Thermal Zone Research Articles

Model order reduction of building energy simulation models using a convolutional neural network autoencoder

Building energy simulation (BES) tools are fundamental for predicting energy performance and comfort. However, detailed models are computationally complex and demand high simulation times. These lead to difficulties in parametric runs and numerical optimizations. Performing numerous retrofit scenarios is hardly feasible, especially in multi-zone buildings with complex geometries.This paper introduces a novel approach to model order reduction (MOR) of BES models. The approach utilizes a deep learning-based unsupervised convolutional neural network autoencoder (CNN-AE). The method decomposes complex time series data derived from detailed simulations into lower dimension features. The low-dimension representations can be grouped through clustering algorithms to build a reduced-order model (ROM). The approach in this study automatically finds archetype zones of the original model that represent the energy behavior of a group of rooms, and removes redundant ones. The energy demand of the whole building can be estimated through these archetype zones.Our investigation shows that CNN-AE can be efficiently applied to reduce complex building energy simulation models. As proof of concept, a detailed model of a multi-zone campus building with 889 thermal zones is compared to the ROM derived from the CNN-AE. Comprehensive autoencoder hyperparameter training to optimize the accuracy of the model is provided. The ROM supports different purposes, such as energy scenario developments, with a total error of less than 1% compared to the original model, and reduced simulation times by a factor of more than 16.

Tuna keep their cool during heatwaves

Pacific bluefin tuna are majestic, torpedo-fast, super-sized apex marine predators. They're also delicious, according to sushi lovers around the world, which has led to a high-priced tuna fishery and a worrying decline in their numbers. Unlike most other fishes, tuna are warm-blooded and, just like humans, have a preferred temperature range at which the cost of keeping warm is lowest. Tuna occupy a vast interconnected habitat in the northern Pacific and migrate long distances to find patches of prey that are also on the move. Some marine predators survive by following rigid migration routes, a strategy that works well when conditions and prey are predictable. However, with climate change looming large, more flexible migrations might have benefits, by allowing predators to target prey as they become available. Surprisingly little is known about how tuna balance the needs for finding prey and staying warm, which is critical for protecting their vulnerable populations against overfishing and environmental change.But how could one possibly track a wild torpedo-fast fish in the open ocean and measure its success at finding prey? Gemma Carroll at the University of California Santa Cruz, USA, with an international team of collaborators led by Barbara Block at Stanford University, USA, found a way. They caught tuna in California and surgically implanted high-tech bio-loggers into their bellies that recorded the fishes’ location, depth and water temperature, before releasing the fish to continue with their migration. But best of all, the devices also measured the fishes’ internal body temperature and the heat produced when digesting a meal, which revealed how much prey each fish consumed and where. The team repeated the procedure on hundreds of tuna over a staggering 15-year period, yielding a wealth of novel findings.During this long-term experiment, ocean temperatures varied greatly between seasons and years. And yet, bluefin tuna managed to spend most of the time in waters that were within their thermal comfort zone. In warmer years, tuna shifted their migration pole-ward to colder waters; in cooler years, they headed south. This strategy even worked during the heatwave of 2015 when some tuna deviated from their usual routes by more than 1500 km and kept their cool by foraging in northern waters. This tremendous flexibility in migration patterns allows tuna to dampen the negative impacts of a warming and increasingly variable climate. But whether their prey follow suit is a different question.Ocean heatwaves can disrupt entire food chains, first impacting primary producers, such as tiny algae, and then propagating the effects up to the apex predators. During the heatwave of 2015, tuna found less prey than they had in cooler years, but the northward shift in their migration route helped their foraging success. Therefore, tuna avoided the more devastating effects of the heatwave experienced by sea lions, grey whales and some seabirds, which are a more inflexible group of marine predators. To find scarce prey, tuna were even willing to leave their thermal comfort zone, spending more time hunting in northern waters that were colder than their usual preference. Being cold and miserable surely beats starvation.Commercial fishery for Pacific bluefin tuna is seeing increasing catches, but that is not due to a recovery in their stocks, as their populations remain at an all-time low. Rather, it appears that changes in the temperature and prey landscape are pushing tuna into the fisher's nets, yielding record catches that, in the long run, are unsustainable. Exceptionally flexible migration patterns allow bluefin tuna to keep their cool during heatwaves, but may not protect them entirely from climate change at large. This is bad news for everyone: tuna, fishers and sushi lovers alike.

