Please see pdf.

General comments

• This paper provides a novel approach to co-optimise the wind turbine layout and yaw angles for wake steering. This method greatly accelerates the co-design process by avoiding nested optimisation loops that are computationally very expensive. Together with the understanding of the dependency of the optimal yaw angle with respect to the relative position of the nearest waked wind turbine, these are the biggest contributions from this research. The outcome of this paper is directly applicable in engineering processes in our industry.
• It is enourmously appreciated the transparency and repeatability that comes with the code being publicly available. Also want to congratulate the authors on the high quality of the figures, which communicate the outcomes more clearly.
• I would like to read follow up research ideas stemming from this first step, to reduce the uncertainty and risks associated with the assumptions made here (power density, wake model). With more research, industry would deploy this method with more confidence, as the layouts optimised with co-design perform worse than without it, when not operated with wake steering.
• Additionally, could the authors mention something with respect to the turbine fatigue loads expected from implementing these yaw angles?

Specific comments

• Line 2: it says "...currently optimized separately... more and more wind plants
  
  implement wake steering as their primary form of operation" (gives impression that wake steering is already implemented in wind plants in operation, is this true?)
• Line 54: "...per wind condition". What is meant here, wind speed and direction? Can you be more specific?
• Figure 1: Don't the number of wind speed bins count? Or is a single wind speed per direction used to make this figure? This could be stated explicitly. Over 150 hours for a "small" wind farm is already too long for a single wind speed.
• Line 75: In my opinion, it's somewhat exaggerated the statement that this new approach alone can accelerate the deployment of wind energy and reach goals.
• Line 85: All downstream turbines are waked (if by small amounts) according to Gaussian models, so it would good to be explicit say what model is used here (looks like a top hat Jensen profile). And can you mention what wake decay factor corresponds rougly to the wake radius formula? I am curious about how "optimistic" this wake radius is and how the conclusions can change depending on this wake expansion factor.
• Fig 2c: are there orange or blue coloured points underneath the black dots? Are there clearly many more black dots than coloured? How did you determine the 1D threshold?
• Line 121: why do you re-optimise the yaw angle after a layout has been optimised with co-design? What are the quantitative improvements before this step? 
• Do the final re-optimised yaw values correlate nicely with the deterministic yaw angles found during the co-optimisation?
• Line 115: doesn't SLSQP require multiple initial conditions to get closer the global optimum? What were the initial conditions (layout) in 3.1?
• What is the turbine nameplate capacity in example 3.2? What is the plant power density? 2 km x 2 km seems small even for a 3.5 MW WTG rated capacity (14 MW/km²). Is the AEP increase of co-design as big as 0.8% for sites with smaller but more realistic power density (e.g. 5 MW/km²)?
• Does wake steering optimisation for existing plants still have any value after finding this geometric relationship? What's the trade-off between "slow" optimisation and finding the optimal angles deterministically?

Technical corrections

• Figure 1: shouldn’t it say "with 24 wind direction bins" instead of "with the 24 wind direction bins"? 
• Line 115: typo - should say "optimizer" where it says "optimzer"