scholarly journals Analysis of the Unstable Behavior of a Pump-Turbine in Turbine Mode: Fluid-Dynamical and Spectral Characterization of the S-shape Characteristic

2015 ◽  
Vol 138 (2) ◽  
Author(s):  
Giovanna Cavazzini ◽  
Alberto Covi ◽  
Giorgio Pavesi ◽  
Guido Ardizzon
Keyword(s):  
Power Plants ◽  
Renewable Energy Sources ◽  
Load Condition ◽  
Rotating Stall ◽  
Electricity Production ◽  
Mechanical Equipment ◽  
Pump Turbine ◽  
Time Frequency ◽  
Unstable Behavior ◽  
Turbine Mode

The most common mechanical equipment adopted in the new generation of pumped-hydro power plants is represented by reversible pump-turbines (RPT), required to rapidly switch between pumping and generating modes in order to balance the frequent changes in electricity production and consumption caused by unpredictable renewable energy sources. As a consequence, pump-turbines are required to extend their operation under off-design conditions in unstable operating areas. The paper presents a numerical analysis of the unstable behavior of a pump-turbine operating in turbine mode near the no-load condition. To study in depth the unsteady phenomena which lead to the S-shape of the turbine characteristic, a load rejection scenario at constant and large guide vane opening (GVO) was numerically analyzed by running through the flow-speed characteristic up to the turbine brake region. The flow field analysis led to the onset and development of unsteady phenomena progressively evolving in an organized rotating stall (RS) (65.1% of the runner rotation frequency) during the turbine brake operation. These phenomena were characterized by frequency and time–frequency analyses of several numerical signals (static pressure, blade torque, mass flow rate in blade passages). The influence of the development of these unsteady phenomena on the pump-turbine performance in a turbine operation was also analyzed, and the potential causes that generated the S-shaped characteristic curve were also investigated.

scholarly journals Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
J. Yang ◽  
G. Pavesi ◽  
S. Yuan ◽  
G. Cavazzini ◽  
G. Ardizzon
Keyword(s):  
High Speed ◽  
Dynamic Pressure ◽  
Load Condition ◽  
Rotating Stall ◽  
Pump Mode ◽  
Pump Turbine ◽  
Part Load ◽  
Time Frequency ◽  
Speed Flow ◽  
Dynamic Pressure Measurements

The unsteady phenomena of a low specific speed pump–turbine operating in pump mode were characterized by dynamic pressure measurements and high-speed flow visualization of injected air bubbles. Analyses were carried out on the pressure signals both in frequency and time–frequency domains and by bispectral protocol. The results obtained by high-speed camera were used to reveal the flow pattern in the diffuser and return vanes channels The unsteady structure identified in the return vane channel appeared both at full and part load condition. Furthermore, a rotating stall structure was found and characterized in the diffuser when the pump operated at part load. The characteristics of these two unsteady structures are described in the paper.

scholarly journals IMPACT OF PHOTOVOLTAIC POWER PLANTS ON THE OVERALL ELECTRIC POWER SYSTEM OF THE REPUBLIC OF MACEDONIA

2013 ◽  
Vol 4 (2) ◽  
Author(s):  
Aleksandra Kanevče ◽  
Igor Tomovski ◽  
Ljubčo Kocarev
Keyword(s):  
Renewable Energy ◽  
Electric Power ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Electric Power System ◽  
Electricity Production ◽  
Energy Sources ◽  
Republic Of Macedonia ◽  
Photovoltaic Power ◽  
The Republic

In this paper we analyze the impact of the renewable energy sources on the overall electric power system of the Republic of Macedonia. Specifically, the effect of the photovoltaic power plants is examined. For this purpose we developed an electricity production optimization model, based on standard network flow model. The renewable energy sources are included in the model of Macedonia based on hourly meteorological data. Electricity producers that exist in 2012 are included in the base scenario. Two more characteristic years are analyzed, i.e. 2015 and 2020. The electricity producers planned to be constructed in these two years (which include the renewable energy sources) are also included. The results show that the renewable energy sources introduce imbalance in the system when the minimum electricity production is higher than the electricity required by the consumers. But, in these critical situations the production from photovoltaic energy sources is zero, which means that they produce electricity during the peak load, and do not produce when the consumption is at minimum.

