GOOD, BETTER, BEST SUN

3TIER US Solar Performance Maps Show Substantial Variability; Significant Anomalies Underline the Value of Solar Assessment and Performance Reconciliation
October 12, 2011 (3TIER)

"…3TIER®…solar performance maps of the US for June, July, and August 2011…[illustrate] how solar irradiance varied from its long-term norm…[and show] strong correlation with a series of weather events that impacted the US this past summer. The findings demonstrate that solar energy is not immune to climatic variability, the risk of which needs to be factored into the financial structure of projects and regularly monitored…

"Findings…June…saw the most significant, widespread irradiance anomalies of the summer…[A] broad area extending from Texas and Oklahoma to the Carolinas [experienced] direct normal irradiance (DNI) values ranging from 15%-40% above normal…[associated with] hot, dry, drought conditions and wildfires in Texas…DNI values ranging from 15%-30% below normal were seen in the West Coast, interior Pacific Northwest, and Upper Midwest…"

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"July…Texas and Oklahoma…[had] DNI values ranging from 10%-20% above normal. Farther east, the Deep South transitioned to a below average irradiance regime connected to wet weather along the Gulf Coast. Along the East Coast, positive anomaly shifted north to the mid-Atlantic and New England…[I]n the Northwest…below average DNI values [continued], although parts of California and the Northern Rockies transitioned to normal or above normal irradiance.

"August…[T]he breakdown of the persistent upper-level trough over the Northwest…[yielded] above normal DNI values, particularly in the interior Pacific Northwest where DNI ranged from 10%-20% above normal…[H]ot, dry weather and DNI levels 20%-30% above normal [persisted] over Texas and the Ohio Valley. The Gulf Coast transitioned to dryer weather, yielding well above normal DNI…[I]n Florida and the Northeast, Tropical Storm Emily and Hurricane Irene contributed to DNI values 10%-20% below normal."