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"Heating and cooling"
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Performance Evaluation of Two Machine Learning Techniques in Heating and Cooling Loads Forecasting of Residential Buildings
Nowadays, since energy management of buildings contributes to the operation cost, many efforts are made to optimize the energy consumption of buildings. In addition, the most consumed energy in the buildings is assigned to the indoor heating and cooling comforts. In this regard, this paper proposes a heating and cooling load forecasting methodology, which by taking this methodology into the account energy consumption of the buildings can be optimized. Multilayer perceptron (MLP) and support vector regression (SVR) for the heating and cooling load forecasting of residential buildings are employed. MLP and SVR are the applications of artificial neural networks and machine learning, respectively. These methods commonly are used for modeling and regression and produce a linear mapping between input and output variables. Proposed methods are taught using training data pertaining to the characteristics of each sample in the dataset. To apply the proposed methods, a simulated dataset will be used, in which the technical parameters of the building are used as input variables and heating and cooling loads are selected as output variables for each network. Finally, the simulation and numerical results illustrates the effectiveness of the proposed methodologies.
Journal Article
Micro/macro physical and mechanical variation of red sandstone subjected to cyclic heating and cooling: an experimental study
Since rock mass in many fields of rock engineering usually undergoes a cyclic heating and cooling process, it is very meaningful to investigate the variations of rock micro/macro physical and mechanical properties subjected to cyclic heating and cooling. However, due to the complex and invisible characteristics of rock microstructure, the effect of cyclic heating and cooling on rock macro/micro physical and mechanical properties still requires further investigation. In this study, to explore the microscopic mechanism underlying the variations of rock macroscopic properties during cyclic heating and cooling, uniaxial compression tests and P-wave velocity tests were conducted to obtain the macromechanical properties of red sandstone specimens subjected to varying numbers of heating and cooling cycles. Acoustic emission (AE) tests were also carried out to capture the variations in the microscopic damage process during each heating and cooling cycle. A scanning electron microscope and differential thermal analysis–thermal gravimetric analyzer were used to analyze the development of the microcracks and variations in the micrograin mass after each cyclic heating and cooling. The test results demonstrate that after being heated to 500 °C, some of the minerals (microcline, albite and calcite) in the sandstone decomposed and microcrocks developed due to the uneven thermal stress. When the sandstone was cooled in water, more microdefects were induced to the microstructure due to mineral transformations and uneven contractions, causing further deterioration to the integrity and compactness of the rock matrix. This phenomenon was also reflected in the uniaxial compression tests and AE tests. Due to the damage caused by each heating and cooling cycle, the AE hit rate decreased and the macrophysical and mechanical properties of rock deteriorated as the number of cycles increases. Comparison of the test results obtained from samples subjected to different heating and cooling cycles reveals that although each cycle could cause damage to the rock sample, the first and fifth cycles induced more severe damage, as indicated by the sharp decrease in the physical and mechanical properties of the rock after the first and fifth cycles.
Journal Article
Stakeholder Perspectives on District Heating and Cooling for Climate-Neutral and Smart Cities: A Romanian Analysis
District heating and cooling systems represent a great pillar of European cities aiming to achieve climate neutrality. This study investigates stakeholders’ perspectives on district heating and cooling to analyze the challenges, barriers, and potential accelerators of a sustainable low-carbon energy transition in urban areas. This study was performed via a survey-based approach, targeting multi-level stakeholders, both from the supply and demand side. This study employed a structural methodology involving customized surveys tailored to different stakeholder groups, aiming to understand challenges, advancement, and opportunities in Romania’s district heating systems. The results highlighted the diverse interests of stakeholders, emphasizing the need for financial support to reduce reliance on fossil fuels from the supply side while addressing concerns about infrastructure and current operations from the demand side. This study laid the groundwork for shaping national and regional policies and promoting local partnerships to reduce fossil energy demand and support the transition to renewable energy sources. Using a multi-stakeholder, cross-sectorial approach, and SWOT analysis in Romania, it systematically addresses technical, financial, and regulatory challenges for the greater sustainability of these systems in the urban environment.