Renewable Energy: Myths, Legends, and Reality

2005 ◽  
Author(s):  
Charles A. Powell ◽  
Thomas W. Johnson
Keyword(s):  
Renewable Energy ◽  
Power Plants ◽  
High Efficiency ◽  
Renewable Energy Sources ◽  
Paper Industry ◽  
Electricity Production ◽  
Electricity Pricing ◽  
Department Of Agriculture ◽  
Industry Waste ◽  
The Us

With many States setting goals in the 2010–2020 timeframe for increased U.S. electricity production from renewable energy sources totaling nearly 100,000 MW nationwide, innovative solutions are required; as well as the suspension of several myths of conventional wisdom concerning renewable energy. Since Wind, Hydro and Solar are “opportunity” energy supplies not necessarily available when electricity demands are high; there is a great need for a renewable, “dispatchable” energy source that would be available anytime. Building on the experience of the Pulp and Paper Industry, waste-wood fueled IGCC units of 100MW size are practical today; and new gasification technologies being developed for power plants promise high efficiency, and competitive electricity pricing. With these new IGCC technologies, the US Department of Agriculture estimates there is more than enough wood waste to meet the renewable energy goals currently being considered, cost-competitively and environmentally responsibly.

scholarly journals Legal Pathways to Coal Phase-Out in Italy in 2025

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5605 ◽  
Author(s):  
Matteo Fermeglia ◽  
Paolo Bevilacqua ◽  
Claudia Cafaro ◽  
Paolo Ceci ◽  
Antonio Fardelli
Keyword(s):  
Power Plants ◽  
State Of The Art ◽  
Renewable Energy Sources ◽  
Energy Generation ◽  
Electricity Production ◽  
Coal Power Plants ◽  
Coal Power ◽  
Phase Out ◽  
Existing Data

This contribution aims to provide an in-depth outlook of the phase-out of coal-fired energy generation in Italy. In particular, this article analyzes the state-of-the-art with regard to both the current role of coal generation and the performance of the main legal and regulatory tools as implemented in Italy thus far to ensure the closure of all coal power plants by 2025 as announced in the Italian National Climate and Energy Plan. Based on existing data and scenarios on both electricity production and demand trends, this article unfolds the marginal role played by coal-fired generation in the Italian energy mix. In addition, this paper aims to highlight the outstanding technical uncertainties and regulatory hurdles in the way towards de-carbonization of energy generation in Italy. This paper argues that several remarkable improvements are needed in order to avoid over-generation (especially through natural gas), to upscale the penetration of renewable energy sources, and develop the necessary infrastructures to adequately deliver on the full phasing-out of coal within the expected timeframes.

scholarly journals Numerical Study of Pump-Turbine Instabilities Under Pumping Mode Off-Design Conditions

2015 ◽  
Author(s):  
Uroš Ješe ◽  
Regiane Fortes-Patella ◽  
Matevž Dular
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Guide Vane ◽  
Characteristic Curve ◽  
Rotating Stall ◽  
Electrical Network ◽  
Pump Turbine ◽  
Wide Range ◽  
Pumping Mode ◽  
And Performance

Pumped storage power plants, using reversible pump-turbines, are a great solution to maintain the stability of an electrical network. The continuous operating area of reversible pump-turbines machines is usually delimited by cavitation or a hydraulic instability called hump phenomena at part load. If the machine operates under these off-design conditions, it might be exposed to vibrations and performance losses. The paper focuses on the numerical analysis of the pumping mode regime and pays special attention to the prediction of the hump shaped characteristic curve and associated rotating stall. The investigations were made on a high head pump-turbine design (nq=27) at model scale for four different guide vane opening angles and a wide range of flow rates. Numerical simulations were performed and analyzed in LEGI and were compared to the global experimental data, provided by Alstom Hydro.

