U.S. Department of Energy

National Solar Thermal Test Facility

SNL logo Photo of the solar tower and heliostat field at the National Solar Thermal Test Facility taken from above.

The NSTTF at SNL provides an extensive infrastructure for research, development, and testing of CSP subcomponents. Image from Sandia National Laboratories
SAND 2013-1883W

The first solar receivers ever tested in the world were tested at the National Solar Thermal Test Facility (NSTTF). The receivers were each rated up to 5 megawatts thermal (MWt). Receivers with various working fluids have been tested here over the years, including air, water-steam, molten salt, liquid sodium, and solid particles. The NSTTF has also been used for a large variety of other tests, including materials tests, simulation of thermal nuclear pulses and aerodynamic heating, and ablator testing for NASA.


Construction of the NSTTF began in 1976. The decision to build this facility was a result of the 1973 Oil Embargo imposed by the Organization of the Petroleum Exporting Countries. The Carter administration supported building the facility to support research into concentrating solar power (CSP) technologies.

Since completion of the original NSTTF, the DOE CSP program has supported expansion of the facility to include a solar furnace, solar troughs and dishes, engine test facility (ETF), rotating platform, and the molten salt test loop (MSTL) over the years. All of these additional facilities provide the NSTTF with capabilities that allow for the testing of various components and systems that support development and improvements in concentrating solar power technology.

Current Capabilities

The facilities at the NSTTF include the following:

  • The 200-foot high solar tower has multiple flux panels for accurate evaluation of reflector performance and solar flux.
  • The heliostat field can generate a peak flux of up to 350 W/cm2 and 6 MWt total power. The heliostat field has foundations, power, and communications available for testing of innovative custom heliostats utilizing the NSTTF's world-class heliostat evaluation and metrology systems. These include beam characterization, heliostat canting and alignment, long-range beam analysis, wind modal analysis, and tracking and pointing analysis. The heliostat field can also be used for tracking celestial bodies other than the sun, as well as for tracking other objects such as satellites.
  • The solar furnace can provide a peak flux of up to 500 W/cm2 and 16 kWt of power. The facility has been used for activities such as the screening of material samples and prototype receivers.
  • The MSTL provides CSP plant–like conditions (flow rate >600gpm, pressures up to 600psi, and temperatures ranging from 300 to 585°C with a 1.4 MW cooling capacity) with flowing molten nitrate salt for the evaluation of components and solar receiver systems.The MSTL also serves as a corrosion test facility for heat transfer fluids.
  • The dish-Stirling test field has various test bed dishes available for testing solar engines.
  • The Optical Characterization Laboratory┬áprovides high-resolution slope error analysis of concentrating optics as well as in-field alignment tools for dishes, canting tools for heliostats, and trough alignment.
  • The ETF has two test bays, an assembly bay and a control room for developing and testing dish engines prior to their mounting on a solar dish. The assembly building provides a machine shop with welding, assembly, and testing capability for large structures and test rigs.

Planned Work

With funding provided by DOE under the National Laboratory R&D competitive funding opportunity, the NSTTF will maintain an operational facility that can be used to conduct testing on the solar tower using the heliostat field as well as testing at the solar furnace.

SunShot logo

Progress Reports

Program Fact Sheet

Learn about other DOE competitive awards for concentrating solar power research that are in progress.