Pub Date : 2026-02-02DOI: 10.1016/j.energy.2026.140205
Zhikai Liu , Ting Dai , Lian Zhang , Xin Xu , Qi Zhang , Yaran Wang , Feng Tao
Accurate hydraulic resistance is essential for optimal pump control in meshed district heating networks (DHNs). However, actual resistances often deviate from design values due to pipeline aging, corrosion, or topology changes, which can reduce control effectiveness. Identifying hydraulic resistance is further complicated by the underdetermined nature of the network, as measurements are typically available only at heating substations, while the number of pipelines far exceeds the number of observable nodes in the absence of additional sensors. To address this issue, a physics-constrained gradient descent-based identification framework is proposed. Hydraulic resistance is iteratively updated using gradient descent with analytically derived gradients, relying only on pressure data under multiple operating conditions. A loss function is first defined to quantify discrepancies between observed and simulated pressures, and its analytical gradient with respect to normalized resistance is derived. The estimated resistance converges to consistent and stable equivalent values across a wide range of perturbation levels. These identified resistances effectively capture the hydraulic behavior of the network and form the basis for the optimal pump control (OPC) strategy proposed in this study. Compared to the constant pressure difference control (CPDC) strategy, the OPC strategy can save approximately 10.4% of pumping energy during the heating period.
{"title":"Gradient-based identification of hydraulic resistance for optimal pump control in meshed district heating network","authors":"Zhikai Liu , Ting Dai , Lian Zhang , Xin Xu , Qi Zhang , Yaran Wang , Feng Tao","doi":"10.1016/j.energy.2026.140205","DOIUrl":"10.1016/j.energy.2026.140205","url":null,"abstract":"<div><div>Accurate hydraulic resistance is essential for optimal pump control in meshed district heating networks (DHNs). However, actual resistances often deviate from design values due to pipeline aging, corrosion, or topology changes, which can reduce control effectiveness. Identifying hydraulic resistance is further complicated by the underdetermined nature of the network, as measurements are typically available only at heating substations, while the number of pipelines far exceeds the number of observable nodes in the absence of additional sensors. To address this issue, a physics-constrained gradient descent-based identification framework is proposed. Hydraulic resistance is iteratively updated using gradient descent with analytically derived gradients, relying only on pressure data under multiple operating conditions. A loss function is first defined to quantify discrepancies between observed and simulated pressures, and its analytical gradient with respect to normalized resistance is derived. The estimated resistance converges to consistent and stable equivalent values across a wide range of perturbation levels. These identified resistances effectively capture the hydraulic behavior of the network and form the basis for the optimal pump control (OPC) strategy proposed in this study. Compared to the constant pressure difference control (CPDC) strategy, the OPC strategy can save approximately 10.4% of pumping energy during the heating period.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"347 ","pages":"Article 140205"},"PeriodicalIF":9.4,"publicationDate":"2026-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187723","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.energy.2026.140268
Yonghao Zeng , Baowei Fan , Haidong Yang , Jianfeng Pan , Chao Jiang , Wenming Yang
Methanol, a promising low-carbon alternative fuel synthesized via CO2 hydrogenation, enhances combustion efficiency in internal combustion engines due to its high oxygen content and rapid flame propagation. To further leverage its potential, fuel reforming technology is employed to generate hydrogen-rich gas. Nevertheless, studies on in-cylinder reforming for rotary engines are notably scarce. In response, this study develops a novel in-cylinder methanol reforming method, which utilizes the high-temperature and low-oxygen conditions during the end of the combustion stroke to produce hydrogen. The hydrogen is introduced into the next working cycle through exhaust gas recirculation (EGR). This research systematically examines how reformate injection position and angle affect reforming efficiency and combustion performance. The results indicate that injection position and angle determine the distribution of methanol across different temperature-pressure regions in the cylinder, significantly influencing reforming efficiency. In addition, the distribution of reforming hydrogen in the exhaust stage significantly determines the quality of hydrogen available for the next cycle, thereby enhancing the efficiency of pure-methanol rotary engines. According to the simulation results, when applying methanol reforming technology in jet ignition methanol rotary engines, it is recommended to place the reforming fuel nozzle on the cylinder block 40 mm away from the long axis, with an injection angle of −20°.
