by Nancy Spring, Managing Editor
No, no, no. No coal plants, no nuclear plants, no LNG ports. That’s the gist of the public’s attitude toward new power generation. Which leaves us what? Renewables and energy efficiency. Sadly, that won’t be enough-electricity usage in the U.S. is projected to grow more than twice as fast as committed resources over the next 10 years.
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Lucky for us, the generation fleet we have right now is doing a super job of keeping us out of the dark and cold, and if we continue to be lucky, more plants will come on line.
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The top 20 coal, nuclear and combined cycle plants are in peak form, running full tilt and with the latest technological advancements, getting more efficient and cleaner every day, according to Tom Hewson, principal at Energy Ventures Analysis, an Arlington, Va.-based firm that specializes in energy and environmental market analysis and forecasting. Hewson directs the firm’s environmental studies and provides analysis for our Operating Performance Rankings each year. With Hewson, we get good, realistic analysis instead of wishful thinking. Read on for his thoughts on nuclear, coal and natural gas combined cycle generators in the U.S.
Nuclear: A small but powerful community
From year to year, there’s not much change in the top 20 nuclear plants ranked by generation (see Table 1). To be a member of this exclusive club, basically a plant needs 2,000 MW of capacity and multiple units. It’s the timing of scheduled outages and refueling that makes the difference in rankings.
In fact, for 2006, there’s only one newcomer. Entergy’s Arkansas Nuclear One is now No. 20, squeaking in with 1,842 MW. Pinnacle West is still No. 1. “Pinnacle West’s been No. 1 for what seems like forever and it’s unlikely that it will be displaced,” said Hewson.
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Capacity increased a bit over 2005, partly because the nuclear industry has gotten better at spreading out the timing between various refuelings and scheduled outages, taking out some of the bottlenecks. “We’ve also had some reratings,” Hewson said. “We’ve added 110 MW, but the number of plants hasn’t changed.”
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The cost of power produced by these plants is low, so they’re dispatched first in their respective systems and tend to run all the time. “They’re running like a top, with extremely high capacity factors,” said Hewson. “But the question is, can we do any better? With an average capacity factor of close to 90 percent, there’s a limit to how long this trend can continue until we put on new generation.” Luckily, there are new nuclear plants on the drawing board and incentives for expanding U.S. capacity of nuclear plants in the Energy Policy Act.
This is a small, concentrated community, Hewson explained. Eleven companies own 75 percent and one company has close to 20 percent of all the nuclear generation: Exelon. “Entergy’s right behind Exelon,” Hewson said. “Between those two companies, you’re close to 30 percent of the total.” And who stands to gain from climate change policies? Nuclear. “If we’re really going to do something about climate change, this is where we’re going to see it.”
The capacity factor rankings for nuclear plants, however, (see Table 2) do change every year-it all depends on when a plant takes its refueling outages. There are only five plants from 2005 still in the top 20 for 2006.
In 2005, the Top 20 cutoff for capacity factor was 93 percent. In 2006, the cutoff point increased to 95.08. As Hewson pointed out, the average capacity factor for 2006 was 97 percent. “You can’t do much better,” he said. “It just shows how important nuclear plants are for meeting our total electricity needs and they’ll become more attractive in a carbon constrained world.”
Coal: Big and cheap
Nationally, coal generation dropped between 2005 and 2006. Hewson said a lot of factors triggered that decrease. “We increased nuclear generation and we built a lot of gas combined cycle plants. Something in terms of dispatch had to give, and that was coal. We dropped a little bit more than 1.2 percent in coal generation from the year before.”
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But coal is still heavily utilized because it is so inexpensive. Dispatched after nuclear, the biggest coal plants can achieve very high capacity factors. “On the whole, there are no surprises here. These plants are big and cheap, and some of the lowest cost sources of power in their power pools.”
