reduction in the foreseen PV purchase costs will be also supported by the slight positive effect of climate change on PV manufacturability. [ABSTRACT FROM AUTHOR]

The performance of an enhanced vapor-injection heat-pump drying system was designed and theoretically studied in cold areas. According to the simulation findings, the ideal vapor-injection charge of the system ranges from 12.3 to 13.9%, and its ideal intermediate pressure is between 1.278 and 1.498 MPa when the evaporation temperature is above 0 °C. The ideal vapor-injection charge of the system ranges from 13 to 20%, and its optimal intermediate pressure ranges from 1.078 to 1.278 MPa when the evaporation temperature is −15–0 °C. The ideal vapor-injection charge of the system ranges from 20 to 24%, and the intermediate pressure ranges from 0.898 to 1.078 MPa when the evaporation temperature is below −15 °C. The heat and humidity exhausted air source heat-pump drying (HHE–ASHPD) system has higher dehumidification efficiency than the closed heat-pump drying (CHPD) system under the same air temperature, humidity, and volume parameters. [ABSTRACT FROM AUTHOR]

The article presents the results of research on the range of the impact of a cooling facility on the surrounding ground. An analysis of the heat exchange with the ground and through the building partitions was carried out. The analysis was carried out on the basis of the results of actual field tests carried out throughout the measurement year. The object of the research was an agricultural cold store located in southern Poland. The computational analysis of the interaction between the cooling facility and the ground was based on the numerical elementary balances method. The validation of the calculation model was performed based on the adopted boundary conditions. Calculations for the analyzed variants were carried out on the basis of a geometric model of the cooling facility built in the WUFI®plus program, corresponding to the actual dimensions. The analysis of the energy balance of the studied facility showed that the share of energy flow through the floor to the ground constitutes 8.2% of all energy flows through other partitions and the ventilation system. In order to maintain the set air temperature inside the studied building, intensive cooling was required with an energy demand of 5184.5 kWh/year. The results of the research showed that the range of the thermal impact of the building changes depending on the location of the studied ground area in terms of cardinal direction. The external and internal microclimate characteristics also affect the extent of the impact of the cooling facility on the surrounding ground. Under the assumption of stable values of Θi within a range of 0.0–4.0 °C, the largest range of influence (4.0 m) occurs in the summer. [ABSTRACT FROM AUTHOR]

The detonation initiation characteristics of a single tube liquid-fueled pulse detonation combustor (PDC) is investigated at different inlet air temperatures in this paper. The inner diameter of the PDC is 62 mm. Gasoline and air are used as fuel and oxidant, respectively. The inlet air temperature is 288–523 K and the operating frequency of the PDC is 10~30 Hz. The experimental results show that the deflagration to detonation transition (DDT) distance, detonation initiation time, DDT time and jet ignition time decrease with the increasing operating frequency at the same inlet temperature. When the inlet temperature is 288 K, the DDT distance is shortened from 860.5 mm to 787.7 mm as the operating frequency increases from 10 Hz to 30 Hz. The detonation initiation time, the jet ignition time and the DDT time are reduced from 10.01 ms, 7.66 ms and 2.35 ms to 6.55 ms, 4.99 ms and 1.56 ms, respectively. When the inlet air temperature increases, the atomization and evaporation of the gasoline is improved, which also leads to the decrease in the DDT distance, the detonation initiation time, the jet ignition time and the DDT time. For example, when the inlet air temperature increases from 288 K to 523 K at the frequency of 10 Hz, the DDT distance is shortened from 860.5 mm to 747.2 mm and the detonation initiation time, the jet ignition time and the DDT time is reduced to 5.867 ms, 2.51 ms and 1.11 ms, respectively. Additionally, the self-ignition caused by high inner wall temperature occurs when PDC is operating at high frequency under high inlet air temperature. [ABSTRACT FROM AUTHOR]

