Recession finally impacts generation, but only slightly.
by Teresa Hansen, editor in chief
Until 2009, the worse recession on record had little impact on U.S. electricity generators. In 2009, however, the recession was partly to blame for a decrease in the amount of electricity generated by coal-fired power plants. U.S. coal-fired power plants generated 236 million MWh fewer in 2009 than they did in 2008, a decrease of about 12 percent.
“Coal is being utilized less,” said Tom Hewson, principal at Arlington, Va.-based Energy Ventures Inc., a firm that specializes in energy and environmental market analysis.
This decrease is caused partially by an increase in natural gas use.
“The interplay between gas and coal is always interesting,” Hewson said.
Gas prices continued to stay low in 2009, while Appalachian coal prices remained about the same as they were in 2008, which was fairly high, Hewson said.
“Favorable gas prices have resulted in more efficient gas units replacing coal,” he said.
In addition to favorable gas prices, more renewable energy displaced some coal-fired generation.
Hewson and Dave Pressman, an analyst at Energy Ventures, generated Tables 1-7 for this annual Electric Light & Power report from data contained in Form EIA (Energy Information Administration) 906, “Power Plant Report.”
Past Electric Light & Power operating performance articles have included operating data from gas-fired combined-cycle plants.
The EIA changed its reporting schedule for the 2009 data and, therefore, the gas-fired data was not available at press time.
The tables and analysis for gas-fired combined-cycle plants will, however, be published in a later issue.
The top 20 coal-fired generating plants didn’t change much. Only three new plants broke into the top 20, and the top 12 from 2008 kept the top 12 slots in 2009 with a slight change in order.
Utilities aren’t building new coal plants, Pressman said.
“No new large plants are coming online to displace the existing plants,” Pressman said.
Santee Cooper’s Cross generating station was an exception. Unit 4, a $755 million, 600-MW unit, was added to the site Oct. 1, 2008, making Cross large enough to make 2009’s top 20 list.
Even with a 56.9 percent capacity factor, the 2,931-MW facility moved onto the list.
To make the top 20, plants must be big; generally greater than 2,000 MW. Luminent’s Monticello plant at 1,931 MW was another exception. It made the list because of its high capacity factor.
“There is little turnover on this list,” Pressman said. “These plants are the workhorses of their perspective fleets. They run all out. They are baseload units and operate at low cost.”
Coal Capacity Factor
Two factors put a plant at or near the top of the capacity factor list, Hewson said. First, being a co-generator almost always increases a plant’s capacity factor.
“Plants that provide industrial loads, which are typically required 24 hours a day, run all the time,” Hewson said. “They are unlike plants that provide electricity based on typical load profiles, which fluctuate.”
No. 1, Rio Bravo Poso, and No. 2, Yellowstone Energy Ltd., are co-generators.
The second factor that affects a plant’s capacity factor is its location, Hewson said.
“Plants located in areas where power can be transmitted to large load centers usually run a lot and thus have higher capacity factors because they can sell electricity around the clock,” Hewson said. “Easy access to transmission capacity means plants that do not have a local market for their off-peak power can feed that power through transmission lines to load centers at all time.”
Most coal plants run at minimum load during off-peak hours and crank up during the day.
A 70 percent capacity factor is typical, Pressman said.
Only four plants on the 2008 list made the 2009 list. This is mainly because of maintenance outage schedules.
“Generally, coal plants must come down annually for maintenance outages, which usually last about 40 days,” Pressman said. “Those that didn’t come down for maintenance had a higher capacity factor.”
Capacity factor for the 2009 top 20 was 2.5 percent lower than the 2008 top 20, while capacity factor for all plants reporting was down 11 percent in 2009 compared with 2008.
In addition, in 2008 three coal-fired units operated at capacity factors above 100 percent. That did not occur in 2009, where the highest capacity factor was 99.5 percent.
These lower numbers reinforce Hewson’s statement that less coal-fired generation was dispatched in 2009 than 2008.
Coal Heat Rate
“Overall, the 2009 heat rates were not as good as 2008 heat rates,” Hewson said. “I suspect it has to do with load.”
Generally, a facility must be very efficient to get on the heat rate list.
“The easiest way to make the list is to be a supercritical plant,” Hewson said. “Higher-pressure steam is more efficient.”
Supercritical plants can make up for efficiency lost during cycling, which commonly lowers capacity factor and heat rate.
Twelve units on the top 20 list are supercritical; two others are circulating fluidized bed (CFB) plants. The remaining six are subcritical plants.
Hewson was surprised to see Intermountain, a subcritical plant, move from No. 6 in 2008 to the top of the 2009 heat rate list.
“I’m still trying to figure out how Intermountain did so well,” Hewson said. “Intermountain sells steam for enhanced oil recovery, which is needed 24/7, so the plant runs all the time. This does help, but I’m still surprised the plant made the No. 1 spot.”
Intermountain is No. 18 on the capacity factor list, Table 2, with an 85.9 percent capacity factor.
