Prior to this project, the use of yttrium aluminum garnet (YAG) materials as thermal barrier coatings (TBCs) has been limited by the difficulty of processing them with a sufficiently compliant microstructure to achieve the required strain tolerance and durability. This project will use a proprietary solution precursor plasma spray (SPPS) process—developed at the University of Connecticut (UConn) and demonstrated successfully on other materials such as yttria-partially stabilized zirconia (YSZ) —to fabricate YAG-based TBCs with markedly improved temperature characteristics relative to YSZ. In Phase I, the team demonstrated the feasibility of utilizing the SPPS process to deposit TBC coatings of sufficient thickness and desirable microstructures that yielded superior thermal cycling resistance compared with state-of-the-art air plasma sprayed (APS) YSZ coatings. In Phase II, HiFunda and UConn—working closely with major turbine manufacturers and coating service providers—will optimize the process, demonstrate that SPPS YAG TBCs can meet test criteria specified by the turbine manufacturers, and scale up the process to coat components for third party testing.
Turbines convert heat energy to mechanical energy by expanding a hot, compressed working fluid through a series of airfoils. Combustion turbines compress air, mix and combust it with a fuel (natural gas, coal-derived synthesis gas [syngas], or hydrogen), and then expand the combustion gases through the airfoils. Expansion turbines expand a working fluid like steam or supercritical carbon dioxide (CO2) that has been heated in a heat exchanger by an external heat source. These two types of turbines are used in conjunction to form a combined cycle— with heat from the combustion gases used as the heat source for the working fluid— improving efficiency and reducing emissions. If oxygen is used for combustion in place of air, then the combustion gases consist mostly of carbon dioxide (CO2) and water, and the CO2 can be easily separated and sent to storage or used for Enhanced Oil Recovery (EOR). Alternatively, the CO2/steam combustion gases can be expanded directly in an oxy-fuel turbine. Turbines are the backbone of power generation in the US, and the diverse power cycles containing turbines provide a variety of electricity generation options for fossil derived fuels. The efficiency of combustion turbines has steadily increased as advanced technologies have provided manufacturers with the ability to produce highly advanced turbines that operate at very high temperatures. The Advanced Turbines program is developing technologies in four key areas that will accelerate turbine performance, efficiency, and cost effectiveness beyond current state-of-the-art and provide tangible benefits to the public in the form of lower cost of electricity (COE), reduced emissions of criteria pollutants, and carbon capture options. The Key Technology areas for the Advanced Hydrogen Turbines Program are: (1) Hydrogen Turbines, (2) Supercritical CO2 Power Cycles, (3) Oxy-Fueled Turbines, and (4) Advanced Steam Turbines.
Hydrogen turbine technology research is being conducted with the goal of producing reliable, affordable, and environmentally friendly electric power in response to the Nation's increasing energy challenges. NETL is leading the research, development, and demonstration of technologies to achieve power production from high hydrogen content (HHC) fuels derived from coal that is clean, efficient, and cost-effective; minimize carbon dioxide (CO2) emissions; and help maintain the Nation's leadership in the export of gas turbine equipment. These goals are being met by developing the most advanced technology in the areas of materials, cooling, heat transfer, manufacturing, aerodynamics, and machine design. Success in these areas will allow machines to be designed that have higher efficiencies and power output with lower emissions and lower cost.
HiFunda and the University of Connecticut will use a proprietary solution precursor plasma spray (SPPS) process—developed at the University of Connecticut (UConn) and demonstrated successfully on other materials such as yttria-partially stabilized zirconia (YSZ) —to fabricate yttrium aluminum garnet (YAG)-based TBCs with markedly improved temperature characteristics relative to YSZ. The SPPS process seeks to overcome the processing difficulties that prevent YAG materials from achieving the required strain tolerance and durability. Materials research conducted under the Advanced Turbine Program seeks to improve coating materials that will allow for higher temperature operation and increased durability. These improvements will improve turbine efficiency and reduce maintenance, leading to lower capital costs, reduced operating costs, and reduced costs of electricity for consumers.
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