Weather Forecasting for Renewables

Nicole Bell

Renewable Energy Forecaster

2017 IRP WorkshopNovember 2, 2016

Why is forecasting needed?

• Major issue with renewable energy = Intermittency

• Why is renewable energy intermittent?

– RE relies on what’s going on in the atmosphere.

– Instability causes weather events, such as clouds, gusty winds, & precipitation.

• Reserves of traditional generation must be available.

– To remain reliable.

– Reserves can be costly.

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What We Use to Forecast

• Weather Forecast Models

– Numerical Weather Prediction (NWP) model• Arizona Weather Regional Forecast (AZ WRF) model

– Created & maintained by the University of Arizona

– Specific to southwestern US, because it’s terrain-based

– Run at higher resolution

– Better forecasts are produced

– Traditional weather models • Over/under forecasts weather events

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What We Use to Forecast

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Forecast Image

- 10 m Wind (knots) Forecast

- Valid @ 17:00Z (10:00L)

- 1.8 km resolution

- 12:00Z (05:00L)RUN of AZ WRF -NAM

Power Forecasts

• The UA generated renewables power forecast

– Contains different runs of the following models:• North American Model (NAM)

• Global Forecast System (GFS) model

• Rapid Refresh (RR) model

– Contains• Utility-scale solar & wind site data

• Residential-scale solar site data

– Is an ensemble of models that ranges from 48 hours up to 7 days

– Is run up to 8 times a day

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Power Forecasts

• Wholesale Marketing department uses power forecasts to

– Make real-time & day-ahead power purchase decisions

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Power Forecasts

• Forecast confidence is higher within 3 days

– Can utilize information on forecast site to determine forecast confidence.

• High spread = Forecast models disagree– Adjustments to forecast are needed

• Low spread = Forecast models agree– Adjustments to forecast are not needed

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Questions??

• Weather is not an easy science. – Trying to predict something that is highly unpredictable.

– Forecast information is still useful.

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