Pub Date : 2024-11-09DOI: 10.1016/j.energy.2024.133705
Linfei Yin, Yi Xiong
Deep reinforcement learning (DRL) has garnered growing attention as a data-driven control technique in the field of built environments. However, the existing DRL approaches for managing water systems cannot consider information from multiple time steps, are prone to overestimation, fall into the problem of locally optimal solutions, and fail to cope with time-varying environments, resulting in an inability to minimize energy consumption while considering water comfort and hygiene of occupants. Therefore, this study proposes an incremental learning user profile and deep reinforcement learning (ILUPDRL) method for controlling hot water systems. This study employs hot water user profiles to reflect the hot water demand (HWD) habits. The proposed ILUPDRL addresses the challenges arising from evolving HWD through incremental learning of hot water user profiles. Moreover, to enable the ILUPDRL to consider information from multiple time steps, this study proposes the recurrent proximal policy optimization (RPPO) algorithm and integrates the RPPO into the ILUPDRL. The simulation results show that the ILUPDRL achieves up to 67.53 % energy savings while considering the water comfort and water hygiene of occupants.
{"title":"Incremental learning user profile and deep reinforcement learning for managing building energy in heating water","authors":"Linfei Yin, Yi Xiong","doi":"10.1016/j.energy.2024.133705","DOIUrl":"10.1016/j.energy.2024.133705","url":null,"abstract":"<div><div>Deep reinforcement learning (DRL) has garnered growing attention as a data-driven control technique in the field of built environments. However, the existing DRL approaches for managing water systems cannot consider information from multiple time steps, are prone to overestimation, fall into the problem of locally optimal solutions, and fail to cope with time-varying environments, resulting in an inability to minimize energy consumption while considering water comfort and hygiene of occupants. Therefore, this study proposes an incremental learning user profile and deep reinforcement learning (ILUPDRL) method for controlling hot water systems. This study employs hot water user profiles to reflect the hot water demand (HWD) habits. The proposed ILUPDRL addresses the challenges arising from evolving HWD through incremental learning of hot water user profiles. Moreover, to enable the ILUPDRL to consider information from multiple time steps, this study proposes the recurrent proximal policy optimization (RPPO) algorithm and integrates the RPPO into the ILUPDRL. The simulation results show that the ILUPDRL achieves up to 67.53 % energy savings while considering the water comfort and water hygiene of occupants.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133705"},"PeriodicalIF":9.0,"publicationDate":"2024-11-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661539","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133744
Haiteng Xue , Gongda Wang , Xijian Li , Feng Du
In the experimental process of separating coal seam gas using the CO2 displacement method, establishing a predictive model for key variables is essential to optimize displacement parameters, increase coal seam gas recovery, and improve CO2 sequestration efficiency. Traditional modeling methods often struggle with the complex nature of industrial data and are susceptible to overfitting due to multicollinearity caused by long-term datasets. This paper presents a hybrid predictive model based on variational mode decomposition (VMD), a spatiotemporal attention mechanism (STA), a bidirectional long short-term memory network (BiLSTM), and an extreme learning machine (ELM). During the offline phase, VMD is used to decompose raw data into intrinsic mode functions (IMFs). The hidden state from the last time step of the STA-BiLSTM is then added to the original data to enrich the features for ELM training. In the online prediction phase, the outputs from the VMD-STA-BiLSTM and VMD-STA-BiLSTM-ELM models are combined using an error reciprocal method to generate the final prediction. The proposed model is validated with experimental datasets from CO2 displacement for coal seam CH4 under various conditions, as well as with N2-ECBM and CO2-ECBM engineering datasets. The results show that the hybrid model surpasses VMD-ELM, STA-BiLSTM-ELM, BiLSTM, STA-BiLSTM, ELM, TCN, and Attention-TCN models in predictive accuracy. Even in multi-step and rolling predictions, the model exhibits minimal impact from cumulative errors, maintaining accurate forecasts with strong generalization and robustness. It effectively captures feature patterns across different datasets and accurately predicts unknown data. The model shows potential for application in diverse scenarios and complex environments, offering reliable support and decision-making for the field application of CO2 displacement in coal seam CH4 separation. It is an effective and promising predictive approach to enhance coal seam gas recovery and CO2 sequestration efficiency.
