| 1. |
- Du, Banghua, et al.
(författare)
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Energy management and performance analysis of an off-grid integrated hydrogen energy utilization system
- 2024
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Ingår i: Energy Conversion and Management. - 0196-8904. ; 299
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Tidskriftsartikel (refereegranskat)abstract
- In integrated hydrogen energy utilization systems, due to the low efficiency of hydrogen/electricity conversion, coordination of energy management and efficient waste heat recovery is required to optimize performance. To address this challenge, this paper presents a comprehensive and sophisticated modeling and energy management strategy to enhance the off-grid energy utilization rate while prolonging the main components' lifetime. The developed model incorporates multiphase flow and heat transport balance for electricity and heat production, enabling a highly accurate representation of real-world behaviors of the system. The proposed off-grid operation strategy is complemented by a designed heat recovery scheme, ensuring the use of energy resources and waste heat. In addition, the proposed energy management strategy monitors the real-time status of each subsystem, actively reducing the number of harmful start-stop cycles of the hydrogen production system, thereby mitigating short-term power impacts and delaying its aging. Specifically, the voltage degradation of the reduction cell is reduced from 4.67 mV to 4.48 mV, the energy utilization rate is increased from 47.6 % to 53.9 %, and the energy efficiency of fuel cells significantly increases from 53.6 % to 78.1 %.
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| 2. |
- Menkveld, Albert J., et al.
(författare)
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Nonstandard Errors
- 2024
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Ingår i: JOURNAL OF FINANCE. - : Wiley-Blackwell. - 0022-1082 .- 1540-6261. ; 79:3, s. 2339-2390
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Tidskriftsartikel (refereegranskat)abstract
- In statistics, samples are drawn from a population in a data-generating process (DGP). Standard errors measure the uncertainty in estimates of population parameters. In science, evidence is generated to test hypotheses in an evidence-generating process (EGP). We claim that EGP variation across researchers adds uncertainty-nonstandard errors (NSEs). We study NSEs by letting 164 teams test the same hypotheses on the same data. NSEs turn out to be sizable, but smaller for more reproducible or higher rated research. Adding peer-review stages reduces NSEs. We further find that this type of uncertainty is underestimated by participants.
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| 3. |
- Zhu, Shihao, et al.
(författare)
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A novel fuel cell cathode hybrid intake structure design and control for integrated hydrogen energy utilization system
- 2024
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Ingår i: Energy. - 1873-6785 .- 0360-5442. ; 308
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Tidskriftsartikel (refereegranskat)abstract
- The typical Integrated Hydrogen Energy Utilization System (IHEUS) does not recycle oxygen. For maximizing the system's efficiency, this study proposes a method for recycling byproduct oxygen in a Fuel Cell (FC) hybrid cathode intake structure and its control. By introducing the pure oxygen produced as a byproduct of hydrogen production into the FC, a hybrid cathode intake structure is formed with the air branch. To control this structure, models of the oxygen and air branch, and the FC stack are established. Subsequently, using BiLSTM network to learn historical data and extract relevant features, the output power demand of the FC system is predicted. Based on the prediction results, the required gas flow is calculated, and a fuzzy PID control strategy is employed to adjust the opening of the solenoid valve to change the gas flow to meet the demand. Finally, comparative studies show that our FC system, operating in a pure oxygen state, outperforms conventional air intake design: heat production increases by 13 %, electric efficiency improves by 20 %, and pure water savings reach 65.57 %. The air compressor witnesses a substantial 37.63 % reduction in power consumption, contributing to an overall energy efficiency increase of 8.92 % for the IHEUS.
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| 4. |
- Zhu, Shihao, et al.
(författare)
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Design and optimization of a cascade hydrogen storage system for integrated energy utilization
- 2024
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Ingår i: Journal of Energy Storage. - 2352-152X. ; 96
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Tidskriftsartikel (refereegranskat)abstract
- In an integrated hydrogen energy utilization system, the hydrogen storage device needs to meet hydrogen supplies and demands of different pressure levels, traditional hydrogen storage systems will lead to more energy consumption and lower hydrogen supply efficiency. To address this problem, a cascade hydrogen storage system (CHSS) is proposed in this study. By configuring three hydrogen storage tanks (HSTs) with three pressure levels, the CHSS is capable of serving hydrogen for fuel cell supply, long-term storage, and refueling stations. The corresponding control strategy of hydrogen flow between HSTs is proposed. It shows that an optimal capacity configuration scheme with pressures of 3 MPa, 24.44 MPa, and 45 MPa and a hydrogen storage capacity of 401.7 kg, optimized by NSGA-II, can meet the stable operation of the system. Comparative studies show that the proposed CHSS configuration can reduce the cost by about 3.78 %, the energy consumption by about 6.92 %, and the hydrogen supply loss rate by about 12 % compared to the existing solutions under the tested conditions.
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