BRAYTON ENERGY LLC — Department of Energy SBIR Phase II: 06c

Description

Reliable, cost-competitive thermal storage is critical to the growth of the concentrated solar power market. The proposed program focuses on a key component which impacts future trough systems, addressing chronic reliability problems, and providing a pathway to higher plant operating temperatures and resulting higher efficiency. Todays solar trough plants use synthetic oil heat transfer fluids which limit the power plant boiler temperature to 400C. When the heat transport oil is connected to a thermal salt energy storage system, this temperature is further reduced. The proposed program focuses on developing a rotary coupler for molten salt. With this rotary coupler, direct salt transport through the solar trough can be used, which eliminates the cost and complexity of heat transfer from oil to salt in the storage system. Molten salt has the potential to operate at considerably higher temperatures, from 500 to 650C, thereby significantly boosting the power plant efficiency. Based on the temperature ratio increase, this represents a roughly 10 percentage-point improvement in steam turbine efficiency. Working closely with the major solar trough manufacturers and plant operators, Brayton has identified the problems with todays rotating joints and performed a detailed characterization of this challenging environment. Working from concept through successful lab testing, Brayton has developed the product from idea to prototype over the course of Phase-I activities. Brayton has followed an aggressive product development path achieving all program goals, including the following accomplishments: 1. Rigorous analytical design and optimization of a novel product solution 2. Manufacturing process development, cost modeling, and capitalization planning. 3. Developed accelerated build, test, and quality assurance processes. 4. Conducted comprehensive laboratory tests, performed failure analysis, and validated life prediction models. 5. Successfully demonstrated 16,000 full diurnal (230 of rotation) cycles on early prototype Salt Couplers. Phase II will improve the flexible Salt Coupler design, perform rigorous laboratory accelerated life testing, and develop robust manufacturing processes for pilot production volumes. The resulting production prototypes will have upgraded functional capabilities including increased pressure and temperature capacity. In cooperation with our established partners, the project will also install up to six (6) field test units, likely operating at 500C in commercial solar trough plants. A third-party qualification plan with an industry-accepted testing laboratory will prepare the Salt Coupler for initial sales. Braytons Salt Coupler is an enabling technology for molten salt concentrating solar plants, and this Phase II SBIR will see it evolve from a functioning prototype to a viable, trusted, commercial product.