scholarly journals Specific Features of Renewable Energy Development in the World and Russia

2021 ◽  
Vol 13 (5) ◽  
pp. 93-107
Author(s):  
Victoria I. Bushukina ◽  
Keyword(s):  
Renewable Energy ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Multivariate Regression Analysis ◽  
Electricity Production ◽  
Thermal Generation ◽  
Systematic Analysis ◽  
Energy Projects ◽  
The World ◽  
The Impact

The purpose of the article is to study the theoretical and practical aspects of investment activities in the field of renewable energy in the world and in Russia. To achieve this goal, during the development of theoretical material, a systematic analysis of existing approaches to the assessment of financing mechanisms for renewable energy projects was carried out. Statistical and econometric research tools include correlation analysis and multivariate regression analysis. The article examines the development of renewable energy, its benefits, and investments in the industry. The financial risks and barriers associated with financing renewable energy projects are considered. The development of the industry over the past 10 years is analyzed, taking into account the impact of the COVID-19 pandemic on the electricity industry in general and on renewable energy in a number of countries. It is established that the world is shifting to the use of renewable energy sources, and in Russia they are not being given due attention. It is revealed that the existing thermal generation units in Russia are of great age and are to be decommissioned in the near future. The current state of renewable energy in Russia, measures to support it and the rate of its development are investigated. The technical potential of wind and solar power plants in the Russian Federation is considered within the aim of diversifying electricity production. The factors that negatively affect the development of the renewable energy industry are identified.

scholarly journals A Case Study of a Virtual Power Plant (VPP) as a Data Acquisition Tool for PV Energy Forecasting

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6200
Author(s):  
Tomasz Popławski ◽  
Sebastian Dudzik ◽  
Piotr Szeląg ◽  
Janusz Baran
Keyword(s):  
Power Plant ◽  
Power Systems ◽  
Power Plants ◽  
Distribution Systems ◽  
Missing Values ◽  
Renewable Energy Sources ◽  
Electric Energy ◽  
Electricity Production ◽  
Virtual Power ◽  
Virtual Power Plants

This article describes problems related to the operation of a virtual micro power plant at the Faculty of Electrical Engineering (FEE), Czestochowa University of Technology (CUT). In the era of dynamic development of renewable energy sources, it is necessary to create alternative electricity management systems for existing power systems, including power transmission and distribution systems. Virtual power plants (VPPs) are such an alternative. So far, there has been no unified standard for a VPP operation. The article presents components that make up the VPP at the FEE and describes their physical and logical structure. The presented solution is a combination of several units operating in the internal power grid of the FEE, i.e., wind turbines, energy storage (ES), photovoltaic panels (PV) and car charging stations. Their operation is coordinated by a common control system. One of the research goals described in the article is to optimize the operation of these components to minimize consumption of the electric energy from the external supply network. An analysis of data from the VPP management system was carried out to create mathematical models for prediction of the consumed power and the power produced by the PVs. These models allowed us to achieve the assumed objective. The article also presents the VPP data processing results in terms of detecting outliers and missing values. In addition to the issues discussed above, the authors also proposed to apply the Prophet model for short-term forecasting of the PV farm electricity production. It is a statistical model that has so far been used for social and business research. The authors implemented it effectively for technical analysis purposes. It was shown that the results of the PV energy production forecasting using the Prophet model are acceptable despite occurrences of missing data in the investigated time series.

scholarly journals Waste-to-Wealth: The Economic Reasons for Replacing Waste-to-Energy With the Circular Economy of Municipal Solid Waste

