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Difficulties Integrating Wind Generation Into Urban Energy Load PowerPoint PPT Presentation

Difficulties Integrating Wind Generation Into Urban Energy Load Russell Bigley Shane Motley Keith Parks Currently in 2009: Xcel Energy is the #1 utility provider of wind in the nation ~2,876 MW’s of Wind Generation on Xcel Energy system Utility Overview Primary goal Keep the lights on

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Difficulties Integrating Wind Generation Into Urban Energy Load

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Difficulties integrating wind generation into urban energy load l.jpg

Difficulties Integrating Wind Generation Into Urban Energy Load

Russell Bigley

Shane Motley

Keith Parks


Currently in 2009 xcel energy is the 1 utility provider of wind in the nation l.jpg

Currently in 2009: Xcel Energy is the #1 utility provider of wind in the nation

~2,876 MW’s

of Wind Generation on Xcel Energy system


Utility overview l.jpg

Utility Overview

  • Primary goal

    • Keep the lights on

  • Secondary goals

    • Run at peak efficiency

    • Prepare for plant maintenance and other outage issues such as transmission


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Utility Overview-Load

  • Understanding Power Usage (load)

    • Power Load Forecasts

      • Highly dependent on weather conditions

        • Temperatures

        • Cloud Cover

        • Precipitation


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Utility Overview-Load

  • Load Forecast Error

    • Error comes from 2 sources

      • Model Error

      • Weather Forecast Error

  • Load forecast Error (MAE) is typically less than 3%-averaged over the 24 hour period (even day ahead)


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Generation Forecasting

Optimizing Power Plant Output for forecasted Load—Typically this involves scheduling

  • Coal Power Plants

  • Gas Power Plants

  • Hydro/Geothermal Facilities

  • Wind Plants--highly variable output


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Generation Assets

  • Many physical differences in power producing assets

    • Main concern: Assets that can be dispatched and assets that cannot be dispatched

    • Wind Generation is non-dispatchable

      • wind generation can be curtailed

    • Wind Generation is forecasted and scheduled

      • Thus there is risk associated with the generation


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Scheduling Wind Generation?

  • Many Issues with wind generation

    1) Generation is dependent on wind

    • Generation is typically not static

  • Requires an excellent wind forecast

    • Even a great wind forecast doesn’t result in an accurate generation forecast

  • Accurate Power Curves for wind turbines

  • A better understanding of generation output on a large farm scale basis

    • Many estimates for total farm output are overestimated (Danish Wind Industry)


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Wind Generation Forecast Error

  • Wind Generation forecast Error average around 20% for the 24 hour day ahead period

  • Persistence is a good forecast in real time, but misses the ramps

    • How can the forecast be sooo bad!!!


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Why is generation so variable & the forecast performance poor.

  • Wind speeds are variable

  • Terrain differences

  • Elevation and hub height difference

  • Turbine availability/turbine types

  • Turbine induced wake effects

  • Turbulent eddies induced by terrain

  • Wind speed variations with height

  • Turbine blades build up debris and affect the aerodynamics

  • Weather model resolution

  • Data Data Data

  • Communication with wind farm operators….and there’s more!!!!!


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Peetz/Logan Wind Farm

Wind farm over 40 miles across and over 200 turbines


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Turbines size:

HUGE!!

These are 2.3MW

Seimens turbines located near Adair, IA.


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Generation Forecasting

  • Wind fields tend to be variable and output is even more variable

    • Small changes in wind speed tend to make large differences in power generation

    • Air Density differences also affect the power output (i.e. Summer vs. Winter)

    • Power Curves are not well documented and are performed at sea level and at standard temperatures


Pa 1 2 a v3 2 where efficiency of the windmill in general less than 0 4 or 40 l.jpg

Pa = 1/2 ρ μ A v3         (2)where μ = efficiency of the windmill (in general less than 0.4, or 40%)


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Wind Forecasting

  • Wind direction can make a huge impact on power generation as turbine placement enhances turbine wake effects

    • Wake effects can propagate up to 10 times the blade diameter of the turbine (Danish Wind Industry Assocation)

Blade Lengths are ~35 meters (~114 ft) long

Wake can propagate up to 700 meters (~2296 ft)

The Diameter is then over 70 meters (~230 feet


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A rare, aerial photo of an offshore windfarm in Denmark clearly shows how turbulence generated by large turbine rotors continues to build with each successive row of turbines.


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Weather Impacts

  • High Winds

    • Turbines ‘cut-out’ at a predetermined wind speed to prevent damage to the turbine (blades, generator, etc.)

  • Cold Temps

    • Turbines ‘cut-out’ at predetermined temperatures to prevent damage

  • Precipitation

    • Rain and snow reduce power output

    • Freezing Rain may damage blades and throw ice

      • Decreases power output


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Other impacts

  • Debris buildup on blades

    • Dirt and insect buildup reduce the aerodynamics around the blade


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Communication

  • Information from the wind plant operators is critical in this whole process

    • Downtime due to different causes

      • Maintenance

      • Weather

      • Weather

      • Weather


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Key Issues and Solutions

  • Wind and generation data

    • Attempting to acquire all wind speed, wind direction, and generation data by turbine

      • 1000’s of pieces of data to stream to a database

  • Modeling

    • Acquired the assistance of NCAR and NREL (National Central for Atmospheric Research and the National Renewable Energy Lab)

      • Use latest modeling technology and bias corrections to achieve better results for real-time and day-ahead wind and generation forecasts


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Without improvements in Communication with wind plant operatorsData at the Turbine Level& Modeling we head down a dangerous path if we plan on integrating even more wind on our systems.

youtube video: turbine failure


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