2020
Wang, Wenjie; Pavesi, Giorgio; Pei, Ji; Yuan, Shouqi
Transient simulation on closure of wicket gates in a high-head Francis-type reversible turbine operating in pump mode Journal Article
In: Renewable Energy, vol. 145, pp. 1817-1830, 2020, ISSN: 09601481.
Abstract | Links | BibTeX | Tags: Closure of Wicket Gate, Dynamic Mesh, Energy storage, Francis-type Reversible Turbine, PHES, power reduction scenario, Pumped-hydro energy storage plant, transient flow
@article{Wang2020,
title = {Transient simulation on closure of wicket gates in a high-head Francis-type reversible turbine operating in pump mode},
author = {Wenjie Wang and Giorgio Pavesi and Ji Pei and Shouqi Yuan},
url = {https://doi.org/10.1016/j.renene.2019.07.052},
doi = {10.1016/j.renene.2019.07.052},
issn = {09601481},
year = {2020},
date = {2020-01-01},
journal = {Renewable Energy},
volume = {145},
pages = {1817-1830},
abstract = {To solve the problem of grid instabilities, regulation in the Pumped Hydro Energy Storage (PHES) plants should quickly respond to the variation of electricity produced by unpredictable renewable energy. In this paper, a power reduction scenario applied to a pump turbine of a PHES is simulated considering the transient closure process of wicket gate. A novel dynamic mesh technique is applied to simulate the rotation of wicket gate vanes from best efficiency point to shutdown condition. Detached Eddy Simulation (DES) turbulence model is utilized to capture complex unsteady flow and the water weak compressibility effect is considered in the transient simulation. Flow rate, torque, power and pressure are analysed by the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. The results illustrate the delay between the performance parameters flow rate and power and the wicket gate opening angle. The closure of wicket gates affects the flow characteristics downstream the wicket gates greatly, causing intensive pressure fluctuations. The magnitude of pressure fluctuations downstream the wicket gate becomes the highest with the wicket gate closure of about 60%. Aside the blade passage frequency, a low frequency occurs, with the appearance of unsteady flow in pump turbine. Moreover, strong torque pulsations occur on the pin of the wicket vane when the percentage of closure is between 60% and 80%, with peaks much higher than that at the best efficiency point. The transient results can provide meaningful reference to the regulation law of wicket gate for safe operation of the pump turbine.},
keywords = {Closure of Wicket Gate, Dynamic Mesh, Energy storage, Francis-type Reversible Turbine, PHES, power reduction scenario, Pumped-hydro energy storage plant, transient flow},
pubstate = {published},
tppubtype = {article}
}
To solve the problem of grid instabilities, regulation in the Pumped Hydro Energy Storage (PHES) plants should quickly respond to the variation of electricity produced by unpredictable renewable energy. In this paper, a power reduction scenario applied to a pump turbine of a PHES is simulated considering the transient closure process of wicket gate. A novel dynamic mesh technique is applied to simulate the rotation of wicket gate vanes from best efficiency point to shutdown condition. Detached Eddy Simulation (DES) turbulence model is utilized to capture complex unsteady flow and the water weak compressibility effect is considered in the transient simulation. Flow rate, torque, power and pressure are analysed by the Fast Fourier Transform (FFT) and Continuous Wavelet Transform (CWT) methods. The results illustrate the delay between the performance parameters flow rate and power and the wicket gate opening angle. The closure of wicket gates affects the flow characteristics downstream the wicket gates greatly, causing intensive pressure fluctuations. The magnitude of pressure fluctuations downstream the wicket gate becomes the highest with the wicket gate closure of about 60%. Aside the blade passage frequency, a low frequency occurs, with the appearance of unsteady flow in pump turbine. Moreover, strong torque pulsations occur on the pin of the wicket vane when the percentage of closure is between 60% and 80%, with peaks much higher than that at the best efficiency point. The transient results can provide meaningful reference to the regulation law of wicket gate for safe operation of the pump turbine.
2019
Benato, Alberto; Stoppato, Anna
Integrated Thermal Electricity Storage System: Energetic and cost performance Journal Article
In: Energy Conversion and Management, vol. 197, iss. July 2019, pp. 111833, 2019, ISSN: 01968904.
