Comanche 3 Power Station Expansion, CO, USA

Xcel Energy has begun constructing its first new coal-fired electric generating unit in nearly 30 years. The Comanche Station near Pueblo, Colorado, is the site for a new 750MW supercritical pulverized coal-generating unit. This adds to two existing units that generate about 660MW. When the Comanche 3 unit is complete, the site will provide enough electricity for about one third of Colorado’s communities. The project is estimated to cost about $1.3 billion.

Alstom won the contract from Public Service Co. of Colorado, doing business as Xcel Energy. Alstom will design, supply, erect and commission a high-efficiency, supercritical boiler for the unit. Mitsubishi Heavy Industries (MHI) will supply the supercritical steam turbine for the plant, MHI’s first such order from the US. Delivery is planned for June 2007. MHI’s Nagasaki Shipyard and Machinery Works will design and manufacture the turbine. Construction and installation work will be done locally.

The plant is planned to go into commercial operation in 2009, and will provide Xcel Energy customers with reliable electricity from the United States' large domestic coal resources.

Comanche Unit 3 will feature advanced emission controls, with extra controls being fitted on the two existing units at the plant. These will help reduce overall emissions of sulphur dioxide (SO2, by 65%) and nitrogen oxide (NOX, by 30%) emissions, even despite the doubling in overall electric generation. The Colorado Public Utilities Commission has approved construction.

LOW-SULPHUR COAL

Alstom’s boiler will be the core of one of the most advanced steam plants to have been built in the US. It will burn low-sulphur Powder River Basin coal and has Alstom's TFS 2000 firing system. This system, coupled with a selective catalytic reduction system, will have some of the lowest nitrogen oxide emissions in the USA.

Supercritical units operate at higher temperatures and pressures than sub-critical units (Comanche 1 and 2 are sub-critical). The higher pressures increase turbine efficiency and power output, so less coal is used to produce the same amount of electricity. While initial capital costs of a supercritical unit are slightly higher than sub-critical units, the total cost is much less over a unit's life.

The high pressure, high temperature advanced steam cycle also significantly increases plant efficiency, minimizing emissions and fuel costs. Similar ALSTOM boilers already operate in Europe and Asia.

RESIDENTIAL, BUSINESS AND WHOLESALE CUSTOMERS

Xcel Energy is a major US electricity and natural gas energy company based in Minneapolis, Minnesota. The company proposes to own 500MW of the 750MW unit. Two wholesale customers - Intermountain Rural Electric Association of Sedalia, and Holy Cross Energy of Glenwood Springs- may take ownership of the remaining 250MW.

Xcel Energy serves residential and business customers as well as wholesale customers. These include Aquila in Pueblo, Holy Cross Energy in Glenwood Springs, Grand Valley Power in Grand Junction, Yampa Valley Electric in Steamboat Springs, Intermountain REA in Sedalia, and the cities of Julesburg, Burlington and Center.

Comanche Station is located a quarter mile from Rocky Mountain Steel Mills in Pueblo. The steel mill is the single largest commercial account for Xcel Energy in Colorado, and the only direct electric customer in the immediate area. All other electricity that Comanche generates is transported to the power grid or sold to the Pueblo-area electric distribution company, Aquila.  Aquila is one of Xcel Energy’s largest wholesale customers, purchasing two-thirds of its power from Xcel Energy.

UNION-ONLY CONSTRUCTION

Over 1,000 workers will be needed over three to four years, with around 40 extra full-time employees once the unit is online. Only union labor will be utilized to complete the Comanche 3 project according to an agreement reached between Xcel Energy and the Colorado Building Trades Council. The council represents 23 unions across the state including carpenters, laborers and others. Preference will be given to local workers, even if contractors are based out of state.

A low water-use system for Comanche Unit 3 will use both water and air for cooling, reducing water use by about half. The Pueblo Water Board has determined that water supplies are adequate. Road improvements will make it easier for equipment, materials and workers to travel to Comanche Station. The road project is expected to cost approximately $4 million.

Coal supplier and railroad provider have not yet been determined. Fuel will be delivered using the existing rail spur. The plant currently uses about 75 railcars of coal a day. That should double when the new unit is in service. Additional transmission is needed to link the Comanche Station to the Daniels Park substation, south of Denver. 

As part of a Least-Cost Plan Settlement agreement, Xcel Energy will make donations to the local Pueblo community.