| 1. |
- Bai, Fan, et al.
(författare)
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Application of similarity theory in modeling the output characteristics of proton exchange membrane fuel cell
- 2021
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Ingår i: International journal of hydrogen energy. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0360-3199 .- 1879-3487. ; 46:74, s. 36940-36953
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Tidskriftsartikel (refereegranskat)abstract
- Proton Exchange Membrane Fuel Cell (PEMFC) has attracted widespread interest. In the present work, similarity analysis is adopted for a three-dimensional single-phase isothermal model of PEMFC to derive similarity criteria. Seven kinds of input criteria (Pi(1) similar to Pi(7)) are obtained, relevant to the fluid flow, pressure drop, flow resistance in a porous medium, activity loss, diffusion mass transfer, convective mass transfer and ohmic loss in PEMFC respectively. Dimensionless voltage and dimensionless current density are defined as two output criteria. Numerical verifications show that if the seven criteria keep their individual values with their components vary in a wide range, the dimensionless polarization curves keep the same with a deviation about 1%, showing the validity and feasibility of the present analysis. From the effect on the dimensionless polarization curve, sensibility analysis shows that the seven criteria can be divided into three categories: strong (Pi(4) and Pi(7), -94.9% similar to +349.2%), mild to minor (Pi(5) and Pi(6), -4.5% similar to +5.0%), and negligible (Pi(1), Pi(2) and Pi(3), -1.2% similar to +1.1%). The similarity analysis approach can greatly save computation time in modeling the output characteristics of PEMFC. (C) 2021 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.
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| 2. |
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| 3. |
- Wang, Fengjuan, et al.
(författare)
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Physical–cyber–human framework‐based resilience evaluation toward urban power system: Case study from China
- 2024
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Ingår i: Risk Analysis. - : Wiley. - 0272-4332 .- 1539-6924.
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Tidskriftsartikel (refereegranskat)abstract
- Because the increased frequency, intensity, and duration of extreme weather events have significantly challenged power systems, there has been an increased interest in resilient power systems. This article establishes a multicriteria resilience evaluation framework for urban power systems from a physical-cyber-human system perspective, in which the two principal elements responsible for power system function degradation are described, the three major domains comprising urban power systems are explained, four core capacities that positively contribute to power system resilience are proposed, and 15 (11 objective and four subjective) power system resilience evaluation indicators are identified. Fuzzy hesitant judgment and a Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) aggregation method are employed to minimize the expert divergence and maximize the group consensus. A validation method is designed and a comparison with commonly applied performance-based and attributes-based evaluation methods is conducted. The applicability of the evaluation framework is verified using data from four Chinese municipalities: Shanghai, Beijing, Chongqing, and Tianjin. It was found that Shanghai's resilience was the best, and Chongqing's physical resistance disadvantages would result in the greatest difficulties in coping with extreme event disturbances. Physical, cyber, and human domain resilience enhancement strategies are given for different cities separately. This study provides a practical tool to evaluate, compare, and enhance power system resilience for governments and public utilities.
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| 4. |
- Zhang, Haoran, et al.
(författare)
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Urban power load profiles under ageing transition integrated with future EVs charging
- 2021
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Ingår i: Advances in Applied Energy. - : Elsevier BV. - 2666-7924. ; 1, s. 100007-100007
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Tidskriftsartikel (refereegranskat)abstract
- Understanding ageing transition caused fine-grained changes of electricity profile is the significant insight for coping with future threatens in grid flexibility management. The research gaps for the hourly-basis knowledge exist due to challenges in microanalysis on user-side behavior. Based on billions of users’ behavior data, we investigated the changes on the load profiles due to population aging. We found that owing to ageing transition, the participation population in high electricity-density activities decreases by about 8%. The corresponding shift in driving behavior rises the 14% difference between peak charging load and valley. We concluded that population aging will dramatically change both the magnitude and shape of future dynamic-load profiles. Therefore, we further suggested a new solution with comprehensive and quantitative management for PVs development and the smart charging market with smooth operation of the grid in coupling the potential challenges caused by the ageing issue.
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| 5. |
- Chen, S., et al.
(författare)
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Advanced approaches and applications of energy footprints toward the promotion of global sustainability
- 2020
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 261
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Ever-increasing energy demands pose huge environmental challenges globally. The strategies and methods that are chosen to address the energy crisis will, in part, determine the possibility of fulfilling the 1.5-degree global warming target set by the Paris Agreement, and of achieving the United Nations Sustainable Developmental Goals, two vital and ambitious objectives for humans in the coming decades. While numerous inventory and modelling approaches have been developed to evaluate direct and indirect energy requirements at multiple scales from industries to cities and to the global economy, a discussion on their implications for environmental sustainability is long overdue. In this study, we provide an overview of the research paradigm and the important approaches that have been developed to address energy sustainability and review the papers included in this Special Issue, which are representative of some of the major advancements in energy, carbon, and other hybrid footprint approaches. This Special Issue aims to gather and harmonize state-of-the-art energy accounting frameworks, models, and metrics that benefit the promotion of global sustainability.
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| 6. |
- Chen, S., et al.