{"title":"Predictive combination model for CH4 separation and CO2 sequestration with CO2 injection into coal seams: VMD-STA-BiLSTM-ELM hybrid neural network modeling","authors":"Haiteng Xue , Gongda Wang , Xijian Li , Feng Du","doi":"10.1016/j.energy.2024.133744","DOIUrl":"10.1016/j.energy.2024.133744","url":null,"abstract":"<div><div>In the experimental process of separating coal seam gas using the CO<sub>2</sub> displacement method, establishing a predictive model for key variables is essential to optimize displacement parameters, increase coal seam gas recovery, and improve CO<sub>2</sub> sequestration efficiency. Traditional modeling methods often struggle with the complex nature of industrial data and are susceptible to overfitting due to multicollinearity caused by long-term datasets. This paper presents a hybrid predictive model based on variational mode decomposition (VMD), a spatiotemporal attention mechanism (STA), a bidirectional long short-term memory network (BiLSTM), and an extreme learning machine (ELM). During the offline phase, VMD is used to decompose raw data into intrinsic mode functions (IMFs). The hidden state from the last time step of the STA-BiLSTM is then added to the original data to enrich the features for ELM training. In the online prediction phase, the outputs from the VMD-STA-BiLSTM and VMD-STA-BiLSTM-ELM models are combined using an error reciprocal method to generate the final prediction. The proposed model is validated with experimental datasets from CO<sub>2</sub> displacement for coal seam CH<sub>4</sub> under various conditions, as well as with N<sub>2</sub>-ECBM and CO<sub>2</sub>-ECBM engineering datasets. The results show that the hybrid model surpasses VMD-ELM, STA-BiLSTM-ELM, BiLSTM, STA-BiLSTM, ELM, TCN, and Attention-TCN models in predictive accuracy. Even in multi-step and rolling predictions, the model exhibits minimal impact from cumulative errors, maintaining accurate forecasts with strong generalization and robustness. It effectively captures feature patterns across different datasets and accurately predicts unknown data. The model shows potential for application in diverse scenarios and complex environments, offering reliable support and decision-making for the field application of CO<sub>2</sub> displacement in coal seam CH<sub>4</sub> separation. It is an effective and promising predictive approach to enhance coal seam gas recovery and CO<sub>2</sub> sequestration efficiency.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133744"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661542","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}
To advance the application of zero-carbon fuels in micro combustion, enhance energy conversion, and reduce NOx emissions in NH3/H2-fueled micro power generators, a micro-combustor with an inserted block is proposed and tested under various chamber configurations and operational conditions. Experimental and numerical tests are conducted in micro-combustors with varied block settings, burner dimensions, NH3 blended ratios (mN), and fuel flow rates (Vf). The results indicate that mN significantly impacts the generation and consumption of H, O, and OH radicals, as well as NO, affecting flame regime and heat transfer. Specifically, adding 5∼15 % NH3 improves the operating performance of the burner, with the highest mean temperature achieved in combustor #24C3-0.4 at mN = 15 %. Block insertion alters flame characteristics and enhances gas-wall heat transfer, and the combustor with thinner blocks at higher mN and thicker blocks at lower mN contributes to better thermal performance. Furthermore, combustors with thinner blocks exhibit lower NO emissions. The working performance of the micro-thermophotovoltaic system can be enhanced by selecting the appropriate burner length with block thickness W = 0.4 mm and position Lb = 7 mm based on Vf. The maximum electrical power of 3.7 W is achieved with a burner length of 28 mm for the system using InGaAsSb cells at Vf = 1200 mL/min.
