2011 Operating Performance

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Generation Remains Fairly Constant, No Surprises

by Teresa Hansen, editor in chief

The 2011 power plant operating performance report didn’t uncover anything unexpected about U.S. electricity generation. Coal-fired, nuclear and gas-fired combined-cycle power plants generated less electricity in 2011 than in 2010, but the decrease was slight and could be the result of a mild winter, slow economic growth in the U.S. and energy efficiency measures. In addition, robust mandates allowed wind and other renewable technologies to capture a large portion of the power industry’s relatively small incremental growth. Wind generators, which are not included in this report, generated more electricity in 2011 than ever before. The Energy Information Administration (EIA) reports that the nearly 48 gigawatts of wind power facilities installed in the U.S. contributed 120,000 gigawatt-hours (GWhr) of electricity to the grid in 2011. The only way for a fossil fuel to expand its generation share is at the expense of another fossil generating source.

GenPower’s Longview plant was No. 1 on the top 20 list of coal generators ranked by heat rate. Courtesy: First Resource Corp.

Last year’s power plant performance report predicted U.S. coal-fired generation would decline. That prediction held true. Coal-fired plants generated some 4 percent less electricity in 2011 than in 2010. The decrease likely will be much larger than 4 percent in coming years; many utilities have announced they will retire significant numbers of coal-fired power plants rather than upgrade them to adhere to the Mercury and Air Toxics Standards (MATS) rule released by the Environmental Protection Agency in December 2011.

In addition, coal has lost some generation share to natural gas combined-cycle facilities. Superior heat rates and fuel price economics have allowed gas combined-cycle generators to displace coal as a baseload generation source.

Gas-fired combined-cycle power plants generated some 63,500 GWhr more in 2011 than in 2010. Tom Hewson, principal at Arlington, Va.,-based Energy Ventures Analysis Inc., predicted this trend when he was interviewed for this article last year. Energy Ventures Analysis specializes in energy and environmental market analysis and has compiled the data for this industry report from Form EIA 906 “Power Plant Report” for many years. The increase in gas-fired generation can be attributed to low natural gas prices and stricter environmental regulations on coal-fired generation.

The tables in this report are easy to understand. They require little explanation, but following are a few observations.

Coal-fired Power Plant Performance

Coal Generation (Table 1). The generation threshold to qualify as a top 20 coal generator in 2011 dropped 4 percent from 2010 rankings.

As in past years, to be in this group, a plant must have multiple large units and a high utilization rate.

“With no exceptions, units (on this list) are dispatched early because of their low variable costs,” said Adam Picketts, an energy analyst at Energy Ventures Analysis.

Some of the units listed experienced limited displacement from low natural gas prices, he said.

Southern Co.’s Bowen Plant, which was No. 1 in 2010 and No. 13 in 2011, dropped 33 percent—a result of outages for environmental control retrofit work and low natural gas prices.

“Four Corners’ appearance on the list (No.16) will be short-lived,” Picketts said.

Arizona Public Service Co.'s Palo Verde nuclear generating station was No. 1 on the list of top nuclear plant performers based on generation.  Courtesy: Arizona Public Service Co.

California’s carbon dioxide regulation will force Southern California Edison to sell its 739-MW share in Four Corners units 4 and 5 to Arizona Public Service in mid-2013. Arizona Public Service then will shut down units 1, 2 and 3, which have a combined capacity of 560 MW, he said.

Several large plants that ranked in the top 20 generating units in 2010 dropped off the list in 2011, including Colstrip, Roxboro, Jim Bridger, Paradise and Cumberland.

Coal Capacity Factor (Table 2). Typically, the coal capacity factor list varies much more from year to year than the top generating list, and 2011 was no exception. Only three plants from the 2010 list made the 2011 list; Rawhide, Wilson and Black Hills. Some eastern units lost generation to low-cost natural gas.

“Sixty percent of the plants on the list are cogenerators that run to supply steam for industrial users,” Picketts said. “And, as in years past, several of the units on the list burn western coal and sell power into California—a combination that boosts capacity factor.”

Coal Heat Rate (Table 3). The top 20 heat rate plants’ threshold was reduced in 2011 to 9.754 million British thermal units (mmBtu)/MWhr from 9.648 mmBtu/MWhr in 2010. Even with the reduced threshold, average heat rate for the top 20 was nearly the same in 2011 as in 2010: 9.46 vs. 9.41 mmBtu/MWhr.

