Wind generation in the region managed by the slowed in the months of May and June compared to the averagemonthly generation in the first four months of this year.
Wind generation fell to about 3.2 million MWh and 3.1million MWh in May and June, respectively, from an average of 4.4 million MWhin the first four months of 2016, according to S&P Global's analysis ofMISO data.
The slump in wind generation as temperatures pick up in thesummer months is a trend that also occurred in MISO last year. In 2015, monthlygeneration fell to about 2 million MWh in July, down from 2.1 million MWh inJune, 3.8 million MWh in May and an average of about 4 million MWh in the firstfour months of 2015, MISO data shows.
For most regions across the U.S. other than California, "windplant performance is highest in the early and later months of the year, not thesummer," the U.S. Energy Information Administration said in a February2015 "Today in Energy" report.
Most of the wind generation in MISO comes from windresources registered as dispatchable intermittent resources, or DIR, whichrefer to wind plants with more firm output that are able to participate in MISO'sreal-time and day-ahead markets. Dispatchable wind resources accounted forabout 85.5% of the 3.2 million MWh of generation in May 2016 and 84.3% of the4.9 million MWh generated in April while intermittent resources, whose outputis less predictable, accounted for the remainder, according to MISO's "May2016 Monthly Market Assessment Report."
Wind plant capacity factors, a percentage that indicates aplant's actual output relative to its potential, also dropped off in May ofthis year, a month earlier than last year's performance. Wind plant capacityfactors averaged 28.8% in May 2016, down 16.6 percentage points from 45.4% inApril. Last year, wind plant capacity factors slumped to 20.3% in June from 37%in May and 40.5% in April, according to MISO's "December 2015 MonthlyMarket Assessment Report."
In May 2016, wind was the marginal fuel for about 52.5% ofthe time, just behind coal that was on the margin 77.1% of the time, accordingto MISO's May 2016 report. Combined-cycle gas generation was on the margin 40%of the time and traditional gas turbines were on the margin 51.6% of the time,according to the report. The marginal fuel indicates which fuel tends to runand sets the locational marginal price, the price of power at a specific timeand location. Hydropower was on the margin about 25.4% of the time. Because oftransmission constraints, more than one fuel can be on the margin at a point intime, MISO said in the report.
Generally, wind is on the margin a higher percent of thetime during off-peak hours, which runs from 10 p.m. to 6 a.m. ET each day. Windwas on the margin 44.4% of the time during peak hours, but 59.1% of off-peakhours, according MISO's report.
Wind generation formed about 7.1% of MISO's fuel mix in May2016, overshadowed by coal and natural gas, which formed 41.2% and 26.7%,respectively. Nuclear generation formed another 18.4%. The remainder of the mixwas made up of a mix of hydropower, other renewables, petcoke, and oil and gasgeneration, according to MISO's report.