{"title":"A study on direct in-cylinder methanol-reforming strategy for performance enhancement of rotary engines","authors":"Yonghao Zeng , Baowei Fan , Haidong Yang , Jianfeng Pan , Chao Jiang , Wenming Yang","doi":"10.1016/j.energy.2026.140268","DOIUrl":"10.1016/j.energy.2026.140268","url":null,"abstract":"<div><div>Methanol, a promising low-carbon alternative fuel synthesized via CO<sub>2</sub> hydrogenation, enhances combustion efficiency in internal combustion engines due to its high oxygen content and rapid flame propagation. To further leverage its potential, fuel reforming technology is employed to generate hydrogen-rich gas. Nevertheless, studies on in-cylinder reforming for rotary engines are notably scarce. In response, this study develops a novel in-cylinder methanol reforming method, which utilizes the high-temperature and low-oxygen conditions during the end of the combustion stroke to produce hydrogen. The hydrogen is introduced into the next working cycle through exhaust gas recirculation (EGR). This research systematically examines how reformate injection position and angle affect reforming efficiency and combustion performance. The results indicate that injection position and angle determine the distribution of methanol across different temperature-pressure regions in the cylinder, significantly influencing reforming efficiency. In addition, the distribution of reforming hydrogen in the exhaust stage significantly determines the quality of hydrogen available for the next cycle, thereby enhancing the efficiency of pure-methanol rotary engines. According to the simulation results, when applying methanol reforming technology in jet ignition methanol rotary engines, it is recommended to place the reforming fuel nozzle on the cylinder block 40 mm away from the long axis, with an injection angle of −20°.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"346 ","pages":"Article 140268"},"PeriodicalIF":9.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098546","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-01DOI: 10.1016/j.energy.2026.140104
Jiwei Wang , Xiangtian Xu , Mingyi Zhang , Yuhang Liu , Ruiqiang Bai , Yongtao Wang , Wansheng Pei , Xiangbing Kong
Heat-reflective technologies reduce solar heat gains of asphalt surfaces and can contribute to energy-efficient, low-carbon transport systems. Their relevance is amplified for cold-region highways, where disturbed surface energy exchange can accelerate permafrost warming and intensify freeze-thaw distress. However, the evidence base remains dispersed and often fails to connect optical engineering with roadway performance and life-cycle implications. This review synthesizes laboratory measurements, outdoor-model experiments, and field monitoring through a surface-energy-balance framework, covering coating and material systems, spectral-property characterization, cooling effectiveness, functional performance, and life-cycle assessment considerations. Reported datasets consistently indicate that increasing albedo yields a monotonic, often near-linear, reduction in surface temperature and radiation indices, with measurable cooling in shallow pavement layers. Among deployable options, coating-based solutions dominate current practice, particularly multilayer epoxy or acrylic matrices formulated with near-infrared selective pigments. Evidence underscores the roles of binder chemistry and surface texturing in resisting aging. Their benefits are strongly modulated by embankment slope and aspect, which govern short-wave radiation. Functional outcomes show systematic trade-offs: lower operating temperature can improve rutting resistance and moisture sealing, whereas skid resistance, adhesion, and optical retention depend on surface texture, freeze-thaw exposure, snowplowing abrasion, and de-icing chemicals. Based on these insights, we propose a cold-region evaluation framework and research priorities including standardized spectral sensing, predictive optical-aging models, coupled thermo-mechanical simulation, AI-enabled field assessment or material design, and context-specific life-cycle accounting. As this technology matures and its adoption scales, it is expected to enhance the whole-life service performance of cold-region road transport infrastructure while reducing life-cycle costs.
