bluuebunny/crossref_metadata_2025 huggingface dataset:
In-situ characterization of the relative humidity at the surface of building materials
Authors: Andersen Helle Vibeke , Morelli Martin , Hansen Tessa Kvist , Peuhkuri Ruut
Published: December 2023

Standardized laboratory testing is normally used for characterization of building materials and components. In real life, especially when assessing buildings in terms of water-damaged building materials, built-in moisture, rising damp or other problems, information on the hygrothermal state of the constructions may be relevant, but is often sparse. This paper presents a study where application of a newly developed non-destructive experimental method is used to measure the relative humidity (RH) at the surface of four types of building materials. Knowing the RH at the surface, a risk assessment of fungal growth can be made. The materials include concrete, brick, aerated concrete, and gypsum, with and without a surface treatment. The method is based on the idea of establishing a water vapor transport towards equilibrium within a small air volume in contact with the surface of interest. In the laboratory the specimens were conditioned at respectively 65 % RH and 90 % RH in a climate chamber, and then transferred to conditions with 50 % RH. The open side of a Petri dish, equipped with a temperature and relative humidity sensor, was attached to the materials using reusable adhesive. The development of the relative humidity over time within the petri dish was monitored and parameterized mathematically, solving an exponential rate equation. The parameterization and certain sets of assumptions allow among other things a calculation of time to equilibrium which makes it possible to assess the reproducibility and comparison in between materials. As the materials were tested with and without surface treatment, it was possible to estimate the effect of a typical surface treatment on the moisture transport. The measurements compared well to simulations made by a model, though the model predicts slightly faster achievement of equilibrium. Despite the limited number of cases in the current study, the presented results are promising with regards to enable rough estimates of RH at the surface of building materials outside the laboratory with a very simple, inexpensive, and non-destructive method.
Development of Plugins for seamless Integration of the SIMULTAN Meta Data Model with IDA-ICE and RFEM 6
Authors: Steiner Bernhard , Sarkany Andreas , Járosi Zsombor , Paskaleva Galina , Bednar Thomas , Bauer Christoph
Published: December 2023

SIMULTAN ComponentBuilder plugins enable individualized development of connections to simulation tools, easing data management of the simulation-driven interdisciplinary planning processes in civil engineering. The Software Development Kit (SDK) is an integral part of ongoing research projects, which aim to exhibit and expand the capability of the SIMULTAN Meta Data Model. The goal is to store digital information necessary for the planning processes in civil engineering and operation and operational performance analysis of buildings via digital twins. A theoretical outline of the plugin structure is given, and the usability of the SDK is shown by presenting two example plugins. Two plugins were developed to enable seamless integration with the proprietary simulation software IDA ICE and RFEM 6 within the same data model. Furthermore, it is shown that the existing data in the SIMULTAN Data Model can be reused by utilizing already existing information and avoiding duplication. Limitations of the SDK will be explained, and concepts for future data model extensions will be discussed. The development and deployment of the two plugins show the benefits of using a Big-open-real-BIM Data Model for civil engineering planning processes, enabling individualization and workflow-enhancing expansion.
Data-driven modelling of building retrofitting with incomplete physics: A generative design and machine learning approach
Authors: Yu Haitao , Feng Kailun , Penaka Santhan Reddy , Man Qingpeng , Lu Weizhuo , Olofsson Thomas
Published: December 2023

Building performance simulation (BPS) based on physical models is a popular method for estimating the expected energy savings from energy-efficient building retrofitting. However, for many buildings, especially older buildings, built several decades ago, an operator do not have full access to the complete information for the BPS method. Incomplete information comes from the lack of detailed building physics, such as the thermal transmittance of some building components due to the deterioration of components over time. To address this challenge, this paper proposed a data-driven approach to support the decision-making of building retrofitting selections under incomplete information conditions. The data-driven approach integrates the backpropagation neural networks (BRBNN), fuzzy C-means clustering (FCM), and generative design (GD). It generates the required big database of building performance through generative design, which can overcome the problem of incomplete information during building performance simulation and energy-efficient retrofitting. The case study is based on old residential buildings in severe cold regions of China, using the proposed approach to predict energy-efficient retrofitting performance. The results indicated that the proposed approach can model the performance of residential buildings with more than 90% confidence, and show the variation of results. The core contribution of the proposed approach is to provide a way of performance prediction of individual buildings resulting from different retrofitting measures under the incomplete physics condition.
Analysis of Thermal Bridges with an Automated Framework using BIM
Authors: Bollez M. , Klein R. , Saelens D.
Published: December 2023