{"title":"Experimental and numerical investigations on NH3/H2 fueled combustion in the combustor with block for improved micro power generation","authors":"Peng Teng, Qingguo Peng, Long Zhang, Ruixue Yin, Xinghua Tian, Hao Wang, Zhixin Huang","doi":"10.1016/j.energy.2024.133733","DOIUrl":"10.1016/j.energy.2024.133733","url":null,"abstract":"<div><div>To advance the application of zero-carbon fuels in micro combustion, enhance energy conversion, and reduce NO<sub>x</sub> emissions in NH<sub>3</sub>/H<sub>2</sub>-fueled micro power generators, a micro-combustor with an inserted block is proposed and tested under various chamber configurations and operational conditions. Experimental and numerical tests are conducted in micro-combustors with varied block settings, burner dimensions, NH<sub>3</sub> blended ratios (<em>m</em><sub>N</sub>), and fuel flow rates (<em>V</em><sub>f</sub>). The results indicate that <em>m</em><sub>N</sub> significantly impacts the generation and consumption of H, O, and OH radicals, as well as NO, affecting flame regime and heat transfer. Specifically, adding 5∼15 % NH<sub>3</sub> improves the operating performance of the burner, with the highest mean temperature achieved in combustor #24C3-0.4 at <em>m</em><sub>N</sub> = 15 %. Block insertion alters flame characteristics and enhances gas-wall heat transfer, and the combustor with thinner blocks at higher <em>m</em><sub>N</sub> and thicker blocks at lower <em>m</em><sub>N</sub> contributes to better thermal performance. Furthermore, combustors with thinner blocks exhibit lower NO emissions. The working performance of the micro-thermophotovoltaic system can be enhanced by selecting the appropriate burner length with block thickness <em>W</em> = 0.4 mm and position <em>L</em><sub>b</sub> = 7 mm based on <em>V</em><sub>f</sub>. The maximum electrical power of 3.7 W is achieved with a burner length of 28 mm for the system using InGaAsSb cells at <em>V</em><sub>f</sub> = 1200 mL/min.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133733"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661484","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133770
Wenyu Mo , Beichen Yu , Long Jiang , Kai Xu , Jun Xu , Yi Wang , Sheng Su , Song Hu , Jun Xiang
Biomass-to-liquid fuels technology offers a promising method for high-value biomass conversion, addressing environmental toxicity and fossil fuel non-renewability. However, challenges such as low system efficiency and identifying efficiency losses persist. In this study, a comprehensive process model of a low-carbon alcohols production system via biomass gasification was developed, based on the first demonstration project in China. The innovation of this study lies in its detailed experimental validation, as the model simulation was performed using laboratory data and verified with pilot-scale platform data ensuring high accuracy. Additionally, the study conducted a thorough sensitivity analysis of system parameters, energy, and exergy assessments to find the proper operating conditions, including equivalent ratio, biomass type, and reactor temperature and pressure. The simulation results demonstrated an energy efficiency of 34.67 % and an exergy efficiency of 31.24 %. Through operating parameters and heat recovery measures, these efficiencies increased by 11.66 % and 8 %, respectively. This research not only obtains improved operating parameters for the pilot-scale platform but also provides actionable insights for enhancing the yields of target products and upgrading low-grade energy utilization. These findings offer valuable guidance for the commercialization of bio-syngas alcohols production systems, highlighting significant advancements in efficiency and system performance.
{"title":"Process simulation, thermodynamic and system optimization for the low-carbon alcohols production via gasification of second-generation biomass","authors":"Wenyu Mo , Beichen Yu , Long Jiang , Kai Xu , Jun Xu , Yi Wang , Sheng Su , Song Hu , Jun Xiang","doi":"10.1016/j.energy.2024.133770","DOIUrl":"10.1016/j.energy.2024.133770","url":null,"abstract":"<div><div>Biomass-to-liquid fuels technology offers a promising method for high-value biomass conversion, addressing environmental toxicity and fossil fuel non-renewability. However, challenges such as low system efficiency and identifying efficiency losses persist. In this study, a comprehensive process model of a low-carbon alcohols production system via biomass gasification was developed, based on the first demonstration project in China. The innovation of this study lies in its detailed experimental validation, as the model simulation was performed using laboratory data and verified with pilot-scale platform data ensuring high accuracy. Additionally, the study conducted a thorough sensitivity analysis of system parameters, energy, and exergy assessments to find the proper operating conditions, including equivalent ratio, biomass type, and reactor temperature and pressure. The simulation results demonstrated an energy efficiency of 34.67 % and an exergy efficiency of 31.24 %. Through operating parameters and heat recovery measures, these efficiencies increased by 11.66 % and 8 %, respectively. This research not only obtains improved operating parameters for the pilot-scale platform but also provides actionable insights for enhancing the yields of target products and upgrading low-grade energy utilization. These findings offer valuable guidance for the commercialization of bio-syngas alcohols production systems, highlighting significant advancements in efficiency and system performance.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133770"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661537","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133742
Subha Mondal , Sudipta De
Combined flash binary geothermal cycle (CFBGC) is an efficient geothermal energy conversion technology. Natural gas (NG) is a preferred fuel in the current energy scenario. LNG gasification is a needed step for delivering NG among the end users. In the present study, a self-superheated single-flash geothermal steam cycle, a transcritical CO2 power cycle and an LNG gasification unit are integrated into a CFBGC. This study shows that the LNG gasification rate and power output can be increased simultaneously by increasing the steam turbine inlet pressure. At a higher steam turbine inlet pressure, desirable steam quality (i.e., 0.9) at the steam turbine exit is maintained by implementing self superheating of the steam. It is observed that 15 °C DSH of steam enables the CFBGC to operate at a steam turbine inlet pressure that substantially enhances the output power without a noticeable increase in levelized electricity cost (LEC). The CFBGC operating at this condition yields 9.97 % higher power output compared to that of the CFBGC operating at steam turbine inlet pressure requiring no DSH of steam. As a geothermal-based power plant emits very low CO2, the proposed energy system may emerge as a future sustainable energy option.