Twelve plants that made the 2008 list returned in 2009. One plant that has been on the top 20 list for several years but did not show up in 2009 is SCANA Corp.’s McMeekin Station, a 250-MW subcritical plant whose presence on the list always baffled Hewson.
Last year Hewson said he would like to ask the plant’s management “what they are doing right.”
That comment spurred a response from Joe Todd, general manager of fossil hydro operations at SCANA/South Carolina Electric and Gas Co.
Todd said three major factors drive heat rate at McMeekin.
They are year-round cold cooling water used at the plant, the cross compound turbine design and the ongoing maintenance and efficiency efforts of the plant staff.
By far the biggest impact comes from the 50 F cooling water that McMeekin receives year-round from Lake Murray, Todd said.
“It is extremely unique for a power plant to have this circulating water temperature even in the summer months,” he said. “It results from our taking circulating water from the bottom of Lake Murray at a depth of almost 160 feet.”
Plant staff conducted a performance computer model simulation, changing the cooling water temperature to a level consistent with SCANA’s Canadys Station.
|Georgia Power’s 3,045 MW Robert W. Scherer plant generated 22,971,057 MWh of electricity in 2009, Photo courtesy of Georgia Power.|
The simulated result indicated that the lower cooling water temperature lowers the plant’s heat rate by about 450 Btu/KWh, Todd said.
Another driver that is not as easily quantified is the cross compound turbine design that provides an efficiency benefit, but not to the degree of the cooling water, he said.
In addition, Todd credited the plant staff with the unit’s performance.
“The staff is extremely cognizant of heat rate, and they use a performance-monitoring work station to help identify areas for heat rate improvement,” he said.
Although McMeekin didn’t make the 2009 top 20 list, it was close, coming in at No. 23 with a 9,757 Btu/KWh heat rate.
“How low can you go? Incredibly low,” Hewson said of the SO2 emissions rate list.
To make this list, a plant must have scrubbers. It also helps to burn low-sulfur coal.
As Table 4 shows, only three of the top 20 plants were not burning Powder River Basin (PRB) or Central Appalachian (CAPP) coal: Duck Creek (Illinois Lower Basin coal), Mount Storm (Northern Appalachian) and Oak Grove (lignite).
“Oak Grove made the list because it’s new and just started in late 2009,” Hewson said. “The other two made the list because they are doing an exceptionally good job at scrubbing–efficient use of equipment.”
Just more than one-half of all U.S. coal-fired capacity has scrubbers, and that percentage is growing, Pressman said.
“Lower and lower rates in the top 20 should continue as more units are scrubbed,” he said.
The 2008 top 20 average was .054 lbs/mmBtu. The 2009 average was better with .044, Hewson said.
It doesn’t take much to fall off the list. In addition to scrubbers, plants also must have high availability.
To make this list, a plant must have post-combustion selective catalytic reduction (SCR) equipment or CFB combustion, which requires less air for efficient combustion resulting in less air to be converted to NO2.
Three CFBs made the 2009 list: Northeastern Power Co., Thames and AES Warrior Run. All three were on the 2008 top 20 list.
Although SCR equipment is expensive, more plants are installing it, Pressman said. This is reflected in the 2008 vs. 2009 NO2 emission numbers.
As Table 5 shows, the top 20 coal-fired plants’ average NO2 emission in 2009 was .055 lbs/mmBtu. In 2008, the top 20 average was .058 lbs/mmBtu.
“No. 20 in 2009 would have been No. 12 in 2008,” Hewson said, “so the emissions rate is going down.”
The average NO2 rate for U.S. coal-fired plants in 2009 was .09 lbs/mmBtu. Pressman expects the average to continue to decrease.
“Plants are operating their equipment better, but the emission rate also is dropping because more SCRs are coming online,” Pressman said.
Little changes year to year on the top 20 nuclear generation list.
|Progress Energy’s H.B. Robinson nuclear power plant had the highest capacity factor in 2009. Photo courtesy of NRC.|
“The biggest plants make the list,” Hewson said. “Those brought down for outage during the year might drop off.”
Pressman said these plants run hard.
“Like the large, baseload coal-fired plants, they are the workhorses of their utilities’ fleets,” he said.
While the top 20 nuclear generators generated a bit more in 2009 than the top 20 in 2008, the nation’s entire nuclear fleet generated about 14.7 million MWh fewer in 2009 than in 2008.
Nuclear Capacity Factor
Like nuclear generation, capacity factor ranking also depends heavily on outage schedule.
Usually those plants in the top 20 were not brought down for refueling.
In 2008, three of the top 20 plants had capacity factors above 100 percent. In 2009, only one had a capacity factor above 100 percent.
Even so, the average capacity factor of the top 20 was higher than 2008: 97.4 vs. 96.4 percent.
The capacity factor of the entire U.S. nuclear fleet, however, was lower in 2009 than in 2008: 90.5 vs. 91.1 percent.
Overall, the country’s nuclear fleet performance has changed little during the past few years.
These plants continue to perform well.More Electric Light & Power Articles
Past EL&P Issues