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Expression for calculating wind speed at different heights #2118
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Here is a public copy of SAND 84-2530: https://web.archive.org/web/20230418202422/https://www2.jpl.nasa.gov/adv_tech/photovol/2016CTR/SNL%20-%20Est%20Wind%20Speed%20vs%20Height_1985.pdf |
A word of caution here: some temperature model coefficients (e.g. those for the SAPM) implicitly account for the difference between anemometer and PV module height above ground. They do so by regressing measured module temperature to wind speed at 10m. The proposed function is worth adding but I would be cautious about suggesting it needs to be in a PV modeling pipeline. |
Great insight @cwhanse. Let's add this info in a warning admonition for the proposed wind speed function. Probably worth checking out if there is similar functionality in metpy. |
Good point, @cwhanse! From a quick search, I can see that only the SAPM models and the generic_linear require the wind speed at 10 m as an input. The rest of the temperature models either require wind speed at module height or don't specify (e.g., Fuentes), but I would still imagine it requires at module height... |
I agree with @cwhanse we we need to tread cautiously because in my experience there is already a lot of misunderstanding about correlation coefficients and their relation to wind speed height measurements.
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This is my view on the subject:
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Thanks Anton! Can we get those references? |
Here is a link to my temperature model equivalence paper that contains the above excerpt: |
Thanks Anton. So I think there is a case for pvlib to include an expression to account for wind speed height measurement, but IMO. I still think the documentation takes precedence so that folks don’t misuse it. In particular I’d like to see a table of weather resources that shows the wind speed height. Eg ground campaigns most often measure at about 3-m while satellite is usually at 10-m. Also a corresponding table of temperature models. Finally some gallery examples that show when and how an adjustment should be made. My personal preference is to adjust the wind coefficient rather than the wind speed measurements which is associative (ie: |
I think this is another area where the PV modellers are just muddling along. Someone needs to access a large amount of data and do some thorough analysis in order to develop some well-founded correlations that are useful for PV systems! |
Most times, the wind speed provided in weather files is measured at a height of 10 m. However, in many cases it is required to estimate the wind speed at panel height. Which equation should be used in order to do this?
I found this issue (#1814), which mentions an equation from a Sandia report (I couldn't find the report, though... some help from Sandia people? @cwhanse @kandersolar). This is what is mentioned:
Estimate wind speed at module height - use technique developed by menicucci and hall (sand84-2530) */
windmd=ws2*pow(height/9.144,0.2) + 0.0001
And then there is the expression used in wind engineering, described here (for a more official reference, it is also mentioned in the book by Siegfried Heier (2014), Grid Integration of Wind Energy Conversion Systems (publisher: Wiley))
I am willing to take up the task of making the PR, etc., but first, I would like to know your thoughts on which expression should be added (maybe both?) or if there is some other equation you think is more relevant.
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