{"title":"Self-superheated combined flash binary geothermal cycle using transcritical-CO2 power cycle with LNG heat sink as the secondary cycle","authors":"Subha Mondal , Sudipta De","doi":"10.1016/j.energy.2024.133742","DOIUrl":"10.1016/j.energy.2024.133742","url":null,"abstract":"<div><div>Combined flash binary geothermal cycle (CFBGC) is an efficient geothermal energy conversion technology. Natural gas (NG) is a preferred fuel in the current energy scenario. LNG gasification is a needed step for delivering NG among the end users. In the present study, a self-superheated single-flash geothermal steam cycle, a transcritical CO<sub>2</sub> power cycle and an LNG gasification unit are integrated into a CFBGC. This study shows that the LNG gasification rate and power output can be increased simultaneously by increasing the steam turbine inlet pressure. At a higher steam turbine inlet pressure, desirable steam quality (i.e., 0.9) at the steam turbine exit is maintained by implementing self superheating of the steam. It is observed that 15 °C DSH of steam enables the CFBGC to operate at a steam turbine inlet pressure that substantially enhances the output power without a noticeable increase in levelized electricity cost (LEC). The CFBGC operating at this condition yields 9.97 % higher power output compared to that of the CFBGC operating at steam turbine inlet pressure requiring no DSH of steam. As a geothermal-based power plant emits very low CO<sub>2</sub>, the proposed energy system may emerge as a future sustainable energy option.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133742"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661535","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133735
Jianshu Yu, Pei Yong, Juan Yu, Zhifang Yang
With the high penetration of wind turbines, the necessity of incorporating frequency security considerations into power system scheduling rises. Existing methods achieve the explicit modeling of frequency security constraints by simplifying the frequency response behavior of wind turbines. However, simplifications might lead to inaccuracy. To address this issue, this paper models the frequency response from wind turbines in detail and proposes a novel framework to construct the frequency security constraint for unit commitment (UC). First, the frequency security constraint is positioned at the segment that is effective for the dispatch decision instead of the whole boundary, which is unnecessary and complicated. Then, an analytical linear surrogate expression of the frequency security boundary is constructed through a data-driven approach. To ensure the accuracy of the surrogate constraint, a neighborhood sampling strategy is proposed to collect balanced samples. Furthermore, to reduce the linearization error of the surrogate constraints, supplementary constraints are added to restrict the width of the surrogate constraint. Finally, to address the modeling errors that may deviate from the frequency security requirements, a correction strategy is proposed. Case studies validate the proposed method and verify that it exceeds existing methods in the modeling accuracy of the power system frequency security.