In response to increasingly stringent energy performance requirements for buildings, the need for energy-efficient construction becomes ever more important. Although new construction technologies have emerged, thermal bridges are still common in new and especially in to-be renovated buildings. To facilitate analysing the effect of thermal bridges this paper investigates the development of a method to automatically integrate their effect into energy simulations. The developed workflow starts with integrating thermal bridges into Building Information Modeling (BIM) software. Subsequently, the thermal bridges are exported to the open source format Industry Foundation Class (IFC). Finally, a conversion of the IFC file to a readable file for the energy simulation software Modelica, using the ifc2modelica tool is shown. Furthermore, it investigates the impact of thermal bridges on different key performance indicators (KPIs) for both renovation and new build cases. This research aims at efficiently integrating thermal bridges in energy simulations during early design stages. The foundation for a BIM-library for standard thermal bridges has been developed, allowing an easy integration in existing BIM models with good simulation results.
Over- and underconsumption of residential heating: Analyzing occupant impacts on performance gaps between calculated and actual heating demand
Authors: Hansen Anders Rhiger , Gram-Hanssen Kirsten
Published: December 2023

Previous research estimates that building physics and occupant practices equally contribute to the explanation of variations in residential heating consumption. However, the so-called performance gap, where calculated heating demand diverge from actual heating consumption, indicates that the relation between occupant practices and building physics vary across energy efficiency of the building. In this paper, using data from 2019 to 2021, we investigate such interactions 1) by comparing the calculated heating demand with actual energy consumption for residential space heating and domestic hot water (DHW) across energy performance certificates (A to G), and 2) by investigating variations in over- and underconsumption (deviance from calculated to actual) across socio-economic characteristics of households. In line with previous studies, we find that households living in energy inefficient houses tend to have lower heating demand than expected. Moreover, we find that lower-income households and households living in rural area has less overconsumption, indicating that they have more frugal heating practices.
Airtightness of Estonian dwellings – median and base-values for heat loss estimation.
Authors: Hallik Jaanus , Kalamees Targo , Pikas Ergo
Published: December 2023

The field measurements of airtightness in Estonian detached houses and apartment buildings, conducted between 2003 – 2022, were combined into a large dataset for statistical analysis. The buildings (539 in total) constructed between 1810 and 2022 were classified based on dwelling type, building structure, number of storeys, year of construction, energy classification and compactness factors. The data was statistically analysed to determine the mean and median air leakage rates at 50 Pa and tested (Kruskal-Wallis test with post-hoc Conover test) for significant differences within the grouping factors. Buildings constructed after the enforcement of the compulsory Energy Performance certification have on average across all building structure types significantly lower mean air leakage rate (1.6 m3/(h·m2)) than older buildings (6.9 m3/(h·m2)), although log-wood and brick construction types feature slightly higher average air leakage rate. Previous experience with air leakage measurements help to achieve better airtightness on building site. A systematic and recurring measurement practice within a single construction company leads to significantly lower air leakage also for new concrete buildings. Detailed assessment of older buildings showed that all timber-based construction types had significantly higher air leakage rate along with higher variability compared to precast large concrete panel stone and small block wall and brick buildings. All apartment buildings built before 2010 had significantly lower air leakage rate compared to detached houses while there was no difference in new buildings. Along with the mean and median value a base value of air leakage rate q
E50,base was calculated for all construction types and age groups including 50% of measured buildings around the mean within each group with 84 % confidence interval. The calculated mean, median and base values of air leakage rate provide a way for more accurate heat loss estimation at the district-level or building-level modelling of energy saving potential of different retrofitting strategies based on building age, construction type and other building information data.
Exploring the variability of hygrothermal material properties in historic bricks in London
Authors: Xu Bingyu , Cambray Toby , Marincioni Valentina , Mavrogianni Anna
Published: December 2023

In the UK, a large number of traditional buildings are made of solid brick walls. If appropriate retrofit measures are taken, these buildings can contribute to achieving the UK Government’s pledge to reduce greenhouse gas emissions. The vast majority of solid brick buildings in London are non-insulated. Adding internal wall insulation is one possible energy retrofit measure, however, the insulation layer can alter the moisture balance of the wall. Since the hygrothermal properties of the existing building materials can influence the moisture balance of the wall considerably, identifying the wall type and understanding its hygrothermal properties is extremely important in building retrofit. The objective of this study is to explore the variability of the hygrothermal properties of different bricks from one wall located in London. Several brick samples are selected from one case study wall in London. The hygrothermal properties of 21 historic bricks were measured, including the absorption coefficient, bulk density, drying coefficient, water content at capillary saturation to determine the variability. The experimental results show variability of some material properties, particularly the absorption coefficient. This can potentially have significant implications for solid wall retrofit and material property characterization.
Effect of demand-controlled ventilation strategies on indoor air pollutants in a classroom: A Norwegian case study
Authors: Yang Aileen , Andersen Kamilla Heimar , Hak Claudia , Mikoviny Tomas , Wisthaler Armin , Holøs Sverre B.
Published: December 2023