Abstract | Links | BibTeX | Tags: Air cycle, Economic analysis, Energy analysis, Energy storage, Numerical modelling, Thermal electricity storage
@article{Benato2019,
title = {Integrated Thermal Electricity Storage System: Energetic and cost performance},
author = {Alberto Benato and Anna Stoppato},
url = {https://linkinghub.elsevier.com/retrieve/pii/S0196890419308155},
doi = {10.1016/j.enconman.2019.111833},
issn = {01968904},
year = {2019},
date = {2019-01-01},
journal = {Energy Conversion and Management},
volume = {197},
issue = {July 2019},
pages = {111833},
publisher = {Elsevier},
abstract = {The spread of wind turbines and photovoltaic modules for green electricity generation is stressing the need of installing large-scale electricity energy storage. Among the in-developing storage technologies, those which store electricity in the form of thermal energy are considered the most promising due to the absence of geological restrictions and long cycle life. In this context, the Authors of the present work, developed a large-scale electricity energy storage unit which uses air as working fluid and stores electrical energy as sensible heat in a man-made tank. As other thermal storage technologies, the proposed one does not suffer of geographical limitations, is characterized by long cycle life and can be assembled with decommissioned devices originally designed for gas turbine plants. In this work, the Authors analyse the plant energetic performance and the construction cost for different storage materials and plant management strategies. Results show that the thermo-physical properties of the storage medium and the charging tolerance affect the plant performance and costs. For these reasons, it is essential selecting the material based on the plant purpose: if the plant works with daily charge/discharge cycle, packed bed made up by limestone or masonry material is suggested while, for weekly charge/discharge cycles, aluminium oxide can be a better storage option.},
keywords = {Air cycle, Economic analysis, Energy analysis, Energy storage, Numerical modelling, Thermal electricity storage},
pubstate = {published},
tppubtype = {article}
}
The spread of wind turbines and photovoltaic modules for green electricity generation is stressing the need of installing large-scale electricity energy storage. Among the in-developing storage technologies, those which store electricity in the form of thermal energy are considered the most promising due to the absence of geological restrictions and long cycle life. In this context, the Authors of the present work, developed a large-scale electricity energy storage unit which uses air as working fluid and stores electrical energy as sensible heat in a man-made tank. As other thermal storage technologies, the proposed one does not suffer of geographical limitations, is characterized by long cycle life and can be assembled with decommissioned devices originally designed for gas turbine plants. In this work, the Authors analyse the plant energetic performance and the construction cost for different storage materials and plant management strategies. Results show that the thermo-physical properties of the storage medium and the charging tolerance affect the plant performance and costs. For these reasons, it is essential selecting the material based on the plant purpose: if the plant works with daily charge/discharge cycle, packed bed made up by limestone or masonry material is suggested while, for weekly charge/discharge cycles, aluminium oxide can be a better storage option.
2014
Stoppato, Anna; Cavazzini, Giovanna; Ardizzon, Guido; Rossetti, Antonio
In: Energy, vol. 76, pp. 168-174, 2014, ISSN: 03605442.
Abstract | Links | BibTeX | Tags: Energy storage, Particle swarm theory, Photovoltaic pumping systems, Pump as Turbine, Water cooling, Water saving
@article{Stoppato2014a,
title = {A PSO (particle swarm optimization)-based model for the optimal management of a small PV(Photovoltaic)-pump hydro energy storage in a rural dry area},
author = {Anna Stoppato and Giovanna Cavazzini and Guido Ardizzon and Antonio Rossetti},
url = {http://linkinghub.elsevier.com/retrieve/pii/S0360544214006999},
doi = {10.1016/j.energy.2014.06.004},
issn = {03605442},
year = {2014},
date = {2014-01-01},
journal = {Energy},
volume = {76},
pages = {168-174},
abstract = {In developing countries, the exploitation of renewable sources is an opportunity to increase the number of people who have simple access to electricity and to water. Among other technologies, stand-alone photovoltaic pumping systems are often installed in remote areas where the grid is not available: they are used for irrigation and/or other local water needs and can supply also electricity to small consumers. In this paper, by means of an optimization model based on the Particle Swarm Theory, the managing strategy of a system aimed at supplying electricity and water to an isolated small village in Nigeria has been optimized in order to fulfill the requirement of the users and to improve the system efficiency. Ground water is pumped into a storage reservoir and can be used both for irrigation and domestic use. The system is composed by a photovoltaic plant, a pump as turbine, a pack of batteries and a diesel internal combustion engine for integration purposes. A simultaneous optimization of both devices size and plant management has been performed in order to achieve the best economic performances or to fulfil the requirement only by renewable sources. In the first case, the use of a pump as turbine permits to save about 4% of diesel oil, even if the low cost of fuel makes it convenient to use the engine. In the latter case the optimum size of photovoltaic plant is about 16 times higher than in the first one, while the batteries' and pump's optimum sizes are strictly connected to the maximum allowable value for the water storage volume. © 2014 Elsevier Ltd. All rights reserved.},
keywords = {Energy storage, Particle swarm theory, Photovoltaic pumping systems, Pump as Turbine, Water cooling, Water saving},
pubstate = {published},
tppubtype = {article}
}
In developing countries, the exploitation of renewable sources is an opportunity to increase the number of people who have simple access to electricity and to water. Among other technologies, stand-alone photovoltaic pumping systems are often installed in remote areas where the grid is not available: they are used for irrigation and/or other local water needs and can supply also electricity to small consumers. In this paper, by means of an optimization model based on the Particle Swarm Theory, the managing strategy of a system aimed at supplying electricity and water to an isolated small village in Nigeria has been optimized in order to fulfill the requirement of the users and to improve the system efficiency. Ground water is pumped into a storage reservoir and can be used both for irrigation and domestic use. The system is composed by a photovoltaic plant, a pump as turbine, a pack of batteries and a diesel internal combustion engine for integration purposes. A simultaneous optimization of both devices size and plant management has been performed in order to achieve the best economic performances or to fulfil the requirement only by renewable sources. In the first case, the use of a pump as turbine permits to save about 4% of diesel oil, even if the low cost of fuel makes it convenient to use the engine. In the latter case the optimum size of photovoltaic plant is about 16 times higher than in the first one, while the batteries' and pump's optimum sizes are strictly connected to the maximum allowable value for the water storage volume. © 2014 Elsevier Ltd. All rights reserved.
