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His ULTIMATE Materials: Dr. Zak Fang and the Future of Gas Turbine Tech

"BIG BBQ" by ART-Ko is licensed under CC BY-NC-ND 2.0

ARPA-E announced up to $28 million in funding for a new program, ULtrahigh Temperature Impervious Materials Advancing Turbine Efficiency (ULTIMATE), in April 2020. The ULTIMATE program will fund projects to develop and demonstrate materials that can operate in the high temperature and high stress environment of a gas-turbine blade. Innovative technologies launched by the ULTIMATE program will specifically target gas turbine applications in the power generation and aviation industries.

ARPA-E Program Director Dr. Zak Fang built the ULTIMATE program from a wealth of experience in advanced materials and manufacturing technologies for energy production, storage, and efficiency applications. Dr. Fang served as a professor of metallurgical engineering at the University of Utah prior to joining ARPA-E in 2019, where he led a number of innovative research projects and was recognized with an R&D 100 Award for his efforts. Dr. Fang founded two small technology companies and is the sole or co-inventor on more than 50 U.S. patents.

We recently spoke with Dr. Fang to find out more about his interest in energy and to gain additional insight into the ULTIMATE program.

How did you become interested in materials sciences and engineering?

I have trained and worked in this profession for 30 years, so it is difficult to recall exact reasons behind my choice of engineering careers. One reason is that there are countless examples of technology challenges that hinge on the development or improvement of material properties, including those tackled by ARPA-E programs over the last decade. So, materials are enablers; materials make it possible to tackle these challenges.

You have a diverse energy research and industry background amassed from your time as a professor and researcher at the University of Utah and as the founder of two technology businesses. What drew you to work at ARPA-E, and how does your background assist in your role as a Program Director?

The attraction of ARPA-E for professionals like myself is that the agency empowers Program Directors to dream up ideas without the limitations of plans or roadmaps. ARPA-E is also relentless in its pursuit of cutting edge technologies that could bring about changes to the field. The way a program is born at ARPA-E is a rigorous process of continuous evaluation by top notch scientists, engineers, and innovators in our fields. It is not for the faint-of-heart, but it’s challenging and exciting to believe you can make a significant long-term impact in your field.

What drove you to create the ULTIMATE program?

At ARPA-E, Program Directors are tasked with developing high-potential and high-impact energy technology programs that are too early for private-sector investment. The agency focuses on technologies that can be meaningfully advanced with a modest investment over a defined period of time in order to catalyze the translation from scientific discovery to early-stage technology. Having a strong materials and manufacturing background, I wanted to develop a comprehensive program focused on developing new alloys and manufacturing processes for high temperature structural applications. When it comes to gas-turbine efficiency improvements efforts are scattered and focused on incremental changes. For example, industries are looking at 50degrees Fahrenheit improvements through system optimization, advanced manufacturing experts are focused on developing processes for existing alloys, and alloy modeling teams don’t have enough resources to validate their results. The goal of ULTIMATE is to mitigate these challenges by providing a platform for experts of diverse but critical teams (alloy modeling, advanced manufacturing, coating, and high-temperature testing) to develop and demonstrate novel alloys for critical applications.

What challenges do gas turbines currently face? How can the development of ultrahigh temperature materials help to mitigate those challenges?

Natural gas fueled turbines produce approximately 35 percent of the total electricity production in U.S. The efficiency of a gas turbine depends to a large degree on the peak temperature of the working fluid. The higher the peak temperature, the higher the efficiency. However, the peak operating temperature of gas turbines is limited by the capability of the material used to construct the components (e.g. blades, vanes, nozzles and shrouds) in the hottest part of the cycle.  Among them, the turbine blades experience the most demanding environment because they must withstand not only the highest temperatures in a turbine, but also the highest stresses during operations. Currently, turbine blades are made of single crystal nickel-based alloys. The temperature capability of nickel (Ni) superalloys has been improved steadily over the last few decades but has reached plateau. Thus, there is a strong need to discover, develop, and implement novel ultrahigh temperatures materials that work at temperatures significantly higher than that of the Ni or copper-based (Co) superalloys if further efficiency gains are to be realized.

The ULTIMATE program seeks to fund the development and demonstration of ultrahigh temperature materials that can operate continuously at 1300 ºC or higher in a standalone material test environment (or with coatings, enabling gas turbine inlet temperatures of 1800 °C), targeting gas turbine applications in the power generation and aviation industries. The program will foster research and development of novel refractory metal alloys, including refractory metal high entropy alloys, as well as necessary coatings, for high temperature turbine blade applications. Additionally, ULTIMATE will concurrently fund the development of manufacturing processes for turbine components using these materials, enabling complex geometries that can be seamlessly integrated in the system design. Coatings including both environmental barrier coatings (EBC) and thermal barrier coatings (TBC) are also within the scope of this program.

What are the technical topics of interest for this program and how do they address the critical need?

Technical topics of interest include (i) Novel alloy development (ii) coating development (iii) manufacturing process development (iv) comprehensive solutions (v) testing and resource support for topics i-iv awardees as well as cost modeling. Novel alloy development is at the core of this program. It involves modeling, experimentation, characterization, mechanical testing, and iterations of all of the above. The objective is to develop novel alloys that can operate continuously at 1300 °C. Due to the high temperatures, oxidation, and other possible corrosive environments turbine materials are exposed to operate in, coatings are likely a necessary part of the total solution. Refractory metals are known to be prone to oxidation if left exposed. Therefore, project efforts that focus on the development of coatings, including both EBC and TBC coatings, for refractory metal alloys are also of interest. Another key objective of this program is the concurrent development of manufacturing processes with the materials.  No materials development effort is successful without a realistic manufacturing process that can concurrently deliver both geometric designs and the desired mechanical properties, for example by the control of a specific microstructure. It is also a prerequisite that development of both the materials and manufacturing processes are conducted within the confines of the full system design, and as an integral part of the system development.

What is the potential impact of the ULTIMATE program on the use of natural gas turbines in the power generation and aviation industries (and beyond)?

It is expected that the development of novel ultrahigh temperature materials in combination with compatible coatings and manufacturing technologies will enable the efficiency of gas turbines to be improved by up to 7 percent. A 7 percent improvement in efficiency in the natural gas turbines used for electricity generation in the U.S. represents a chance to save up to 15-16 quads of energy by 2050. A similar improvement in the turbines used for civilian aircraft represents another 3-4 quads of potential savings for U.S. air travel over the same time span. Beyond the energy savings, the economic impacts will also be significant. A new unit that is 7 percent more efficient could save its owner up to $20k/MW above current SOA (the H-Series turbine) over the lifetime (assumed to be 20 years) of a baseload generator, or $5k/MW above SOA for a peaker plant (at a fuel cost of $3/MMBtu). In addition, novel materials with better temperature capability will provide an opportunity for utilizing these materials in additional markets. 

For more information on ARPA-E’s ULTIMATE program, click here. To apply for funding, visit ARPA-E eXCHANGE here.