Journal Article
Effect of heating–cooling cycles on mechanical properties and microscopic characteristics of shale
Shale gas will become an important substitute of conventional fossil fuels in the future, and the reservoir characteristics of shale are closely related to its pore structures. In order to explore the change characteristics of pore structures and mechanical properties of shale under the cyclic heating and cooling effect, from the perspectives to analyze of physical and mechanical properties and microscopic pore structure, etc. First, the ultrasonic wave velocity test and triaxial compression test were carried out. Afterward, the change law of macroscopic physical and mechanical parameters was microscopically verified based on X-ray diffraction technology, Fourier infrared spectroscopy and low-field nuclear magnetic resonance technology. The research results showed that the specimens drilled perpendicular to stratification direction were more likely to be damaged under the effect of heating–cooling cycles; under the temperature shock brought about by heating–cooling effects, the physical parameters of shale would vary at different degrees; however, chemical properties of shale basically remained unchanged; temperature effect would promote the further propagation of primary fractures and the initiation of secondary fractures and the fractures coalesced to form larger ones. Through the change of T2 spectra obtained based on NMR, it can be inferred that the number of micropores in shale declined while that of macropores increased; with the growth of heating–cooling cycles, the pores in rocks constantly developed under the effect of repeated temperature shocks, which resulted in the increase of the porosity. Additionally, the compressional wave velocity and uniaxial compressive strength generally decreased and the reduction amplitudes of the peak strength of shale treated through 5, 10 and 15 cycles were 4.12, 24.18 and 24.58%, respectively. The research result provides effective reference for efficient mining of shale gas and reconstruction engineering of tight reservoirs.
Journal Article
Microscopic characterization of microcrack development in marble after cyclic treatment with high temperature
Crack density of rocks is greatly affected by high temperature treatment and the induced thermal damage influences the strength and deformation characteristics of the rock. A good understanding of thermal cracking behavior is useful for geological evaluation of engineering structures associated with high temperature problems. This study investigates the characteristics of thermally-induced microcracks in a fine-grained dolomitic marble with different degrees of thermal damage using an optical microscope. Different degrees of thermal damage were first generated by treating the rock specimen with different heating and cooling cycles. Optical microscopy was then used to characterize the microcrack type and statistically examine the width, length, and anisotropy of thermally-induced microcracks. The results reveal that most of the generated microcracks induced by cyclic high temperature treatment are grain boundary microcracks. The width and length of microcracks significantly increases with an increasing number of heating and cooling cycles. It is also found that both grain boundary microcracks and intra-grain microcracks do not show predominant direction after thermal treatment. Finally, a quantitative relation is established to correlate the mechanical behavior of rocks (i.e., strength and modulus) with the crack density. The proposed relation is useful in understanding how the microstructure affects the properties of rocks after treatment with high temperature.
Journal Article
Bridging Heritage Conservation and Energy Efficiency: Retrofitting Historic Social Housing in Mediterranean Cities
Historic social housing in Mediterranean cities faces the dual challenges of energy inefficiency and cultural preservation. This study presents a pilot methodological framework for energy retrofitting of historical residence buildings, using the Kaisariani Asia Minor refugee housing complex in Athens as a case study. A bibliometric analysis revealed a research gap, as clusters concerning heritage retrofitting and social housing remain weakly connected, highlighting limited interdisciplinary integration between cultural conservation and energy-efficient design. The proposed framework combines historical analysis, energy consumption assessment, and technical evaluation to examine three retrofit scenarios that integrate thermal insulation, upgraded HVAC systems, renewable domestic hot water, and photovoltaic installations. Results demonstrate that substantial performance improvements can be achieved without compromising architectural authenticity. The most comprehensive scenario achieved a 97% reduction in primary energy demand, a 63–76% decrease in heating and cooling loads, and significant CO2 emission reductions, maintaining economic feasibility with a payback period of approximately ten years. The findings emphasize that conservation-compatible retrofitting can transform obsolete housing into low-energy buildings, fostering environmental, social, and cultural sustainability. Beyond quantitative energy gains, the study underlines the importance of integrating heritage values and community identity into urban regeneration strategies, offering a transferable model for Mediterranean municipalities seeking to align climate action with cultural continuity.
