The Losses page allows you to account for system performance losses that are not included in the wind turbine power curve from the Wind Turbine page and other assumptions. Each loss is expressed as a percentage of the total annual system output before losses.

The losses inputs are designed to work with the inputs on the Uncertainties page when you enable the uncertainty model.

Notes.
 
The losses you specify on the Losses page apply in addition to any losses you specify on the Wind Farm and Grid pages.
 
You can use the Losses inputs in conjunction with the inputs on the Uncertainties page to include losses in your uncertainty analysis.

The following notes supplement the descriptions on the Losses input page:

Wake Losses

The internal wake value comes from the Wind Farm page when you choose the Constant Loss option for the wake model. If you choose one of the other wake model options, SAM sets the internal wake value to zero.

Internal wake effects are generated by turbines. External wake effects are generated outside of the wind farm. Future wake effects are due to confirmed or predicted new project development or decommissioning.

Availability Losses

Previous versions of SAM used an "availability and curtailment" matrix to model the effect of both system availability losses due to maintenance downtime and other operational considerations, and energy curtailment due to power output limits imposed by the electricity off-taker or grid operator. In the current version of SAM, you can use the availability losses here to account for operational availability, and use the inputs on the Grid page to account for curtailment.

Turbine availability considers warranted availability, non-contracted availability, restart after grid outage, site access, downtime or reduced speed to energy ration, and first-year or plant start-up availability. Balance of plant availability includes substation and collection system availability, other non-turbine availability, warranted availability, and site access. Grid availability accounts for grid operating outside of the grid connection agreement parameters, physical grid downtime, and restart delays after grid outages.

Electrical Losses

Electrical efficiency is for electrical losses between the low or medium voltage side of the transformer and the energy measurement point. Facility parasitic consumption is for extreme weather packages and other parasitic loads while operating or not.

Turbine Performance Losses

Sub-optimal performance are deviation from the optimal plant performance due to software, instrumentation, and control setting issues. Generic power curve adjustment is the "inner range" of expected deviation between the advertised and actual power performance. Site-specific power curve adjustment is the "outer range" and accommodates for inclined flow, TI, density, shear, and other site- or project-specific adjustments. High wind hysteresis accounts for energy lost in the hysteresis loop between high wind speed cut-out and recut-in.

Environmental Losses

Environmental losses account for performance degradation and shut downs caused by environmental factors. Degradation includes blade fouling, efficiency losses and other performance degradation. Environmental loss accounts for shut downs or derating due to high or low temperatures, as well as weather-related shut downs for lightning, hail, etc. Exposure accounts for the effects of tree growth, logging, or building development that affects the wind resource.

Curtailment / Operational Strategies Losses

These losses apply in addition to the curtailment losses from the Grid page. If your project earns revenue for curtailment payments, SAM calculates that revenue from the grid limits curtailment rather than from the curtailment losses defined here. Grid curtailment may be required by the PPA or off-taker, or by physical limitations of the grid. Load curtailment are to mitigate loads. Environmental and permit curtailment may be required for birds, bats, marine mammals, flicker, and noise. Operational strategies accounts for periodic up-rating, down-rating, optimization, or shut-down not captured in the power curve or availability carve outs.