Owner/operator: Xcel Energy
Xcel Energy has completed the third and final project required by its 2003 Metropolitan Emissions Reduction Project agreement: repowering the Riverside Plant with a gas-fired 2 x 1 combined-cycle plant and tearing down the old coal-fired plant. Saved from demolition was the Unit 7 steam turbine system that now serves the new plant. Xcel staff expertly managed the project to an on-time start-up and accepted many important construction tasks, harkening back to the days when utilities took a more active role in the design and construction of projects.
May Day 2009 marked the commercial operation of Xcel Energy’s (Xcel) newly repowered Riverside Plant and achievement of the emissions reduction goals defined by the Metropolitan Emissions Reduction Project (MERP) in 2003. MERP grew from an emissions reduction bill passed during the 2001 Minnesota legislative session that requested Xcel to make a series of voluntary emissions reductions; in return, the costs of making qualified emissions reductions could be passed on to ratepayers.
MERP required Xcel to complete three specific projects: rehabilitate and add state-of-the-art emissions controls to the coal-fired King Plant in Oak Park Heights, Minn.; replace the aging coal-fired High Bridge Plant, located near downtown St. Paul on the banks of the Mississippi River, with a 570-MW natural gas – fired combined-cycle plant (a POWER 2008 Top Plant); and repower the century-old coal-fired Riverside Plant, the oldest plant in the Xcel system, with natural gas – fired combustion turbines and heat-recovery steam generators (Figure 1). Xcel completed the $380 million King Plant upgrades in 2007, and High Bridge entered commercial service in May 2008. Commercial operation of the newly repowered Riverside Plant on May 1 completed Xcel’s winning trifecta.
1. Before and after. Xcel repowered its century-old coal-fired Riverside Plant (top) with gas-fired state-of-the-art combustion turbines and heat-recovery steam generators to drastically reduce plant emissions while getting another 80 MW of power generation from the plant. The Unit 7 steam turbine was reused by the repowering project, while the Unit 7 boiler and the entire Unit 8 were retired from service and are in the process of being demolished and removed from the site. The repowered Riverside Plant (bottom) entered commercial service on May 1, 2009. Courtesy: Xcel Energy
At a cost of $1 billion, MERP was expensive but effective, because it represented a common goal that perennial power plant opponents could rally around. "It set up this odd situation.... You found yourself allying yourself with people you’d been arguing with for years," said Darrell Gerber, a board member of Environmental Justice Advocates of Minnesota. Xcel formed alliances with environmentalists, legislators, and neighborhood groups to win support for MERP in general and repowering the Riverside Plant in particular.
Xcel President Dick Kelly noted during the April 20, 2006, groundbreaking ceremony and tree-planting in Marshall Terrace Gardens, adjacent to the plant, the importance of the Riverside Plant to the neighborhood as well as all Twin Cities residents: "We got here through a partnership with you the community, a partnership with you the elected officials, and you the employees. This is a big compliment to all of you, and we’re excited about it." Kelly went on to make a promise to the plant’s neighbors: "As we look to the future, this is part of who we are. We understand that as a utility we do have an impact on the environment, and we’ll do whatever we can to minimize that impact."
Contain Rising Costs
The first, and perhaps foremost, technique for minimizing the impact on ratepayers of constructing new power plants is to keep costs as low as possible. MERP appears to be a good deal for Xcel’s ratepayers. The three projects have not only significantly decreased power plant emissions in the Twin Cities and surrounding areas, but also, the cost to ratepayers by 2010 will be only about $3.50 to $5.00 per month over the costs otherwise expected from building new plants to supply the incremental power added to the grid by Riverside and High Bridge.
MERP is a template for how a utility can work closely with legislators and other stakeholders to bring about dramatic emissions reductions while simultaneously squeezing more electrical generation from critically placed urban plants.
The Riverside Plant, located about 4 miles north of Minneapolis along the Mississippi River, was originally developed in 1911 through 1938, although the early units were retired 20 years ago. Units 1 and 2 were built in 1911; Units 3, 4, and 5 followed in close succession in 1914, 1917, and 1931 respectively. Two more units were added in the 1930s, and another major addition was made to the plant during the 1940s. By 1966, Riverside Plant consisted of eight operating units with a net capacity of 512 MW. By the 1980s only two units continued to operate; the remainder were mothballed. Units 7 (165 MW) and 8 (223 MW) continued to serve critical loads in downtown Minneapolis and surrounding areas until construction began on the $249 million repowering project. All the existing units at Riverside Plant were coal-fired.
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