Experimental investigation of extreme loads
The purpose of the project is to perform an experimental investigation of extreme load on wind turbines, measuring both the wind field and the structural load response on high wind speed sites.
The objective of the project is to carry out a combined experimental and theoretical analysis of blade, rotor and tower loads at extreme wind conditions. The experimental part includes measurement on four stall and two pitch regulated wind turbines erected at very windy sites. The extreme wind conditions include both wind conditions in the wind speed range where the turbine is in normal operation and loads during standstill at extreme high wind speeds. The Danish designers of wind turbines mainly apply the DS472 as basis for estimation of the loads which come for extreme wind conditions. The loads during standstill estimated according to the simplified calculation scheme from annex B in DS472 and from aeroelastic simulations show significant difference. Therefore the need for further experiment and improvement of the theoretical basis is essential. The experimental investigation includes measurement of blade, rotor and tower loads together with operational conditions such as electrical power, yaw error and status parameters for the control system. The wind field investigation include measurement on two met-masts erected close to the wind turbine in order to gain detailed information of the 3 dimensional turbulence structure. The stability of the atmosphere is measured as the temperature difference between 10 m above ground level and hub height. The analysis and the theoretical considerations include identification of extreme events concerning wind conditions and load response, investigation of coherence between extreme wind condition and extreme load response and verification and improvement of the aeroelastic simulation
The final analysis and reporting are not carried out the due to extension of the project. The experimental part of the project includes measurement from two sites one in Tobøl, Denmark and one in Oak Creek, California, US. Tolbøl is located in the westerly part of Jutland near the cost line, during the measurement period an extreme storm hits Denmark and the site. The storm is classified as a 400-year event according to Danish codes. The measurements in US are made on two NEG Micon 650kW wind turbines. The site is a very complex high wind speed site. The turbines are located on the top of a ridge. The prevailing wind direction is perpendicular to the ridge, and the annual mean wind speed is 9.5 m/s. The associated wind field measurement, are taken from two instrumented masts erected less than one rotor diameter in front of the turbine indirection of the prevailing wind diretion. Both masts are instrumented at different heights in order to gain insight of the 3D-wind speed structure over the entire rotor plane. Extreme distributions, associated with different recurrence period, conditioned on the mean wind speed and the turbulence intensity are derived. Combined with the wind climate model proposed in the IEC standard, these distributions are used to predict extreme distributions with recurrence periods equal to one and fifty years, respectively which are normally used as design of the turbine
Key figures
Category
Participants
| Partner | Subsidy | Auto financing |
|---|---|---|
| Nordtank Energy Group A/S. Udvikling og Konstruktion | ||
| Bonus Energy A/S | ||
| VESTAS WIND SYSTEMS A/S |
Contact
P. O. Box 49
DK-4000 Roskilde, Denmark
Larsen, Gunner ; Projektleder: Petersen, Søren M. (ing.), 46775043, soeren.m.petersen@risoe.dk
Øvr. Partnere: Nordtank Energy Group A/S; Bonus Energy A/S; Vestas Wind Systems A/S
