Over the course of two and a half years, the Generation 3 Concentrating Solar Power Systems (Gen3 CSP) funding program evaluated three technology pathways that could enable high temperatures and, thereby, highly efficient CSP plants. Each pathway was a phase of matter used to transfer heat: liquid, solid particle, or gaseous/supercritical fluid. On March 25, 2021, the U.S. Department of Energy (DOE) announced that Sandia National Laboratories (SNL) would be awarded $25 million to build a next-generation CSP plant using the solid-particle pathway, with the goal of de-risking commercial CSP systems operating above 700° Celsius.
DOE selected the solid-particle heat-transfer pathway following an extensive review of the work done in the first two phases of the Gen3 program by all the competing teams who worked to retire the key technology risks identified in the Gen3 Roadmap commissioned by DOE in 2017. To make the selection, DOE evaluated whether the concept for the new CSP plant had been de-risked in the first two phases of the funding program and whether the plant could meet the solar office’s 2030 goals. Specifically, DOE considered the following three factors:
- The technical maturity of the heat-transfer pathway and development of key components. This research was done by the competing teams leading the design of each pathway, in collaboration with industry, as well as by projects funded in Topic 2 of the Gen3 funding program and the wider CSP research and development community.
- The potential for the heat-transfer pathway to enable commercial plant designs that can achieve SETO’s goal of $0.05/kWh by 2030 for baseload configurations of CSP with 12 or more hours of thermal energy storage.
- The quality and likelihood of success for the proposed Phase 3 construction and test plan for the megawatt-scale test facility for the fully integrated heat-transfer pathway.
After this review, DOE determined that particle-based systems require fewer components and are less complex to operate compared with liquid- and gas-based systems. Additionally, particle-based systems need relatively few high-cost materials to collect and transport thermal energy. These factors could increase plant availability and reliability and enable simpler plant construction and commissioning.
And unlike the other two pathways, ceramic, sand-like particles can withstand temperatures greater than 800° Celsius, making them useful in electricity production and other solar-thermal heat applications, including industrial process heat, thermochemical energy storage, and solar fuel production.
Conventional CSP power towers have tubular receivers with a fluid, such as molten salt, flowing through the system and absorbing thermal energy. In a falling-particle receiver, sand or manufactured particles are heated directly by a beam of concentrated sunlight as they fall through open air. The SNL project team uses particles based on aluminum oxide, with a diameter of about 300 micrometers. The heated particles are then stored in an insulated bin before passing through a particle-to-working-fluid heat exchanger. The heat exchanger's working fluid will simulate a high-efficiency Brayton cycle using supercritical carbon dioxide (sCO2) with an exit temperature of 720°C. Then the cooled particles are collected and moved back to the top of the receiver via a bucket elevator or skip hoist.
-- Award and cost share amounts are subject to change pending negotiations –
Sandia National Laboratories
Project Name: Gen 3 Particle Pilot Plant (G3P3): Integrated High-Temperature Particle System for CSP
Location: Albuquerque, NM
DOE Award Amount: $25 million
Awardee Cost Share: $5 million
Project Summary: The project team will build, test, and operate a multi-megawatt-thermal CSP test facility with a falling-particle receiver system that can operate for thousands of hours, store six hours of thermal energy, and heat a working fluid, such as sCO2 or air, to more than 700°C. The integrated pilot system will be built at the National Solar Thermal Test Facility, leveraging the existing heliostat field and extensive experience at the site.
To accelerate deployment and commercialization, the team is working with leading international particle-technology researchers who are building a second facility in Saudi Arabia to test variants of key system components, allowing the research consortium to simultaneously test different potential configurations for deployment. The team is also collaborating with researchers from Australia, who have helped advance key components and are performing system-level analysis of the solid-particle design, as part of the Australian Solar Thermal Research Initiative. This large-scale, integrated CSP system will help the research team address risks associated with receiver thermal efficiency, performance and cost of particle heat exchangers, material erosion, minimization of heat loss, and particle attrition and conveyance.
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