Warm, Wet First Quarter Negatively Impacts U.S. Solar Performance

Solar plant
Francesca Davidson
Published: Jul 19, 2017
Wind and Solar Energy 
Weather & Environment

A Review of How Weather Influenced Solar Performance in Q1 2017

​Vaisala regularly monitors solar performance around the world to give the industry a perspective on how weather is influencing solar power generation. The early months of 2017 brought a departure from normal global horizontal irradiance, the key variable for PV plant production, caused by warm and wet conditions across much of the contiguous U.S. 

US Q1 2017 Solar Performance Map

As illustrated by Vaisala’s Q1 map, wet conditions prevailed in the West, Southwest, and south-central Midwest regions, while warm and dry conditions were experienced in the Southeast. The regional pattern of above- and below-normal solar conditions across the country is also consistent with extreme temperature and precipitation recorded by National Oceanic and Atmospheric Administration (NOAA) for the first quarter of 2017.

Key statistics from Q1 2017: 

  • Southeast had 5th driest February-March in nearly 5 decades
  • West had 5th wettest January-March in nearly 2 decades
  • South had warmest 3-month period to date 

Impact on Solar and the Larger Energy Industry

Warm wintertime conditions have a direct effect on the energy industry at large because they reduce energy demand related to heating. To place these recent conditions in context, the contiguous U.S. temperature-related energy demand during this year’s winter period was 85 percent below average. That is the third lowest in the 123-year period of record, according to data from NOAA’s Residential Energy Demand Temperature Index (REDTI).  

In terms of the effect on solar energy, almost 30 percent of U.S. solar energy capacity is concentrated in California, Arizona and Nevada. All of these states experienced large, negative global horizontal irradiance (GHI) anomalies during the first quarter, with some areas exceeding 10 percent below normal. This heavy rain and cloud cover negatively impacted many solar operators within the region.

Interestingly, despite the low solar conditions in the Southwest, the anomalously high precipitation amounts in the West and Southwest, in combination with lower-than-normal energy demand, resulted in an oversupply of hydroelectricity. Consequently, energy generation from both wind and solar was strongly curtailed within the CAISO region during the first quarter. Even with this heavy curtailment, the CAISO real-time electricity price went negative on two occasions in March. 

Looking solar performance in the first quarter, the observed regional pattern of negative anomalies and positive anomalies, speaks to the importance of strategic portfolio design, especially in terms of diversifying by technology and geographic distribution of assets.  

For more information and month-by-month solar analysis, please read the full article written by Gwendalyn Bender and Louise Leahy published in Greentech Media. 

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