By Ted Caddell

Exelon Generation is joining with two other companies to build what they are calling an emission-free natural gas-fired power plant.

Exelon is partnering on the project with CB&I, an energy infrastructure company in The Woodlands, Texas, and technology commercialization firm 8 Rivers Capital of Durham, N.C., under the name NET Power. The $140 million, 50-MW plant, which will incorporate carbon-capture technology, will be built in an undisclosed location in Texas.

Using an 8 Rivers technology called Allam Cycle, the new plant will be radically different from conventional combined-cycle plants, which use waste heat to make steam that turns a turbine. Much of the steam’s energy potential is lost when it is condensed.

Pure Oxygen

The Allam Cycle uses natural gas as a fuel. But instead of using air as part of the combustion process, it uses pure oxygen, which eliminates emissions such as nitrogen oxides.

The Allam Cycle uses another byproduct of typical combustion, carbon dioxide, as a type of fuel itself. Rather than having to expend energy to capture CO₂ as in other carbon-capture processes, the Allam Cycle collects the CO₂, pressurizes it into a liquid and uses it to turn a Toshiba-designed CO₂ fluid turbine, instead of a steam turbine. When the power plant is done with the CO₂, it is pipeline-grade material ready either for sequestration or to be sold off for industrial uses.

“The by-products of combustion in this system are high pressure CO₂ and a small amount of water,” NET Power Spokesman Walker Dimmig said.

“This technology is a potential game-changer in reducing carbon emissions from power generation,” Exelon President and CEO Chris Crane said.

The consortium can’t look to other models of this technology. “This is a true, first-of-a-kind demonstration of a brand new technology,” Dimmig said in an interview Friday. “The first commercial facility, which will be 295 MW, is in the planning stages. Following successful demonstration at this small-scale plant, we of course hope to build many, many more of these.”

Dimmig said he anticipates the Texas plant to be commissioned in 2016.

Holy Grail

Carbon capture is the Holy Grail in low-emissions power generation, but previous attempts have been over budget and behind schedule. Perhaps the most well-known is the FutureGen project, a coal-fired plant using integrated gasification combined-cycle technology, combined with carbon capture and storage. After funding battles and significant cost overruns, FutureGen, which was announced in 2003, is still not operational.

Another carbon-capture project is being built by Southern Co. with engineering and construction firm KBR Inc., in Kemper County, Miss. Originally estimated to cost $2.4 billion, latest estimates for the plant are $5.5 billion. Construction began in 2010. It is projected to go operational in May 2015, a year behind schedule.

How will NET Power avoid these pitfalls?

“First, FutureGen and Kemper are full-scale commercial facilities of a much larger size than this 50-MW facility,” Dimmig said. “Second, this plant has been under design for nearly four years, and we believe we have a very strong handle on costs. Finally, while novel, this is a far simpler process that uses far less piping and exotic alloy as compared to those other projects.”

Dimmig wouldn’t say if the plant must be sited near oil and gas wells, the typical sequestration sites used in carbon-capture plans, to be economically viable. Exelon, too, declined comment on where it planned to site similar plants if the NET Power plant turns out to be a success.