Cooling garments against environmental heat conditions in occupational fields: measurements of the effect of a ventilation jacket on the total thermal insulation

Personal cooling garments (PCGs) can represent an adaptation solution to counteract heat strain and to improve worker's health and productivity (especially for some outdoor work activities as in agriculture and in the construction industry). The cooling effect of a ventilation jacket was preliminarily investigated carrying out “dry” tests in a climatic chamber on a thermal manikin. A standardized condition with air temperature, ta = 22.4 °C, three different adjustments of the fan velocity (vf= 0, vf = 2 and vf = 4), and three different ensembles (the single jacket, a work ensemble and a combination of both) were considered. Results showed significant increases in dry heat losses (through convection) for the trunk thermal zones, higher when the fans were on, for all the ensembles considered. Percent changes greatly exceeded 100 % for the thermal zones close to the fans. The air ventilation determined significant decreases of the total thermal insulation (IT) values (up to 35 %) compared to the fans-off condition, confirming and quantifying the cooling effect of the ventilation jacket.

On the cooling potential of elastocaloric devices for building ventilation

Refrigerants in vapor-compression systems have a global warming potential thousands of times that of carbon dioxide, yet their spread on the market is unrivalled. Elastocaloric systems, based on solid state cooling, feature among the most promising alternatives. In this paper, an elastocaloric device for air ventilation (ECV) composed by parallel and serial connection of multiple shape memory alloy (SMA) films, is investigated via volume-based finite difference simulation in MATLAB and dynamic building simulation in TRNSYS considering eight cities across the globe. The models assume experimentally demonstrated thermal parameters for the elastocaloric phase transformation around room temperature and a single-storey reference building. The ECV operates according to an optimized, energy-saving logic that includes load partialization and recirculation. Parametric analyses suggest that moderate terminal velocities (∼2 m/s) and a climate-specific design aimed at maximizing the use of the ECV device at nominal cooling capacity are key to reach building cooling needs reductions up to 70% in the considered scenarios. Partialization results in enhanced energy flexibility and conservation, whereas recirculation extends the ECV usability to extreme heat conditions. In absolute terms, the ECV works best under hot climates (e.g. Cairo, Dubai, Brisbane), with monthly cooling load reductions about 2/3-fold compared to cold locations (e.g. Milan, Hobart). The performance is extremely sensitive to the ventilation rate. Thermal zones requiring 1 to 2 air changes per hour are best suited. These findings provide initial insight into design criteria, opportunities and limitations on the use of elastocaloric devices for building ventilation to guide future experimental verification.

Ground characterization of building energy models

The calibration of building energy models is crucial for their use in some applications that depend on their accuracy for adequate performance, such as demand response and model predictive control (MPC). In general, energy models offer many possibilities/strategies when characterizing a construction system, and such a characterization is key when analyzing both its thermal behavior and its energy impact. This research analyzes the different ways to characterize the thermal interaction of the building energy model (BEM) with the ground, comparing conventional approaches with new approaches based on both optimization of the former and dynamic ground characterizations. Using a model adjusted to a real case study, each of the existing options are analyzed, in which a different control of the ground temperature both in terms of its temporal oscillation and its location in the building (based on thermal zones) is taken into account. Exhaustive monitoring of a real building and measuring the ground and ground floor surface temperatures have made establishing which EnergyPlus components/objects best characterize the ground-slab interaction possible, both in terms of the simplicity of modeling and the cost (economic and technical) required for each of them. As will be seen, there are objects with an excellent cost/effectiveness ratio when characterizing the ground.