The choice of the minimum ventilation rate (Vmin) in a demand-controlled ventilation strategy can influence energy demand but also introduce outdoor air pollutants. The latter may have direct health effects, as well as affect indoor chemical reactions. In this paper, we evaluate the effect of ventilation rates and operation hours on the level of CO2, nitrogen dioxide (NO2), and ozone (O3) in a classroom during normal use. We compared the baseline ventilation scenario (S0) with a Vmin of 430 m3/h with S1; Vmin of 150 m3/h for normal ventilation operation time (6:30-17:00) and continuous ventilation for 24h (S2). We found that S1 with reduced Vmin would lower the ozone concentration by 35% during the hours before occupancy compared to S0. Moreover, continuous ventilation during night time with a low Vmin resulted in almost as high O3 concentrations as the baseline ventilation scenario. As O3 reacts easily with certain VOCs to produce secondary organic aerosols, the level of Vmin and the ventilation duration would impact the indoor air quality upon entering the classroom.
Dynamic modeling of airflow rate through window openings based on CO2 data
Authors: Schreck Cédric , Rouchier Simon , Foucquier Aurélie , Wurtz Etienne
Published: December 2023

Better estimation of air change rate in naturally ventilated buildings is a key for supporting passive summer thermal comfort strategies. In window aired configurations, this estimation is challenging either with measurements or building simulation methods. In this study, we describe and apply the state space modeling methodology based on the carbon dioxide concentration (CO2) mass balance equation to a simple test case with numerically generated data. We show that a two-state CO2 / Air Change Rate model is suitable. As a modeling novelty, we demonstrate the benefit of improving the formulation with a variable diffusion term for the air change rate state equation. From the test case study findings, we emphasize that a lower interior-exterior CO2 difference results in weaker performance and we list some prospects for future work.
Potential for Electricity Reduction in Demand Response Using Building Thermal Storage
Authors: Nagai T , Tanno K , Kuboi D , Kakegawa T , Yokoyama K , Nambu H
Published: December 2023

Demand response (DR) contributes to filling the gap between electricity supply and demand by controlling energy resources on the consumer side and promoting the installation and use of renewable energy. This study is performed to identify the potential of building thermal storage for power reduction in DR. In addition, the optimal conditions are identified, in particular the on/off status of air-conditioning and changes in room temperature setpoints. A simulation model for an office building equipped with packaged air-conditioners is developed, and dynamic programming is applied to calculate the on/off and load ratios to minimize the cumulative electricity during the DR period. Based on the results, two types of operations are suggested: one is to maintain the temperature at the upper allowable limit (in cooling) during the DR period, and the other is to repeatedly turn the air-conditioner on and off. In addition, the following factors affect power reduction: the allowable room temperature range, the time between the request for reduction and the start of the DR period, and the partial load characteristics of the air-conditioning equipment.
Linking dataset quality and MPC in buildings: impact of temporal resolution
Authors: Erfani Arash , Jafarinejad Tohid , Roels Staf , Saelens Dirk
Published: December 2023

This study aims at assessing the impact of dataset quality on the performance of Model Predictive Control (MPC). The dataset feature, which is the target of this study, is temporal resolution, which applies to both data logging and the controller time step. A high temporal resolution might result in a more accurate predictive model, but it increases the need for data storage as well as the computational load on the model training. From the controller side, increasing the temporal resolution might lead to better control performance, but it sabotages the real-time response of the system. First, predictive models are developed based on datasets with different temporal resolutions. Subsequently, these predictive models are implemented within an MPC. Results reveal that decreasing the time step lower than 1 hour does not significantly improve the performance of the MPC. However, increasing the time step of MPC above 1 hour deteriorates its performance. Real-time response of the controller is a crucial criterion which deteriorates as the time step shortens. Hence, a suitable choice of temporal resolution is essential for developing a predictive model and MPC. In our case, a resolution of 1 hour is enough to guarantee a good performance of the controller.
Development of smart control system for leakage warning in compact roofs
Authors: Asphaug Silje , Geving Stig , Moschetti Roberta
Published: December 2023

