Rainfall Wind Turbine or Turbulence – RW-Turb

RW-Turb scientific program is made of three main work packages:
- WP 1: Experimental set-up and data collection. An observatory for combined high resolution measurements of wind (speed, direction, shear and turbulence), rainfall (drop size velocity, and fall velocities) and power production will be installed for 2 years on a wind farm operated by Boralex and having a 86 m meteo mast. A user friendly data base will be created and data carefully validated.
- WP 2: Analysis and simulation of rainfall effects on the wind power available. It aims at analysing mainly with Universal Multifractals tools (UM, a parsimonious framework that enables to quantify the variability across scales of fields extremely variable across wide range of scales) the collected data to quantify the influence of rainfall conditions on wind turbulence and air density. A classification of rainfall events will be designed for this purpose. Interpretation will require the development of innovative models. A new 3+1D model of drop fields in a 3D turbulent wind at wind turbine scale will be also developed. Scalar and vector spatio-temporal wind fields for scales ranging from few cm and to wind turbine size over few tens of seconds will be simulated by improving existing tools based on continuous UM cascades.
- WP 3: Analysis and simulation of rainfall effects on energy conversion by wind turbine. The transfer of wind intermittency to power production will be analysed from the collected data (WP1). Then, two numerical modelling chains with increasing complexity will be developed to simulate and quantify the effect of wind turbulence on power production. The wind fields simulated in WP2 will be used (i) to compute available torque fluctuations, and (2) as input in a multi-disciplinary model for numerical simulation of wind turbine behaviour (existing to be customized). Ensembles of possible inputs will be used to quantify the sensitivity of the modelling chains to various input parameters corresponding to the different rainfall conditions.

RW-Turb measurement campaign has started in December 2020. Indeed six instruments were installed on the meteorological mast of the Pays d’Othe wind farm (city of les Sièges in Yonne county) which is operated by Boralex, a wind power producer. More precisely, two 3D sonic anemometers, two disdrometers and two mini meteorological stations were installed at roughly 75 m and 45 m. These instruments gives access to respectively high resolution measurement (up to 100 Hz) of wind, rainfall, temperature, pressure and humidity. Data is currently under analysis.
A presentation of the project, links to daily quicklooks of the measurement campaign (updated each day with the data from the day before), as well as the kick-off’s talks are available on the project’s website (https://hmco.enpc.fr/portfolio-archive/rw-turb/). The latter will be regularly updated with obtained results.

The share of renewable energy is rapidly growing in France and Europe. Hence it is highly relevant to understand the uncertainty affecting the electricity production by such resources, notably because its intermittent nature raises complex challenges in terms of grid management. WR-Turb will have a strong impact on this field by providing a quantification of rainfall effects of wind power production and opening perspectives for improving nowcasts. Results will be up-scalable to other site because they will mainly be event-based. The novel findings of WR-Turb, which will be disseminated to both the scientific and professional community, will also open the path for future investigations.

.Peer-reviewed journals
- Jose, J., Gires, A., Tchiguirinskaia, I., Roustan, Y., and Schertzer, D.:Scale invariant relationship between rainfall kinetic energy and intensity in Paris region: An evaluation using universal multifractal framework. Journal of Hydrology. 2021 (submitted)

Conference communications
- García Gago, Á., Schertzer, D., and Gires, A.: Interactions between rainfall and wind turbulence in a Universal Multifractal framework, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10799, doi.org/10.5194/egusphere-egu21-10799, 2021
- Gires, A., Tchiguirinskaia, I., and Schertzer, D.: Guessing the missing half of a geophysical field with blunt extension of discrete Universal Multifractal cascades, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10550, doi.org/10.5194/egusphere-egu21-10550, 2021.
- Jose, J., Gires, A., Tchiguirinskaia, I., and Schertzer, D.: Multifractal analysis of extinction coefficient and its consequences in characterizing atmospheric visibility, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-11242, doi.org/10.5194/egusphere-egu21-11242, 2021
- Gires, A., Tchiguirinskaia, I., and Schertzer, D.: Temporal evolution of rain drops’ velocities in a turbulent wind field, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11648, doi.org/10.5194/egusphere-egu2020-11648, 2020
- Jose, J., Gires, A., Schertzer, D., Roustan, Y., Ruas, A., and Tchiguirinskaia, I.: Variability in Rainfall and Kinetic Energy across scales of measurement: evaluation using disdrometers in Paris region, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-994, doi.org/10.5194/egusphere-egu2020-994, 2019

Few studies showed that the effects of rainfall (rain rate and drop size distribution –DSD-) on wind turbine efficiency are significant, but have surprisingly received little attention. The main goal of WR-Turb is to overcome the current lack of knowledge on this topic through a genuine collaboration between an academic institution (the Hydrology, Meteorology and Complexity laboratory of Ecole des Ponts ParisTech) and a wind power production firm (Boralex).
Literature review shows that: (i) wind turbulence is a complex feature requiring appropriate framework such as Universal Multifractals (UM, a parsimonious framework that enables to quantify the variability across scales of fields extremely variable across wide range of scales) for analysis and simulations; and intermittency of the input power is further propagating to the wind turbine and power output; (ii) Rainfall also exhibits scale invariant multifractal features. WR-Turb will combine the existing knowledge on wind turbulence and rainfall fields to create a coupled framework enabling to tackle its objectives. Two distinct aspects will be studied: first the rainfall effect on the wind energy resources notably taking into account its non Gaussian extreme small spatio-temporal scale fluctuations and second the rainfall effect on the conversion process of wind power to electric power by the wind turbine.
A scientific programme to be primarily implemented through two PhD projects was designed:
- WP 1: Experimental set-up and data collection. An observatory for combined high resolution measurements of wind (speed, direction, shear and turbulence), rainfall (DSD, and fall velocities) and power production will be installed for 2 years on a wind farm operated by Boralex and having a 86 m meteo mast. A user friendly data base will be created and data carefully validated.
- WP 2: Analysis and simulation of rainfall effects on the wind power available. It aims at analysing mainly with UM tools the collected data to quantify the influence of rainfall conditions on wind turbulence and air density. A classification of rainfall events will be designed for this purpose. Interpretation will require the development of innovative models. A new 3+1D model of drop fields in a 3D turbulent wind at wind turbine scale will be also developed. Scalar and vector spatio-temporal wind fields for scales ranging from few cm and to wind turbine size over few tens of seconds will be simulated by improving existing tools based on continuous UM cascades
- WP 3: Analysis and simulation of rainfall effects on energy conversion by wind turbine. The transfer of wind intermittency to power production will be analysed from the collected data (WP1). Then, two numerical modelling chains with increasing complexity will be developed to simulate and quantify the effect of wind turbulence on power production. The wind fields simulated in WP2 will be used (i) to compute available torque fluctuations, and (2) as input in a multi-disciplinary model for numerical simulation of wind turbine behaviour (existing to be customized). Ensembles of possible inputs will be used to quantify the sensitivity of the modelling chains to various input parameters corresponding to the different rainfall conditions.

The share of renewable energy is rapidly growing in France and Europe. Hence it is highly relevant to understand the uncertainty affecting the electricity production by such resources, notably because its intermittent nature raises complex challenges in terms of grid management. WR-Turb will have a strong impact on this field by providing a quantification of rainfall effects of wind power production and opening perspectives for improving nowcasts. Results will be up-scalable to other site because they will mainly be event-based. The novel findings of WR-Turb, which will be disseminated to both the scientific and professional community, will also open the path for future investigations.