High Flux Solar Furnace


National Renewable Energy Laboratory (NREL)

Capability Expert

Judy C. Netter


System Integration

Node Readiness Category

1: Solar Thermochemical (STCH)
2: High-Temperature Electrolysis (HTE)


NREL's HFSF has been in operation since 1990 and consists of a tracking heliostat and 25 hexagonal slightly concave mirrors to concentrate solar radiation. The solar furnace can quickly generate up to 1,800°C over a 1-cm2 area—and up to 3,000°C with specialized secondary optics to generate concentrations greater than 20,000 suns. Flux levels and distributions can also be tailored to the needs of a particular research activity.
The HFSF test building is equipped with computers and data acquisition tools, video monitors of the outside equipment, sophisticated instruments to monitor solar radiation, and automated devices that enable researchers to control and measure the power of the concentrated sunlight.
The operational characteristics and size of the facility make it ideal for testing over a wide range of technologies with a diverse set of experimental requirements. The high heating rates create the perfect tool for testing high-temperature materials, coatings on metals and ceramics, and other materials-related applications. The power generated can be used to evaluate many components—such as receivers, collectors, and reflector materials—used in CSP systems.
The facility can provide a platform for testing prototype advanced converters and chemical reactors for solar-electric and solar-chemistry applications. Researchers can also use the HFSF to evaluate and develop state-of-the-art measurement systems for the extreme solar environment.

Capability Bounds‎

NREL's solar furnace is ideally suited for small-scale feasibility studies. The HFSF is rated to deliver 10 kW of thermal power at the aperture of the control room. The concentration ratio can achieve 2500 suns over a 4 inch diameter. Higher concentrations over smaller areas are possible when using secondary optics.

Unique Aspects‎

NREL's High Flux Solar Furnace (HFSF) is available for on-sun functional component performance testing. For example, the furnace has been used for solar thermochemical hydrogen (STCH) solar receiver and materials testing for over 20 years based on funding through DOE's FCTO. On-sun testing of photo-electrochemical (PEC) hydrogen production cells could also be supported if applicable.
The HFSF is co-located with NREL's internationally renowned Solar Radiation Research Laboratory (SRRL). The SRRL is the home of the world's largest collection of radiometers in continuous operation including pyranometers, pyrheliometers, pyrgeometers, photometers, and spectroradiometers that can provide the solar resource information necessary for characterizing the performance of solar hydrogen components.


NREL's HFSF is used consistently in summer months to fulfill test commitments on current projects. Shorter days in late fall through early spring limit test times. Winter days historically yield the highest direct normal irradiance due to clear skies, yielding excellent test conditions.
We anticipate the solar furnace will be roughly 50% uncommitted in FY17 for testing beyond current commitments.


NREL's HFSF has been used historically for on-sun testing of prototype receiver designs at relevant scales, including those designed to demonstrate solar-to-hydrogen and solar-to-fuels conversion. Tests are performed under realistic, rather than simulated conditions. The facility can be used to support high-flux conditions (design point or accelerated) of components and materials envisioned within the HydroGEN mission.



1. Martinek, J., Bingham, C., & Weimer, A. W. (2012). Computational modeling and on-sun model validation for a multiple tube solar reactor with specularly reflective cavity walls. Part 1: Heat transfer model. Chemical engineering science, 81, 298-310.
2. Martinek, J., Bingham, C., & Weimer, A. W. (2012). Computational modeling and on-sun model validation for a multiple tube solar reactor with specularly reflective cavity walls. Part2: Steam gasification of carbon. Chemical engineering science, 81, 285–297.
3. Lichty, P., Liang, X., Muhich, C., Evanko, B., Bingham, C., & Weimer, A. W. (2012). Atomic layer deposited thin film metal oxides for fuel production in a solar cavity reactor. International Journal of Hydrogen Energy, 37(22), 16888-16894.