Smart Sensor technologies to monitor temperature and moisture conditions in building components, can be used to give automatic warnings for abnormal high levels of moisture. Flat compact roofs are of particular interest, especially due to their vulnerability to rain leakages through the roofing membrane. Installing moisture sensors in such a roof measuring relative humidity (RH) or free water may give an early warning of rain leakages or condensation due to air leakages from indoors – before they start to get problematic. One challenge is, however, that normal moisture redistribution in the insulation layer over the season or day may give very high levels of RH in the top or bottom part of the insulation. The sensor system must be able to distinguish between these normal levels and leakage events. Together with a sensor technology and control system producer we have previously developed a semi-quantitative system that defines typical or normal RH levels in the insulation layer during the year. This system was based on hygrothermal simulations for various conditions, such as different exterior climate and levels of built-in moisture. This paper presents the preliminary findings from the further development of the system using real measurements from two pilot buildings located in Norway.
Experimental study of a heat recovery ventilator preheated by a Building Integrated Photovoltaic system in a cold climate
Authors: Li Jing , Ye Kai , Baril Daniel , Ge Hua , Zmeureanu Radu , Athienitis Andreas K.
Published: December 2023

The use of heat recovery ventilators (HRVs) in cold climate housing is becoming increasingly common, to provide outside air to the occupied space while recovering heat from the exhausted air. However, frosting of the heat exchanger core impedes HRV operation in cold climate conditions. Strategies for defrosting the core include recirculating the exhaust airstream while stopping the supply of the outside air during the defrost cycle. Preheating the air using heating coils is also used, but its application is limited by the increased energy use of the preheater. This study aims to investigate the impact of a building integrated photovoltaic/thermal (BIPV/T) system on the HRV thermal performance by using it to preheat the outside air. In this experimental study, measurements of a heat recovery ventilator preheated by the BIPV/T system are carried out in a test cell of the Future Buildings Laboratory (FBL) at Concordia University in Montreal, Canada. The results are compared to a HRV without BIPV/T preheating. The relative humidity, temperature and airflow rate of the fresh air and exhaust airstreams are monitored at the inlet and outlet of the HRV. The experiments are conducted during two weeks from January 26th, 2023 to February 08th, 2023. The change of the sensible heat recovery effectiveness ∈
sens
of the HRV, outside air outlet temperature T

2
from the HRV and outside air flow rate, ṁ1 and exhaust air flow rate ṁ4 are determined. The primary experimental results indicate that preheating the outside air by the BIPV/T system before entering the HRV can help to increase the outside air outlet temperature T

2
by up to 2.7°C at an outdoor temperature of -25 °C, and the sensible heat recovery effectiveness ∈
sens
, outside air flow rate, ṁ1 (23L/s) and exhaust air flow rate ṁ4 (43L/s) of the HRV are kept constant at the same level with preheating by BIPV/T on the HRV at -5 °C to -25 °C of outdoor temperature.
In-use conditions of air-tightening materials applied in the air gap of ventilated building envelope constructions: A parametric study for different European climates
Authors: Brozovsky J , Nocente A , Rüther P
Published: December 2023

Materials used in the building envelope have to withstand a wide range of varying and harsh conditions over their life cycle. Particular relevance falls upon the materials used for tightening buildings, such as wind barriers and tapes, as air infiltration was found to be responsible for between 10 and 30 % of heat losses of different national building stocks in Europe. However, there is large uncertainty about the conditions a material is exposed to over a building’s service life. A validated, hygrothermal model of a zero emission office building in Trondheim, Norway was simulated with 10-year climate files from different European locations: Bergen (NO), Berlin (DE), Oslo (NO), Paris (FR), Rome (IT), Tromsø (NO), and Trondheim (NO). This was done to investigate the temperature and humidity conditions in the ventilated air gap. The results show the total and median values for temperature in the ventilated air gaps of the simulated building’s walls and roof for the investigated locations. Moreover, the maximum change compared to the previous hour and the distribution of hours in 5 °C temperature and 10 % relative humidity intervals of the roofing underlay and wall to the west are reported.
Numerical sensitivity analysis of the energy performance of building envelope with dynamic conditions
Authors: Veit Martin , Johra Hicham , Jensen Rasmus Lund , Rask Nikolaj , Roesgaard Simon
Published: December 2023

The accurate energy performance assessment of building elements remains an active research topic. Studies have indicated that the thermal mass of building envelopes could influence heat losses in dynamic conditions and lead to significant difference in performance compared to steady-state conditions. This article aims to identify the relevance of using dynamic simulations instead of steady-state calculations for the energy performance assessment of building elements in Denmark. A numerical sensitivity analysis is performed on various parameters. The Monte-Carlo approach is used to perform numerous BSim simulations, which are then compared to standard steady-state calculations. The varied parameters include solar absorptance, ventilation in cavities, insulation material, insulation thickness, and orientation. Preliminary results indicate that dynamic conditions can significantly alter the wall heat losses, by up to 20% when compared to steady-state conditions. However, when aggregated, the differences average out to only 4% lower heat losses. When focusing on the thermal inertia of insulation materials, denser insulation materials only slightly delay the heat loss in the building element, but this effect is nullified over longer periods. The sensitivity analysis indicates that the most influential parameter is the solar absorptance, while the type of material is close in significance to the other parameters. The specific heat capacities and density of the insulation layer does not have a significant influence compared to its thermal conductivity. Thus, insulation materials with higher thermal mass do not seem to significantly improve the thermal performance of a building envelope.
Thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor – first year measurements
Authors: Lomp Siim , Kalamees Targo , Hallik Jaanus , Needo Roomelt
Published: December 2023