{"title":"Heat-reflective technology for cold-region roads: Mechanisms, materials, performance and life-cycle perspectives","authors":"Jiwei Wang , Xiangtian Xu , Mingyi Zhang , Yuhang Liu , Ruiqiang Bai , Yongtao Wang , Wansheng Pei , Xiangbing Kong","doi":"10.1016/j.energy.2026.140104","DOIUrl":"10.1016/j.energy.2026.140104","url":null,"abstract":"<div><div>Heat-reflective technologies reduce solar heat gains of asphalt surfaces and can contribute to energy-efficient, low-carbon transport systems. Their relevance is amplified for cold-region highways, where disturbed surface energy exchange can accelerate permafrost warming and intensify freeze-thaw distress. However, the evidence base remains dispersed and often fails to connect optical engineering with roadway performance and life-cycle implications. This review synthesizes laboratory measurements, outdoor-model experiments, and field monitoring through a surface-energy-balance framework, covering coating and material systems, spectral-property characterization, cooling effectiveness, functional performance, and life-cycle assessment considerations. Reported datasets consistently indicate that increasing albedo yields a monotonic, often near-linear, reduction in surface temperature and radiation indices, with measurable cooling in shallow pavement layers. Among deployable options, coating-based solutions dominate current practice, particularly multilayer epoxy or acrylic matrices formulated with near-infrared selective pigments. Evidence underscores the roles of binder chemistry and surface texturing in resisting aging. Their benefits are strongly modulated by embankment slope and aspect, which govern short-wave radiation. Functional outcomes show systematic trade-offs: lower operating temperature can improve rutting resistance and moisture sealing, whereas skid resistance, adhesion, and optical retention depend on surface texture, freeze-thaw exposure, snowplowing abrasion, and de-icing chemicals. Based on these insights, we propose a cold-region evaluation framework and research priorities including standardized spectral sensing, predictive optical-aging models, coupled thermo-mechanical simulation, AI-enabled field assessment or material design, and context-specific life-cycle accounting. As this technology matures and its adoption scales, it is expected to enhance the whole-life service performance of cold-region road transport infrastructure while reducing life-cycle costs.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"344 ","pages":"Article 140104"},"PeriodicalIF":9.4,"publicationDate":"2026-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146090388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-31DOI: 10.1016/j.energy.2026.140248
Linhong Chen , Siyuan Fan , Mingyue He , Shixian Ji , Shengxian Cao , Tianyi Sun , Yanhui Zhang , Yangwu Shen
The lack of high-quality image datasets with quantifiable labels hinders the development of deep learning models for photovoltaic (PV) panel dust detection. To address this, this paper proposes a novel physical consistency modeling approach to generate a large-scale synthetic dataset with precise dust concentration labels. A particle cluster generation model is developed to simulate multiscale, heterogeneous dust aggregation governed by lognormal distributions, while an adaptive error feedback mechanism ensures accurate concentration estimation. Furthermore, an optical attenuation model based on the Beer-Lambert law and nonlinear hue, saturation, and value (HSV) color mapping is employed to ensure visual realism. Multi-dimensional evaluations demonstrate that the synthetic images achieve a histogram similarity exceeding 0.86, an entropy similarity above 0.94, and a comprehensive similarity score over 0.82 compared to real-world ground truth. These results significantly outperform conventional mask-based and generative adversarial networks (GANs) techniques, providing a reliable data source for training advanced dust detection algorithms.
