New NETL research examines turbomachinery design for advanced, natural gas-fired direct supercritical carbon dioxide (sCO₂) power generation systems that offer potential for high efficiency and high rates of carbon dioxide capture. The research was captured in a new manuscript published in Energy Conversion and Management Journal.

Energy Conversion and Management Journal is a biweekly peer-reviewed scientific journal that provides a forum for publishing original contributions and comprehensive technical review articles of interdisciplinary and original research on all important energy topics. The manuscript was written by Selcuk Can Uysal, Charles White, Nathan Weiland, and Eric Liese.

Conventional power plants produce power with turbines that use air (combustion turbines) or steam (steam turbines) as the working fluid.

As the name suggests, sCO₂ cycles use CO₂ under high pressure supercritical conditions as the working fluid. According to Weiland, a senior fellow at NETL, CO₂ fluid properties at these conditions yield more compact turbomachinery and heat exchangers than conventional power cycles.

“The working fluid facilitates highly-recuperated cycle designs with the potential for higher plant efficiencies than conventional alternatives, while the process produces CO₂ for either sequestration or reuse purposes,” Weiland said.

The NETL paper describes details associated with the modeling of one of the most important cycle components, the sCO₂ power turbine. Uysal was the lead author of the new manuscript. He said the turbines require special turbomachinery design considerations compared to typical gas or steam turbines. The NETL team worked on creating an axial turbine design and cooling scheme for maximum plant efficiency.

NETL developed an axial turbine design at a scale of 950 MW ─ the first design at that power rating described in a published paper. The turbine delivers an incredibly high power density characteristic of sCO₂ power cycles, producing nearly a gigawatt of shaft power from a turbine that is about 7 feet long and 7 feet in diameter in one of the turbine designs. The cooling design of the turbine required an interesting approach that involved simultaneously calculating the cycle performance metrics while iterating on the design details of the turbine cooling system.

“Since these cycles have a high degree of thermal integration, this approach is important for understanding the impact on overall plant design and its overall economic outlook,” Uysal added. “This allowed us to achieve modeled plant thermal efficiencies of 54-56%, which are exceptionally high for a plant with 98% carbon capture.”

Improvements to sCO₂  power generating technology is consistent with efforts to attain the Administration’s energy goals: net zero carbon emissions by 2050; 100% clean electricity by 2035, and 50% emissions reduction by 2030.

NETL is a DOE national laboratory that drives innovation and delivers technological solutions for an environmentally sustainable and prosperous energy future. Using its world-class talent and research facilities, NETL is ensuring affordable, abundant and reliable energy that drives a robust economy and national security, while developing technologies to manage carbon across the full life cycle, enabling environmental sustainability for all Americans.