Materials Improvements for Improved Economy of High-Temperature Components in Future Gen 3 CSP Systems

The development of Generation 3 (Gen 3) concentrated solar power (CSP) plants is progressing with the goal of reduced overall costs through a combination of innovative design and improved cycle efficiency. The envisaged systems couple a high efficiency power block using supercritical CO2 (sCO(2)) as a working fluid with temperatures >715 degrees C and either novel salts, solids, or gas for the new receivers and heat-transfer media. Nickel-based structural alloys, already used in limited quantities in today's molten salt CSP receivers, will be required in higher quantities for multiple power plant components due to the significant increases in fluid/media temperatures compared to today's plants. In this work, a preliminary study has been completed to assess the feasibility of using welded tube manufacturing to produce INCONEL (R) Alloy 740H (R) thin-wall tubes, which are a key component in most solar receiver designs. Alloy 740H (R) is an age-hardenable nickel-based alloy with significantly greater high-temperature strength up to similar to 800 degrees C compared to traditional solid solution alloys such as alloy UNS N06230. Due to its higher utilization of material, lower wear on processing equipment, and reduced intermediary steps, welded tube manufacturing offers significant cost reduction potential (up to 30%) compared to seamless tube produced via several draw plus anneal operations. The results presented herein show that successful production of Alloy 740H (R) is possible with properties that can meet the basic materials standards. Based on these successful results, the need and outline of a more extensive evaluation plan is provided to ultimately allow the use of this material through the more stringent requirements of boiler and pressure vessel codes which will be used to construct future Gen 3 systems.