{"title":"A multi-scale photovoltaic (PV) panel dust accumulation simulation dataset based on physical consistency modeling","authors":"Linhong Chen , Siyuan Fan , Mingyue He , Shixian Ji , Shengxian Cao , Tianyi Sun , Yanhui Zhang , Yangwu Shen","doi":"10.1016/j.energy.2026.140248","DOIUrl":"10.1016/j.energy.2026.140248","url":null,"abstract":"<div><div>The lack of high-quality image datasets with quantifiable labels hinders the development of deep learning models for photovoltaic (PV) panel dust detection. To address this, this paper proposes a novel physical consistency modeling approach to generate a large-scale synthetic dataset with precise dust concentration labels. A particle cluster generation model is developed to simulate multiscale, heterogeneous dust aggregation governed by lognormal distributions, while an adaptive error feedback mechanism ensures accurate concentration estimation. Furthermore, an optical attenuation model based on the Beer-Lambert law and nonlinear hue, saturation, and value (HSV) color mapping is employed to ensure visual realism. Multi-dimensional evaluations demonstrate that the synthetic images achieve a histogram similarity exceeding 0.86, an entropy similarity above 0.94, and a comprehensive similarity score over 0.82 compared to real-world ground truth. These results significantly outperform conventional mask-based and generative adversarial networks (GANs) techniques, providing a reliable data source for training advanced dust detection algorithms.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"347 ","pages":"Article 140248"},"PeriodicalIF":9.4,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187720","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-31DOI: 10.1016/j.energy.2026.140275
Xiaoming Chen , Gui Cheng , Quan Zhang
A novel micro channel separated heat pipe system coupled with radiative sky cooling is proposed to reduce the cooling energy consumption in data centers. The system can operate in two modes, including the conventional heat pipe mode and the coupled heat pipe mode with radiative sky cooling. Two prototype systems with different structures of radiative cooling heat exchanger (RCHE) were designed, built and experimentally tested. The surface of RCHE is pained with a spectrally selective absorbing material, which has a low absorptivity in the solar irradiation band and a high emissivity in the atmospheric window band. The temperatures of air and refrigerant along with the refrigerant pressure were measured. The subcooling degree, cooling capacity and energy efficiency ratio (EER) were calculated and analyzed. Experimental results indicate that compared to the conventional system, refrigerant can be cooled further in the coupled system due to the assistant cooling by the RCHE through radiating heat to the cold outer space, with a higher subcooling degree at the inlet of evaporator by 0.4 °C on average. Moreover, the coupled system had 18.91% more cooling capacity and higher EER. Then, the performances of the coupled system with different structures of RCHE were compared. It was observed that 10.7% more cooling capacity and higher EER were obtained by the coil tube structure coupled system over the parallel tube structure coupled system.
{"title":"Experimental study on thermal performance of a novel micro channel separated heat pipe system coupled with radiative sky cooling","authors":"Xiaoming Chen , Gui Cheng , Quan Zhang","doi":"10.1016/j.energy.2026.140275","DOIUrl":"10.1016/j.energy.2026.140275","url":null,"abstract":"<div><div>A novel micro channel separated heat pipe system coupled with radiative sky cooling is proposed to reduce the cooling energy consumption in data centers. The system can operate in two modes, including the conventional heat pipe mode and the coupled heat pipe mode with radiative sky cooling. Two prototype systems with different structures of radiative cooling heat exchanger (RCHE) were designed, built and experimentally tested. The surface of RCHE is pained with a spectrally selective absorbing material, which has a low absorptivity in the solar irradiation band and a high emissivity in the atmospheric window band. The temperatures of air and refrigerant along with the refrigerant pressure were measured. The subcooling degree, cooling capacity and energy efficiency ratio (EER) were calculated and analyzed. Experimental results indicate that compared to the conventional system, refrigerant can be cooled further in the coupled system due to the assistant cooling by the RCHE through radiating heat to the cold outer space, with a higher subcooling degree at the inlet of evaporator by 0.4 °C on average. Moreover, the coupled system had 18.91% more cooling capacity and higher EER. Then, the performances of the coupled system with different structures of RCHE were compared. It was observed that 10.7% more cooling capacity and higher EER were obtained by the coil tube structure coupled system over the parallel tube structure coupled system.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"346 ","pages":"Article 140275"},"PeriodicalIF":9.4,"publicationDate":"2026-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146098547","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-30DOI: 10.1016/j.energy.2026.140258
Jingchao Xie , Junlong Li , Haotian Huang , Guangkai Zhang , Jiaping Liu
Under extreme hot-humid climatic conditions, the regeneration efficiency of liquid desiccant air conditioning systems significantly decreases due to insufficient vapor pressure difference. Although internal heating regeneration has emerged as a promising solution, comprehensive understanding of its thermal contribution mechanism and energy matching principle remains limited. This study developed a microchannel-corrugated fin internal heating regenerator (MF-IHR) and systematically investigated its regeneration performance from the perspective of thermal contribution. Experimental results demonstrate that the MF-IHR enhances the solution moisture removal rate by up to 72.0% compared to adiabatic operation. Thermal contribution analysis reveals that as the temperature of hot water rises, the heating power ratio of water (HPRW) increases from 33.3% to 87.5%, the heat loss power ratio of solution (HLPRS) decreases from 66.7% to 12.5%, and the regeneration efficiency drops from 58.8% to 26.4%. Under extreme environmental conditions, air humidity dominates thermal contribution distribution, with HPRW increasing from 62.1% to 87.2% as humidity rises from 18.3 g/kg to 26.7 g/kg. These findings demonstrate that balancing thermal contributions, rather than maximizing heat input, is key to optimizing regeneration performance. This study provides valuable insights for achieving efficient liquid desiccant regeneration in extreme hot-humid climates.