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In 2006, three new plants made the top 20 generation rankings (see Table 3)-W.H. Sammis, Roxboro and Bridger-and three dropped out-Jeffrey, Marshall and Colstrip. In 2006, there were two more facilities reporting.
As far as capacity factor, (see Table 4) if a plant’s on the list one year, it’s likely it won’t make it the next. That has a lot to do with outages, said Hewson. For 2006, there are only five plants repeating.
“What’s interesting to me,” said Hewson, “is that historically, the top 20 has been dominated by western units. They get on the list because California uses a lot of energy and has to import a lot of power and coal plants are the cheapest.” But this year, quite a few eastern plants are in the picture. Plant operators are finding that taking the plants down for a full 40 days for scheduled maintenance isn’t always necessary.
What can also put a plant in the top 20 is being a cogenerator. “In cogeneration, you’re producing steam for industrial use and since the production facility runs all the time, because that’s how they make money, the cogenerator has to operate all the time.” In fact, No. 1 Kenecott is a cogenerator and new to the list, because 2006 was its first full year of operation. “My hat’s off to these plant operators, for figuring out how to get such high capacity factors.”
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Hewson focused on Intermountain, No. 12 in the capacity factor rankings for 2006. Intermountain is operated by the city of Los Angeles. “California is expecting to do a lot about climate change,” said Hewson, “and one way is by not approving long-term power purchase contracts if they don’t achieve certain emissions standards. Los Angeles decided to get out of its contract with Intermountain [as did several other smaller California municipals]. A lot of low cost sources of power can’t be approved under these laws.
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“I think California doesn’t quite realize how much higher the prices will go,” added Hewson, “and it’s the ratepayers who will pick up the difference. Are we really going to meet the future demand in California with wind, natural gas, solar and efficiency? I think it will blow up in their face, but that’s another story.”
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Fundamentally, if a plant’s a supercritical unit it can be one of the top 20 plants ranked by heat rate. (See Table 5.) Supercritical units operate under higher steam pressures and they’re much more efficient than subcritical units. “People like to say these are old plants, but they are all extremely efficient. Take Dominion’s Clover plant: it’s as efficient as a combined cycle plant.”
In the discussion of climate change, Hewson said that the cheapest way to lower CO2 emissions is to be more efficient. “Some people say we should go to coal gasification, the IGCC plants. The IGCC plant that reports, [Tampa Electric’s] Polk County unit, is ranked No. 319. It actually has higher CO2 emissions per amount generated than the supercritical units.” To lower CO2 emissions, Hewson suggests going to ultrasupercritical technology.
For the most part, the top 20 units have scrubbers and Hewson said plants are even getting cleaner in terms of emissions. “AEP, Southern and Duke, for instance, are spending a lot of money for environmental controls. But as NOX and SO2 emissions go down, we may slightly increase our CO2 emissions.”
“Coal has a bad reputation. People think all coal is ‘dirty,’ but we have continued to improve in terms of lowering emissions. It’s unfortunate that some people believe that the only way to solve our environmental problems is to turn them all off.
“We’re using our coal fleet heavily because it’s cheap. We’re trying to save people money, not poison them.”
Natural gas combined cycle: A growth area
“This is where we’ve added a lot of capacity. In 2005, we were reporting 177,000 MW and this year we’re up to 210,000,” said Hewson. (See Table 6.)
There are some newcomers for 2006. For instance, No. 10, FPL Group’s Manatee plant, used to be an oil plant; No. 13, Tenaska, was No. 23 last year; and No. 20 McIntosh was just starting up in 2005.
“To make this list, capacity is what’s important-and it doesn’t hurt to be in an area where you’re backing out gas steam plants or oil steam plants,” said Hewson. That’s why there are so many plants on the list from Florida, some of which actually started out as gas steam plants that were retrofitted to more efficient combined cycle plants.
Massachusetts, New Jersey, California and Texas are all like this -and then there’s Georgia, where Southern Co.’s Mcintosh plant is located. “Georgia is just a growing place to be,” said Hewson.