Groundwater heat transfer and thermal outflow plume modelling in the Alps

Thermal water discharge within the gravity-driven groundwater flow system in the Alps and other similar areas around the world may be hidden in Quaternary deposits which, in these regions, often cover the regional aquifer. When thermal water drains into Quaternary deposits, the mixing of the deep thermal component and the cold shallow groundwater forms a thermal plume that extends parallel to the main groundwater flow in shallow system. In the Bled case study in Slovenia, the thermal water discharges from carbonate rocks into Quaternary glaciofluvial sediments, and as the Toplice spring at a rate of 5 l/s at an average temperature of 21.5 °C. Knowing the spatial extent and intensity of thermal outflow is essential to decision making related to the development and protection of this renewable resource. By approximating the thermal water outflow from a discharge zone as a planar source, a planar advective heat transport model can be used to evaluate its geometry and quantify rates. An analytical procedure follows rough assumptions leading to conservative results. Moreover, a numerical model using the FEFLOW code was applied for comparison with the simulations of the analytical model. The heat transport model was based on measured hydraulic parameters (e.g. groundwater levels) and borehole temperatures as well as on-site and international literature (e.g. dispersivity, thermal conductivity). Nine scenarios were applied accounting for different dimensions of the heat source and compared to the results of numerical simulations. Each scenario was verified by calculating the relative error between the analytical models and the measured borehole temperatures. The results confirm that the main outflow of thermal water can be determined using planar geometry, and is 200–300 m wide. The height of the thermal outflow zone is approximately 25 m, corresponding to the expected thickness of the direct contact between the fractured dolomite and the shallower Quaternary aquifer. Using the proposed widths and depths, the hidden natural thermal outflow rates are estimated at 57–86 l/s.

Physiological Respons of Bali and Simbal Cattles on the Thermal Environtment of Lowland and Highland Areas in Lombok Island

The effort to increase productivity of Bali cattle in Lombok Island made use of crossbreeding with exotic breeds, such as Simmental, Limousine, Charolais, Hereford, and Brahman breed, in which Simmental was suggested the best one. However, replacing indigenous with exotic breed might in fact create significant problem, especially low tolerance on harsh environment condition and increased work to feed each animal because of higher growth and greater size at maturity. This study that mean objective to investigate the physiological respons of Bali and Simbal cattle on the thermal environment of lowland and highland areas in Lombok island, was carried out by measure the rectal temperature (BT, oC), respiration rate (RR, resp/min), and heat tolerance coefficient (HTC) of 320 cattles in lowland and 280 cattle in highland, each consisted of pure Bali breed (B), crossbred of B x Simmental (SB), backcross of SB x Simmental (SBS), and backcross of SB x Bali (SBB). Each genotype consist of male and female, and 24-36 months of age. All cattle observed are ordered to be similar condition with BCS 3-5. The thermal condition of lowland and highland are measured from air temperature (oC), relative humidity (%), and temperature humidity index (THI). Data were analysed by using Anova and further test using HSD-test. Results of the study shows, the daily temperature and THI data obtained for the lowland environment are in considered to thermal stress zone for beef cattle, whereas those of found for the highland are within range of safety zone for cattle production. Physiological response shuch as BT, RR, and HTC, were significantly higher for cattle in the lowland than those in highland. The crossbreds cattle with higher proportion of Simmental genetic showed higher BT, RR, and HTC in the lowland, but became decrease in highland environment by higher decreasing index. It could be conclused that environmental condition in lowland with average THI of 80.02 lead to coused thermal stress to genotypes of Simbal cattle based on HTC wich in average of 2.91; however in highland wich average THI of 69.39 each genotype of cattle shows physiological responses in the normal range.ÂÂ

Numerical simulation of earth-air heat exchanger application for Indonesian simple house air conditioning system

Research on an air-conditioning (AC) system that uses soil as a heat storage is still not widely conducted in Indonesia. The soil functions as a hot or cold storage medium by flowing fresh air through a heat exchanger due to its constant temperature tendency throughout a year. Earth-air exchanger (EAHE) application was simulated and got the results that soil with a volume of 12 m3 is potentially used as a heat exchange medium with a heat transfer surface area of 24.4 m2. The EAHE cooling capacity obtained is 1,002–1,282 watts depending on soil condition. Increasing the pipe diameter and airflow velocity decreases the average temperature difference by 42.9% per inch and 47.2% per m/s, respectively. Meanwhile, increasing the pipe thickness and soil depth increases the average temperature difference by 1.59% per millimeter and 6.06% per meter, respectively. The pipe interface distance recommended is greater than or equal to 200 mm. The EAHE can meet the Indonesian National Standard thermal comfort standard and ASHRAE breathing zone outdoor airflow for ventilation standard but can only meet 23.5%–30.0% of simple house-cooling loads. It consumes 75.8% lower energy and has an 139%–230% higher coefficient of performance than a split AC system.

