US power plants capable of burning coal and natural gas

by Saad Hameed, SNL
Coal-to-gas switching has become part of the energy vernacular during the past several years as shale-driven natural gas prices continue to hold steady at significantly lower levels. There is, however, some ambiguity surrounding the term, as it has been used at different times to mean different things.
Most commonly, coal-to-gas switching has been used to identify the phenomenon of natural gas combined-cycle plants’ moving ahead of less efficient coal plants in the dispatch curve because of relatively low natural gas prices.
The term also has been used at times to identify a switch from coal to natural gas at power plants capable of burning both fuels, as well as to identify the trend of coal plants undergoing conversion to be able to burn natural gas.
The latter has been of growing interest as the nation moves closer to implementation of the Environmental Protection Agency’s (EPA’s) Mercury and Air Toxics Standards, also known as the MATS rule. Because natural gas plants are not covered under MATS, a possible conversion of some coal plants to natural gas has become a compliance option worth examining for generators.
Some steam turbine coal plants across the nation have the capability to burn both natural gas and coal and might be a starting place for identifying possible plants for conversion. SNL Energy examined plant fuel burn data to identify plants capable of burning both fuels.
Overall, 197 facilities with a total operating capacity of 78,544 MW have been identified as using coal and natural gas for electricity generation during at least one month since 2008. For those plants, the volume of gas burned increased 11 percent in 2011 compared with 2008. During the same period, the volume of coal burned by the plants fell 9 percent.
Although plants capable of burning both fuels have increased their natural gas usage in the low-gas-price environment, the overall increase in gas consumption has been minimal. This reflects that most plants do not have units capable of burning natural gas alone and instead use gas largely during periods of startup. Some of the increase in natural gas burned can be attributed, then, not to a switch at the facility from coal to natural gas but rather to a switch to using natural gas in lieu of oil during periods of start-up. Many coal plants also have moved from baseload operation in recent months, which has increased plant cycling and the number of start-ups, thus increasing the amount of start-up fuel burned.

Although many coal plants that burn some natural gas might not have full capability to burn all or mostly gas at some units, there might be some value in identifying plants that burn both fuels.

In the EPA’s planning analysis for MATS, conversion to natural gas was a modeled compliance option. The EPA identified two types of costs for gas conversion: boiler modification costs and the costs of building a natural gas feeder system to connect with a nearby gas transmission network.

Plants that already burn some natural gas might have some advantage here when it comes to the gas feeder system component of fuel conversion. That the plants already burn some gas indicates proximity to a natural gas network. The feeder system probably would require significant upgrade in many cases, but there is likely some infrastructure in place that would tend to lower the costs of expanding the feeder system.
The ReliabilityFirst Corp. (RFC) region of the North American Electric Reliability Corp. has 55 power plants with a total operating capacity of 24,103 MW that burned coal and natural gas during at least one month since 2008. The network of gas pipelines in RFC is most dense around the border of West Virginia, Ohio and Pennsylvania. RFC is followed by Southeastern Electric Reliability Council (SERC) in operating capacity, with 38 power plants with an operating capacity of 16,815 MW having burned coal and gas. The Midwest Reliability Organization followed RFC with 45 power plants that burned coal and natural gas during the period studied, with a total operating capacity of 10,082 MW.
When looking at the nation’s regional transmission organizations, MISO has the most plants that burn both coal and natural gas – 76 – with a total operating capacity of 21,268 MW, averaging 280 MW.
MISO was followed by PJM, where 32 power plants burned coal and natural gas, with a total capacity of 14,932 MW. CAISO had 4 power plants with a total operating capacity of 2,757 MW for the largest average size of plants, 689 MW.
A significant number of power plants fell outside the RTOs and accounted for some 27 percent of the total capacity of plants’ burning both natural gas and coal.
The top 20 power plants accounted for roughly 40 percent of the total operating capacity of the plants that burned coal and natural gas in 2011. The James H. Miller Jr. station owned by Alabama Power Co. and PowerSouth Energy Cooperative was the largest power plant burning both fuels in the U.S. The plant has an operating capacity of 2,739 MW and is in SERC. Miller burned 1.3 million Mcf of natural gas in 2011, which was more than double the volume of natural gas it burned in 2008. The quantity of coal burned at the plant declined slightly in 2011, falling 2 percent compared with 2008.
The Four Corners plant in New Mexico was the second-largest plant that burned both fuels in 2011. Four Corners, which is jointly owned by various parties and operated by Arizona Public Service Co., has five units with an aggregate operating capacity of 2,100 MW. It burned some 650,000 Mcf of natural gas in 2011, which is an increase of 76 percent from 2008 when it burned only 370,000 Mcf of natural gas. The delivered natural gas cost at Four Corners decreased significantly in 2011. The price fell from some $13 per Mcf in 2008 to $7.50 per Mcf in 2011, a decrease of about 42 percent. The price for coal during the same time period fell by only 7 percent.
The Harrison power plant, owned by Allegheny Energy Supply Co. and Monongahela Power Co., comes in third in the list of top 20 power plants that burned coal and natural gas in 2011. The Harrison County, W.Va., plant’s three units burned 4.6 million tons of coal in 2011, which was down 18 percent compared with the coal burned in 2008. The amount of gas burned at the plant increased 34 percent over the same period.
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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at

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