{"title":"Frequency security constraint in unit commitment with detailed frequency response behavior of wind turbines","authors":"Jianshu Yu, Pei Yong, Juan Yu, Zhifang Yang","doi":"10.1016/j.energy.2024.133735","DOIUrl":"10.1016/j.energy.2024.133735","url":null,"abstract":"<div><div>With the high penetration of wind turbines, the necessity of incorporating frequency security considerations into power system scheduling rises. Existing methods achieve the explicit modeling of frequency security constraints by simplifying the frequency response behavior of wind turbines. However, simplifications might lead to inaccuracy. To address this issue, this paper models the frequency response from wind turbines in detail and proposes a novel framework to construct the frequency security constraint for unit commitment (UC). First, the frequency security constraint is positioned at the segment that is effective for the dispatch decision instead of the whole boundary, which is unnecessary and complicated. Then, an analytical linear surrogate expression of the frequency security boundary is constructed through a data-driven approach. To ensure the accuracy of the surrogate constraint, a neighborhood sampling strategy is proposed to collect balanced samples. Furthermore, to reduce the linearization error of the surrogate constraints, supplementary constraints are added to restrict the width of the surrogate constraint. Finally, to address the modeling errors that may deviate from the frequency security requirements, a correction strategy is proposed. Case studies validate the proposed method and verify that it exceeds existing methods in the modeling accuracy of the power system frequency security.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133735"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661428","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133766
Emad M.S. El-Said
The pipe layout design has a great effect on the thermal-hydraulic characteristics of earth air heat exchanger (EAHE) systems. So, in the current study proposed four new buried pipe design configurations; low to high to low, high to low to high, spiral, and circular, in addition to the straight or uniform for comparison. These five configurations are tested and analyzed experimentally depending on the thermo-hydraulic performance for summer cooling requirements with variation of Re in the range of 18041–40843. The results show that changing the uniform design of the EAHE with fixed pipe length enhances both the heat transfer process and pressure loss values. At the same operating conditions, the circular design has the best performance compared to the other ones. For all pipe shapes, the cooling effect increases with the increase of air Re. The thermal-hydraulic performance of the circular design pipe is higher than that of the other pipe designs. The highest coefficient of performance (COP) average values that can be obtained at Re = 18041 is 3.05 for circular shape and enhances by 48.08 % compared to uniform shape. The effectiveness of EAHE with circular shape is improved by about 3.52 % compared to uniform shape at Re = 18041. Spiral design is optimum design based on the Nu value which reaches about 48 with enhancement 12.56 % and 0.34 % compared to uniform and circular shapes respectively, at Re = 40843. The hydrothermal performance factor is highest in the case of circular shape with value about 21.9 at Re = 21257. By increasing Re, the drawbacks of the increasing in the total entropy generation are reflected negatively on the exergy efficiency. The specific cost of the circular shape at Re = 40843 is the optimum value by about 0.7 $/W. Spiral and circular shapes have a decrease of CO2 emissions less than uniform shape by percentage varied from 2.93 % to 13.84 % for decrease in the Re from 21257 to 40843. It is concluded that using EAHE with four new shapes is highly efficient in increasing cooling capacity and energy consumption in buildings.
管道布局设计对土风换热器(EAHE)系统的热工水力特性有很大影响。因此,本研究提出了四种新的地埋管设计配置:低到高到低、高到低到高、螺旋和圆形,此外还有直管或均匀管供比较。根据夏季制冷要求的热工水力性能,对这五种配置进行了实验测试和分析,Re 变化范围为 18041-40843 。结果表明,改变管道长度固定的 EAHE 的均匀设计可提高传热过程和压力损失值。在相同的运行条件下,圆形设计与其他设计相比性能最佳。对于所有形状的管道,冷却效果都随着空气 Re 的增加而增加。圆形设计管道的热液压性能高于其他管道设计。在 Re = 18041 时,圆形管道的最高性能系数(COP)平均值为 3.05,比均匀形状的管道提高了 48.08%。在 Re = 18041 时,圆形 EAHE 的效率比均匀形状提高了约 3.52%。在 Re = 40843 条件下,根据 Nu 值,螺旋形设计是最佳设计,其 Nu 值约为 48,与均匀形和圆形相比,分别提高了 12.56 % 和 0.34 %。在 Re = 21257 时,圆形的水热性能系数最高,约为 21.9。随着 Re 值的增加,总熵产生量增加的缺点会对放热效率产生负面影响。在 Re = 40843 时,圆形的具体成本是最佳值,约为 0.7 美元/瓦。当 Re 值从 21257 降至 40843 时,螺旋形和圆形比均匀形的二氧化碳排放量减少了 2.93 % 至 13.84 %。由此得出结论,使用四种新形状的 EAHE 能够高效地提高建筑物的制冷能力和能耗。
