The company filed the information with the Indiana Utility Regulatory Commission (IURC) as part of its semi-annual update.
Still to be determined is how much will need to be added over and above the $150 million as contingency funds necessary to complete a project of this size and type. Duke Energy Indiana is asking the commission to schedule a separate proceeding by next March, when most of the project's engineering will be complete, so that the company can provide a more detailed, revised cost estimate.
The company will use the next few months to examine future cost projections associated with labor, engineering, procurement and plant start-up. After next spring, labor costs will be a key variable driving the final project cost.
"We worked with General Electric, Bechtel and other design firms to perform an engineering study early on; however, as engineering progressed, the scope of the project has increased," said Duke Energy Indiana President Jim Stanley.
"The engineering has required more steel, piping, electric cable and other materials than originally expected," he added. "Because this is the first time this technology has been used on this scale, there was not nearly as much guidance on size and quantity as there would be for a typical project with a design that had been constructed many times."
Previously, Duke Energy Indiana estimated the project would result in an average 18 percent customer rate increase between 2009 and 2013. By March, the company will file revised rate impact estimates.
The IURC granted the company permission in 2007 to construct the technologically advanced clean coal power plant in Edwardsport, Ind. The commission will need to approve any cost increase for the plant. The project is scheduled to be completed in 2012.
The approximately 630-megawatt plant will use advanced integrated gasification combined cycle (IGCC) technology. The new plant will produce 10 times as much power as the existing plant at Edwardsport, yet it will emit less sulfur dioxide, nitrogen oxide and mercury than the much smaller plant it replaces. Due to the plant's superior efficiency, it also will emit 45 percent less carbon dioxide per megawatt-hour than the existing facility.
"The Edwardsport project is the first major new coal-fired power plant to be constructed in Indiana in more than 20 years," Stanley said. "It is key to modernizing our Indiana generating fleet.
"Coal fuels the vast majority of electricity produced in this state and half of the power produced in the nation," he added. "Coal gasification is a way to use an abundant, local resource and burn it cleanly with high efficiency. It's critical we find ways to further technologies like this."
The plant is slated to receive more than $460 million in local, state and federal tax incentives, which will help reduce the customer cost impact. The company will retire the existing plant - with coal and oil units built between 1944 and 1951 - upon completion of the new facility.
IGCC technology uses a coal gasification system to convert coal into a synthesis gas (syngas). The syngas is processed to remove sulfur, mercury and ash before being sent to a traditional combined cycle power plant, using two combustion turbines and a steam turbine to efficiently produce electricity.
The technology is also capable, based on certain modifications, of removing the carbon dioxide from coal during the syngas conversion process to enable it to be stored or sequestered in underground geologic formations.
The company has a request pending before state utility regulators to study permanent underground carbon storage of a portion of the plant's carbon dioxide emissions.
Duke Energy also is meeting increased Indiana power demands through green power sources such as wind energy. Duke Energy Indiana has a 20-year contract with the Benton County wind farm. The company also has filed a plan with state utility regulators to increase tenfold its customer energy efficiency program savings.