Generation increases slightly while emissions decline
by Teresa Hansen, editor in chief
Last year’s power plant operating report revealed U.S. electricity generation declined in 2009, which Electric Light & Power attributed to the recession. This year’s data indicates electricity generation rose slightly in 2010 but remained less than that reported in 2008. The increase, although small, could signal what many economists have said: The U.S. is coming out of the worst recession the country has experienced since the Great Depression.
Average megawatt-hours generated in all three categories—nuclear, traditional coal-fired and natural gas combined cycle—increased in 2010. Many experts, however, expect coal-fired generation will decline during the next few years as some plants struggle to meet increasing environmental regulations, said Tom Hewson, principal at Arlington, Va.-based Energy Ventures Analysis Inc., which specializes in energy and environmental market analysis.
“The utility MACT (Maximum Achievable Control Technology) rule that is supposed to take effect in December will certainly result in the retirement of coal-fired plants,” Hewson said. “Some utilities will choose to shutter some of their coal plants rather than spend the money needed to bring them into compliance.”
The Environmental Protection Agency (EPA) created the MACT rule to fulfill the Supreme Court order to regulate toxic air emissions from power plants. Critics of the rule and people in the utility industry predict MACT will challenge the power sector in the years ahead.
“Plants will have three to four years to comply with the rules once they take effect,” Hewson said.
Hewson expects some of the retired coal-fired capacity to be replaced with cleaner-burning natural gas-fired combined-cycle plants, as well as unconventional generating sources.
Unconventional generating sources, of which wind, solar and biomass are most common, could be problematic if society becomes too dependent on them to replace traditional sources such as coal, Hewson said.
Wind is the most common unconventional source of electricity, but its capacity factor never will be close to those of traditional generators’ capacity factors, he said.
“Some people predict wind can reach an average capacity factor of 35 to 40 percent, but that will never happen,” Hewson said.
An accurate average capacity factor for wind is hard to find; different sources report different figures, but most are reported somewhere between 20 and 35 percent.
“With new wind farms coming online so often, it’s hard to calculate an accurate nationwide capacity factor average,” Hewson said. “The newer facilities, however, will have a lower capacity factor than the older established wind farms. The older farms were built in the best (windiest) locations, so the newer wind facilities will not improve on the current capacity factor.”
As in years past, Hewson generated the tables for this annual industry report from data contained in Form EIA (Energy Information Administration) 906 “Power Plant Report.” Because more renewable sources are being added to the generation mix, Hewson and Electric Light & Power might add renewable generation to the annual report in a year or two.
Generally, the tables in this report speak for themselves, but following are a few observations.
Nuclear Power Plant Performance
Nuclear Generation (Table 1)
“Little changes in this list from year to year,” Hewson said. “There were no real unanticipated changes.”
Nuclear plants generate electricity at low incremental costs and, therefore, typically run flat out. They have high capacity factors and provide a lot of power.
Nineteen of the top 20 plants made the list last year, and the first six plants appear in the same order. One new plant made the 2010 list: Donald C. Cook, which came in at No. 20.
“The only way this list will vary much is for some new, large units to be built,” Hewson said. “The cost of new units keeps going up, so the question remains: Will a new unit ever be added to the list?”
Costs for new construction are so high that a new unit will be built only by a regulated utility or a group of regulated utilities, not by an independent power producer, he said.
“A new unit will be cost-effective only if CO2 legislation that drives up the cost of carbon is enacted or if natural gas prices go through the roof,” Hewson said.
Nuclear Capacity Factor (Table 2)
The average capacity factor for the top 20 nuclear plants, as well as the entire fleet, was a little higher in 2010 than 2009.
Colstrip Power Plant in Montana is one of the lowest cost coal-fired units in the U.S. It ranked No. 13 on the list of top coal-fired generators.
“The best capacity factor is a little higher in 2010 than it was in 2009,” Hewson said. “This could indicate that units have been modified to increase their (nameplate) capacity and the paperwork needs to be updated.”
Nuclear plant owners are spending money on retrofits to increase capacity. That trend shows up in the higher capacity factor numbers, he said.
The plants on this list likely did not refuel during the reporting year and have plenty of cooling water. Most nuclear units run flat out because their variable costs are so much less than fossil-fueled units.
