Xcel Energy to repower coal-fired Black Dog units with natural gas

Source: Xcel Energy

Xcel Energy (NYSE: XEL) has asked Minnesota regulators to approve a certificate of need for a project to retire its last two coal-burning units (Units 3 and 4) at the Black Dog plant in Burnsville, Minn., and replace them with natural gas-burning units. Units 1 and 2 were converted to natural gas combined-cycle operation in 2002. 

“We propose to use the existing Black Dog plant site to meet our customers’ energy needs in the most cost-effective way possible,” said Judy Poferl, president and CEO of Northern States Power Co.-Minnesota, an Xcel Energy company. “Repowering this plant with state-of-the-art natural gas technology is more economical than any of the alternatives available to us, makes great use of an existing plant site and existing transmission resources and will help meet our customers’ needs in an environmentally sound manner. The project presents a great opportunity to modernize our power supply in a way that takes advantage of Black Dog’s unique location and the infrastructure that has developed there over time.” 

The repowering project calls for construction of a combined-cycle facility on the Black Dog site, separate from the main building. The new facility will include two combustion turbines, two heat recovery steam generators and a steam turbine generator located in what is now the plant’s coal yard. Integrating combustion turbine and steam turbine technology provides an extremely efficient electricity production process. Combined-cycle technology is about 50 percent more efficient than the existing traditional steam plant. The project will include a new substation and connection to the on-site 345 kilovolt transmission lines. A higher capacity natural gas line will also be installed to serve the facility. 

The proposed Black Dog repowering project would replace the remaining 253 megawatts of coal-fired generating capacity at the site with about 700 megawatts of natural gas-fired generation. The project will provide generating capacity that can ramp up and down quickly as demand for electricity changes or production from wind turbines fluctuates with wind speeds. In addition, replacing the coal-burning units with natural gas-fired units will significantly reduce air emissions, including mercury, sulfur dioxide, nitrogen oxides, fine particulates and carbon dioxide. 

The Black Dog proposal requires review and approval by various state agencies, including the Minnesota Pollution Control Agency and Minnesota Public Utilities Commission. As part of the certificate of need process, independent power suppliers will have the opportunity to propose alternative developments. 

If the Black Dog project is approved, site preparation could begin in 2012 and foundation construction could begin in 2013. The new natural gas powered facility is expected to cost approximately $600 million and is proposed to come on line in 2016. The project will employ an estimated 300 construction workers over the construction period. 

Xcel Energy’s Black Dog repowering project is similar to the company’s Minnesota Metro Emissions Reduction Project, which led to repowering the High Bridge and Riverside plants from coal to natural gas and upgrades to the Allen S. King plant. Combined with the previous emissions reduction project, the conversion of the Black Dog plant supports the utility’s overall goals to make strategic use of critical locations, expand generating capacity, keep rates reasonable and reduce emissions to meet environmental requirements. 

The Black Dog plant has been generating power since 1952. By 1960 Black Dog was NSP’s second largest base load plant.



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