Advanced Design for Scalable sCO2 Turbomachinery Systems

Supercritical CO2 power cycles offer the promise of high efficiency in a compact footprint with a potential to offer disruptive changes to the US energy infrastructure. Applications include bottom cycles for electric co-generation power plants, nuclear power production, concentrated solar and other renewables as well as propulsion engines for space propulsion. Aerodynamic design theory dictates that the turbomachinery components for such power conversion cycles will operate at high rotation speed with high-power density. To effectively implement S-CO2 technology in commercial sized power conversion systems, scaled test systems must be created in order to address potential issues with full-scale designs from tens to hundreds of MW. Given the high operating pressures (20 to 30 MPa) and temperatures (700 to 800oC) in S-CO2, turbomachinery system scaling from the current sub-megawatt demonstration systems needs to be validated in more near scale sizes such as 10 MW output power scale. The proposed program begins with a review of the performance requirements for systems from 3 to 300 MW power systems, followed by a preliminary design study that will encompass all key aspects of turbogenerator design, including: 1) parametric thermodynamic analyses to establish the key system requirements and identify optimal operating condition; 2) aerodynamic component sizing, operating speeds and matching of turbine and compressor to maximize component efficiencies, 3) selection of generator approach and basic rotor layout (direct or geared) to accommodate the optimum aero component speeds; 4) size the recuperator, gas chiller and heat exchanger to minimize pressure drop and maximize efficiency; and 5) establish a notional model of the integrated system showing the overall system configuration layout. Commercial Applications and Other Benefits: The proposed research program will offer an improved understanding of the scalability of S-CO2 turbomachinery systems for power conversion in the 3 to 300 MW classes. These results will benefit the both scientific and engineering communities by providing improved understanding of methods and resources needed to develop efficient and reliable power conversion systems. Through evaluation of key design parameters, results will aid in design of future power cycle concepts in both small and large scale. The development of advanced turbomachinery concepts and proper understanding of scaling issues in large scale power conversion systems will directly contribute to a path towards commercial acceptance of the S-CO2 power cycle both for near term 1 to 10 MW systems and longer term for 100+ MW scale. The acceptance of S-CO2 cycles will benefit renewable energy technology such as waste-heat recovery and concentrated solar energy, as well as working in future nuclear plants and as bottoming cycles in existing fossil plants thereby reducing the nation’s use of fossil fuels and reducing environmental impact of existing plants. Key Words: Supercritical CO2, Closed Brayton Cycle, Energy Efficiency, Turbomachinery, Recuperator, Compressor, Centrifugal Compressor, Radial Turbine. Axial Turbine