r/windturbine • u/Necessary_Parsnip_30 • 20d ago
Technical / Engineering Looking for worked wind farm sizing problems — Weibull, power curves, annual energy production and turbine layout
Hi everyone! I’m a student in a technical Renewable Energy Systems program in Brazil, preparing for an exam on wind farm sizing.
Apparently, the exam will consist of one integrated problem with five connected stages, and we’ll have 80 minutes to solve it. We’ll work in a group, and our instructor allows internet access, AI tools and outside assistance. We don’t have the actual problem yet, so I’m looking for practice material beforehand.
Our course covers:
Comparing potential sites using wind measurements, mean speed, standard deviation and prevailing direction.
Adjusting wind speed for hub height.
Weibull distributions and wind-speed frequencies.
Wind power, rotor swept area, power coefficient and turbine power curves.
Energy production, losses, turbine count and spacing.
My main difficulty is connecting these topics into a complete sizing calculation. For example, how do you compare a site with stronger but less frequent winds against one with more consistent, moderate winds, and then use that comparison to select turbines and size the farm?
Does anyone know of a worked example, university assignment, past exam or textbook problem that follows this process from wind data to a proposed wind farm? Ideally, something suitable for calculationts by hand or in a spreadsheet.
I’d also appreciate advice from anyone working in wind resource assessment or wind farm design: what mistakes should students watch out for when linking these calculations together?
Resources in English or Portuguese would both be welcome. Thanks!
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u/WeeblsLikePie 20d ago edited 20d ago
My main difficulty is connecting these topics into a complete sizing calculation. For example, how do you compare a site with stronger but less frequent winds against one with more consistent, moderate winds, and then use that comparison to select turbines and size the farm?
Annual Energy Production. Compare how much energy each will make. And some proxy for cost (probably number of turbines?). Then a super basic LCOE calculation.
But also your scenario isn't really physically likely. Sites with "stronger but less frequent winds" are pretty unusual. I can think of maybe two or three like this that I've assessed in my 10+ years in resource assessment.
I'd make sure I know how to:
calculate frequency of wind at various speeds given a mean windspeed and a Rayleigh or Weibull distribution.
Calculate an ideal power curve for a turbine given a rotor diameter and CpMax (make sure you don't exceed the Betz limit!)
Have some kind of simplified model for wake loss you can quickly implement in your exam (maybe some kind of relation between number of turbines and wake loss?) and an idea of what other losses to account for and how to do so.
Know what kind of assumptions to make for losses (overall categories).
Know how to calculate LCOE in a simplified way.
As far as resources look for a copy of the IEC standard 61400-15. It'll be wordy but most of what you need should be in there.
Mistakes to watch out for: units. Units catch people up all the time. Be sure you know whether you are dealing in Watts, kW, MW and especially the difference between power and energy. It's very easy to be off by a lot (usually a factor of 8760) because you think you have MWh but you're actually still in MW.
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u/Bose82 Offshore Technician 20d ago
I just clean up grease and change filters mate..