{"title":"Thermal contribution-driven energy matching for internal heating regeneration in microchannel-corrugated fin regenerators under extreme hot-humid climate","authors":"Jingchao Xie , Junlong Li , Haotian Huang , Guangkai Zhang , Jiaping Liu","doi":"10.1016/j.energy.2026.140258","DOIUrl":"10.1016/j.energy.2026.140258","url":null,"abstract":"<div><div>Under extreme hot-humid climatic conditions, the regeneration efficiency of liquid desiccant air conditioning systems significantly decreases due to insufficient vapor pressure difference. Although internal heating regeneration has emerged as a promising solution, comprehensive understanding of its thermal contribution mechanism and energy matching principle remains limited. This study developed a microchannel-corrugated fin internal heating regenerator (MF-IHR) and systematically investigated its regeneration performance from the perspective of thermal contribution. Experimental results demonstrate that the MF-IHR enhances the solution moisture removal rate by up to 72.0% compared to adiabatic operation. Thermal contribution analysis reveals that as the temperature of hot water rises, the heating power ratio of water (<em>HPRW</em>) increases from 33.3% to 87.5%, the heat loss power ratio of solution (<em>HLPRS</em>) decreases from 66.7% to 12.5%, and the regeneration efficiency drops from 58.8% to 26.4%. Under extreme environmental conditions, air humidity dominates thermal contribution distribution, with <em>HPRW</em> increasing from 62.1% to 87.2% as humidity rises from 18.3 g/kg to 26.7 g/kg. These findings demonstrate that balancing thermal contributions, rather than maximizing heat input, is key to optimizing regeneration performance. This study provides valuable insights for achieving efficient liquid desiccant regeneration in extreme hot-humid climates.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"347 ","pages":"Article 140258"},"PeriodicalIF":9.4,"publicationDate":"2026-01-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146187285","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.energy.2026.140247
Xianli Li , Fei Zhao , Yi Xu , WenQiang Liu , Haoran Dai , Ru Chang
This paper introduces a double-layer anti-reflective coating composed of ethylene propylene fluoride (FEP) and alumina (Al2O3), capitalizing on the superior optical and chemical properties of FEP, including its low refractive index, exceptional chemical inertness, and weatherability. This structure possesses ideal characteristics for serving as the functional surface of photovoltaic modules, which are fabricated sequentially via magnetron sputtering followed by ultrasonic spray deposition. In the coating structure design, with optoelectronic synergy as the guiding principle, electrical requirements are proactively incorporated upfront into the optimization of coating parameters. By combining the equivalent interface theory with the quarter-wavelength principle, the simplex optimization algorithm is utilized. Experimental validated optical model by TFCalc confirms that this coating structure achieves a weighted average reflectance of merely 1.26 % within the 400–1100 nm spectral range. The design enables the reflectance to consistently maintain below 1.1 % across the incident angle of 0°–55°. The thickness of coating with low refractive index exhibits greater effects to reflectance, especially for the double-layer structure with a 157 % fluctuation. An electrical model developed by PC1D software employing dual-diode model demonstrates a significant enhancement in photovoltaic conversion efficiency compared to uncoated glass. Furthermore, a comprehensive year-round simulation model has been established to integrate inclined-surface irradiation, energy yield, economic analysis, and carbon emission assessment. Model projection reveals that, the FEP/Al2O3 structure achieves annual energy yield gain of 2431.85 kWh and carbon emission reduction of 1510.18 kg relative to uncoated system.