To solve the series of heat balances that EN ISO 52016-1 uses to simulate the dynamic hourly energy requirements of a building, detailed climatic data are required as input. Differently from air temperatures, relative humidity and wind speed, which are easily measurable and available in databases, the direct and diffuse solar irradiances incident on the different inclined and oriented surfaces, which are fundamental for the evaluation of solar gains, must be estimated using one of the many regression models available in the literature. Therefore, in this work, the energy needs of buildings were evaluated with the simplified hourly dynamic method of EN ISO 52016-1 by varying the solar irradiance sets on inclined and oriented surfaces obtained from EN ISO 52010-1 and three other pairs of solar irradiance separation and transposition models. Five European locations and two different window solar transmission coefficients (ggl) were analysed. The results showed that on average, for the heating period and for both ggl, the use of the different methods causes an average error on the calculation of the annual demand of less or slightly more than 5%; while for the cooling period, the average error on the calculation of the annual demand is 16.4% for the case study with ggl = 0.28 and 25.1% for the case study with ggl = 0.63. On the other hand, analysing the root-mean-square-error of the hourly data, using the model contained in TRNSYS as a benchmark, for most of the cases, when varying window orientations, cities and ggl, the model that diverges furthest from the others is that contained in EN ISO 52010-1. [ABSTRACT FROM AUTHOR]

The built-in refrigerator has been popular in China in recent years due to users' high requirements for the integration of home appliances and furnishings. However, the built-in configuration will cause a significant performance deterioration, which has been less quantitively studied. The condenser and its refrigerator performance are compared experimentally and numerically between built-in and free-standing configurations. By contrast with the free-standing condition, the built-in condenser has poor performance attributed to two reasons: 28.6% lower condenser air flowrate and 10.72 °C higher condenser inlet air temperature caused by the hot short-circuited airflow. This heat dissipation deterioration increases the condensing temperature and discharge temperature, resulting in a refrigerator cooling capacity loss. Correspondingly, the compressor increases the rotating speed and power to compensate for the loss. The compressor ON-time ratio reduces by 8% but the average power during the compressor-on period increases by 56.9%, finally increasing the energy consumption by 43.4%. This study also provides some guidance for further heat dissipation and airflow field optimization of built-in refrigerators. [ABSTRACT FROM AUTHOR]

Global warming, along with increasing global energy demands, has led to the need for a sustainable and low-carbon-based energy economy. In addition to renewable energy technologies, such as biomass, solar, hydro, and wind, another possible strategy to mitigate climate change is the capture/conversion and recycling of CO2. In recent years, many methods for both CO2 capture (mainly adsorption, absorption, and membrane) and conversion (many electrolysis, catalyst, and plasma) have been investigated. Conversion technology is less studied but seems to be very promising. Within that, non-thermal plasma technology has received much interest because it works at low temperatures and atmospheric pressure, and there is no need for high temperature and high electricity consumption, which are typical of the catalyst and electrolysis conversion processes, respectively. Therefore, in order to optimize this emerging technology, simulative kinetic models have been developed with the aim of maximizing both energy efficiency and CO2 conversion. In the present paper, an overview of the most common non-thermal plasma technologies was carried out to highlight the advantages and disadvantages of each method. Then, an overview of the most significant kinetic models available in literature was carried out to point out the main reactions occurring during CO2 conversion and also the parameters that most affect the performance of a plasma reactor during CO2 conversion. Then, a brief recap of the literature available on economic studies of the plasma process is given. [ABSTRACT FROM AUTHOR]

Comfort temperature is important to investigate because the chosen office indoor temperatures affect the energy used in a building, and a thermally comfortable environment makes the occupants be more productive. The effects of temperature on comfort are broadly recognized for thermal comfort. Japanese office buildings are well equipped with air-conditioning systems to improve the thermal comfort of the occupants. The main objectives of this research were to compare the winter comfort temperature in mixed mode (MM) and heating, ventilation and air-conditioning (HVAC) office buildings and to investigate the relationship between the comfort temperature and the indoor air temperature. This study measured the thermal environmental conditions of the office buildings and surveyed the thermal comfort of the occupants. The field survey was conducted during winter in seven office buildings located in the Aichi prefecture of Japan. In total, 4466 subjective votes were collected from 46 occupants. The result suggested that the occupants were found to be more satisfied with the thermal environment of MM buildings than that of HVAC office buildings. Overall, 95% of comfort temperatures were in the range 22~28 °C in MM and HVAC buildings, which were higher than the indoor temperature of 20 °C recommended by the Japanese government. The comfort temperature was highly correlated to the indoor air temperature of the MM buildings than to that of HVAC buildings. This indicated that the occupants were more adapted towards the given thermal environment of MM buildings. [ABSTRACT FROM AUTHOR]