“Overall, the capacity factor decreased from 2005 to 2006, from 35 percent to 32 percent, because we added so many new combined cycle plants,” said Hewson. “That affects the overall dispatch. When you add faster than the generation growth, you end up with lower capacity factors.” (See Table 7.)
Heat rate (see Table 8) is always controversial, “at least in my mind,” said Hewson. Overall, the efficiency for all gas combined cycle plants is 8,600 Btu per kilowatt hour, but “when people do their modeling, they often use numbers like 6,500,” said Hewson. “For planning, it would be better to use efficiencies that we can actually achieve.”
Hewson explained that when we convert to gas, we’re not lowering CO2 emissions by as much as we think, and the price of gas is very sensitive to what the cost of that implication is. The price of CO2 credits necessary to displace a coal unit with a gas combined cycle unit, given the difference of fuel prices, is very high.
“It’s not a very efficient way of reducing CO2 emissions. Mother Nature does a better job; when we plant trees, that’s roughly $2 to $5 a ton for CO2 removal. And if we’re trying to be efficient and take the low hanging fruit, we get a lot more bang for our bucks by decreasing methane emissions at landfills. Methane has 24 times the global warming potential of CO2.”
Environmental
Looking at the combined cycle plants in the combined cycle NOx rankings, (see Table 9) what do they all have in common? They all have selective catalytic reduction, so they’re all very low emitting plants. (In California and Massachusetts, these plants cannot be built without SCRs.) Commenting on the average for 2006 for all gas plants, not just the combined cycles, Hewson said, “We’ve decreased overall by 10 percent since 2005, most likely because we’ve built a lot of new plants.”
The average for all natural gas combined cycle stations that report to EPA was 0.0271#NOx/MMBtu, showing how well the top 20 performed vs the average. “I have often wondered if the extremely low rates may be more an indication of the difficulties in percisely measuring the very low NOx concentrations in the gas turbine flue gas stream using continuous monitoring devices rather than the rates actually being that low,” said Hewson.
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What most of the top 20 plants on the coal SO2 rankings (see Table 10) have in common is that they did not start out with gas desulfurization scrubbers. (Trimble County, for example, did.) Hewson said technology continues to improve and there’s still room for upgrades.
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“This is the first year we actually met the limitations for Acid Rain Program Phase II,” said Hewson. “When we talk about dirty old coal plants, they’re much lower than they were. Look at the acid rain maps; most of the “red” areas are getting wiped out.”
Hewson said that emissions are going to go down farther with the stricter rules that have been adopted for fine particulates.
“We are reducing NOx to reduce smog. We have a smog problem when it gets hot, not when it’s cold. That’s why we have an ozone season, May 1 to Sept. 30-unless you’re in Houston or Los Angeles. Generally all our problems with meeting the standards occur during that five-month period. A lot of plants put on controls and control their emissions during the ozone season and outside the ozone season, they may turn them off, to reduce operating costs and costs to the consumer.” Nationwide, Hewson explained tht there’s also an east-west differential.
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“Selective catalytic reduction is our most efficient way of reducing our NOx emissions,” said Hewson, “but that’s not the only way.” A large portion of the NOx emissions comes from using air for combustion, because air is 65 percent nitrogen and at very high temperatures, the nitrogen air becomes nitrogen oxide. “A lot of the nitrogen is coming from the air and not necessarily from the fuel, so unlike sulfur, which is heavily dependent upon what the sulfur content of the coal is, here in NOx, a lot of it has to do with the type of technology used. Some of the plants here are circulating fluidized bed units. You don’t get as high a temparature when you burn, and you form less NOx.”
And if a plant burns Powder River Basin coal, like NRG’s Parish plant in Houston, combustion temperatures are lower, “and then you can put in SCRs and minimize the amount of air needed. As a result, NRG’s No. 1, 2, 3 and 9.
“We’re continuing to reduce our emissions and the technology is evolving. How far we have come.”