In the Nordic countries frost insulation is necessary if the foundation is above the frost-free depth. The thermal performance of the pile foundations is between a shallow ground foundation and a frost wall foundation. The pile ends extend below the frost line to help insulate the ground beneath a building’s foundation. The ends of the piles extend below the frost line to prevent the foundation of the building from frost heaving. However, there may be a risk that the ground below the slab on ground may freeze and frost heaving may occur there. The risk of frost below the slab on ground floor and/or basement increases because increasing thickness of floor insulation remarkable influences frost insulation dimensioning. In this study a 6.5 × 17-meter size uninsulated wedge pile slab foundation with highly insulated (U=0.07 W/(m2·K)) slab on ground floor was constructed for a heated building and equipped with temperature, soil moisture, relative humidity, and heat flux sensors. Seven temperature measurement piles below the building and one for reference 8 meters far from the building reached a depth of up to 3.2 meters, which is deeper than the usual 1.4 m depth to avoid freezing in foundation design. In three places, the temperature below the insulation of slab on the ground is measured at 0.5 meters step up to 3 meters from the outer wall of the building. The first-year measurement results showed that temperature did not drop below the zero degree below the foundation and floor. Even though during winter the daily average absolute minimum temperature was -24 °C the sum of degree hours below the zero degree was -7300 °Ch. The historic 50-year absolute sum of minimum degree hours below the zero degree was -28600 °Ch. In addition to real measurement results this three-dimensional temperature sensor field helps to calibrate and validate dynamic model for temperature simulation of thermal performance of wedge pile slab foundation without frost protection insulation and highly insulated slab on ground floor.
Influence of the active irrigation system on the vegetation façade
Authors: Chabada Marek , Juras Peter , Durica Pavol
Published: December 2023

Urban population growth has resulted in land use changes and the replacement of many vegetated areas with hard dark surfaces. The altered surfaces warm the urban climate, a phenomenon known as the urban heat island (UHI) effect. Green systems such as vegetated facades significantly affect the outdoor microclimate through evapotranspiration cooling. In particular, the method of irrigation has a major influence on evaporation efficiency. This paper investigates the effect of an active vegetated façade irrigation system on the surface temperature behaviour of the envelope. The maximum difference between the surface temperature of the actively irrigated vegetation wall and the vegetation wall irrigated by hourly interval was almost 14°C. When comparing the surface temperatures of the actively irrigated vegetated façade with the non-vegetated façade - dark cladding, the maximum difference was almost 15°C. The difference between the surface temperature of the actively irrigated vegetated façade and the surface temperature behind the air cavity was almost 9°C. This reduction in temperature results in a shading effect of the vegetation wall. The use of vegetated structures is proving to be an effective tool and mitigation of temperatures in urban environments.
Heat loss characteristics of typology-based apartment building external walls for a digital twin-based renovation strategy tool
Authors: Iliste Elisa , Lomp Siim , Pikas Ergo , Arumägi Endrik , Hallik Jaanus , Õiger Karl , Kisel EInari , Liiv Innar , Kalamees Targo
Published: December 2023

Information about existing building structures is necessary for creating a renovation strategy. Older buildings are often built using typical building envelope structures. However, this information is presented in the building register at a general level, specifying the material type but not its characteristics. For a cross-regional reconstruction strategy, it is necessary to link the scarce information in the building register with the heat loss characteristics of the building envelope structures. In the current study, we classified external wall solutions according to building typologies and linked this with building register information. The typology database includes log, timber frame, brick, concrete, and aerated lightweight concrete external wall structures. Comparing the typology-based values and the actual situation showed that the wall structures’ expected and actual heat loss characteristics agreed. However, there were also significant deviations, primarily because the data from the building register did not allow for precise classification. Nevertheless, data showed that building typology-based heat loss properties are necessary for developing a district-based renovation strategy.
Time-evolving Impact of Trees on Street Canyon Microclimate
Authors: Li Haiwei , Zhao Yongling , Bardhan Ronita , Kubilay Aytac , Derome Dominique , Carmeliet Jan
Published: December 2023

