1. Engineering, Policy, Finance
Wind Energy Basics
Engineering, Policy, Finance

10. “Lift Force”
Land sailer record:

11. How Do You Figure Out How Much Power A Wind Turbine Will Produce?
Pwind = (1/2) ρ A V3
Pwind = Power in the wind (watts)
Note: 1 Watt = 1 kg-m² / s³
ρ = Air density (kg/m3)
= kg/m³ at sea level
A = Rotor swept area = π r2
r = Radius of turbine rotor (meters) or length of the turbine blade
= ½ the rotor diameter
V = Velocity of the wind (meters /second)
But the net power actually produced from a wind turbine will be slightly less than ½ of the available power in the wind. Will discuss this in more detail later. r

13. Wind Shear
Snyder Wind Farm
100 m hub height
10 mps 13

15. Average Wind Speed vs Height
TTU 200 Meter Tower Data 15

16. Estimating Wind Speeds
Wind speed is best estimated with a Rayleigh/Weibull distribution function

17. Wind Rose: Shows Direction of Wind17

18. Wind Rose: Showing Energy in the Wind
P = (1/2) ρ A V3 18

19. Pitch of Blades Changes Wind Speed (meters per second)
Many Utility-Scale Turbines Begin to Produce Power at ~ 3 m/s They May Reach Rated Capacity at ~ 15 m/s, & Shut Down at ~ 25 m/s
Blades
at Full
Feather
Blades Fixed at 0 to 1°
Pitch of Blades Changes
Rated Capacity = 2,300 kW
Wind Speed At
Rated Capacity
Cut-In
Speed
Cut-Out
Speed
Wind Speed (meters per second)
Region I
Region II
Region IV
Region
III

21. Gross vs. Net Capacity Factors
Gross Capacity Factor
Capacity Factor of a single wind turbine without any reductions for electrical losses, wake losses, turbulence losses, maintenance outages, transmission outages or curtailments, icing, blade soiling.
Gross Capacity Factor at excellent wind sites can be around 50%.
Net Capacity Factor
Capacity Factor of a group of wind turbines which does include losses within the project
Reflects actual energy sold at meter of customer as percentage of Maximum Production
Net Capacity Factor at excellent wind sites around 40%

22. Types of Losses to Account For
Turbine unavailability 3 to 5%
Power curve to 2%
Substation unavailability to 0.5%
Transmission outages / maintenance 0.1 to 0.5%
Transmission curtailment 0 to 30%
Electrical losses 2 to 3%
Wake effect to 4%
Turbulence to 2%
Blade contamination to 1%
Icing % to 2%

23. Calculating Total Loss Factor Losses Are Not Additive!
Gross Capacity = Expected Production w/o Losses per Time Period x 100
Factor (in %) Maximum Production
Maximum Production in One Year = MW x 365 days x 24 hours/day = MWH
Net Capacity Factor = Gross Capacity Factor x (1 – Total Loss Factor)
Losses Are Not Additive!
Turbine Unavailability Factor: 2.0% = 0.980
Substation Unavailability Factor: 0.2% = 0.998
Transmission Unavailability Factor: 1.4% = 0.986
Electrical Loss Factor: 3.5% = 0.965
Wake and Turbulence Loss Factor: 5.0% = 0.950
Blade Contamination / Icing Loss Factor: 1.5% = 0.985
Total Loss Factor = [1 – (0.98*0.998*0.986*0.965*0.95*0.985)] = = 12.92%

24. Investment Problem Assume the following:
Upfront cost per MW is $950,000
Energy sales taxed at 10%
Net Capacity Factor is .486
Total Capacity is 200 MW
20 year project life span
Discount Rate of 8%
Find the minimum (break-even) PPA price
If the PPA price is $35, what is the NPV and IRR?

25. Investment Problem (extensions)
Debt/Equity Ratio and loan repayment (cost)
MACRS depreciation (benefit)
Tax Credits (benefit)
Royalty payments to landowners (cost)
Land lease payments (cost)
Energy price escalation (*)
PVWatts for solar