{"title":"Thermal-hydraulic characteristics of an earth air heat exchanger: An experimental analysis","authors":"Emad M.S. El-Said","doi":"10.1016/j.energy.2024.133766","DOIUrl":"10.1016/j.energy.2024.133766","url":null,"abstract":"<div><div>The pipe layout design has a great effect on the thermal-hydraulic characteristics of earth air heat exchanger (EAHE) systems. So, in the current study proposed four new buried pipe design configurations; low to high to low, high to low to high, spiral, and circular, in addition to the straight or uniform for comparison. These five configurations are tested and analyzed experimentally depending on the thermo-hydraulic performance for summer cooling requirements with variation of Re in the range of 18041–40843. The results show that changing the uniform design of the EAHE with fixed pipe length enhances both the heat transfer process and pressure loss values. At the same operating conditions, the circular design has the best performance compared to the other ones. For all pipe shapes, the cooling effect increases with the increase of air <em>Re</em>. The thermal-hydraulic performance of the circular design pipe is higher than that of the other pipe designs. The highest coefficient of performance (COP) average values that can be obtained at Re = 18041 is 3.05 for circular shape and enhances by 48.08 % compared to uniform shape. The effectiveness of EAHE with circular shape is improved by about 3.52 % compared to uniform shape at Re = 18041. Spiral design is optimum design based on the <em>Nu</em> value which reaches about 48 with enhancement 12.56 % and 0.34 % compared to uniform and circular shapes respectively, at Re = 40843. The hydrothermal performance factor is highest in the case of circular shape with value about 21.9 at Re = 21257. By increasing <em>Re</em>, the drawbacks of the increasing in the total entropy generation are reflected negatively on the exergy efficiency. The specific cost of the circular shape at Re = 40843 is the optimum value by about 0.7 $/W. Spiral and circular shapes have a decrease of CO<sub>2</sub> emissions less than uniform shape by percentage varied from 2.93 % to 13.84 % for decrease in the Re from 21257 to 40843. It is concluded that using EAHE with four new shapes is highly efficient in increasing cooling capacity and energy consumption in buildings.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133766"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661532","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133775
Zichan Xie , Haichao Wang , Pengmin Hua , Maximilian Björkstam , Risto Lahdelma
The computational complexity involved in modelling district heating (DH) networks impedes the integration of network operations into comprehensive DH system studies. We developed a flexible, accurate, and fast dynamic thermal simulation model utilising discrete event simulation (DES). This model is versatile, suitable for any tree-shaped DH network with a central heating plant and can estimate node temperatures and calculate pipe heat losses. The speed of the model is improved via using variable time steps and by incorporating two advanced techniques: lazy evaluation and a customised priority queue. To further improve the computational speed, we developed a technique to eliminate redundant sampling points. This model was tested and demonstrated excellent consistency with actual measurements. Remarkably, reducing sampling points can speed up the simulation by a factor of three without compromising the temperature accuracy. A 72-day simulation of a network with 102 pipes was completed within 0.219 s. Our findings highlight the significant potential of the DES model for large-scale dynamic network simulations and offer a promising solution for DH network simulations and system optimisation.
区域供热(DH)网络建模所涉及的计算复杂性阻碍了将网络运行纳入全面的 DH 系统研究。我们利用离散事件仿真(DES)开发了一种灵活、准确、快速的动态热仿真模型。该模型用途广泛,适用于任何带有集中供暖设备的树状 DH 网络,可估算节点温度并计算管道热损失。通过使用可变时间步长并结合两种先进技术:懒惰评估和定制优先队列,该模型的速度得到了提高。为了进一步提高计算速度,我们开发了一种消除冗余采样点的技术。经过测试,该模型与实际测量结果具有极佳的一致性。值得注意的是,在不影响温度精度的情况下,减少采样点可将模拟速度提高三倍。我们的研究结果凸显了 DES 模型在大规模动态网络模拟方面的巨大潜力,并为 DH 网络模拟和系统优化提供了一个前景广阔的解决方案。
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This study addresses the challenge of improving Global Tilted Irradiation (GTI) predictions, with Jordan serving as the case study. The novelty of the work lies in developing machine learning models that predict GTI at national, regional (3 regions), and city-specific (12 cities) levels, a previously unexplored approach in the literature. The research examines the comparative efficiency of using a single model for an entire country versus tailored models for individual regions and cities, shedding light on the trade-offs in model evaluation. Various regression models, including Neural Networks (NNs), Linear Regression (LR), Regression Trees (RTs), Ensemble of Regression Trees (ERTs), Support Vector Machine (SVM), and Kernel Approximation, were evaluated using performance metrics such as Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), and coefficient of determination (R2). NNs consistently performed best, achieving the lowest RMSE (1.5787 kWh/m2) and highest R2 (99.8600 %) at the regional level. Sensitivity analysis further explored the impact of different time resolutions, revealing that monthly data outperformed daily data in terms of accuracy and computational efficiency. Ultimately, we conclude that region-specific models and monthly data resolution are optimal for practical GTI prediction.