Indoor temperature in perimeter spaces on warm humid tropical courtyard housing model

In general, Indonesia housing provides open space at front and fence. Open space inside that expose to sky is predicated as inner courtyard. Housing provide open or green space on side rarely. In humid tropics, high temperatures most of the year have an effect on thermal comfort. To fulfill thermal comfort, a housing model with inner courtyards on side and fence is proposed. In this case, representation of warm humid tropic is Surabaya. Simulation method is used to predict indoor temperature of spaces in perimeter courtyard. Spaces located on inner courtyard perimeters are living room, bedrooms and kitchen. These rooms have duration of occupancy more than one hour. With the existence of these inner courtyards, inhabitants can connect with green open space. The result show, on the hottest month, side and fence of inner courtyard model could support indoor temperature. For 14 hours, living room and bedrooms in thermal neutral zone. Except kitchen, only for 4 hours in thermal neutral zone

Optimal Partitioning of Multithermal Zone Buildings for Decentralized Control

In this article, we used an optimization-based systematic methodology for the challenging, less studied, and important problem of optimal partitioning of multithermal zone buildings for decentralized control. The proposed methodology consists of: i) construction of a graph-based network to quantitatively characterize the thermal interaction levels between neighboring zones and ii) the application of two different approaches for optimal clustering of the resulting network graph: 1) stochastic optimization and 2) robust optimization. The proposed optimization methods were tested and compared with each other on two case studies: 1) a five-zone building (a small-scale example) which allows one to consider all possible partitions to assess the success rate of the developed methods and 2) a 20-zone building (a large-scale example) for which the developed methods were used to predict the optimal partitioning of the thermal zones. Compared to the existing literature, our approach provides a systematic and potentially optimal solution for the considered problem.

A GIS-Based Procedure for Estimating the Energy Demand Profiles of Buildings towards Urban Energy Policies

Assessing the existing building stock’s hourly energy demand and predicting its variation due to energy efficiency measures are fundamental for planning strategies towards renewable-based Smart Energy Systems. However, the need for accurate methods for this purpose in the literature arises. The present article describes a GIS-based procedure developed for estimating the energy demand profiles of urban buildings based on the definition of the volumetric consistency of a building stock, characterized by different ages of construction and the most widespread uses, as well as dynamic simulations of a set of Building Energy Models adopting different energy-related features. The simulation models are based on a simple Building Energy Concept where selected thermal zones, representative of different boundary conditions options, are accounted. By associating the simulated hourly energy density profiles to the geo-referenced building stock and to the surveyed thermal system types, the whole hourly energy profile is estimated for the considered area. The method was tested on the building stock of Milan (Italy) and validated with the data available from the annual energy balance of the city. This procedure could support energy planners in defining urban energy demand profiles for energy policy scenarios.

Data-Driven Distributionally Robust Hierarchical Coordination for Home Energy Management

Home energy management (HEM) is conventionally formulated using central control or local control methods assuming known accurate probability distributions of uncertainties. Without coordination between the central and the local control hierarchies, mutual impacts cannot be properly considered and addressed, which undermine operation efficiency of HEM. Moreover, the probability distributions always have errors, even in emerging data-based methods. To address these unsolved issues, firstly, this paper proposes a new hierarchical coordination method for HEM. On the central hierarchy, a central controller optimizes schedule of non-thermal loads to minimize daily operating cost. On the local hierarchy, automatic local controllers respond to real-time variations of their corresponding thermal zone temperatures to fulfill customer thermal comfort requirements. Secondly, using a finite training dataset, a data-driven distributionally robust optimization (DRO) method is proposed to guarantee solution robustness against worst probability distribution of multiple uncertainties. The hierarchical coordination method is formulated as a DRO model using the Wasserstein metric, which can be solved with high computing efficiency. Numerical simulations validate high solution robustness and overall optimum of the proposed method, fully addressing mutual impacts and uncertainties. Moreover, the proposed method could efficiently save the daily electricity bill by 11%, compared to conventional methods.