Coal-fired Power Plant Performance
Coal Generation (Table 3)
The top 20 coal generation story is similar to the nuclear generation story. The plants on this list are large plants with high utilization rates.
Hewson pointed out that Colstrip, No. 13, is one of the lowest-cost units around. In addition, it has a high capacity factor because its electricity is sent west to California. It’s one of the cheapest incremental cost units of all coal plants, he said.
Jim Bridger and Martin Lake also made the list because they are mine mouth plants and have no fuel transportation costs, making them fairly cheap generators among coal units. Thus, their utilization rates are high.
“Many of the units on this list are huge, scrubbed units, so they will likely be operating for some time to come,” Hewson said. “Rockport, however, is an unscrubbed unit that uses Powder River Basin coal, so it’s highly utilized. I expect it will be scrubbed in the next 10 years.”
Coal Capacity Factor (Table 4)
The top capacity factor list changes more from year to year than the top generating list.
Some things that lead to a high capacity factor for coal units, Hewson said, are:
à¢— Selling into a market that needs the power most of the time, so power is seldom, if ever, turned down. For example, being in the West and selling into the California market often results in a high capacity factor.
à¢— Being next to an industrial facility that can use the electricity, steam or both most of the time increases capacity factor.
à¢— Generating at low cost keeps plants high on the dispatch list and allows them to run near full out most of the time, increasing capacity factor. A plant that is competitive in its power pool is likely to be high on the capacity factor list.
Hewson explained why a few of the plants made the list.
“Rio Bravo Poso and ACE Cogen Co. are co-gen facilities that sell steam to refineries when their electricity isn’t needed,” he said. “Wood River also is next to a refiner. Ray Nixon is owned by a municipality, so it is utilized a lot and has a high capacity factor.”
Coal Heat Rate (Table 5)
The top 20 heat rate plants’ cumulative heat rate was markedly better in 2010 than in 2009: 9,414 vs. 9,615, respectively. The average heat rate of all reporting plants, however, was only slightly lower than the average in 2009. Eleven plants from the 2009 list returned in 2010.
Hewson said the coal heat rate top 20 list is hard to compile because many of the units on it are co-generators and their accounting practices vary from owner to owner. Because co-generators sell electricity and steam, the way they divide the products can differ.
Generally, units that operate in co-generation mode are more efficient than those that generate only electricity, Hewson said.
Some of the plants that normally end up on this list are CFB (circulating fluidized bed) and co-generation plants. Supercritical plants also do well, as do plants with a high capacity factor.
“Interstate P&L is a bit misleading,” Hewson said. “The numbers are reported based on the entire station, not plant-by-plant. Interstate P&L has two small gas-fired turbines that aren’t particularly efficient and don’t run all the time. It also has a larger (212 MW) coal-fired plant that runs a lot and is efficient, so it managed to make the list.”
Several units on the list have low capacity factors, but they made the list because they are supercritical plants. Bull Run usually has a higher capacity factor, but a control project took it offline for part of the year, so its capacity factor is significantly lower than in past years.
Plum Point Energy Station is a new “super duper critical unit,” Hewson said. “It started up in 2010, so its capacity factor is low but should be much higher in 2011.”
After falling off the list in 2009, McMeekin Station, the subcritical plant that is an anomaly, was back on the list in 2010. Last year’s article mentioned the factors that drive heat rate at the plant. Year-round cold (50 F) cooling water has the most impact. (Editor’s note: Read more about McMeekin in “Operating Performance Rankings, 2009—Top 20 Power Plants,” Electric Light & Power Nov/Dec 2010.)
“I was surprised at the difference cold cooling water could make in capacity factor,” Hewson said. “I didn’t appreciate what a difference it made.”
Coal SO2 (Table 6)
The average pounds per million British thermal unit (lbs/mmBtu) is much lower for the top 20 and all reporting plants than it was in 2009. The top 20 average sulfur dioxide (SO2) emissions dropped to 0.036 lbs/mmBtu from 0.044 lbs/mmBtu and to 0.544 lbs/mmBtu from 0.790 mmBtu for all reporting plants.
