WISDEM tower_monopile scaled IEA15MW: optimal-design LCoE higher than initial-design LCoE

Hello everybody,

When I run the example case in 18_rotor_tower_monopile folder with the IEA15MW_FB_scaled.yaml geometry file, after a while openMDAO output the message

Optimization terminated successfully…
Optimization Complete

and the run stops.
Then, as I run compare_designs to compare the initial design with the final (optimized) one, I see that the LCoE of the optimized design is higher than the LCoE of the initial design. Is this result really optimal? I mean, LCoE is the merit figure of the optimization, and must be minimized. So, should not I expect that the optimization is successful when LCoE reaches a value lower than the LCoE value of the design I start from?

I am using WISDEM version 3.10.1.

Thank you in advance for your time and attention


That example problem upscales the 15MW reference turbine design to a higher power rating. The initial condition therefore does not satisfy all of the design constraints that are applied. The optimization algorithm must first satisfy the constraints before turning its attention to minimizing the objective function (LCOE). That is why the final LCOE value may be higher than that of the first iteration.

Thank you Garrett for the fast and complete explanation.