“To make the top 20 list, it helps to be relatively new and supercritical,” Picketts said.

Fourteen of the top 20 plants are supercritical. Nos. 1 and 3 on this list, Longview and Trimble County, respectively, are new supercritical units. Longview came online late in 2011 and Trimble County Unit 2 early in 2011. Unlike past years, cogenerators were not included in the 2011 heat rate rankings.

Nuclear Power Plant Performance

Nuclear Generation (Table 4). The nuclear generation story changes little from year to year. No new plants have been added to the U.S. nuclear fleet in many years, so refueling cycles are about the only variable that impacts annual generation numbers. High capacity and multiple units at a plant site help plants stay on the list.

“Alternating outages between units allows a plant to run consistently high,” Picketts said.

For example, Palo Verde, the largest nuclear plant in the U.S., kept the No. 1 spot because units 1 and 3 refueled in 2010 and units 1 and 2 refueled in 2011, he said.

Because most nuclear plants refuel every 18 to 24 months, Picketts said, the top performers should be different every other year as each unit comes down for refueling.

Southern California Edison’s San Onofre Plant is the only plant on the 2011 top 20 list that was not on the 2010 list. This is because both units experienced extended outages in 2010.

Nuclear Capacity Factor (Table 5). The average capacity factor of the top 20 nuclear plants was slightly lower in 2011 than in 2010: 97.0 percent vs. 98.2 percent.

In addition, the U.S. nuclear fleet’s total capacity factor was lower in 2011 than in 2010: 89.0 percent vs. 91.4 percent.

The top 20 nuclear plant capacity factor list changes much more from year to year than the nuclear generation list because refueling outages have a bigger impact on capacity factor than on megawatt-hours generated.

Even though a large plant may make the top 20 list in generation, an outage at one of its units can weigh down the entire station’s capacity factor.

Some smaller single unit facilities commonly make the list because their alternating refueling schedule allows them to run flat out every other year, Picketts said.

“Because refueling outages are cyclical, we expect the 2012 nuclear capacity factor list to look similar to the 2010 list, as most of the same units will come offline at some point in 2012,” he said.

Gas-fired Combined-cycle Power Plant Performance

Combined-cycle Generation (Table 6). As with nuclear and coal-fired generation, the plants that make the top 20 gas-fired combined-cycle generation list are large and have a lot of units on one site.

The threshold to make the top 20 list in 2011 was similar to the 2010 threshold. West County Energy Center, which held the No. 1 position, added 1,200 MW in 2011 and increased its capacity nearly 60 percent from 2010 levels.

Sixteen of the top 20 generators in 2011 returned from 2010.

Fairless Energy, new to the list in 2011, likely made the list because of shale gas, Picketts said.

“An increase in Pennsylvania shale gas production likely decreased its deliverezd fuel cost, allowing it to dispatch ahead of older and less efficient coal units in the region,” he said.

Although natural gas prices were lower in 2011 than 2010, in some areas, above average rainfall and snowpack—particularly in the West—helped hydroelectric displace natural gas as a generation source, Picketts said.

Combined-cycle Capacity Factor (Table 7). The threshold capacity factor for the top 20 combined-cycle plants was about 13 percent higher in 2011 than 2010.The fleetwide capacity factor remained about the same.

As in years past, this list includes cogeneration facilities. Some of these plants provide steam for industrial use, keeping them running year-round.

Combined-cycle Heat Rate (Table 8). Unlike the capacity factor list, the combined-cycle heat rate list does not include cogenerators. Because cogenerators can calculate and report heat rate in various ways by assigning heat losses between steam and electricity, Energy Ventures Analysis eliminated them from the heat rate list and included plants that produce only electricity.

Half of the top 20 plants on the 2011 heat rate list were on the 2010 top 20 list. Southern Co.’s 840-MW Jack McDonough plant that came online in 2011 was a newcomer to the 2011 top 20 list.

Editor’s note: Energy Ventures Analysis Inc. provided all tables in this article, as well as tables listing the 20 combined-cycle plants with the lowest NOX emission rates in 2011; the 20 coal-fired generators with the lowest SO2 and NOX emissions rates. These tables are included in this online addition of the article and not in the printed version.

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