The Experts below are selected from a list of 234 Experts worldwide ranked by ideXlab platform
João C.c. Henriques - One of the best experts on this subject based on the ideXlab platform.
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The spring-like air compressibility effect in oscillating-water-column wave energy converters: Review and analyses
Renewable and Sustainable Energy Reviews, 2019Co-Authors: António F.o. Falcão, João C.c. HenriquesAbstract:Abstract The oscillating-water-column (OWC) wave energy converter with air turbine has been object of extensive research and development effort, including the deployment of floating and fixed-structure full-sized prototypes into the sea. It consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface in a chamber, which forces air to flow through a turbine coupled to an electrical generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is rarely accounted for in theoretical modelling, and even more rarely in physical model testing at reduced scale, as appears from the literature review. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the Isentropic Process model; (iii) and the (more difficult and rarely adopted) adiabatic non-Isentropic Process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine. Results are shown for regular and irregular waves, and for a theoretical simulation of model testing in wave tank at small scale.
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The Spring-Like Air Compressibility Effect in OWC Wave Energy Converters: Hydro-, Thermo- and Aerodynamic Analyses
Volume 11A: Honoring Symposium for Professor Carlos Guedes Soares on Marine Technology and Ocean Engineering, 2018Co-Authors: António F.o. Falcão, João C.c. HenriquesAbstract:The oscillating-water-column (OWC) wave energy converter consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface, which forces air to flow through a turbine coupled to a generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is normally not accounted for in model testing at reduced scale. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the Isentropic Process model; (iii) and the (more difficult and rarely adopted) adiabatic non-Isentropic Process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is examined and discussed. The validity of the three models is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine subject to irregular waves.
António F.o. Falcão - One of the best experts on this subject based on the ideXlab platform.
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The spring-like air compressibility effect in oscillating-water-column wave energy converters: Review and analyses
Renewable and Sustainable Energy Reviews, 2019Co-Authors: António F.o. Falcão, João C.c. HenriquesAbstract:Abstract The oscillating-water-column (OWC) wave energy converter with air turbine has been object of extensive research and development effort, including the deployment of floating and fixed-structure full-sized prototypes into the sea. It consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface in a chamber, which forces air to flow through a turbine coupled to an electrical generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is rarely accounted for in theoretical modelling, and even more rarely in physical model testing at reduced scale, as appears from the literature review. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the Isentropic Process model; (iii) and the (more difficult and rarely adopted) adiabatic non-Isentropic Process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine. Results are shown for regular and irregular waves, and for a theoretical simulation of model testing in wave tank at small scale.
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The Spring-Like Air Compressibility Effect in OWC Wave Energy Converters: Hydro-, Thermo- and Aerodynamic Analyses
Volume 11A: Honoring Symposium for Professor Carlos Guedes Soares on Marine Technology and Ocean Engineering, 2018Co-Authors: António F.o. Falcão, João C.c. HenriquesAbstract:The oscillating-water-column (OWC) wave energy converter consists of a hollow (fixed or floating) structure, open to the sea below the water surface. Wave action alternately compresses and decompresses the air trapped above the inner water free-surface, which forces air to flow through a turbine coupled to a generator. The spring-like effect of air compressibility in the chamber is related to the density-pressure relationship. It is known to significantly affect the power performance of the full-sized converter, and is normally not accounted for in model testing at reduced scale. Three theoretical models of increasing complexity are analysed and compared: (i) the incompressible air model; (ii) the Isentropic Process model; (iii) and the (more difficult and rarely adopted) adiabatic non-Isentropic Process model in which losses due to the imperfectly efficient turbine are accounted for. The air is assumed as a perfect gas. The hydrodynamic modelling of wave energy absorption is based on linear water wave theory. The validity of the various simplifying assumptions, especially in the aero-thermodynamic domain, is examined and discussed. The validity of the three models is illustrated by a case study with numerical results for a fixed-structure OWC equipped with a Wells turbine subject to irregular waves.
Feng Han - One of the best experts on this subject based on the ideXlab platform.