The effect of forced cooling during friction stir welding on the structure and properties of 1565ChN116 aluminium alloy joints

This paper describes the results of a study that looked at mechanical and corrosion performance of joints between 3 mm thick 1565ChН116 aluminium alloy sheets produced by friction stir welding in atmosphere and in water. It was established that a higher in-water cooling rate resulted in a higher tensile strength of the weld joint and slightly impacted its properties. It is the thermomechanical impact zone of the joint that sees fracture during tensile testing when aluminium alloy 1565ChН116 is friction stir welded in atmosphere and in water. The strength of such joint is 95 to 99% of the strength of the base metal. When conducting friction stir welding in water, the thermal impact zone is approximately 1.6 to 2.2 times shorter than when the process takes place in atmosphere. For the alloy 1565ChН116, friction stir welding conducted in water is associated with a 10 to 12% higher microhardness of metal in the thermomechanical impact zone and the stirring zone. The grain size in the stirring zone was observed to decrease from 6.8 to 4.5 μm. In this zone (the core of the joint), small angle boundaries account for approximately 15% of the total number of boundaries. This suggests that the structure mainly consists of equiaxed grains with large angle boundaries. A transmission electron microscopy study of foil obtained in the joint core area confirmed the results of phase and microtexture analysis (carried out by means of the EBSD technique) indicating that a recrystallized structure formed in the centre of the joint. A higher cooling rate during friction stir welding increases the intercrystalline corrosion resistance of all areas of the joint by approximately 1.4 to 1.7 times. The biggest increase in the intercrystalline corrosion resistance was observed in the thermal impact zone.

Multi-step building energy model calibration process based on measured data

Building energy models are a key element in regulatory compliance calculations. These energy performance calculations often do not accurately reflect actual operating conditions. Therefore, evaluation of energy performance comparing actual energy use of a building with the outcome of dynamic simulation models can be misleading, this difference is also known as the energy performance gap. The reduction of the gap is an important task aimed to provide confidence in the use of models for evaluation of energy efficiency. This paper is focused on reducing the technical issues (e.g. poorly adjusted thermal parameters in the envelope, inefficient boiler operator or lack of adjustment in parameters of heat pumps, baseboard radiators or air handling units) which are one of the main causes of the energy performance gap. The application of a multi-step, optimization-based, calibration methodology performed in a white-box simulation environment (EnergyPlus) using three months of ten minute time-step data to adjust HVAC parameter values with a genetic algorithm software (Jeplus) is validated on a real test site. Resulting in a BEM that fits the building’s hourly performance benchmark into international standards on three key levels: indoor temperature by Thermal Zone (TZ), heat production and electric consumption from heat pumps, which comprise all the components of a building energy model. A batch of 1500 h of heating operation, obtained from the building management system, has been used to calibrate the model. The results complied with the requirements of the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Guideline 14–2002 at hourly interval, with NMBE ⩽±10%,Cv(RMSE) ⩽30% and R2 ⩾75% and with the International Performance Measurement and Verification Protocol (EVO) for Cv(RMSE) ⩽20% and R2 ⩾75% in the three aforementioned levels, which can be considered a step forward in the area of calibrating white box models. In addition, to prove the strength and robustness of the results, the model has been checked in a long testing and independent period of 2.500 h of heating operations with the same level of compliance. The demonstrator is the library of a school located in Denmark. The HVAC system is composed of four air–water heat pumps that deliver heating to the whole compound with the backup support of a gas boiler. The library is heated with baseboard radiators system with the support of an air handling unit used for ventilation purposes.

