National Solar Thermal Test Facility (NSTTF)


Sandia National Laboratories (SNL)

Capability Expert

Kenneth Armijo


Process and Manufacturing Scale-Up
System Integration

Node Readiness Category

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


For over 40 years, Sandia has led R&D in solar thermal energy technologies and operates the National Solar Thermal Test Facility (NSTTF). The only facility of its kind in the U. S., the NSTTF includes a 6 MW central receiver test facility with 200+ heliostats (currently being utilized for particle receiver development and testing), a 16 kWth solar furnace, a rotating test platform, a solar simulator with automated sample handling and exposure system, particle and sCO2 R&D systems, an industrial-scale molten salt test loop (MSTL), and a particle/sCO2 heat exchanger test bed, among other sCO2 and solid particle CSP/CST test systems. The NSTTF’s primary goal is to provide experimental engineering data for the design, construction, and operation of unique components and systems in proposed solar thermal plants.

In addition, the site was built and instrumented to provide test facilities for a variety of solar and non-solar applications. The expertise of NSTTF staff covers every scientific and engineering field needed to develop, operate, test, and evaluate complex solar systems and facilitate their use. Key competencies include engineering systems design and analysis, system testing and evaluation, and optical and thermal materials research and development. NSTTF staff have worked on virtually every major concentrating solar power project in the United States and has led or shared lead responsibility on many of them.

Capability Bounds‎

Heliostat field: 350 W/cm², and total power in excess of 6 MWt.

Tower: The tower is a 61 m (200 ft) high concrete structure with three test locations on the north side and the top of the tower. The tower can support testing for CSP experiments and large-scale, high-flux materials samples. Equipment in the tower includes a 100-ton capacity elevating module for lifting experiments to the top of the tower, internal cranes for receiver fabrication, water glycol cooling systems and air coolers to provide heat removal from experiments, air compressors, control valves, generators, uninterruptible power supplies, piping systems, and pressure-relief valves.

Solar furnace: 95 m² heliostat, 6.7056 meter diameter dish, 16 kW total thermal power, peak flux up to 500 W/cm². The furnace has a power control to simulate nuclear and other thermal transients.

Solar simulator: Four 1.8 kWe metal halide lamps, up to 1200 suns, peak irradiance ~1.1 MW/m² with an average irradiance of ~0.9 MW/m² over a spot size of ~1 inch (2.5 cm).

Molten Salt Test Loop: Industrial-scale nitrate solar molten salt test loop with 6 in. ID SS347H piping, 600 GPM flow, 1.4 MWth cooling capacity and up to 600°C testing.

Particle/sCO2 Test Loop for Accelerated Heat Exchanger: A heat exchanger testbed available to future particle heat exchanger and component developers for performance evaluation of prototypes. Testing of prototype heat exchangers with design temps >800 C and heat transfer coefficients >400W/m2-K.

Unique Aspects‎

The NSTTF is the only facility of its kind in the United States.


The NSTTF welcomes all users. Several mechanisms are available for non-SNL researchers to contract with SNL to use the facility. Previous users include government contractors and agencies, research institutes, universities, and private companies.


Enables on-sun testing for any HydroGEN concepts that require concentrated solar energy inputs.


Solar Tower with heliostats in stowed position, parabolic dishes seen in foreground.

Solar Tower with heliostats in stowed position, parabolic dishes seen in foreground.

Solar furnance with heliostat (right), control louvers (center) , and heliostat (left in building).

Solar furnance with heliostat (right), control louvers (center) , and heliostat (left in building).

Solar simulator models

Solar simulator.

SNL National Solar Thermal Test Facility interior
SNL National Solar Thermal Test Facility