The post construction analysis is concerned with computing standard comparable quantities from operational SCADA data.

Wind/Power Model

The following schematic provides the working wind/power model which is used in the post construction analysis.

Wind/Power Model

Variable Description
W0 Wind resource (m/s) in unobstructed environment (no turbines present). This cannot be measured in post-construction analysis.
P0 Theoretical potential power (kW) in unobstructed environment due to wind resource W0. This cannot be measured in post-construction analysis.
L0 Losses in power due to wakes from upwind turbines. This cannot be readily measured, but might be approximated through simulation.
W1 Wind resource directly in front of turbine, including interference from neighboring and upwind turbines and met towers. This cannot be directly measured, but can be approximated using W2 and the Nacelle transfer function.
P1 Theoretical potential power due to wind resource at W1 which is P0 reduced by wake losses (L0)
L1 The nacelle transfer function, which describes the conversion from the nacelle measured windspeed W2 and the front-of-turbine approximate wind resource W1. L1 is the loss in power from P1 to P2 as a result of this correction. This is a turbine model-specific correction.
W2 The nacelle-mounted anenometer-measured windspeed. This data is available in common SCADA channels.
P2 The potential power generated by the wind resource W2. This quantity cannot be measured directly, but can be approximated by using a fitted power curve to estimate the P2 value for a given W2.
L2 Performance losses, which describe the difference between acheived power (P3) and potential power (P2) while the turbine is operating.
L3 Environmetal losses, which is the power that would have been generated during times that the turbine is offline for environmental reasons (temperature, icing, high wind).
L4 Curtailment losses, which is the power that would have been generated during times that the turbine is in a curtailed state due to the power grid supply/demand.
L5 Other Availability losses, which is power that would have been generated during times the turbine is offline for any reason beyond Environmental and Curtailment causes.
P3 The generator output (bus bar) power is available in common SCADA channels.
L6 Electrical losses between the turbine and the point of revenue metering.
P4 The summer power for all turbines received at the point of revenue meter.

Calculated Quantities

The following quantities and statistics form the basis for comparison to pre-construction estimates:

ID Category Type Units Description Link
M1 Windspeed vector m/s Median of annual average wind speed as measured at each site reference met tower  
M2 Windspeed vector m/s Standard deviation of annual average wind speed as measured at each site reference tower  
M3 Energy vector MWh Median of annual per turbine gross energy, defined as the potential energy that was available according to the nacelle wind speed, converted to power using a fitted power curve  
M4 Energy scalar MWh Median of annual site-level gross energy, defined as the sum of M3 values for each turbine for each year  
M5 Losses scalar MWh Median of annual site-level energy losses between turbines and point of revenue. This is defined as the difference between the point of revenue metered energy and the total turbine produced energy (M4) during times the turbine is operating  
M6 Energy scalar MWh Median of the annual site-level energy as measured at the point of revenue meter.  
M7 Capacity vector % Median of the annual capacity factor (ratio between generated and rated power during times operating) for each turbine  
M8 Capacity scalar % Median of the annual capacity factor for all turbines combined  
M9 Energy scalar MWh Energy at point of revenue metering for the entire site in the first year of production operation  
M10 Energy vector MWh Energy generated at each turbine in the first year of prouction operation  
M11 Energy vector MWh Gross energy possible at each turbine in the first year of production operation  
M12 Energy scalar MWh Median of annual energy at point of revenue meter for years 1 to 10  
M13 Energy scalar MWh Median of summed potential (gross) energy at all turbines for years 1 to 10  
M14 Energy vector MWh Median of potential (gross) energy at each turbine for years 1 to 10  
M15 Energy scalar MWh Standard deviation of annual energy at point of revenue metering for years 1 to 20