Lifetime calculations for wind turbines

Hello everyone,

I have a doubt about lifetime calculation in MLife (or MCrunch).

In fact, I use TurbSim, Fast and MLife to estimate lifetime of some wind turbines. Or lifetime caculations may require a large number of runs at many wind speeds. Is it the reason why several .out files have to be entered in the primary input file of MLife (or MCrunch)?

I am sorry for my question but I would be grateful if you could help me.

Dear Nadia,

You should use MLife instead of MCrunch for lifetime calculations. MLife is designed to handle the huge number of files required for a proper lifetime calculation. It was designed to take the hundreds or thousands of files generated for a complete IEC loads analysis. It is set up to use a bunch of files for each fatigue-oriented design load case and apply the proper partial safety factor for the loads. It uses a Weibull wind-speed distribution to determine what percentage of the time each wind speed should occur in order to weight the damage produces by each simulation.

We had hoped to make an official release of the software last month, but management redirected resources to another project. I hope we can finish MLife and publish it’s documentation shortly after the other project completes.

Marshall

Dear Marshall,

Thank you for your quick response. But, does it mean that thousands of files have to be generated by changing wind speed in TurbSim or in Fast? Which is the parameter (in TurbSim or in Fast) for changing this wind speed?

Thank you so much for your help,

Nadia.

Nadia,

You could use TurbSim to create a series of of wind files with a sweep of wind speeds and multiple random seeds for each wind speed. Typically, I run 11 wind speeds (4, 6, 8, …, 24) and use six different seeds for a total of 66 files for a single design load case (DLC). If you look at the IEC standard (61400-1 for land-based turbines or 61400-3 for sea-based turbines), it will show which DLCs are used for fatigue analysis and which are used to determine extreme loads. It will also show you what combinations of environment and turbine conditions to use. I cannot give you a copy of the standard as it is a copyrighted document. You can purchase the 61400-1 standard here:

http://webstore.iec.ch/webstore/webstore.nsf/ArtNum_PK/37855!openDocument

Once you have generated the wind files, you could run FAST for each wind file and then run one MLife job with the FAST output files as input.

You should read the user’s guides for each program to learn how to use them, as it is not practical to explain such details here.

Marshall

Marshall,

In TurbSim, I change the random seed by changing the parameter “RandSeed1” but could you please tell me which is the parameter to change the wind speed in TurbSim? Is it “URef”?

I thank you for your help.

Nadia.

Dear Nadia,

Doing this kind of thing is not a trivial exercise–it is quite complicated. You need to thoroughly understand the process and the tools that you will use, or you will be wasting your time. Generating a TurbSim input file requires many more inputs than just the random seed and mean wind speed. Please read the user’s guide. An investment in properly learning the tools is invaluable to producing quality work. If you still need help in understanding the guide after you have read it, please do not hesitate ask.

Marshall

Marshall,

In fact, I have already spent a lot of time to read the user’s guide… :blush: And indeed, I quickly understood that it is not trivial. But currently, the main problem that I have is only to know which is the good parameter that I have to change in order to sweep several wind speeds.
I am sorry for my silly questions but I am novice and I need your expertise to have a better comprehension of your prepocessors.

Best regards,

Nadia.

Please read page 15 of the user’s guide:

http://wind.nrel.gov/designcodes/preprocessors/turbsim/TurbSim.pdf

Thank you Marshall for your help.

Nadia.