Nowadays, cities are frequently exposed to heatwaves, worsening outdoor thermal comfort and increasing cooling energy demand in summer. Urban forestry is seen as one of the viable and preferable solutions to combat extreme heat events and urban heat island (UHI) in times of climate change. While many cities have initiated tree-planting programs in recent years, the evolving impact of trees on street microclimate, in a time span of up to several decades, remains unclear. This study focuses on the cooling effects of a common type of street trees, linden trees, in five age groups, i.e., 10-20, 20-30, 30-40, 40-60, and 60-100 years old, while the diversity of trees is present in nature, that is, various species and crown geometries, The leaf area index (LAI) and leaf area density (LAD) of linden trees vary nonlinearly as they grow, peaking at different ages. Computational fluid dynamics (CFD) simulations were performed for an idealized street canyon with linden trees of various age groups. Turbulent airflow, heat and moisture transport, shortwave and longwave radiation, shading, and transpiration were fully coupled and solved in OpenFOAM. Meteorological data, including air temperature, wind speed, moisture, and shortwave radiation of the heatwave in Zurich (June 2019), were applied as boundary conditions. The results show that young trees in the age group of 10-20 years old provide little heat mitigation at the pedestrian level in an extreme heat event. Optimal heat mitigation by trees is observed for the group of 30-60 years old linden trees. Finally, the potential impact of growing trees on air ventilation in streets is evaluated.
Improved mesoscopic meteorological modelling of the urban climate for building physics applications
Authors: Strebel D , Derome D , Kubilay A , Carmeliet J
Published: December 2023

A meteorological mesoscale model is used to predict the local urban climate at 250 m resolution. The authors propose a hybrid machine learning approach to improve the prediction accuracy and remove simulation bias. Two case studies are presented to show the improvements of the simulation accuracy. Based on the hybrid model results, using cooling degree hours is proposed as an insightful time-dependent index to map local hotspots and assess the difference of cooling loads between rural and urban environments.
Multi-agent Cooperative Optimization Strategy of a Virtual Power Plant Based on Game Theory
Authors: Hong Huawei , Yu Xian
Published: December 2023

This paper proposes a multi-agent collaborative optimization method for virtual power plants based on the Bayesian game. Focusing on the internal scheduling of VPP, taking demand response load as the analysis object, aiming at the interactive optimization relationship between multiple intelligent communities in the virtual power plant under this scenario, a multi-agent collaborative optimization model of the virtual power plant is established by using Bayesian game theory. The effectiveness of the constructed game model and algorithm is verified by solving the actual example of the virtual power plant and analyzing the corresponding simulation results.
Improving the Success Rate of Electricity Information Collection System
Authors: Kang Liyan , Liao Liying , Qin Yuewei
Published: December 2023

The electricity information collection system built in China is the world’s largest user-side data collection, monitoring, and control system. With a total coverage of 540 million electricity users, it has played an important role in the safety production and operation management of the power system. The success rate of data collection in the collection system is an important indicator to measure the quality of system operation. This article analyzes and studies the factors that affect the success rate of collection from the dimensions of the main station, channel, terminal, meter, and synthesis. It provides a large amount of experimental and test data and thus obtains methods to improve the success rate of collection. It provides reference and improvement methods for the construction of power system information engineering.
Experimental study on electric fire based on nitrogen injection technology
Authors: Kuai Shichao , Li Ningning , Zheng Wei , Tong Jingguang , Zhao Feng , Xu Lei , Qi Zibo
Published: December 2023

Electric fire occurs frequently in daily life. The fault arc, overload and short circuit of electric fire phenomena are the important factors of electric fire. In view of this, electric fire test research based on nitrogen injection technology is carried out, focusing on the effect of nitrogen injection technology on fault arc, overload, and short circuits of electric fires. The combustion inhibition characteristics of nitrogen injection technology on electric fires are analyzed through comparative tests, and the application method of nitrogen injection technology in the field of electric fire prevention is explored.
New Topology Design and On-line Charging and Discharging Technology of Substation DC System
Authors: Zhu Minjie , Tang Yiqin , Le Xubo , Zhang Bingye , Su Xingyang , Zou Guoping
Published: December 2023

The substation DC system uses battery packs as a backup power source. It needs to be regularly checked for capacity. In the existing topology, batteries are connected in series as a power source. When checking capacity discharge, an additional backup power supply must be built to replace it, which is costly and complicated to operate. To this end, this paper proposes a new battery topology. The previous 54 series batteries were divided into 3 packs, with each consisting of 18 batteries. The three battery packs are connected in parallel to the DC bus through bidirectional DC/DC converters. The automatic charging and discharging control strategies of the battery packs under the new topology are studied. The system can automatically charge and discharge batteries through bidirectional DC/DC converters, and conduct online capacity testing of battery packs. Simulation results show that the designed new topology not only realizes the online verification of battery capacity but also saves the test cost. The power supply reliability of the DC system of the substation is also greatly improved through the redundant structure.
Security Analysis of Distribution Network Loop Closure Based on Half Invariant Method
Authors: Xu Zhiguang , Chen Dongxu , Chen Shengshuo , Kang Shijia , Li Yansong , Liu Jun
Published: December 2023

