GTI Energy collaborated with the University of California at Merced to upscale the solar thermal transport and storage technology. The solar thermal transport and storage technology integrates a two-stage concentrating solar collector with a particle thermal transport and storage system to provide cost-effective, on-demand high temperature industrial process heat of up to 1,112 degrees Fahrenheit (⁰F) (600 degrees Celsius (⁰C). The aim was to demonstrate the technology at an industrial site to reduce process heating fuel usage and the carbon footprint. The team developed a conceptual system design for the host site retrofit, including heat balance, process flow diagram, and equipment placements. University of California at Merced designed and tested the two-stage collector with multiple connected four-meter-long receivers, while GTI focused on a matching 1,202 °F (650 °C) capable particle thermal transport and storage system. On-sun testing at University of California at Merced revealed bending issues with the absorber tubes under the intense solar radiation generated on the absorber in the two-stage collector. To address the bending issue, a self-consistent iterative model, comprising integrated illumination, thermal, and deformation modules was developed. The model was used to optimize the absorber tube length, considering deformation, overall collector efficiency, and installation complexity, resulting in a 2.7-meter recommended absorber length. The associated particle thermal transport and storage system was successfully designed, built and tested, demonstrating stable particle flow rate, minimal particle degradation and acceptable pressure drop. Collaborating with Stanley Consultants, the team prepared conceptual and preliminary engineering packages to support future development and commercialization efforts. They included diagrams, project definitions, cost estimates, and market evaluation for a 2-megawatt thermal system. The time and efforts spent in addressing the absorber bending issues, however, prevented the team from moving ahead with field demonstration of the system within available project budget and schedule.