Coupled wellbore–reservoir heat and mass transfer model for horizontal drilling through hydrate reservoir and application in wellbore stability analysis

To address the wellbore instability risk during drilling in hydrate reservoirs, a fully coupled wellbore–reservoir model for horizontal drilling through a hydrate reservoir is presented, which considers the dynamic heat and mass transfer between the wellbore and reservoir and the coupling interactions between the fluid flow, heat transfer, and evolution of mechanical properties in hydrate-bearing sediments. A numerical method based on COMSOL Multiphysics + MATLAB was first proposed, and the accuracy of this model was verified by comparing it with experimental data and another mathematical model. The rules of heat and mass transfer between the wellbore and reservoir and the yield failure behaviors of the wellbore are thoroughly analyzed based on the data of hydrate-bearing sediments in the Shenhu area. The simulation results indicate that the temperature of the hydrate reservoir increases with the invasion of drilling fluid. The radii of the thermal disturbance zone at the toe and heel of the horizontal well are approximately 0.48 m and 0.64 m after 20 h, respectively. The formation shear strength near the wellbore gradually decreases from the initial 3.24 MPa–2.09 MPa due to hydrate decomposition; then, the formation begins to yield, and the yield ratio of the borehole reaches 92.56% after 20 h. Compared with the drilling fluid displacement and density, the inlet temperature of the drilling fluid plays an absolute leading role in the wellbore extension length. When the inlet temperature is less than 22.5 °C, the reservoir hydrate will not decompose. This work can provide a theoretical reference for the design of drilling fluids aimed at controlling borehole stability issues and for the design of the length of horizontal wells during drilling in hydrate reservoirs.

Make a difference, open the door: The energy-efficient multi-layer thermal comfort control system based on a graph airflow model with doors and windows

The classical approach to thermal comfort control utilizes fully automatic controllers for temperature, humidity, and other variables. Although commonly used, such systems may need much energy. If speed is not the priority, natural airflow may be considered for the control process. However, this would require a model including airflow changes caused by the opening of windows and doors, which has not been found in the literature yet. This article presents a novel multi-layer control system for thermal comfort control that uses an original graph-based representation of opening and closing doors and windows. It allowed us to model airflow dynamics. The system has two essential advantages. Firstly, the natural airflow between adjacent zones may help the automatic controllers achieve their goals and save energy. Secondly, including the windows and doors into the model lets the human play an active role in an eco-aware control process, which corresponds with the “human-in-the-loop” trends. The concept has been illustrated with an example house with four types of thermal comfort zones. The optimization approach based on finding the optimal subgraph of opened windows and doors between chosen zones led up to 5% energy savings of the electric actuators, compared with the classical fully automated structure.

Prediction of Climate Change Effect on Outdoor Thermal Comfort in Arid Region

Climate change and expected weather patterns in the long-term threaten the livelihood inside oases settlements in arid lands, particularly under the recurring heat waves during the harsh months. This paper investigates the impact of climate change on the outdoor thermal comfort within a multifamily housing neighborhood that is considered the most common residential archetype in Algerian Sahara, under extreme weather conditions in the summer season, in the long-term. It focuses on assessing the outdoor thermal comfort in the long-term, based on the Perceived Temperature index (PT), using simulation software ENVI-met and calculation model RayMan. Three different stations in situ were conducted and combined with TMY weather datasets for 2020 and the IPCC future projections: A1B, A2, B1 for 2050, and 2080. The results are performed from two different perspectives: to investigate how heat stress evolution undergoes climate change from 2020 till 2080; and for the development of a mathematical algorithm to predict the outdoor thermal comfort values in short-term, medium-term and long-term durations. The results indicate a gradual increase in PT index values, starting from 2020 and progressively elevated to 2080 during the summer season, which refers to an extreme thermal heat-stress level with differences in PT index averages between 2020 and 2050 (+5.9 °C), and 2080 (+7.7 °C), meaning no comfortable thermal stress zone expected during 2080. This study gives urban climate researchers, architects, designers and urban planners several insights into predicted climate circumstances and their impacts on outdoor thermal comfort for the long-term under extreme weather conditions, in order to take preventive measures for the cities’ planning in the arid regions.