2020 ◽  
Author(s):  
Mario Pagliaro
Keyword(s):  
Municipal Solid Waste ◽  
Solid Waste ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Waste Incineration ◽  
Mass Scale ◽  
Raw Material ◽  
Waste To Energy ◽  
Electricity Production ◽  
Material Recycling

Sharing the same raw material, recycling and composting are in direct conflict with incineration of municipal solid waste in combined heath and power plants. Indeed, waste-to-energy plants in regions with high recycling rates import urban waste from other countries to use otherwise unused capacity, and raise revenues. Using the case of Italy’s second largest and economically most developed region, I discuss the economic viability of municipal solid waste incineration to produce electricity and heath in the context of the increasing role of electricity production from renewable energy sources as well as of the emerging mass-scale uptake of bioplastics. Four lessons and three guidelines aimed to local authorities and policy makers emerge from the present study.

Problems and Risks of Renewable Energy Sources

2021 ◽  
Vol 18 (4) ◽  
pp. 28-47
Author(s):  
Yu. I. Sokolov
Keyword(s):  
Renewable Energy ◽  
Power Plants ◽  
Fossil Fuels ◽  
Renewable Energy Sources ◽  
Electricity Production ◽  
Energy Sources ◽  
Renewable Generation ◽  
Solar Panels ◽  
Huge Amount ◽  
Wind Power Plants

The article analyzes the problems and risks of new-fangled renewable energy sources in the 21st century, which can radically change the energy picture of the world and to a certain extent reduce the risk of climate change. However, energy generation from wind is usually available 25—35% of the time, from the sun — 10—25%.Renewable energy sources (RES) face the problem of accumulating or supporting capacities that should replace the unstable generation of RES at the time of inevitable failures. RES cannot exist without excess reserve capacities on traditional energy carriers that can quickly increase and reduce electricity production. Abandoning hydrocarbons in the next 30—50 years looks unrealistic if countries want to maintain their competitiveness. The growth of the share of RES in the global energy balance is an extremely politicized phenomenon.The development of renewable generation creates risks for consumers. Especially for large ones. One of these risks is associated with the intermittent, unstable nature of renewable generation, which in recent years has been understood mainly as solar and wind power plants. In addition, to produce more solar panels, wind turbines and batteries for electric vehicles, humanity will need more specific resources — rare earth metals. The production of these metals is unsafe for the environment. It involves the consumption of a huge amount of water and electrical energy.Renewable energy sources may dominate, but it will take centuries. Demand is already growing, but fossil fuels will live long enough.

scholarly journals Dynamics of Electricity Production against the Backdrop of Climate Change: A Case Study of Hydropower Plants in Poland

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3427
Author(s):  
Katarzyna Kubiak-Wójcicka ◽  
Leszek Szczęch
Keyword(s):  
Renewable Energy ◽  
Energy Policy ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Biomass Energy ◽  
Electricity Production ◽  
Lower Amount ◽  
Energy Sources ◽  
Hydropower Plants

Renewable energy sources (RES) play an important role in the European Union’s energy sector as a result of the energy policy framework adopted. Its share in the final energy consumption varies depending on the country and the adopted energy policy. The article presents the structure of electricity production from renewable energy sources in Poland in the years 2002–2019. It was found that the share of energy production from hydroelectric power plants in Poland in relation to the amount of energy produced from renewable energy sources in the analyzed years has strongly decreased. The reason for this state was an increase in the production of energy coming from wind and biomass energy combined with an increase in subsidies for these energy producers. Additionally, unstable hydrological conditions, mainly low river flows, may be the reason for the low share of energy produced in power plants. As a case study, data for five small hydropower plants (SHP) located on the Gwda river (north-western Poland) were analyzed. Electricity production volumes were analyzed depending on the size of the Gwda river flow. It was found that the lower amount of electricity produced at SHPs on the Gwda river is mainly due to lower flows in the river. In the future, unstable electricity production from renewable energy sources may have a significant impact on achieving Poland’s energy targets in 2030.

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