Advanced Design for Scalable S-CO2 Turbomachinery Systems

Supercritical CO2 (S-CO2) power cycles offer high efficiency in a small footprint regardless of the power plant fuel source. Given the high operating pressures (20 to 30 MPa) and temperatures (700 to 800oC) expected with S-CO2 and limited data from kilowatt size laboratory demonstration systems, larger size (i.e., 10 MW) test beds are needed for commercialization efforts; to validate designs; and to identify potential issues when scaling from tens to hundreds of MW. Phase I established a novel high efficiency and scalable turbomachinery concept that uses S-CO2 process fluid lubricated foil bearings in a configuration that minimizes parasitic power losses and operates at optimum speed. This proposed program will build on the established Phase I scalable concept by designing and building a full scale simulated 10 MW turbine hardware test rig. Since system efficiency, reliability, durability and maintainability are crucial to commercialization, integration of the many varied components into a functioning system is crucial. This Phase II hardware test effort will demonstrate key methods to component and system integration and will provide direction for more detailed component development programs. The test rig design will emphasize simulation of relevant full scale turbine operating conditions of load, pressure, temperature and dynamics. The rig design will include: 1) A 10 MW 60,000 rpm turbogenerator rig layout including rotordynamic analysis to ensure dynamic stability over the operating speed range; 2) Capability to sustain 750°C and 20 MPa internal pressures in the bearing compartment; and 3) Analysis to ensure thermal stability. The rig will be tested at relevant turbogenerator system speeds, temperatures and pressures to demonstrate dynamic viability and scalability of the concept. Using the experimental data, component technology limitations will be identified and detailed plans prepared to address the limitations to scaling the component technologies for multi-hundred MW sized turbomachinery. The proposed research program will offer an improved understanding into the scalability and limitations of key S-CO2 components and turbomachinery power conversion systems in sizes from MW to hundreds of MW. The results will also provide directions for future component and system developments needed to realize the commercialization of efficient and reliable S-CO2 power systems. The demonstration of advanced turbomachinery concepts and knowledge of scaling issues will directly contribute to commercial acceptance of the S-CO2 power cycle both for near term 10 MW systems and longer term for 100+ MW scale. The acceptance of S-CO2 cycles will increase efficiency of existing power plants through bottoming cycles thereby increasing power output and reducing cost of operation as well as application in future nuclear and other power plants. Carbon dioxide compressed and heated to high pressures and temperatures can be used to generate electricity from a variety of heat sources including fossil, nuclear, solar and geothermal. This novel power cycle has the potential to be more efficient and cost effective than current steam power plants. The proposed turbomachinery system with process lubricated compliant bearings is crucial to commercializing this technology.