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Direct Thermal Receivers Using Near Blackbody Configurations

National Renewable Energy Laboratory

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Figure 1. Schematic of the cylinder acting as a near-blackbody receiver when solar radiation enters the cylinder&#39;s left end<br />
Figure 1. Schematic of the cylinder acting as a near-blackbody receiver when solar radiation enters the cylinder's left end

Technology Marketing Summary

Current oil and salt based heat transfer fluids have significant limitations such as usable temperature, high cost, and limited thermal conversion efficiency. To achieve the Department of Energy SunShot goal of high efficiency, low cost renewable power generation, a highly efficient and economical way to absorb solar heat and to store the thermal energy is important for broad deployment of concentrating solar power (CSP) plants as baseload power.


Engineers at the National Renewable Energy Laboratory (NREL) have developed a high-temperature “direct” supercritical CO2 (s-CO2) receiver for CSP applications. The direct s-CO2 receiver can be coupled with an s-CO2-Brayton power cycle to meet the DOE SunShot cost and performance goals.  The near-blackbody (NBB) design employs a working mechanism resembling a blackbody furnace, and minimizes thermal losses from convection and radiation through reducing direct exposure of heated surfaces to the cool ambient surroundings. An ideal blackbody furnace design uses a well-known radiative mechanism and captures nearly all incoming radiation. The infrared (IR) re-radiation losses also behave as NBB emission, therefore a significant design emphasis is on minimizing IR emission. The NBB design maximizes solar energy collection efficiency while reducing IR re-radiation and convection losses for high performance.

This receiver design performs at greater than 650°C operating temperature with less than 10% thermal loss (defined as the ratio of energy delivered to the heat transfer fluid divided by the total energy that enters the receiver aperture), while minimizing the thermal stress (and hence material requirements) of the receiver. Such a design enables use in a modular, small tower s-CO2 power system, where the s-CO2 power block may be directly integrated with the receiver on top of the tower, resulting in less piping requirements and parasitic consumptions.

  • Spread flux distribution lowers metal tube temperature, thus reducing metal grade and cost
  • Highly stable material results in higher temperature power cycle and efficiency
  • Prevents convection losses


Applications and Industries
  • Concentrating solar power (CSP)
  • Direct s-CO2 receiver
  • Solar tower
  • Black body


Patents and Patent Applications
ID Number
Title and Abstract
Primary Lab
Application 20150330668
An aspect of the present disclosure is a receiver for receiving radiation from a heliostat array that includes at least one external panel configured to form an internal cavity and an open face. The open face is positioned substantially perpendicular to a longitudinal axis and forms an entrance to the internal cavity. The receiver also includes at least one internal panel positioned within the cavity and aligned substantially parallel to the longitudinal axis, and the at least one internal panel includes at least one channel configured to distribute a heat transfer medium.
National Renewable Energy Laboratory 05/15/2015
Technology Status
Technology IDDevelopment StageAvailabilityPublishedLast Updated
NREL ROI 13-51ProposedAvailable04/29/201604/29/2016

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To: Erin Beaumont<>