To avoid a sharp rise in temperature in the cabin of parked vehicles exposed to solar radiation, experienced drivers leave some windows partly open when the vehicle is parked in the sunlight to achieve cooling through natural ventilation. However, the effectiveness of this measure to reduce the temperature under different weather conditions has not been verified. To this end, this study investigates the effect of open windows on the thermal environment of a vehicle under different environmental conditions. A field measurement, in which two identical vehicles with and without window gaps were used, was carried out in Daxing District, Beijing. The measurements were conducted for 15 days under different window gaps and ambient conditions. The results revealed that open windows resulted in a maximum temperature reduction of 6.7 °C in cabin air temperature under high temperature and high solar radiation, while only 0.6 °C can be reduced under low temperature and low solar radiation. The results also showed that when window gaps effectively reduce the air temperature, lower air temperature can be obtained with larger open-window areas. [ABSTRACT FROM AUTHOR]

Among the alternatives for improving the thermal comfort conditions inside buildings are the thermally activated building systems (TABS). They are embedded in different building components to improve the indoor air temperature. In this work, a review and analysis of the state of the art of TABS was carried out to identify their potential to improve thermal comfort conditions and provide energy savings. Furthermore, this study presents the gaps identified in the literature so that researchers can develop future studies on TABS. The articles found were classified and analyzed in four sections, considering their implementation in roofs, walls, floors, and the whole envelope. In addition, aspects related to the configuration of the TABS and the fluid (speed, temperature, and mass flow rate) were analyzed. It was found that when TABS are implemented in roofs, walls, and floors, a reduction in the indoor temperature of a building of up to 14.4 °C can be obtained. Within the limitations of the TABS, the complexity and costs of their implementation compared to the use of air conditioning systems are reported. However, the TABS can provide energy savings of up to 50%. [ABSTRACT FROM AUTHOR]

The Urban Heat Island (UHI) has a detrimental impact on human thermal comfort and the health of city dwellers through raising average temperatures. Urban geometry is one of the factors that affect the intensity of the UHI phenomena. The purpose of this research is to evaluate and compare traditional vs. modern urban forms with respect to temperature and thermal comfort in the United Arab Emirates. Three of each were chosen based on their densities and form. Traditional buildings in the UAE differ from others in the Middle East in that they are primarily single-story, while in the surrounding countries of the region, such as Iran, Iraq, and Saudi Arabia, they are mainly two stories. The UAE climate also has its distinct characteristics. Each configuration was investigated using the ENVI-met urban microclimate simulation software. The comparisons were made for three seasons: summer, winter, and spring. Each configuration was evaluated through four parameters: building shape, street geometry, orientation, and urban density. The results revealed that the low-density traditional urban form exhibited the lowest air temperature in August because it has a low sky view factor (SVF), high height-to-width ratio, and less density. The highest ambient temperature was observed in the sites with low-medium density, lowest height/width ratio, and maximum SVF. The high-density modern urban form displayed lower air temperatures in the summer season than the low and low-medium-density modern urban sites due to the building form, high height-to-width ratio, low SVF, and wind corridors. The traditional compact urban form in Al Fahidi, which has the highest urban density of the six configurations, achieved the best thermal comfort levels in the summer due to the sizable height-to-width ratio and lowest SVF. [ABSTRACT FROM AUTHOR]

