Fossil Fuels

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• Clean Energy Development Authority
• Renewables
• Senate Bill 07-91
• Transmission

Colorado is an energy rich state in terms of renewable energy and fossil fuels resources. While Governor's Energy Office (GEO) works to enable the expansion of renewables, it is important to recognize the critical role fossil fuels play in generating electricity for Colorado’s utility customers. Below is a brief description of the fossil fuel resources within the state used for electric power generation; coal, natural gas, and to a lesser extent, petroleum.

Coal

Coal-fired power plants currently account for over seven-tenths of Colorado’s energy generation. Readily available at low monetary costs, coal is a widely used fuel for electrical generation across the state. There are several types of coal mined throughout the Unites States for electric power generation and for home heating applications. Below is a brief description of each of these types:

• Anthracite is coal with the highest carbon content, between 86 and 98 percent, and a heat value of nearly 15,000 BTUs-per-pound. Most frequently associated with home heating, anthracite is a very small segment of the U.S. coal market. There are 7.3 billion tons of anthracite reserves in the United States, found mostly in 11 northeastern counties in Pennsylvania.
• The most plentiful form of coal in the United States, bituminous coal is used primarily to generate electricity and for manufacturing by the steel industry. The fastest growing market for coal, though still a small one, is supplying heat for industrial processes. Bituminous coal has a carbon content ranging from 45 to 86 percent carbon and a heat value of 10,500 to 15,500 BTUs-per-pound.
• Ranking below bituminous is subbituminous coal with 35-45 percent carbon content and a heat value between 8,300 and 13,000 BTUs-per-pound. Reserves are located mainly in a half-dozen Western states and Alaska. Although its heat value is lower, this coal generally has a lower sulfur content than other types, which makes it attractive for use because it is cleaner burning.
• Lignite is a geologically young coal which has the lowest carbon content, 25-35 percent, and a heat value ranging between 4,000 and 8,300 BTUs-per-pound. Sometimes called brown coal, it is mainly used for electric power generation.

Colorado produces coal from both underground and surface mines, primarily in its western basins, and large quantities of coal are shipped in and out of the state by rail. Colorado uses about one-fourth of its coal output and transports the remainder to markets throughout the United States. Colorado also brings in coal, primarily from Wyoming, to supplement local production. Most coal-fired generation units use steam turbine technology: coal is burned to heat water in boiler tubes and the steam is run through a steam turbine that drives a generator shaft to create electricity. Most coal units built for generation range in their nameplate capacity between 250 MW to 1500 MW.

Natural Gas

A large percentage of new power generation built in recent years in the U.S. has been natural gas generation, and currently natural gas-fired plants account for close to one-fourth of power generation for Colorado. About three-fourths of Colorado households use natural gas as their primary energy source for home heating, one of the highest percentages in the nation. Colorado is also an exporter of natural gas: about three-fifths of its natural gas production is sold to California and Midwest markets via an extensive gas pipeline network.

Natural gas units can range in capacity from as small as 1 MW of production up to 500 MW or beyond. Natural gas is also used to fuel on-site co-generation units and backup generators for many buildings. Gas-fired generation creates electricity via three primary technologies:

• Combustion turbines that use natural gas directly to fire a turbine which drives the generator shaft. These are termed “peakers,” supplying power at the utility system’s peak time.
• Steam turbines that burn natural gas to create steam in a boiler which is then run through a steam turbine. These are far less efficient peakers and are accordingly used less.
• Combined-cycle units that utilize first a combustion turbine (fired by natural gas) and then a steam turbine (excess heat is used to produce steam, which is then run though a steam turbine). These are very efficient, but more expensive to build than combustion turbines.

Petroleum

A limited number of utilities use fuel oil generation as an alternative to natural gas for peaking power. The technologies used in fuel oil generation are similar to natural gas.