The recent polar vortex cold snap strained the nation's natural gas pipeline systems, but they performed relatively well, and it is unclear how much electricity was not able to be produced due to any lack of available gas, according to a preliminary review presented during FERC's regular monthly meeting Thursday in Washington, DC.
"At this time, it appears that Midwest, Northeast and Southeast regions set record demands for natural gas, while other parts of the Eastern and Central U.S. were near their all-time peaks," according to the review, which was primarily focused on the historically cold weather's impacts on the bulk power system.
Cold that clamped down on much of the country last week prompted constraints on pipelines into New England, and throughput at a central Alabama gas utility ran at 10-year record levels (see Daily GPI, Jan. 6; Jan. 7). One compressor station outage on the Texas Eastern pipeline in western Pennsylvania resulted in throughput reductions of nearly 600,000 Dth/d, or about 10% of the pipeline load.
"Most other pipelines curtailed interruptible or secondary firm transportation and storage services," said the Federal Energy Regulatory Commission (FERC) review.
And high numbers for last week's burn weren't confined to the northern part of the country. AGL Resources in Atlanta reported that its three distribution companies doubled their sendout for Jan. 6 and Jan. 7 to about 15.1 Bcf for the two-day period, setting records along the way (see Daily GPI, Jan. 15). Nicor Gas (IL), and Atlanta Gas Light recorded the second highest deliveries in their history at 4.5 Bcf/d and 2.1 Bcf/d, while Chattanooga Gas in Tennessee set a peak day record of 1.3 MMcf. Piedmont Natural Gas, which provides natural gas to customers in North Carolina, South Carolina and Tennessee, reported 2.41 million Dth sendout on Jan. 7, exceeding by 30% the company's previous winter season single-day record (see Daily GPI, Jan. 14).
But the effect on power generation remained manageable during the polar vortex, according to the FERC review.
"While fuel restrictions certainly stressed the electric supply, system operators were able to maintain reliable electric service. In New England, for example, six units totaling around 1,200 MW were not able to procure fuel initially when called intraday by the ISO [independent system operator]. This request, however, was made on behalf of another RTO [regional transmission operator] and did not affect power supply in New England.
"Electric system operators have also reported that their gas-electric coordination procedures generally worked well. For example, MISO contacted several gas pipelines starting on Jan. 3, and made subsequent schedule adjustments in order to ensure adequate generation."
Power system operators also reported problems such as frozen coal stockpiles at coal-fired generating stations, problems with fuel switching at dual-fuel units, and wind turbines reaching their minimum operating temperatures, FERC said. Two nuclear units tripped due to equipment problems, "but it is not clear at this time if the problems were related to the cold temperatures," according to the report.
Preliminary data indicates that forced generation outages were significant in some regions -- at least 50 GW in the most severely impacted areas of the Eastern Interconnection, higher than the historical wintertime average forced outage of 33 GW -- but more analysis is needed to determine how much of it was weather-related, FERC said.
Demand for natural gas hit 137 Bcf/d on Jan. 7, 11 Bcf/d more than the previous winter record set in 2008-2009, according to FERC, driving prices to record highs and helping push withdrawal from storage for the week to a record high 287 Bcf (see related story).
"Given the storage levels of inventory right now and estimates going through the end of the winter, we anticipate end of withdrawal season storage will be below the five-year minimum, but still about twice as much as the all time low record recorded at the end of March 2003," said Valeria Annabali of FERC's Office of Enforcement. "With robust production, these levels should be enough to supply markets with natural gas, absent any extreme weather events or unusual circumstances."
Some of what went right during the polar vortex might be attributed to lessons learned during investigations by FERC and the North American Electric Reliability Corp. into the causes and aftermath in 2011 of gas end-use customer shutoffs, and gas and electric infrastructure freeze-ups in the midst of a severe winter temperature drop in the Southwest (see Daily GPI, May 11, 2011).
"It is too soon to draw detailed comparisons of performance in 2011 versus last week, or assess the extent to which entities avoided the particular mistakes of 2011, but in broad scope certainly the overall outcome was better, which suggests that the efforts made since 2011 have yielded a change for the better," the report said.