Turbines in wind power generation often operate in complex environments created by atmospheric turbulence and turbine wake, and turbulence has always been an important metric in the wind resource analysis process.
In the wind power industry, turbulence is a magical concept, often appearing in analysis reports such as wind turbine gearbox damage, blade cracking, foundation cracking, power generation does not meet the standard. But what exactly is turbulence?
What is turbulence affecting wind turbine
Turbulence is a state of fluid flow. When the flow rate is very small, the fluid layered flow, do not mix each other, known as laminar flow, also known as steady flow or sheet flow; gradually increase the flow rate, the fluid flow line began to appear wavy swing, swing frequency and amplitude with the increase in flow rate increases, this flow condition is known as the transition flow; when the flow rate increases to a large number of flow line is no longer clearly distinguishable, there are many small vortices in the flow field, the laminar flow is destroyed, not only between the neighboring layers of the flow of sliding, but also mixing. There is also mixed. At this time the fluid for irregular movement, there are perpendicular to the axis of the flow pipe in the direction of the velocity generated, this movement is called turbulence, also known as turbulence, disturbed flow or turbulent flow.
How is turbulence defined in fan design? Experts think of the almighty statistical method. According to IEC61400 (a series of standards for wind turbines developed by the IEC), turbulence intensity (turbulenceintensity, abbreviated as TI) refers to the size of the magnitude of the random change in wind speed over a 10-minute period, and it is the ratio of the standard deviation of the 10-minute average wind speed to the mean wind speed over the same period of time, and it is the normal fatigue loads that wind turbines are operating to It is the normal fatigue load endured by the wind turbine in operation, and is one of the important parameters of the IEC61400-1 wind turbine safety grading.
There are two main reasons for turbulence, one is that when the airflow is flowing, the airflow is subject to the friction or blocking effect of the ground roughness, and the other reason is the vertical movement of the airflow due to the difference in air density and the difference in atmospheric temperature. Typically, both of these causes tend to occur simultaneously resulting in turbulence. In a neutral atmosphere, the air cools adiabatically as it rises and reaches thermal equilibrium with the ambient temperature, so that the intensity of turbulence in a neutral atmosphere depends entirely on the surface roughness.
Impact of turbulence on wind turbine safety
Turbine design is standardized, but nature's winds are not so disciplined, and we need to select turbines based on the turbulence conditions in a given wind field.
In the wind field turbulence level exceeds the fan design level, according to the design standard manufacturing out of the fan is very difficult to achieve the expected life, the original design life of 20 years of the fan, in 10 years or even 8 years when the blade root, spindle, nacelle floor and other structural components may be due to long-term fatigue beyond the design standard and lead to the damage, so that the wind farm revenue will be difficult to achieve.
Then turbulence exceeds the standard, the wind turbine is necessarily not applicable? Considering that the wind turbine design parameters are generally higher than the site wind conditions indicators, it is usually possible to put forward in the empirical range to do load simulation to confirm the demand for safety. For example, the design of the annual average wind speed of 8m / s, turbulence for the class A fan. When a fan location turbulence 0.162, but the annual average wind speed is only 7m / s, we can try to add the parameters at the location of the fan design model, through the simulation, to determine whether the fan can meet the safety requirements of this wind field conditions. If it can be satisfied, then this turbine can be suitable for this wind farm.
The effect of turbulence on wind turbine power production
In the final analysis, what we care most about is how much "real money" our wind farms can generate. But when it comes to the effect of turbulence on the actual power generation of wind farms, we have to first mention the static power curve and dynamic power curve. At present, many occasions in the industry, in the assessment of power generation when the power curve is still used for the "static power curve", which is very unscientific, because the static power curve is the assumption that the environmental turbulence for the situation of the ideal conditions of the power curve drawn up, in the real environment is impossible to exist, which will result in a serious overestimation of power generation. This can result in a gross overestimation of the power generation assessment. The scientific approach should be to use the corresponding "dynamic power curve" based on the actual environmental turbulence of the evaluation site to provide a clearer and more realistic reference for the evaluation of electricity.
شركة بولاند للطاقة المتجددة المحدودة، شركة متكاملة للطاقة الجديدة، تُقدم لكم حلولاً متكاملة عالية الجودة لطاقة الرياح والطاقة الشمسية وأنظمة تخزين الطاقة. بولاند الآن شركة تابعة لشركة CRRC، وهي مسؤولة عن التوسع الخارجي لأعمال CRRC في مجال طاقة الرياح والطاقة الشمسية. نمتلك سلسلة توريد داخلية متكاملة نسبيًا، وشبكة خدمات، وجودة منتجات وتقنيات ممتازة.
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