The integration of distributed power sources requires active power systems to raise new concerns about their safety. In order to scientifically and effectively analyze the safety of active distribution network closing current, taking photovoltaic power supply as an example, a closed-loop equivalent model considering the influence of distributed power sources was proposed, and an equation based on the random fluctuation current of new energy sources was derived. On this basis, a semi invariant method is used to solve the random fluctuation variable of the required current, and corresponding indicators are developed based on the principle of closed loop safety to evaluate the safety of the closed loop current. Based on PSCAD and MATLAB platforms, simulation calculations were conducted, and the simulation and calculation values were compared to verify the feasibility and timeliness of the closed-loop security analysis model based on the semi invariant method.
Feeder Capacity Planning and Reliability Evaluation Model of Distribution Network Based on Support Vector Machine
Authors: Yin Xiang , Liu Yan , Wu Chaoqun , Li Xing
Published: December 2023

Capacity planning and reliability evaluation models of the traditional distribution network feeder mainly use multi-option balance constraints for multi-objective solutions, which are prone to capacity constraints, resulting in lower reliability indicators for planning and evaluation. Therefore, a brand-new distribution network feeder capacity planning and reliability evaluation model based on a support vector machine is designed. By using support vector machines to design the reliability evaluation process of distribution network feeder capacity planning, we establish an optimization model for reliability evaluation of distribution network feeder capacity planning. The experimental results show that the designed feeder capacity planning and reliability evaluation model based on a support vector machine has good evaluation results, high-reliability indicators for planning and evaluation, reliability, and certain application values.
Fault Location and Phase Selection Method of Distribution Network Containing IIDG Based on Online Active Detection
Authors: Cheng Yunxiang , Liu Xiangbo , Wang Sen , Gao Fang , Li Hao , Yu Chengao , Tao Zhengchen
Published: December 2023

This paper proposes a fault location and phase selection method for the distribution network containing IIDG based on online active detection, utilizing online active detection. In this method, the characteristic harmonic current injection control strategy based on d- and q-axis control is obtained by analyzing the structure, control strategy, and short-circuit current of IIDG. During a fault, the distributed power supply injects characteristic harmonic current into line, adapting its magnitude with the short-circuit current’s size. By detecting the difference in harmonic current content rate for both ends of the fault point, the method achieves online location and line selection of fault points. A 10 kV IIDG distribution network model is simulated by using PSCAD to validate the feasibility and accuracy of the proposed fault location and phase selection method.
Simulation and Generation of the In-born Strong Magnetic Environment During Railgun Launch
Authors: Cao Genrong , Qiao Zhiming , Liang Chunyan , Yuan Xichao , Xiang Hongjun
Published: December 2023

The in-born strong magnetic environment during the launch process of the railgun is a potential risk for ammunition applications. Currently, there are no mature means to simulate the magnetic field environment to provide a platform for the electromagnetic safety test of ammunition. Given this problem, a strong magnetic environment generation system was designed. By establishing the theoretical model of the magnetic field generated, the difficulty of generating specific waveforms of strong magnetic fields was broken through. Besides, the strong magnetic field generator’s multi-physical field response was analyzed by using the FEM method, and its stability of structure and temperature was evaluated. Finally, the strong magnetic environment generation experiment was conducted, where the in-born magnetic field during the launch process of the railgun was generated successfully. As a result, the strong magnetic environment generation system can generate the expected strong magnetic fields. The magnetic flux density is 10 T, and the pulse width is 6.1 ms.
Studies of the effect of preset square pores on the mechanical properties of Ag nanopsheets under biaxial stretching
Authors: Qin Muyang , Zhang Yanan , Yang Qinyou
Published: December 2023

This study investigated the mechanical properties of silver nanosheets with preset square pores regarding energy, natural strain, and stress properties. Additionally, the effect of different pore positions on dislocations under symmetrical and asymmetrical loading was analyzed using a model of silver nanosheets with square pores preset under biaxial stretching and molecular dynamics methods. The results revealed that the interaction between shear stress and dislocation can cause fractures, with greater shear stress observed when the pore is closer to the model boundaries. Moreover, the symmetrically positioned pores displayed different mechanical properties under asymmetric loading.
A Compact Split-step Finite Difference Method for Solving the Nonlinear Schrödinger Equation
Authors: Nizam Elminur , Rahman Kaysar
Published: December 2023

