Guest Post by Islandboy

Non-Petroleum comments in this thread please.



The EIA released the latest edition of their Electric Power Monthly on July 25th, with data for May 2017. The April data was revised and re-released after the last report was prepared so some figures from this report may not be consistent with those from the previous report.

In May the contribution from solar reached 2.58%, up from 2.41%d in April. The contribution from All Renewables remained greater than that from Nuclear but, a 1.7% fall in the contribution from wind resulted in a narrowing of the difference from over 3% to about 1.7%. The decline in the contribution from wind also meant that, the combined contribution from Wind and Solar declined to 9.5% from 11% in April and the contribution from Non-Hydro Renewables fell to 10.8% from 12.5%. The contribution of zero emission and carbon neutral sources, that is, nuclear, hydro, wind, solar, geothermal, landfill gas and other biomass fell from 41.75% to 39.87%.

In all of the previous four years the contribution of All Renewables was at it’s peak in April with the exception of last year when it peaked in March. The pattern seems to be holding for 2017 with wind declining and solar and hydro output increasing slightly so the contribution from All Renewables has declined but, still held above 20% for May. It remains to be seen whether or not it will be able to hold above 20% in June.

The graph below shows the total monthly generation at utility scale facilities by year versus the contribution from solar. The left hand scale is for the total generation while the right hand scale is for solar output and has been deliberately set to exaggerate the solar output as a means of assessing it’s potential to make a meaningful contribution to the midsummer peak.


The ramp up of solar output in 2017 appears to be steeper than previous years.  In the previous two reports I looked at possible causes for the steepness of the ramp in between February and March this year (2017). I cited the latest Solar Market Insight Report 2017 Q2 published by the Solar Energy Industries Association and questioned whether a contributing factor could have been the 14.5 GW of PV capacity added since March 2016. About 4 GW was installed in the third quarter of 2016 and about 6.5 GW in the last quarter for a record amount of about 10.5 GW for a six month period in the U.S. Looking at the data for the first quarter of 2017, about 8.5 GW was installed in the six months up to the end of March 2017, the second largest increase in capacity for a six month period. The size of that increase alone did not explain the steep ramp up of solar output between February and March with a far more modest increase between March and April. In the previous report I questioned whether the shape of the output curve for 2017 has been influenced by weather and suggested the output of plants that were commissioned before the beginning of 2016 would have to be examined to confirm this.

I looked at the data from a publicly available site at the SMA Sunny Portal web site by searching for installations in an area with a very good solar resource. I chose the city of Victorville, California and picked a 7.2 kW installation. It just so happens that the installation I selected provides monthly output data going back to July 2009 so, I extracted the data from 2014 onward and de-rated the output from each year before 2017 by 25% to try and get a graph that looks roughly similar to the one above in terms of solar output. Any similarities shapes of the curves for the solar output of the two graphs (above and below) for the years 2014 through 2016 are not particularly significant, especially since the graph above is total US output as opposed to the output of a specific site in Victorville, California. This makes the similarity between the shape of the 2017 curves up to the end of May in both graphs somewhat remarkable and might suggest that there is some widespread weather effect at play. We will have to wait another couple of months to see if the US national output tracks this Victorville site.


The graph below shows the monthly capacity additions for 2017 to date. In May almost 52 percent of capacity additions were Solar with Wind adding just under 30.4 percent. Natural Gas contributed about 14.9 percent while Landfill Gas made a contribution of 0.75 percent. Batteries made up the remaining two percent. I have added a line to indicate the total new capacity added each month to give an idea of what the absolute amounts were added from each source. For example in April NG added about 80% of more than 3,200 MW of new capacity (2330 MW) while in May Solar added almost 52% of 536 MW of new capacity (278 MW).


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