WISDEM - Base year

Dear all,
I’m using WISDEM to estimate costs of an offshore windfarm with two different floating reference structures and turbines:

  1. OC3 Hywind spar with NREL’s 5MW turbine, and
  2. UMaine VolturnUS semisub with IEA 15 MW turbine

Checking the Cost and Scaling Model (CSM), it seems that the cost figures it provides are referenced from 2015 (i.e 2015 USD is the base year and currency). I haven’t found any info about this on ORBIT’s documentation, however, it does say that it’s based on the old 2017 NREL Offshore BOS model, which uses 2010 USD as the baseline.

My questions are:

  1. If different modules of WISDEM use different base years, as it seems to be from my findings above, what overall base year is used when running WISDEM as a whole (not independently by module)?
  2. What are the base years for the CSM and ORBIT modules?

Many thanks in advance for your help.
Gerard Avellaneda

Hello Gerard,

You are correct that different WISDEM components are calibrated differently when it comes to cost models. This is simply a reality that different projects will support the updating of specific component models and these projects come on their own timelines so it is easy for the component cost data to be from a variety of years. The CSM curve fits were last updated in 2016 using data up to 2015. The annual Cost of Wind report from NREL can help inform how these costs have changed over time.

Where possible, WISDEM modules attempt to go beyond the regression-based cost estimation and try to give more bottom-up accounting of costs. This makes it easier to stay current with cost changes by regional market and time as the cost entries would be material unit costs and labor costs. ORBIT has worked hard to be a bottom-up model, although there are still some miscellaneous cost entries that use regression-based sizing or costing dating back to the 2017 Offshore BOS model that you noted. There is no common history with the CSM model here. With so much rapid change in the offshore market, the ORBIT team frequently re-calibrates the model to be cost-current, but with project-to-project variability and the pace of the market, there will always be some amount of error.

If you are concerned about combining current-year ORBIT cost estimates with USD2015 CSM cost estimates, I would use the Cost of Wind reports to scale the CSM values.

Some other key points worth mentioning.

  • The CSM has entries for all major turbine components for a land-based machine. Using these cost curves for turbines that fall outside of the 2016 CSM dataset, which is pretty much all current turbines and certainly all large offshore machines, is something that we all do but we must acknowledge that we are extrapolating beyond the data and the numbers are not validated.
  • ORBIT can be used as a standalone model with its own turbine cost estimation routines. These are informed by the CSM trends but are not exactly the same.


Many thanks for your reply and your final key points, Garrett, that was very helpful.