U.S. Solar Performance During a Record El Niño

US Solar Performance Q1 2016
Naomi Stringfield
Aug 30, 2016
Renewable Energy

Weather has a direct impact on solar energy production since storms and other environmental conditions often bring clouds that reduce the amount of sunlight at a project location. This connection between weather and solar energy is inextricable and the two follow each other on nearly a one-to-one basis. For example, a 2% reduction of solar irradiance usually leads to a 2% reduction in power produced.

So last year when the strongest El Niño in recorded history was predicted, it was expected to wreak havoc on major solar markets like California as well as Texas where the industry is just starting to get off the ground. That is because the El Niño climate signal is associated with cooler, wetter weather across many regions of the U.S. where solar resources are strongest. Since rainy weather typically means clouds, early predictions suggested a significantly below normal year for much of the solar industry in 2016.

US solar performance maps Q1 and Q2 2016

While the El Niño was just as strong as anticipated, fortunately, its effects weren't as disastrous for the solar industry as predicted. According to NOAA, starting in the second quarter of 2015 sea surface temperatures crossed the threshold that indicates El Niño conditions and they continued to rise to some of the highest temperatures seen since records began in 1950.

Typically, El Niño conditions lead to wetter than normal conditions in the southern and southwestern U.S. and drier than normal conditions in the Northwest. However, while this El Niño was quite strong, the typical conditions associated with it didn't follow suit, arriving later than usual and helping the solar industry out considerably.

Monthly sea surface temperature Nino 3.4 index values
Source: NOAA

In fact, much of the region predicted to be wetter than average saw normal or below normal precipitation for the first quarter of 2016. If you look at Vaisala's first quarter map of GHI (Global Horizontal Irradiance, the variable for PV projects) it mirrors these conditions with higher than normal irradiance for the first three months of the year. 

Much of the first quarter's above average anomaly was driven by weather conditions in February 2016. Throughout the month the strong El Niño energized the upper-level circulation pattern over the U.S. Upper-level ridging dominated the West, which kept precipation below normal and temperatures above normal. The upper-level circulation, temperature, and precipitation anomaly patterns suggest that the weather and climate of February 2016 were largely the result of atmospheric drivers originating over the Pacific Ocean characteristic of a strong El Niño. 

In the second quarter, the conditions we typically see during an El Niño finally arrived with higher precipitation and lower irradiance than normal for the southern U.S. Texas and Louisiana specifically saw substantial amounts of cloudy, wet weather during this time period. The El Niño continued during April 2016 and started to dissipate in May 2016. Although it was weakening, it still contributed to a stronger-than-normal Aleutian Low as seen in the first quarter. An upper-level ridge across western North America gave the Pacific Northwest much warmer than normal temperatures, while upper-level troughs spun off from the Aleutian Low and undercut the ridge, bringing wetter-than-normal weather to the Southwest. 

For the solar industry, the lighter than expected 2016 El Niño is a positive change from the lower than normal irradiance conditions experienced for much of 2015. Since production directly correlates to irradiance, weather conditions can dramatically effect project revenue streams.

California, for example, with its 13.9 GW of installed solar capacity would see a potential loss of $22.5 million dollars for every 1% reduction in solar production annually, assuming an average retail rate of $150 per megawatt hour.

​As the solar industry grows so does the financial impact of meeting production expectations, which makes it all the more important to understand how weather trends may boost or hamper operations.   

Click here to download a copy of the 2016 U.S. Solar Performance maps. ​​

To speak with one of our experts, stop by Booth 2970 at SPI 2016 in Las Vegas, September 12-15.

Gwendalyn Bender

Gwendalyn Bender

Gwendalyn Bender
Solar Product and Production Manager

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