Journal Article
Analysis of the Potential of Decentralized Heating and Cooling Systems to Improve Thermal Comfort and Reduce Energy Consumption through an Adaptive Building Controller
Thermal comfort is one of the most important factors for occupant satisfaction and, as a result, for the building energy performance. Decentralized heating and cooling systems, also known as “Personal Environmental Comfort Systems” (PECS), have attracted significant interest in research and industry in recent years. While building simulation software is used in practice to improve the energy performance of buildings, most building simulation applications use the PMV approach for comfort calculations. This article presents a newly developed building controller that uses a holistic approach in the consideration of PECS within the framework of the building simulation software Esp-r. With PhySCo, a dynamic physiology, sensation, and comfort model, the presented building controller can adjust the setpoint temperatures of the central HVAC system as well as control the use of PECS based on the thermal sensation and comfort values of a virtual human. An adaptive building controller with a wide dead-band and adaptive setpoints between 18 to 26 °C (30 °C) was compared to a basic controller with a fixed and narrow setpoint range between 21 to 24 °C. The simulations were conducted for temperate western European climate (Mannheim, Germany), classified as Cfb climate according to Köppen-Geiger. With the adaptive controller, a 12.5% reduction in end-use energy was achieved in winter. For summer conditions, a variation between the adaptive controller, an office chair with a cooling function, and a fan increased the upper setpoint temperature to 30 °C while still maintaining comfortable conditions and reducing the end-use energy by 15.3%. In spring, the same variation led to a 9.3% reduction in the final energy. The combinations of other systems were studied with the newly presented controller.
Journal Article
Effect of Rapid Heating and Cooling Conditions on Microstructure Formation in Powder Bed Fusion of Al-Si Hypoeutectic Alloy: A Phase-Field Study
Al alloy parts fabricated by powder bed fusion (PBF) have attracted much attention because of the degrees of freedom in both shapes and mechanical properties. We previously reported that the Si regions in Al-Si alloy that remain after the rapid remelting process in PBF act as intrinsic heterogeneous nucleation sites during the subsequent resolidification. This suggests that the Si particles are crucial for a novel grain refinement strategy. To provide guidelines for grain refinement, the effects of solidification, remelting, and resolidification conditions on microstructures were investigated by multiphase-field simulation. We revealed that the resolidification microstructure is determined by the size and number of Si regions in the initial solidification microstructures and by the threshold size for the nucleation site, depending on the remelting and resolidification conditions. Furthermore, the most refined microstructure with the average grain size of 4.8 µm is predicted to be formed under conditions with a large temperature gradient of Gsol = 106 K/m in the initial solidification, a high heating rate of HR = 105 K/s in the remelting process, and a fast solidification rate of Rresol = 10−1 m/s in the resolidification process. Each of these conditions is necessary to be considered to control the microstructures of Al-Si alloys fabricated via PBF.
Journal Article
Decarbonising the EU Buildings|Model-Based Insights from European Countries
The European Union faces the pressing challenge of decarbonising the buildings sector to meet its climate neutrality goal by 2050. Buildings are significant contributors to greenhouse gas emissions, primarily through energy consumption for heating and cooling. This study uses the advanced PRIMES-BuiMo model to develop state-of-the-art innovative pathways and strategies to decarbonise the EU buildings sector, providing insights into energy consumption patterns, renovation rates and equipment replacement dynamics in the EU and in two representative Member States, Sweden and Greece. The model-based analysis shows that the EU’s transition towards climate neutrality requires significant investment in energy efficiency of buildings combined with decarbonisation of the fuel mix, mostly through the uptake of electric heat pumps replacing the use of fossil fuels. The Use Case also demonstrates that targeted policy interventions considering the national context and specificities are required to ensure an efficient and sustainable transition to zero-emission buildings. The analysis of transformational strategies in Greece and Sweden provides an improved understanding of the role of country-specific characteristics on policy effectiveness so as to inform more targeted and contextually appropriate approaches to decarbonise the buildings sector across the EU.
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