The nonlinear Schrödinger equation arises from quantum mechanics and is extensively used in many fields of science and engineering. Thus, it is important to construct the high-order and stable numerical scheme of the Schrödinger equation. To solve the high-order and stable numerical solution of the nonlinear Schrödinger equation, the compact split-step finite difference method and the local one-dimensional method are combined in this paper. To attain high-order accuracy in time and space, the 4-order compact finite difference in space discretization is combined with the L-stable Simpson method in time discretization. Therefore, a scheme with 4-order accuracy in space and 3-order accuracy in time is obtained, and the stability of the scheme is analyzed. Finally, numerical results manifest that the devised scheme can supply accurate and stable results to the nonlinear Schrödinger equation.
Mixed Direct Discontinuous Galerkin Method for the Biharmonic Equation
Authors: Wang Huanhuan
Published: December 2023

In this paper, we use the mixed direct discontinuous Galerkin method (DDG) to solve the biharmonic equation. Firstly, by introducing an auxiliary variable, the biharmonic equation is split into two second-order equations. Secondly, the variational problem based on the DDG method of the system is derived and its well-posedness is proven. Next, error estimates of the approximate solution in L
2 norm and energy norm are present. For a given polynomial degree k (k ≥ 1), the optimal convergence rates concerning energy norm and norm are k and k + 1, respectively. Finally, numerical results demonstrate the accuracy and capability of the method.
Bounds for the spectral radius of Schur product of matrices
Authors: Zhong Qin
Published: December 2023

We establish a new upper bound on the spectral radius for the Schur product of two matrices with nonnegative elements by utilizing the eigenvalue inclusion theorem. The new bound is more useful in practical applications because it is simply based on the elements of two matrices. Additionally, a numerical example is taken into account to show that, in some circumstances, the result achieved is superior to some previously reported results.
Simulation Analysis and Lightweight Design of Automotive Transmission Shafts Based on Optistruct
Authors: Zeng Wenhao , Mao Luyao , Huang Dong , Wang Can , Chen Qiyu
Published: December 2023

The transmission shaft is an important power transmission assembly in the automotive transmission system. Its structural mechanical performance is crucial for the comfort and safety of the vehicle. For this purpose, the transmission shaft of commercial vehicles is taken as the research object. Mechanical simulation analysis is conducted based on the finite element analysis software of Optistruct to investigate the stress and displacement distribution of various components on the transmission shaft under maximum torque and to verify its strength and stiffness. In addition, based on the stress distribution and manufacturing process requirements of the transmission shaft, a lightweight design is carried out for the transmission shaft components. The research results indicate that using simulation analysis methods can quickly obtain the force transmission path of the transmission shaft assembly and introducing manufacturing process requirements for lightweight design not only meets the manufacturing requirements but also has a more uniform stress distribution. The overall structure of the transmission shaft has been reduced from 23.8 kg to 16.8 kg with a weight reduction of 30%. The lightweight design method described in this article can quickly achieve weight reduction goals while meeting the structural strength of the transmission shaft.
The correlation between static strength and fatigue strength test and simulation
Authors: Miao Chenglin , Wang Hao , Song Ye
Published: December 2023

In the bogie, the frame plays a vital role. It is not only the installation foundation and direct bearing structure of other components but also can transmit the excitation load from all directions. Therefore, the rationality and reliability of the frame design are particularly critical. In this work, according to EN13749, UIC615-4, JIS E 4207, and JIS E 4208 standards, the load conditions are compiled, and the finite element analysis is carried out. The static strength and fatigue strength are tested on the test bench. The results show that the static strength results of the bogie frame are less than the allowable stress of the corresponding material. The fatigue assessment was carried out by Goodman diagram, and the data all fell within the envelope, which met the requirements of fatigue assessment. Finally, the test results are compared with the simulation results. Through the correlation analysis of the static strength test results and the finite element simulation results of the frame, the stress exceeds 10% of the material yield limit under the exceptional load condition, and the large stress points of the local hanger are compared. The results show that the frame strength test results and the finite element simulation results maintain a good correlation.
Evaluation of Gradation and Stress State Effects on the Resilient Modulus of Crushed Aggregate Materials
Authors: Wei Aozhong , Sun Jiaqian , Li Cheng , Bu Shanshan , Wang Weiwei , Xiang Wen
Published: December 2023

Resilient modulus is a key mechanical parameter for unbound granular base materials. To evaluate gradation effects on the resilient modulus of crushed aggregate materials, the present study conducted laboratory resilient modulus tests on two categories of crushed aggregate materials with seven different gradations. A multi-factor sensitivity analysis was performed on test results and found that the confining pressure and axial stress yield a more significant impact on resilient modulus than the gradation. Different material gradations can yield an average impact of 8%, with a maximum of 21%, and show increased sensitivity with aggregate gradation becoming finer.