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Particle Receiver Integrated with a Fluidized Bed—Novel Components to Overcome Existing Barriers

Advancing concentrating solar power (CSP) systems to the target cost of $0.06 per kilowatt-hour, set by the U.S. Department of Energy (DOE) SunShot Initiative, will require system components that operate at higher temperatures and efficiencies than the current state-of-the-art technology.

With funding from a competitive DOE CSP SunShot Research and Development Award, NREL and its partners are developing a novel power receiver that uses falling particles instead of liquid for heat transfer and storage. The receiver will be an integral component of a low-cost, reliable, high-performance CSP system designed to circumvent the current limitations of CSP systems that use molten salt as a heat transfer fluid (HTF) and/or for thermal energy storage (TES).

Research Motivation

Nitrate salt is the state-of-the-art thermal energy storage for today's CSP systems. But the technology has limitations in cost-reduction margin and performance potential that can hinder the growth and broad deployment of CSP. Because many solar receivers use metal containment structures and nitrate-salt HTF, the operating temperature of receivers is limited to below 650°C (1200°F). Higher operating temperatures are favorable for increased thermal conversion efficiency. Many of the current studies on HTF and storage media target salt; however, it can be a challenge using salt to satisfy performance needs that include high-temperature stability (>650°C), low freezing point (<0°C), and material compatibility with high-temperature metal (>650°C).

Innovative Approach

The research team is pursuing a novel high-efficiency, low-cost CSP system that uses stable, inexpensive materials for the high-temperature receiver, energy storage, the structure, and containment.

The design uses low-cost materials that can withstand temperatures of greater than 1000°C (1830°F)—much higher than oil/salt and ordinary metals or metal alloys—at a fraction of the cost.

The goals of this project are to:

  • Design and develop a high-temperature particle receiver and heat-exchanger system.
  • Build a prototype receiver that targets >90% thermal efficiency with the product receiver capable of operating at >650°C to serve high-efficiency power cycles.

This technology leverages 40 years of successfully developed and commercialized fluidized-bed boiler technology, and it is applied to CSP by adding a critical new component—a near-blackbody (NBB) enclosed solid-particle receiver—to achieve a low-cost, high-performance CSP system with TES for baseload solar power.

Significant Impact

Schematic diagram illustrating the components of a CSP system with thermal energy storage.

Schematic of fluidized-bed CSP system with solid-particle receiver and thermal energy storage.

The development will remove many bottlenecks in today's nitrate-salt-based CSP thermal system by integrating high-efficiency power cycles and providing economic TES, leveraging core work on fluidized-bed TES already being funded by DOE.

Successful development of the proposed NBB receiver and fluidized-bed heat exchanger will achieve high thermal efficiency and higher operating temperatures, and could significantly reduce CSP thermal system capital and operation costs. When integrated with SunShot solar collectors and power cycles, the combined system is expected to achieve a levelized cost of energy of $0.06 per kilowatt-hour.

Learn about other DOE competitive awards for concentrating solar power research that are in progress.