Coal plant outages drop in PJM, but causes persist

OREANDA-NEWS. Fewer coal-fired generators in the largest US power grid went off line this winter but lack of proper weather preparation and mechanical breakdowns remain leading causes of outages, PJM Interconnection says.

The winter 2015 performance report, released this week, will be noted by owners of coal generation who expect a significant increase in revenue if PJM succeeds in pushing through a reform of its forward capacity market later this summer. But a key premise of the "capacity performance" plan is that reliably operating power plants with firm fuel supply will benefit greatly while generators suffering forced outages will face stiff penalties. Power plants as a result have an economic incentive to cut forced outage rates by 2018.

PJM on 20 February recorded a wintertime peak load record at 143,086MW, slightly beating the prior record from January 2014. Both winters were unusually cold. Parts of the mid-Atlantic region this year experienced the coldest February on record. But power prices in winter 2014-15 trailed year-earlier levels because natural gas prices fell and more generation of all types was available for dispatch.

PJM generation running at the time of the 20 February peak included 57GW of coal, or 41pc of the total. That share was slightly higher than in January 2014. Natural gas prices in the mid-Atlantic region spiked in February, making marginal coal and oil units run more often. The share of gas on 20 February was 26pc and nuclear plants provided another 23pc.

The overall rate of forced outages fell by almost half to 13pc, with 24,805MW off line on 20 February. Coal units accounted for 41pc of the total, or 10,224MW. Gas supply interruptions and other outages removed 10,661MW off line.

Forced outages at coal plants in absolute terms fell by 25pc from the January 2014 peak. But the share of coal among plants encountering forced outages rose to 41pc from 34pc last year.

Coal stocks' exposure to cold weather, boiler breaks and tube leaks are among primary causes of outages. Coal that initially may have been frozen can plug chutes after being crushed and contribute to combustion problems. PJM said the incidence of such problems was similar in the last two winters despite a new winterization program implemented prior to last winter. Winterization did not mitigate the risks of fuel exposure to the elements, PJM said.

Another cause of outages is equally troubling given the retirement of coal capacity and greater reliance on natural gas in dispatch. Marginal coal units cycled — restarted and powered down — more often in winter 2014-15 and as a result suffered more mechanical breakdowns. Most coal plants are built under the assumption of consistent use with few starts and stops, so operating them in a different configuration can increase the incidence of outages.

PJM in February dispatched 49pc of units slated for retirement in 2015-18, which total 11,560MW. But forced outage rates were more common among those units, at 31pc. The retiring units typically represent the oldest part of the coal fleet.