High Temperature Performance of High-Efficiency, Multi-Layer Solar Selective Coatings for Tower Applications

Matthew Gray, Paul Ndione, Robert Tirawat, Katelyn Kessinger

Research output: Contribution to journalArticlepeer-review

23 Scopus Citations

Abstract

The roadmap to next-generation concentrating solar power plants anticipates a progression to central towers with operating temperatures in excess of 650°C. These higher temperatures are required to drive higher power-cycle efficiencies, resulting in lower cost energy. However, these conditions also place a greater burden on the materials making up the receiver. Any novel absorber material developed for next-generation receivers must be stable in air, cost effective, and survive thousands of heating and cooling cycles. The collection efficiency of a power tower plant can be increased if the energy absorbed by the receiver is maximized while the heat loss from the receiver to the environment is minimized. Thermal radiation losses can be significant (>7% annual energy loss) with receivers at temperatures above 650°C. We present progress toward highly efficient and durable solar selective absorbers (SSAs) intended for operating temperatures from 650°C to 1000°C. Selective efficiency (ηsel) is defined as the energy retained by the absorber, accounting for both absorptance and emittance, relative to the energy incident on the surface. The low emittance layers of multilayer SSAs are binary compounds of refractory metals whose material properties indicate that coatings formed of these materials should be oxidation resistant in air to 800-1200°C. On this basis, we initially developed a solar selective coating for parabolic troughs. This development has been successfully extended to meet the absorptance and emittance objectives for the more demanding, high temperature regime. We show advancement in coating materials, processing and designs resulting in the initial attainment of target efficiencies ηsel> 0.91 for proposed tower conditions. Additionally, spectral measurements show that these coatings continue to perform at targeted levels after cycling to temperatures of 1000°Cin environments of nitrogen and forming gas.

Original languageAmerican English
Pages (from-to)398-404
Number of pages7
JournalEnergy Procedia
Volume69
DOIs
StatePublished - 2015
EventInternational Conference on Concentrating Solar Power and Chemical Energy Systems, SolarPACES 2014 - Beijing, China
Duration: 16 Sep 201419 Sep 2014

Bibliographical note

Publisher Copyright:
© 2015 The Authors. Published by Elsevier Ltd.

NREL Publication Number

  • NREL/JA-5500-62935

Keywords

  • concentrating solar power
  • power tower
  • receiver coating
  • solar absorber
  • solar selective absorber

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