{"title":"Optical-electrical synergistic optimization of FEP/Al2O3 anti-reflective coating for solar cells","authors":"Xianli Li , Fei Zhao , Yi Xu , WenQiang Liu , Haoran Dai , Ru Chang","doi":"10.1016/j.energy.2026.140247","DOIUrl":"10.1016/j.energy.2026.140247","url":null,"abstract":"<div><div>This paper introduces a double-layer anti-reflective coating composed of ethylene propylene fluoride (FEP) and alumina (Al<sub>2</sub>O<sub>3</sub>), capitalizing on the superior optical and chemical properties of FEP, including its low refractive index, exceptional chemical inertness, and weatherability. This structure possesses ideal characteristics for serving as the functional surface of photovoltaic modules, which are fabricated sequentially via magnetron sputtering followed by ultrasonic spray deposition. In the coating structure design, with optoelectronic synergy as the guiding principle, electrical requirements are proactively incorporated upfront into the optimization of coating parameters. By combining the equivalent interface theory with the quarter-wavelength principle, the simplex optimization algorithm is utilized. Experimental validated optical model by TFCalc confirms that this coating structure achieves a weighted average reflectance of merely 1.26 % within the 400–1100 nm spectral range. The design enables the reflectance to consistently maintain below 1.1 % across the incident angle of 0°–55°. The thickness of coating with low refractive index exhibits greater effects to reflectance, especially for the double-layer structure with a 157 % fluctuation. An electrical model developed by PC1D software employing dual-diode model demonstrates a significant enhancement in photovoltaic conversion efficiency compared to uncoated glass. Furthermore, a comprehensive year-round simulation model has been established to integrate inclined-surface irradiation, energy yield, economic analysis, and carbon emission assessment. Model projection reveals that, the FEP/Al<sub>2</sub>O<sub>3</sub> structure achieves annual energy yield gain of 2431.85 kWh and carbon emission reduction of 1510.18 kg relative to uncoated system.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"345 ","pages":"Article 140247"},"PeriodicalIF":9.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146076515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.energy.2026.140178
Juhani Kotilainen, Henrik Tolvanen
Integrating data centers into district heating systems is on the rise, due to the low cost of the waste heat, and energy efficiency targets for both data center and district heating companies. This study presents a novel method for data center placement using multiobjective optimization with thermohydraulic models. A 1.5 MW data center producing 75 °C waste heat was simulated across the entire distribution lines of existing district heating systems at a 100 m interval. Location suitability index was formed to compare each location based on three performance indicators: total production costs, average and maximum supply temperature reductions for customers. The objective was to determine the data center waste heat utilization potential based on how the waste heat mixes into other high temperature production in each specific location. The results show that the data center placement has a major impact on the waste heat utilization potential and overall profitability. The best locations near other production plants had a utilization potential of 93–99 % compared to full power potential, while the worst locations near demand had less than 60 %. The yearly production cost reduction was up to 5 % at Valkeakoski and 12 % at Kangasala, with a waste heat price of 10€/MWh.
