Session: 05-05 Solar Receiver Design 3

Paper Number: 115294

115294 - Principle of Planar-Cavity Receiver and Its Application in a Particle Csp System 

High efficiency power cycles and chemical reactions often require high operating temperatures, thus necessitating an increase in concentrating solar thermal power (CSP) receiver temperatures. Solar receivers in power tower systems face various challenges to reach a heat transfer media temperature exceeding 700°C including receiver thermal efficiency, scalability, thermal-mechanical performance, and material reliability. Traditional receiver configurations include external cylindrical receiver designs that have been commercialized to heat steam or molten nitrate salt to temperatures up to 600°C. Many other high temperature receivers using cavity configurations have been developed at the laboratory-scale or pilot-scale (<1MWt). Current cavity receivers often have limitations in operability and scalability, and many directly-irradiated thermochemical receiver reactor designs have the added complication of a transparent window to separate the reactants from the ambient environment and reduce heat losses. A transparent window working at high temperature on-sun condition often incur material and operation issues in addition to window size restriction and optical losses. Thus, innovative receiver solutions are needed for power generation and chemical processes, but also can be limited in options.

This presentation introduces a novel light-trapping planar-cavity receiver (LTPCR) configuration. The receiver configuration employs a light trapping mechanism to allow the solar beam to spread across the cavity walls based on the cosine projection. This flux spreading transforms high incident aperture flux to a lower flux level on the receiver panel walls to accommodate the relatively low heat transfer rates by solid particles or gases, thus enabling enclosed particle receivers or thermochemical solar receiver reactors. Meanwhile, the planar cavity minimizes optical and thermal losses to the environment to promote high efficiency at high receiver operating temperatures. Modular planar cavities can be arranged in an array to scale up to a product-scale receiver capacity without the cavity aperture size limitations of open cavity or volumetric cavity receivers, and thus can be suitable for commercial-scale concentrating solar thermal power (CSP) or solar thermochemical processes. A key principle to realize the LTPCR design approach is the solar flux and receiver interaction from the heliostat layout and aiming strategies to the cavity geometry. A modeling tool based on Monte-Carlo ray tracing in SolTrace has been developed to optimize panel layouts for solar flux spreading, and the modeling efforts have identified and verified feasible receiver designs.

The LTPCR development is focused on a scalable particle-based solar receiver that can collect solar energy efficiently and effectively to support particle CSP system. Successful LTPCR development will enable low-cost particle thermal energy storage (TES) for CSP power generation and industry process heat and provide an enclosed receiver reactor design for future thermochemical processes. Particle CSP with TES has strong potentials to serve energy storage needs across a wide range of temperature conditions for those applications. This presentation will show the LTPCR principle and development progress to meet performance goals for a solar particle receiver.

Presenting Author: Janna Martinek National Renewable Energy Laboratory

Presenting Author Biography: Janna Martinek joined the Thermal Systems Group at NREL in 2012 as a postdoctoral researcher. Her work involves developing computational models to evaluate the performance of power tower receiver concepts. For her graduate work, Janna developed models coupling radiative transfer with heat transfer, mass transfer, and chemical reaction kinetics in order to analyze the performance and optimize the geometric configuration of a solar receiver used for high-temperature solar-thermal reaction processes.