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Prediction of state property during hydrogen leaks from high-pressure hydrogen storage systems
International Journal of Hydrogen Energy, 2019Co-Authors: Qiang Zou, Ying Tian, Feng HanAbstract:Abstract In an actual hydrogen leakage Process, heat exchange occurs between the gas in a high-pressure storage system and its surroundings. Therefore, the predictions of models that are established based on the Isentropic Process assumption have large errors. In this study, a high-pressure gas leakage Process model including heat exchange (the HEC model) is established. It includes two parts; one is a high-pressure gas storage model without the Isentropic Process assumption, and the other is a leakage orifice model with the Isentropic Process assumption. Formulas for the pressure variation and temperature variation based on the mass and energy conservation equations, the Abel–Noble equation of state, and an enthalpy formula based on the Helmholtz free energy are used to establish the gas storage model. The leakage orifice model is built using a mass flow rate formula based on the van der Waals equation of state and Perry's flow coefficient formula. Finally, the proposed high-pressure gas leakage Process model including heat exchange is compared with high-pressure hydrogen leakage Process models with the Isentropic Process assumption based on the Abel–Noble and van der Waals equations of state. The results show that the proposed model can yield more promising results in predicting the gas leakage mass flow rate, gas pressure, and temperature inside hydrogen storage systems compared with previous models.
Juncheng Jiang - One of the best experts on this subject based on the ideXlab platform.
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Prediction of state property, flow parameter and jet flame size during transient releases from hydrogen storage systems
International Journal of Hydrogen Energy, 2018Co-Authors: Kuibin Zhou, Jiaoyan Liu, Yuzhu Wang, Meng Liu, Juncheng JiangAbstract:Abstract The accidental leakage of high-pressure gas storage systems including tank, pipe, etc. can lead to hazardous jet fires resulting in a serious of disastrous events. With the Isentropic Process assumption on the high-pressure gas leakage or release, the ideal gas equation of state is firstly used to solve the gas transfer problem, and then the Abel-Noble equation of state (AN-EOS) is adopted for the effect of gas molecule volume. Given both the molecule volume and intermolecular attraction should not be ignored for the high-pressure gas, this paper attempts to build the high-pressure gas leakage Process model based on the van der Waals equation of state. Together with the available notional nozzle model and the flame size model, the gas leakage Process model is used to calculate the gas state property and flow parameter of hydrogen tank leakage and its subsequent jet flame height. The predicted gas mass flow rate, flame height, and gas pressure and temperature are compared to the experimental measurements for validation and the predictions of the model based on ideal gas equation of state and AN-EOS. It is found that the proposed model can give more encouraging results compared to the previous models. The proposed theoretical model shows a great implication for the calculation of other gas tank leakage and can help to predict the thermal radiation field of jet fires.
Mohammad Marefati - One of the best experts on this subject based on the ideXlab platform.
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A new hybrid solar photovoltaic/ phosphoric acid fuel cell and energy storage system; Energy and Exergy performance
International Journal of Hydrogen Energy, 2021Co-Authors: Shen Cheng, Gaiju Zhao, Ming Gao, Yuetao Shi, Mingming Huang, Mohammad MarefatiAbstract:Abstract Present work investigates the performance of a combined solar photovoltaic (PV) and Pumped-Hydro and Compressed-Air energy storage system to overcome the challenges of using solar energy systems. This energy system, which is one of the newest hybrid systems, is able to generate electricity and store energy. To examine the solar PV performance the climatic conditions of Shiraz (in Iran) and Abu Dhabi (in UAE) are considered. The results revealed that, the required pump work, which must be supplied by PV system, is equal to 2.85 and 2.62 MJ/m3 for isothermal and Isentropic Processes, respectively. Furthermore, the total system efficiency is equal to 76.5%. In addition, the total exergy destruction of hybrid system for Isentropic Process is 8.91% less than that isothermal Process. In addition, instead of the solar PV system, a phosphoric acid fuel cell is coupled to the storage system and the results are compared with the main system.