Refrigerant maldistribution severely deteriorates the heat transfer performance of a microchannel evaporator. Compared with the refrigerant distribution among flat tubes along the header, refrigerant distribution among microchannels in the flat tube in the airflow direction has barely been paid attention. In this paper, a heat transfer mathematical model of a microchannel evaporator's flat tube composed of vertically placed parallel microchannels in the airflow direction was developed. The Refrigerant distribution among the microchannels was evaluated and its influence on heat transfer between air and refrigerant was analyzed. The results showed that the refrigerant distribution and heat transfer performance between air and refrigerant were interrelated and interacted with each other. The temperature of the air leaving the microchannel evaporator changed along the microchannel because of uneven refrigerant distribution among the microchannels, and the air temperature difference between air leaving out of the bottom and the top of the evaporator was approximately 2.13 °C. Ignoring the heat transfer from adjacent microchannels will lead to a small heat transfer deviation for the flat tube; thus, heat transfer among microchannels can be neglected. [ABSTRACT FROM AUTHOR]

Putting glass doors on the display cases of refrigerators is one of the most efficient ways to reduce the energy consumption of supermarkets. However, the glass fogs up when opening the door because of the difference in air temperature inside and outside of the refrigerator, thereby obscuring the view. To defog the glass, anti-sweat heaters (ASHs) are used. In this paper, the power usage of ASHs according to changes in the dew point (DP) inside a supermarket were evaluated for two types of ASH, i.e., the door-frame ASH and the glass ASH. The evaluation was based on measurements of the condensation on the glass doors of vertical display cases, used for the preservation of frozen foodstuffs. A mathematical model of the correlation between the ASH's power usage and the DP was developed and used for predicting the long-term energy savings. The savings were calculated based on the measured DPs inside the supermarket, which were extrapolated over a longer time period based on their correlation with the outside DPs. Regulating the door-frame ASH according to the DP resulted in an 84.6% reduction in energy consumption and a 90.1% reduction in the case of the glass ASH, compared to the current state. The correlation between the DPs inside and outside the supermarket served as a basis for the proposed implementation of the power usage regulation of the ASH according to the DP. [ABSTRACT FROM AUTHOR]

There is growing concern that airtight and well-insulated buildings designed to limit heat loss in temperate and cold climates could unintentionally elevate the risk of overheating in summers. Existing literature primarily uses dynamic simulation to investigate this problem due to the difficulty of obtaining large-scale in-performance data. To address this gap, we undertake a meta-analysis of large-scale indoor air temperature data for 195 UK dwellings, as a study of performance in a temperate climate. Of these, 113 are baseline (i.e., typical existing dwellings) and the rest designed to the high-performance Passivhaus standard. Using both Passivhaus and the well-known CIBSE TM59 overheating standards, this study found that there were few overheated cases for any building type. However, the average summer nighttime temperature of Passivhaus bedrooms was 1.6 °C higher than baseline, with 20 out of 31 measured bedrooms exceeding the overheating criterion, and the average overheating hours constituting approximately 19% of the total summertime observation period. These findings suggest that bedrooms in highly insulated dwellings may pose an overheating risk although whole-dwelling overheating risk is low. [ABSTRACT FROM AUTHOR]

The temperature rises hydrogen tanks during the fast-filling process could threaten the safety of the hydrogen fuel cell vehicle. In this paper, a 2D axisymmetric model of a type III hydrogen for the bus was built to investigate the temperature evolution during the fast-filling process. A test rig was carried out to validate the numerical model with air. It was found significant temperature rise occurred during the filling process, despite the temperature of the filling air being cooled down due to the throttling effect. After verification, the 2D model of the hydrogen tank was employed to study the temperature distribution and evolution of hydrogen during the fast-filling process. Thermal stratification was observed along the axial direction of the tank. Then, the effects of filling parameters were examined, and a formula was fitted to predict the final temperature based on the simulated results. At last, an effort was paid on trying the improve the temperature distribution by increasing the injector length of the hydrogen tank. The results showed the maximal temperature and mass averaged temperature decreased by 2 K and 3.4 K with the length of the injector increased from 50 mm to 250 mm. [ABSTRACT FROM AUTHOR]