Load-following power plant

A load-following power plant, regarded as producing mid-merit or mid-priced electricity, is a power plant that adjusts its power output as demand for electricity fluctuates throughout the day. Load-following plants are typically in between base load and peaking power plants in efficiency, speed of start-up and shut-down, construction cost, cost of electricity and capacity factor. Base load and peaking power plants Base load power plants are dispatchable plants that tend to operate at maximum output. They generally shut down or reduce power only to perform maintenance or repair or due to grid constraints. Power plants operated mostly in this way include coal, fuel oil, nuclear, geothermal, run-of-the-river hydroelectric, biomass and combined cycle natural gas plants. Peaking power plants operate only during times of peak demand. In countries with widespread air conditioning, demand peaks around the middle of the afternoon, so a typical peaking power plant may start up a cou

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Power station

A power station, also referred to as a power plant and sometimes generating station or generating plant, is an industrial facility for the generation of electric power. Power stations are generall

Peaking power plant

Peaking power plants, also known as peaker plants, and occasionally just "peakers", are power plants that generally run only when there is a high demand, known as peak demand, for electricity. Becaus

Grid energy storage

Grid energy storage (also called large-scale energy storage) is a collection of methods used for energy storage on a large scale within an electrical power grid. Electrical energy is stored during

Dynamic stall vortex shedding and associated load fluctuations

Julien Dominique Claude Deparday, Sabrina Henne, Karen Ann J Mulleners, Agastya Hemen Parikh

2018

New insight in Francis turbine cavitation vortex rope: role of the runner outlet flow swirl number

François Avellan, Arthur Tristan Favrel, Joao Gomes Pereira Junior, Christian Landry, Andres Müller, Christophe Nicolet

At part load operation, Francis turbines experience the development of a cavitation vortex rope in the draft tube, whose precession acts as a pressure excitation source. In case of resonance, the resulting pressure pulsations lead to unacceptable torque and power fluctuations on the prototype machine, putting at risk the system stability. However, the accurate prediction of resonance conditions at the prototype scale remains challenging since it requires a proper hydro-acoustic modelling of the draft tube cavitation flow. Furthermore, both the head and discharge values have an impact on the precession frequency of the vortex and the natural frequency of the system. The present paper demonstrates for the first time that the influence of both parameters on the frequencies of interest can be represented by a single parameter, the swirl number. Its analytical expression is derived as a function of the operating parameters of the machine. It is used to establish empirical laws enabling the determination of both frequencies and finally the operating parameters in resonance conditions on the complete part load operating range at the model scale. The methodology presented in this paper represents a decisive step towards the prediction of resonances on the complete part load operating range of the prototype.

2018

Local wave speed and bulk flow viscosity in Francis turbines at part load operation

François Avellan, Arthur Tristan Favrel, Christian Landry, Andres Müller, Christophe Nicolet

The operation of Francis turbines at off-design conditions may cause the development of a cavitation vortex rope in the draft tube cone, acting as a pressure excitation source. The interactions between this excitation source and the hydraulic system at the natural frequency may result in resonance phenomena, causing serious hydro-mechanical oscillations. One-dimensional draft tube models for the simulation and prediction of part load resonances require an accurate modelling of the wave speed and the bulk viscosity for the draft tube flow. This paper introduces a new methodology for determining these two hydroacoustic parameters in the draft tube of a reduced scale physical model of a Francis turbine, based on experimental identification of the hydraulic natural frequency of the test rig. Finally, dimensionless numbers are derived to define both the wave speed and bulk viscosity for different operating points of the turbine.

Taylor & Francis Ltd2016

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