CHARACTERISTICS

Gas burning capability can be added to boilers originally designed to burn coal and oil. Boilers can be completely switched to gas, gas can be added to an existing coal boiler and co-fired, or a coal plant can be completely repowered to natural gas. Power plants designed to use natural gas are the most cost-effective plants to convert.

Because natural gas has a lower carbon content than coal or oil, burning natural gas instead of these fuels will reduce carbon emissions. Emissions of NO_x and SO₂ are also significantly lower for gas than for coal or oil. Burning one quadrillion (10¹⁵) Btu of natural gas in electric generation emits about 16.3 MtC compared to 28.2 MtC for coal. Coal-fired power plants that are converted to burn natural gas will emit 60% fewer carbon emissions per kWh generated than coal.

However, natural gas prices are usually considerably higher than coal prices. In addition, considerable capital expenditures may be required to add or upgrade natural gas pipelines and existing on-site equipment to make it suitable for natural gas consumption. Repowering results in significantly higher efficiencies, providing further reduction in GHG emissions, but significant capital investments are also required for the purchase of the new equipment.

SIZE:
Any size power plant can be converted subject to the inter-connection with a gas pipeline.

FEATURES:
Requires access to gas supply lines.

COST:
Cost of a new NG plant is < $400/kW. However, fuel cost of natural gas is almost double that of coal.

CURRENT USAGE:
288 billion kWh (annual natural gas generation in U.S.); over 20 quadrillion Btu gas-fired electricity generated world-wide.

POTENTIAL USAGE:
In the U.S. alone, up to 335 GW of coal capacity could potentially be switched to natural gas. The United Kingdom realized a substantial reduction in fossil fuel emissions when its electric power generation market repowered from coal to natural gas.

ISSUES ASSOCIATED WITH IMPLEMENTING ACTION

• Natural gas prices per Btu are approximately double that of coal and tend to be more volatile.
• Seasonal availability of supply and pipeline capacity.
• There is insufficient natural gas infrastructure (in the U.S.) to reliably supply increased electric generation. Some plant locations may require pipeline installation before they can switch to natural gas.
• Natural gas co-firing with low-sulfur sub-bituminous coals has the potential for boiler fouling problems, leading to a loss of boiler efficiency and necessitating increased maintenance activities.

CLIMATE CHANGE IMPACT

EMISSION EFFECT:
    

CONDITIONS FOR EMISSIONS MITIGATION:

• Emissions/kWh of natural-gas fired power are less than those of coal-fired power, but if demand increases substantially, total emissions may increase as well.

EMISSION ESTIMATE:
0.67 MtC removed/GW converted

COST-EFFECTIVENESS:
$90-104/ton of carbon (U.S. average)

SECONDARY EFFECTS:
40,000 tons SO₂ removed/GW converted; 17,000 tons NO_x removed/GW converted.

RESOURCES

• The U.S. Department of Energy hosts the Climate Challenge Options Workbook online at http://www.eren.doe.gov/climatechallenge/.
• Interlaboratory Working Group on Energy-Efficient and Low-Carbon Technologies, 1997, "Section 7.2, Repowering Coal-Based Power Plants with Natural Gas," Scenarios of U.S. Carbon Reductions, Potential Impacts of Energy Technologies by 2010 and Beyond, prepared for the U.S. Department of Energy Office of Energy Efficiency and Renewable Energy. http://eande.lbl.gov/5lab/index.html
• Smalley, G. and L. Makovich, 1993, Technical Methodology for Analyzing Electric Utility Fuel Switching, Gas Research Institute.
• Under the U.S. Initative for Joint Implementation, a group of three U.S. utilities and the Center for Clean Air Policy worked with the City of Decin, Czech Republic to replace part of a lignite coal-fired district heating system with natural gas powered engines and associated heat exchange equipment. Over the next 25 years, this change is expected to reduce emissions by 165,600 mtC.

CONTACTS

American Gas Association
Arlington, VA
Tel: (703) 841-8400
Fax: (703) 841-8406
http://www.aga.org

Electric Power Research Institute
Palo Alto, CA
http://www.epri.com

IEA International Centre for Gas
Technology Information
Mary Lang
Associate Director
Arlington, VA
Tel: (703) 526-7810
Fax: (703) 526-7811
icgti@gasinfo.gri.org
http://www.icgti.org

U.S. Department of Energy
Office of Fossil Energy
Washington, DC
Tel: (202) 586-1650
http://www.doe.gov

U.S. Initiative for Joint Implementation
Secretariat
Washington, DC
Tel: (202) 586-3288
Fax: (202) 586-3485
http://www.ji.org