{"title":"Novel method for data center placement using multiobjective optimization with thermohydraulic models of existing district heating systems","authors":"Juhani Kotilainen, Henrik Tolvanen","doi":"10.1016/j.energy.2026.140178","DOIUrl":"10.1016/j.energy.2026.140178","url":null,"abstract":"<div><div>Integrating data centers into district heating systems is on the rise, due to the low cost of the waste heat, and energy efficiency targets for both data center and district heating companies. This study presents a novel method for data center placement using multiobjective optimization with thermohydraulic models. A 1.5 MW data center producing 75 °C waste heat was simulated across the entire distribution lines of existing district heating systems at a 100 m interval. Location suitability index <span><math><mrow><mo>(</mo><mrow><mi>L</mi><mi>S</mi><mi>I</mi></mrow><mo>)</mo></mrow></math></span> was formed to compare each location based on three performance indicators: total production costs, average and maximum supply temperature reductions for customers. The objective was to determine the data center waste heat utilization potential based on how the waste heat mixes into other high temperature production in each specific location. The results show that the data center placement has a major impact on the waste heat utilization potential and overall profitability. The best locations near other production plants had a utilization potential of 93–99 % compared to full power potential, while the worst locations near demand had less than 60 %. The yearly production cost reduction was up to 5 % at Valkeakoski and 12 % at Kangasala, with a waste heat price of 10€/MWh.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"345 ","pages":"Article 140178"},"PeriodicalIF":9.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146076514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.energy.2026.140230
Lanxin Wang , Biao Yuan , Decang Lou , Yusen Wang , Chuanjun Tang , Wei Chen
Aircraft engine exhaust nozzles are subjected to extreme thermal loads from high-temperature gases. To improve thermal management and meet onboard power requirements, this study proposes a reheat-regenerative closed Brayton cycle system using a helium-xenon mixture. A nozzle-based generalized heat source model is developed to analyze the system's flow and heat transfer characteristics. Parametric studies reveal that the compressor pressure ratio and heat source geometry significantly impact efficiency. The optimal pressure ratio ranges from 2.5 to 3.5; lower ratios limit turbine output, while higher ratios increase compressor power consumption. Regarding geometry, optimizing the length of the dual heat sources regulates the turbine inlet temperature. Furthermore, channel diameters between 0.023 m and 0.032 m are found to balance flow losses and heat transfer performance. Multi-objective optimization indicates that Heat Source-I parameters remain stable, whereas Heat Source-II varies due to coupling effects. The final design, selected using the TOPSIS method, achieves a thermal efficiency of 32.80 %, a power output of 376.34 kW, and a power-to-weight ratio of 0.387 kW/kg.
{"title":"Performance analysis and multi-objective optimization of a reheat-regenerative closed Brayton cycle for aircraft-engine waste heat recovery","authors":"Lanxin Wang , Biao Yuan , Decang Lou , Yusen Wang , Chuanjun Tang , Wei Chen","doi":"10.1016/j.energy.2026.140230","DOIUrl":"10.1016/j.energy.2026.140230","url":null,"abstract":"<div><div>Aircraft engine exhaust nozzles are subjected to extreme thermal loads from high-temperature gases. To improve thermal management and meet onboard power requirements, this study proposes a reheat-regenerative closed Brayton cycle system using a helium-xenon mixture. A nozzle-based generalized heat source model is developed to analyze the system's flow and heat transfer characteristics. Parametric studies reveal that the compressor pressure ratio and heat source geometry significantly impact efficiency. The optimal pressure ratio ranges from 2.5 to 3.5; lower ratios limit turbine output, while higher ratios increase compressor power consumption. Regarding geometry, optimizing the length of the dual heat sources regulates the turbine inlet temperature. Furthermore, channel diameters between 0.023 m and 0.032 m are found to balance flow losses and heat transfer performance. Multi-objective optimization indicates that Heat Source-I parameters remain stable, whereas Heat Source-II varies due to coupling effects. The final design, selected using the TOPSIS method, achieves a thermal efficiency of 32.80 %, a power output of 376.34 kW, and a power-to-weight ratio of 0.387 kW/kg.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"345 ","pages":"Article 140230"},"PeriodicalIF":9.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146076585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-29DOI: 10.1016/j.energy.2026.140255