(författare)
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Operational flexibility of active distribution networks with the potential from data centers
- 2021
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Ingår i: Applied Energy. - : Elsevier Ltd. - 0306-2619 .- 1872-9118. ; 293
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Tidskriftsartikel (refereegranskat)abstract
- With the development of information technology, the scale and quantity of internet data centers (IDCs) are expanding rapidly. IDCs have emerged as the major electricity consumers in active distribution networks (ADNs), which dramatically increase the electricity load and have a significant impact on the operational flexibility of ADNs. Geographically distributed IDCs can participate in the operation of ADNs with the potential for spatio-temporal load regulation. This paper proposes flexible dispatch strategies of data centers to improve the operational flexibility of ADNs. First, a data-power model of IT equipment is proposed based on piecewise linearization to describe the power consumption characteristics of data centers. The flexible dispatch strategies for the delay-tolerant workload are further proposed from two aspects of temporal transfer and spatial allocation. Then, considering the potential for spatio-temporal load regulation, the operational flexibility analysis model with data centers is formulated to adapt to the operational requirements of ADNs in complex environments. Case studies show that through the spatio-temporal regulation of workload, the energy efficiency of IDCs can be effectively improved. The flexible dispatch of IDCs can also reduce the voltage violation and feeder load imbalance of ADNs, which can facilitate providing the high-quality power supply for IDCs.
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| 7. |
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| 8. |
- Chen, Y., et al.
(författare)
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Theory-guided hard constraint projection (HCP) : A knowledge-based data-driven scientific machine learning method
- 2021
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Ingår i: Journal of Computational Physics. - : Academic Press Inc.. - 0021-9991 .- 1090-2716. ; 445
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Tidskriftsartikel (refereegranskat)abstract
- Machine learning models have been successfully used in many scientific and engineering fields. However, it remains difficult for a model to simultaneously utilize domain knowledge and experimental observation data. The application of knowledge-based symbolic artificial intelligence (AI) represented by expert systems is limited by the expressive ability of the model, and data-driven connectionism AI represented by neural networks is prone to produce predictions that might violate physical principles. In order to fully integrate domain knowledge with observations and make full use of the strong fitting ability of neural networks, this study proposes theory-guided hard constraint projection (HCP). This deep learning model converts physical constraints, such as governing equations, into a form that is easy to handle through discretization, and then implements hard constraint optimization through projection in a patch. Based on rigorous mathematical proofs, theory-guided HCP can ensure that model predictions strictly conform to physical mechanisms in the constraint patch. The training process of theory-guided HCP only needs a small amount of labeled data (sparse observation), and it can supervise the model by combining the coordinates (label-free data) with domain knowledge. The performance of the theory-guided HCP is verified by experiments based on a published heterogeneous subsurface flow problem. The experiments show that theory-guided HCP requires fewer data, and achieves higher prediction accuracy and stronger robustness to noisy observations, than the fully connected neural networks and soft constraint models. Furthermore, due to the application of domain knowledge, theory-guided HCP possesses the ability to extrapolate and can accurately predict points outside of the range of the training dataset.
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| 9. |
- Chen, Z., et al.
(författare)
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Using existing infrastructures of high-speed railways for photovoltaic electricity generation
- 2022
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Ingår i: Resources, Conservation and Recycling. - : Elsevier B.V.. - 0921-3449 .- 1879-0658. ; 178
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Tidskriftsartikel (refereegranskat)abstract
- Cities worldwide are stepping up efforts to reshape their infrastructure to ensure a carbon-neutral and sustainable future, leading to the rapid electrification of transportation systems. The electricity demand of this sector, particularly that of high-speed railways, is increasing. Application of the existing infrastructures of railway stations and available land along rail lines for photovoltaic (PV) electricity generation has the potential to power high-speed bullet trains with renewable energy and supply surplus electricity to surrounding users. In this work, a methodology based on a geographic information system was established to evaluate the PV potential along rail lines and on the roofs of train stations. The Beijing-Shanghai high-speed railway (HSR) was used as a case study. Its total PV potential reached 5.65 GW (of which the station potential accounted for 264 MW, approximately 4.68%, of the total potential), with a lifelong generation capacity of 155 TWh, which corresponds to approximately 12% of the total new installed capacity of China in 2020. Although electricity prices and solar resources differed along the railway line, all PV systems were profitable. Moreover, a comparison between the electricity consumption and generation shows that the PV+HSR system can cover most of the electricity demand of the Beijing-Shanghai HSR without a storage system. This concept can be further expanded to other rail lines and stations. Within the context of global carbon peaks and carbon neutrality, the integration of PV and railway systems should be promoted.
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| 10. |
- Geng, Y., et al.
(författare)
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Recent trend of industrial emissions in developing countries
- 2016
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Ingår i: Applied Energy. - : Elsevier. - 0306-2619 .- 1872-9118. ; 166, s. 187-190
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Tidskriftsartikel (refereegranskat)abstract
- Greenhouse gas (GHG) emissions from industrial sectors are increasing, particularly in the developing world where pursuing industrialization has been highly addressed. This calls for further studies to learn and share experiences for developing countries. In order to fill in such a research gap, this special issue focuses on examining the recent trend of industrial emissions in developing countries. Among the manuscripts submitted to the Special Issue, twelve papers have been accepted after review, covering assessment indicators, tools and methods, and policies. Key industrial sectors, including cement, lime, aluminum, coal, mining, glass, soda ash, etc, have been investigated. Valuable policy insights have been raised, including wide scale upgrading, replacement and deployment of best available technologies, integrated information platforms, cross-cutting technologies and measures, a shift to low carbon electricity, radical product innovations, carbon dioxide capture and storage (CCS), demand on new and replacement products, systematic approaches and collaboration among different industries. These useful suggestions could be shared or learned by industrial policy makers or managers in the developing world so that the overall GHG emissions from their industrial sectors can be mitigated by considering the local realities.
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