The units on this top 20 list are scrubbed units, and many also use Powder River Basin coal, Hewson said. The lower numbers from 2010 vs. 2009 reflect operators’ installing more scrubbers and optimizing them. In addition, some of the plants on the list have relatively new scrubbers, which are more efficient than older scrubbers.
“CSAPR (Cross-State Air Pollution Rule) will change the value for emission credits by increasing the requirements for coal-fired plants,” Hewson said. “Once it becomes effective, there will be even more incentive for coal plants to optimize their scrubbers.
“Currently, the price of SO2 is about $9 per ton, so the financial incentive for utilities isn’t that great, but the numbers show they are still running their scrubbers quite a bit. The price could reach up to $500 a ton, so at that point units with scrubbers will optimize them, and units without scrubbers will install them.”
The CSAPR rules will require all scrubbers to remove at least 95 percent of all SO2. In some cases, the requirement will be as high as 99 percent, Hewson said.
“I wouldn’t feel comfortable reaching 99 percent on a consistent basis, but maybe the new technology and operating procedures will prove me wrong,” he said.
Coal NOx (Table 7)
“The NOx levels show that the ozone rules have been hammering some plants in high-ozone areas to reduce NOx,” Hewson said. “Also, NOx contributes to fine particulates, so in 2009 many units started running NOx control year-round to reduce fine particulates. Prior to that, plants ran NOx units only during ozone season. Some still operate them only during ozone season.”
Portland General Electric’s Port Westward gas-fired combined-cycle power plant had the best heat rate of any gas-fired combined-cycle plant in the U.S.
Ozone season, he said, is May 1 to Sept. 30. In addition, in many areas in the U.S., regulations are being revised to further reduce emission limits.
“It’s harder to reduce ozone because unlike acid rain, which is primarily sulfur and is emitted mainly by power plants, NOx comes from many sources including transportation and other industries,” Hewson said.
Gas-fired Combined-cycle Power Plants
Last year’s operating report did not include gas-fired combined-cycle plants because a change in the reporting schedule didn’t allow Hewson to compile the data in time for Electric Light & Power’s deadline. The article said the tables and data would be published later in the year, but that didn’t happen.
Hewson was able to compile the data by the deadline this year, so the gas-fired combined-cycle information is back in the report.
Combined-cycle Generation (Table 8)
To make this list, like nuclear and coal, it helps to be big and have a lot of units on one site.
Combined-cycle Heat Rate (Table 9)
The top 20 combined-cycle heat rate is difficult to determine because many units are co-generators and, like with coal-fired co-generators, accounting practices vary widely.
“How heat rate is reported or calculated can make a big difference,” Hewson said. “Co-gen can make plants appear much more efficient when heat losses are assigned between various products (steam, electricity). Some owners-operators assign a lot of Btus to the steam cycle, lowering heat rate on the electricity generating side.”
For this list, Hewson tried to eliminate co-generation units and report on units that generate only electricity; therefore, averages and totals for all reporting plants are not included in the table.
Some plants with much better heat rate numbers appear on the other combined-cycle tables that include co-generation units.
Combined-cycle Capacity Factor (Table 10)
Unlike heat rate, this list includes co-generation facilities, explaining why some of the plants listed, such as No. 10’s Palomar Energy Center with a heat rate of 4,019, have much lower heat rates than the lowest heat rate number on the top 20 heat rate table.
“Accounting practices put some low heat rate numbers on the capacity factor table,” Hewson said.
Combined-cycle NOX (Table 11)
“Combined-cycle plants can reach extremely low emission rates with controls,” Hewson said. “It’s hard to verify the numbers’ accuracy because they are measured up to four digits past the decimal. The accuracy of what is reported could vary a lot due to how well and how recently the measuring equipment was calibrated, which plays a big role in the numbers.”
Omaha Public Power District’s Fort Calhoun Nuclear Station had the highest capacity factor of any nuclear plant in the U.S. in 2010.
The industry is pushing it in having four significant digits. It could be overstating equipment limitations by using this many digits, he said.
“Anything after the third digit could be questionable, but the bottom line is that natural gas has much lower NOX emissions than coal,” Hewson said. “Gas-fired combined-cycle postcombustion controls are more advanced than the controls used on coal-fired units, and natural gas doesn’t contain as much nitrogen, so the numbers are much lower.”