{"title":"A geographic multi-scale machine learning framework for predicting solar irradiation on tilted surfaces","authors":"Sameer Al-Dahidi , Bilal Rinchi , Raghad Dababseh , Osama Ayadi , Mohammad Alrbai","doi":"10.1016/j.energy.2024.133767","DOIUrl":"10.1016/j.energy.2024.133767","url":null,"abstract":"<div><div>This study addresses the challenge of improving Global Tilted Irradiation (GTI) predictions, with Jordan serving as the case study. The novelty of the work lies in developing machine learning models that predict GTI at national, regional (3 regions), and city-specific (12 cities) levels, a previously unexplored approach in the literature. The research examines the comparative efficiency of using a single model for an entire country versus tailored models for individual regions and cities, shedding light on the trade-offs in model evaluation. Various regression models, including Neural Networks (NNs), Linear Regression (LR), Regression Trees (RTs), Ensemble of Regression Trees (ERTs), Support Vector Machine (SVM), and Kernel Approximation, were evaluated using performance metrics such as Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), and coefficient of determination (R<sup>2</sup>). NNs consistently performed best, achieving the lowest RMSE (1.5787 kWh/m<sup>2</sup>) and highest R<sup>2</sup> (99.8600 %) at the regional level. Sensitivity analysis further explored the impact of different time resolutions, revealing that monthly data outperformed daily data in terms of accuracy and computational efficiency. Ultimately, we conclude that region-specific models and monthly data resolution are optimal for practical GTI prediction.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133767"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661606","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 : 2024-11-08DOI: 10.1016/j.energy.2024.133751
Mladen Josijevic, Vladimir Vukasinovic, Dusan Gordic, Vanja Sustersic, Dubravka Zivkovic, Jelena Nikolic
Utilizing waste heat that is rejected from thermal processes can greatly enhance the industry's energy balance. Identifying potential waste heat sources in the food and beverage processing industry and making estimations for their possible utilization can be an extremely challenging undertaking. To determine waste heat potentials in the food processing industry and to select an optimal technology for its utilization a novel systematic methodology based on the comprehensive energy audit and mathematical optimization has been developed. The developed mixed integer nonlinear programming model incorporates all novel and the most commonly employed technologies to utilize waste heat.
The developed systematic methodology is tested on a case study, of a milk and dairy production facility. Obtained results have shown that up to 53 % of the available waste heat can be used in the scenario of limited investment costs. Otherwise, in the scenario when investment costs are not set as a limitation, 75 % of waste heat can be used, according to plant demands. Harmonising production processes is necessary to use all the waste heat. The developed systematic methodology can be applied to any food processing industry and other facilities producing waste heat because it presents a universal approach.
{"title":"A systematic methodology for selecting optimal technology for waste heat utilization in food processing industry","authors":"Mladen Josijevic, Vladimir Vukasinovic, Dusan Gordic, Vanja Sustersic, Dubravka Zivkovic, Jelena Nikolic","doi":"10.1016/j.energy.2024.133751","DOIUrl":"10.1016/j.energy.2024.133751","url":null,"abstract":"<div><div>Utilizing waste heat that is rejected from thermal processes can greatly enhance the industry's energy balance. Identifying potential waste heat sources in the food and beverage processing industry and making estimations for their possible utilization can be an extremely challenging undertaking. To determine waste heat potentials in the food processing industry and to select an optimal technology for its utilization a novel systematic methodology based on the comprehensive energy audit and mathematical optimization has been developed. The developed mixed integer nonlinear programming model incorporates all novel and the most commonly employed technologies to utilize waste heat.</div><div>The developed systematic methodology is tested on a case study, of a milk and dairy production facility. Obtained results have shown that up to 53 % of the available waste heat can be used in the scenario of limited investment costs. Otherwise, in the scenario when investment costs are not set as a limitation, 75 % of waste heat can be used, according to plant demands. Harmonising production processes is necessary to use all the waste heat. The developed systematic methodology can be applied to any food processing industry and other facilities producing waste heat because it presents a universal approach.</div></div>","PeriodicalId":11647,"journal":{"name":"Energy","volume":"313 ","pages":"Article 133751"},"PeriodicalIF":9.0,"publicationDate":"2024-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142661608","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}