# NREL 1.5 MW

Dear Jonkman,
Now, i want to know that for a 3- bladed wind turbine as we can gave three different sectional property files or same for all blades as mention in .fst file.Baseline_blade.dat.
Can we do the same for aerodynamic files for three different blades???

Actually i want to eliminate the aerodynamic load from the tip of one blade.(i.e assume if the blade length is 31 m, so i have to eliminate the aerodynamic force at the tip having length of 3 m so for this blade only 28 m blade length will calculate the aerodynamic forces )

And i want this only for one blade, actually i tried but it is taking for all the blades.

Dear Anuj,

In the current version of FAST, the only way to model an aerodynamic imbalance is to set the blade pitch independently for each blade as discussed in the forum topic found here: http://forums.nrel.gov/t/varied-pitch-angles-incorporating-blade-prodn-tolerance/665/1. Without modifications to the source code, it is not possible to eliminate the aerodynamic load from the tip of one blade.

Best regards,

Dear Jonkman,
Thanks for your reply . Now , i need a clarification. I am doing an analysis on 1.5 MW wind turbine .
I analyzed for two wind speeds 14.6 m/s and 20.6 m/s .
But the results (tower base forces and moments ) are coming less in case of wind speed 20.6 compare to 14.6 .
Why ?
Please have a look and clarify the doubt.

Dear Anuj,

In a conventional variable-speed, active blade pitch-to-feather controlled wind turbine, the mean aerodynamic rotor thrust peaks at rated wind speed, then drops with increasing wind speed. So the mean rotor thrust would be higher at 14.6 m/s than at 20.6 m/s.

Best regards,

Dear Jonkman,
Thanks for your reply but can you tell me what is the rated speed for 1.5 MW baseline wind turbine. means after which wind speed it starts decreasing (rotor thrust). And how can we know that what is the optimum wind speed or rated speed for any wind turbine.

Dear Anuj,

The rated wind speed for the WindPACT 1.5-MW baseline wind turbine is about 11.5 m/s.

The “rated” wind speed is not typically an “optimal” wind speed (i.e., a turbine does not typically operate at peak aerodynamic efficiency at the rated wind speed). Instead the “rated” wind speed is the wind speed at which the turbine first produces rated power for its generator. The rated wind speed of a turbine is a design decision and is influenced by the physical components of the turbine and controller settings.

Best regards,

Dear jonkman,
Thanks for your reply one more question i want to ask . In the fast manual co-ordinate system is there in which “a” represents what i mean which component axis.??
And the rotation of wind turbine gives us what ? Forces or Forces and moment both .?

Dear Anuj,

I’m sorry, but I don’t understand your question regarding the FAST coordinate systems.

FAST has force and moment outputs available at points throughout the wind turbine.

Best regards,

Dear Jonkman,
I am talking about the FAST manual Page no.7 Subtitle heading ("Coordinate system). There it is written additional coordinate system i,p,a,s and c. so i am asking what a represents on the wind turbine. Because the output at Hub “LSShftFxa” is difined at “a” coordinate.

Thank you.

Dear Anuj,

The “a” or “azimuth” coordinate system is described on page 9 of the FAST User’s Guide.

Best regards,

Dear Jonkman,
I want to know can we lock the Blades . Means they are not rotating !! If yes then how ??

Dear Anuj,

Please see the “Simulating Special Events” Section of the “Controls” Chapter of the FAST User’s Guide for information on how to simulate parked or idling rotor conditions.

Best regards,

Dear Jonkman,
Thanks for the reply i now read the control chapter and then check .!! I have one more doubt know .
I have disabled the CompAero to False , Made the wind speed to 0.01 m/sec.
But in output RotThrust is coming ?? How this can be possible and if it is correct then what this RotTrust significe ??

Dear Anuj,

A similar question has been answered in the forum topic found here: http://forums.nrel.gov/t/the-effect-of-tilt-angle/769/1. Basically, FAST output RotThrust not only includes the applied aerodynamic thrust, but also the gravity and inertial loads of the rotor. See the link for more information.

Best regards,

Dear Jonkman,
Thanks for your reply i understood that . But now i am running a Parking condition as you mention “special events” in control chapter. Everything is coming correct but why Rotor Torque is coming . We make the blade angle to 0. and the blade are locked then why we are getting the Rotor Torque.

Dear Anuj,

I would expect a rotor torque if the blades are fixed at 0 degrees. To reduce torque when parked or idling, blades are normally fixed at around 90 degrees (leading edge into the wind).

Best regards,

Dear Jonkman,
FIrst of all why we are getting a Rot Torque at 0 angle.
Second if we make to 90 degree the Rot Torque is increasing.I made the BlPitch(1) angle to 90 degree same for all blades. And i am getting more Rot torque. why ??
I know about Rotor Thrust but i am unable to understand Rot Torque because we get Rot torque only when the blades will rotates.

Dear Anuj,

I’m not sure I understand your question. In low winds, a wind turbine normally uses a small pitch angle (typically near 0 deg) so that rotor torque is generated to start up the turbine. Torque can be produced when the rotor spins or not. At high winds, a high pitch angle is used (typically near 90 deg) to minimize torque (and thrust) for the parked or idling case.

Have you disabled the generator in your simulation such that there is zero generator torque? In this case I would expect, the rotor torque would be nonzero at whatever pitch angle is set until the rotor accelerates/decelarates to a steady state speed, at which point the rotor torque should drop to zero. The steady state rotor speed should be near zero for a 90-deg pitch angle.

Best regards,

Dear Jonkman,
I want to know the total center of gravity and mass moment of inertia of the total 1.5 MW wind turbine.
It is available somewhere?? if not then how to calculate??
Because the blades and tower are distributed and i don’t know the center of gravity location of all the components.
Thanking you.

Dear Anuj,

The mass, center of mass, and inertias of the rotor-nacelle assembly of the WindPACT 1.5-MW turbine are documented in my Nov 23, 2009 post in the following forum topic: http://forums.nrel.gov/t/tower-fore-aft-modes-shapes/193/1.

You can derive the mass, center of mass, and inertias of the full wind turbine (rotor + drivetrain + nacelle + tower) using a FAST linearization analysis. The easiest way would be to use the following settings in FAST:

Disable all of the flexible mode DOFs of the wind turbine and only enable the 6 platform DOFs (found in PtfmFile).
Disable all turbine controls, disable aerodynamics, and set RotSpeed to 0.0.
Enable the linearization mode, by setting AnalMod to 2.
In the LinFile, set CalcStdy to False (to linearize about the initial conditions) and set MdlOrder to 2 (to get a second order linearized model).
Run FAST.

This linearization will return the 6x6 rigid-body mass matrix of the full wind turbine, which contains the mass (upper-left quadrant), center of mass (upper-right/lower-left quadrants), and inertias (lower-right quadrant) relative to the platform reference point.

Best regards,