Biochemical and hormonal parameters of goats kept in a controlled environment consuming water with different levels of salinity

ABSTRACT The objective of this work was to evaluate the biochemical and hormonal variables of Moxotó and Canindé goats submitted to two temperatures - 26.0±0.6 (thermoneutral) and 32.0±1.2°C (above thermal comfort zone) - and consuming water with three levels of salinity (1.0, 6.0 and 12.0 dSm-1). Thirty-six animals (18 of each breed) were used, with an average age of 5.0±0.6months and an average weight of 20.0±2.3kg, housed in metabolic cages inside a climate chamber. The animals were distributed in a completely randomized design with a 2 × 2 × 3 factorial scheme (2 breeds, 2 temperatures and 3 levels of salinity) and three replications. The glucose and urea had a significant effect (P>0.05) according to water salinity. Glucose, cholesterol, protein, albumin, globulin, aspartate aminotransferase and hormones (T4, T3 and cortisol) varied according to temperature (P<0.05). There was a significant effect of time on hormonal variables (P<0.05). Biochemical and hormonal variables changed according to temperature and day shift, so that metabolism was reduced in the animals under thermal stress and accelerated when animals were in the thermal comfort zone.

Patterns and drivers of leaf‐litter ant diversity along a tropical elevational gradient in Mexico

AbstractAimGiven their high environmental variation over relatively short distances, mountains represent ideal systems for evaluating potential factors shaping diversity gradients. Despite a long‐standing interest in ecological gradients, ant diversity patterns and their related mechanisms occurring on mountains are still not well understood. Here, we (i) describe species diversity patterns (α and β) of leaf‐litter ants along the eastern slope of Cofre de Perote in Veracruz, Mexico; and (ii) evaluate climatic and spatial factors in determining these patterns.LocationVeracruz, Mexico.TaxonLeaf‐litter ants.MethodsWe sampled 320 m2 of leaf litter spread across eight equally spaced sites from sea level to 3500 m of elevation. We used regression models to predict α‐diversity patterns with climatic (temperature and precipitation) and spatial (geometric constraints) variables. We also assessed, through multiple regression based on distance matrices (MRM), the relative importance of habitat filtering and dispersal limitations for shaping total dissimilarity (βsor), turnover (βsim) and nestedness (βnes).ResultsA hump‐shaped pattern was observed in the α‐diversity. This pattern is best explained by the temperature gradient. β‐diversity showed a nonlinear pattern along the elevational gradient with total dissimilarity and turnover components better explained by habitat filtering (i.e. temperature distances). Turnover had higher contribution to total dissimilarity rather than the nestedness component.Main conclusionsThe significance effect of temperature on both α‐ and β‐diversity patterns reinforces its widespread importance in shaping litter ant diversity patterns across elevational gradients. The hump‐shaped pattern in species richness is probably the result of harsh abiotic conditions at the base and the top of the mountain combined with biotic attrition in lowland sites. The niche specialization of ant species in their optimal thermal zones may explain total dissimilarity and ant species replacement along the studied gradient. Taken all together, these results suggest a high relevance of temperature‐driven mechanisms in the origin and maintenance of the biodiversity of such insects and probably another ectothermic taxa.

Direct chemical looping gasification of pine sawdust using Fe2O3-rich sludge ash as an oxygen carrier: Thermal conversion characteristics, product distributions, and gasification performances

The thermal characteristics and kinetic parameters of direct chemical looping gasification (DCLG) of pine sawdust (PS) were researched using a TGA at a well-defined heating rate. The three-phase product yields, syngas contents, DCLG performances, and multiple reactions were analyzed by a DCLG evaluation apparatus coupled with a gas chromatography (GC). TGA results indicated that, as the SA blending ratio was at 10%, the interactions between PS and SA mainly occurred at lower temperatures, while with the SA ratio increasing, more interactions also happened at the higher temperatures. The kinetics analysis results indicated that the activation energies of the first thermal decomposition zone of PS were independent with the SA ratios, while the values of the second and third zone were related to them. Through DCLG evaluation experiments, it was found that the SA presence, and the increase in SA ratios would promote the conversion of PS, while decrease the gasification performance. As the gasification temperature increased, the DCLG performance of PS would be improved, but the highest heating value of syngas produced would be obtained at 750 °C. The multiple DCLG experiments showed that the reaction performance of Fe2O3-rich sludge ash as an oxygen carrier could almost keep stable. The research results of this paper could give some useful guides for the potential application of Fe2O3-rich sludge ash as an oxygen carrier in direct chemical looping gasification of biomass feedstock.