Chao Zeng , Haixia Cao , Yang Feng , Xiaoshu Lü , Fariborz Haghighat , Yanping Yuan
Rapid urbanization and expanding rail networks drive surging energy demands, necessitating efficiency research. When extreme heatwaves coincide with peak passenger periods, metro station air conditioning systems suffer from severe load fluctuations and performance degradation. Current research on chiller efficiency focuses primarily on standard operating conditions, often overlooking dynamic performance under extreme heat. Furthermore, a lack of high-temperature datasets restricts the adaptability and accuracy of existing predictive models. In response, this study proposes an integrated framework encompassing performance prediction, high-temperature performance degradation warning and operational optimization. To precisely predict COP, energy consumption (E), and degradation rate (η), a multi-output prediction model called N-BEATS-XGBoost is created by integrating gradient boosted trees with deep temporal feature extraction. By combining temporal feature extraction from N-BEATS with gradient boosting from XGBoost, the model achieves high predictive accuracy, with values of 98.5 %, 99.1 %, and 99.1 %, and SMAPE values of 1.56 %, 1.93 %, and 1.47 % for COP, , and , respectively. The increasing frequency and intensity of high-temperature events necessitate optimized system operation under such conditions. Criteria distinguishing functional failure from performance degradation were established, and an IQR-based method identified a degradation-rate warning threshold of 39.8 %, effectively demarcating normal operation from potential degradation. An NSGA-II-based dual-objective optimization framework was applied to historical high-temperature data, targeting energy consumption () and degradation rate (). The results indicate reductions of 3.64 % in and 10.06 % in , demonstrating substantial potential for performance improvement under extreme heat. These findings address a critical challenge at the nexus of climate resilience and energy efficiency.
{"title":"Performance forecasting and optimization for metro station chilled water systems under extreme heat based on field data analysis","authors":"Chao Zeng , Haixia Cao , Yang Feng , Xiaoshu Lü , Fariborz Haghighat , Yanping Yuan","doi":"10.1016/j.energy.2026.140255","DOIUrl":"10.1016/j.energy.2026.140255","url":null,"abstract":"<div><div>Rapid urbanization and expanding rail networks drive surging energy demands, necessitating efficiency research. When extreme heatwaves coincide with peak passenger periods, metro station air conditioning systems suffer from severe load fluctuations and performance degradation. Current research on chiller efficiency focuses primarily on standard operating conditions, often overlooking dynamic performance under extreme heat. Furthermore, a lack of high-temperature datasets restricts the adaptability and accuracy of existing predictive models. In response, this study proposes an integrated framework encompassing performance prediction, high-temperature performance degradation warning and operational optimization. To precisely predict COP, energy consumption (E), and degradation rate (η), a multi-output prediction model called N-BEATS-XGBoost is created by integrating gradient boosted trees with deep temporal feature extraction. By combining temporal feature extraction from N-BEATS with gradient boosting from XGBoost, the model achieves high predictive accuracy, with <span><math><mrow><msup><mi>R</mi><mn>2</mn></msup></mrow></math></span> values of 98.5 %, 99.1 %, and 99.1 %, and SMAPE values of 1.56 %, 1.93 %, and 1.47 % for COP, <span><math><mrow><mi>E</mi></mrow></math></span>, and <span><math><mrow><mi>η</mi></mrow></math></span>, respectively. The increasing frequency and intensity of high-temperature events necessitate optimized system operation under such conditions. Criteria distinguishing functional failure from performance degradation were established, and an IQR-based method identified a degradation-rate warning threshold of 39.8 %, effectively demarcating normal operation from potential degradation. An NSGA-II-based dual-objective optimization framework was applied to historical high-temperature data, targeting energy consumption (<span><math><mrow><mi>E</mi></mrow></math></span>) and degradation rate (<span><math><mrow><mi>η</mi></mrow></math></span>). The results indicate reductions of 3.64 % in <span><math><mrow><mi>E</mi></mrow></math></span> and 10.06 % in <span><math><mrow><mi>η</mi></mrow></math></span>, demonstrating substantial potential for performance improvement under extreme heat. These findings address a critical challenge at the nexus of climate resilience and energy efficiency.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"345 ","pages":"Article 140255"},"PeriodicalIF":9.4,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146076516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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