To research, develop, and test a variety of concentrating solar power technologies, NREL features the following laboratory capabilities:
- Concentrated Solar Radiation Facility
- Large Payload Solar Tracker
- Advanced Optical Materials Laboratory
- Advanced Thermal Storage Materials Laboratory
- Optical Testing Laboratory and Beam Characterization System
- Receiver Test Laboratory
- Heat Collection Element (HCE) Temperature Survey
Concentrated Solar Radiation Facility
At our Concentrated Solar Radiation Facility, the High-Flux Solar Furnace and the Ultra-Accelerated Weathering System concentrate the power of the sun to test the durability of materials and coatings, conduct high-temperature experiments, and demonstrate the potential of solar power in industrial processes.
High-Flux Solar Furnace (HFSF)
The 10-kilowatt HFSF, in operation since 1990, 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 concentrating solar power systems.
Perhaps the most exciting use of the facility is to 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.
Ultra-Accelerated Weathering System (UAWS)
The UAWS is an ultraviolet (UV) concentrator that can simulate 10 years of UV damage in just two months. Studies on aging can be conducted on a wide variety of surfaces—from automotive paint and building materials to coatings on solar panels—by using UAWS' parabolic dish with special mirror facets that concentrate and focus the sun's UV rays.
The UAWS can concentrate the UV solar energy up to 100 times, yet can do so without "cooking" the samples. The breakthrough, which led to UAWS winning an R&D100 Award, was in developing a way to concentrate the UV spectra and redirect the visible and near-infrared spectra. The result is that UAWS achieves ultra-high intensity and acceleration, high fidelity to actual sunlight, and reasonable exposure temperatures.
The HFSF and UAWS are both available to industrial, university, and government researchers. We can provide experienced staff to operate the facility for a variety of experimental objectives. For more information about the HFSF, contact Judy Netter at 303-384-6258. For information about UAWS testing, contact Matthew Gray at 303-384-3917.
Large Payload Solar Tracker
NREL recently acquired a multipurpose, large payload tracker to support testing of solar components that require tracking the sun in elevation and azimuth. Concentrating collectors require 2-axis tracking to focus sunlight on a thermal or photovoltaic (PV) receiver. For flat-plate collectors, flat-plate PV, or solar hot water, this would imply tracking to minimize variation in solar resource during on-sun testing. As applicable, the site can be used to supplement metrology activities that require 2-axis tracking for simultaneous calibration of a large number of solar radiation measurement instrumentation. The large payload tracker is capable of carrying a maximum vertical load of 9,000 pounds with a tracking accuracy of 1 milliradian.
Advanced Optical Materials Laboratory
NREL's Advanced Optical Materials Laboratory provides substantial analytical and measurement capabilities for developing and testing optical materials used in concentrating solar power systems.
The laboratory has many tools and instruments that allow measurement of optical properties and performance. We can measure a wide range of feature sizes (from nanometers to meters) and sample sizes (from millimeters to tens of meters) traceable to the National Institute of Standards and Technology.
We offer three types of exposure testing capabilities for optical materials, which include:
- An international network of instrumented, outdoor exposure test sites
- Accelerated laboratory-controlled exposure chambers
- An ultra-accelerated, natural sunlight exposure testing facility.
Available analytical capabilities include:
- X-ray photoelectron spectroscopy
- Ion scattering spectroscopy
- Auger electron spectroscopy
- Atomic force microscopy
- Scanning electron microscopy
- Fourier-transform infrared.
For more information about NREL's capabilities in this area, see our information about optical analysis and modeling.
Learn more about our research and development in advanced optical materials for concentrating solar power systems.
Advanced Thermal Storage Materials Laboratory
The Thermal Storage Materials Laboratory supports NREL's research and development of advanced heat transfer fluids for the next generation of parabolic trough systems. Our goal is to identify fluids with thermal and oxidative stabilities that can withstand extreme operating conditions, such as temperatures up to 425°C while remaining liquid at or below 0°C, and that can function as advanced thermal storage media.
To develop these heat transfer fluids, we use a synthetic chemistry laboratory that combines a work area for basic wet chemistry with extensive thermal and spectroscopic analysis capabilities. We can synthesize fluids in gram quantities and immediately evaluate their thermal behavior. To evaluate thermal behavior, we use NREL's molecular-beam mass spectrometry system to study the thermal degradation mechanisms by which newly synthesized fluids decompose at elevated temperatures.
Learn more about our research and development in parabolic trough thermal energy storage technology.
Optical Testing Laboratory and Beam Characterization System
To develop and test concentrators for concentrating solar power systems, NREL researchers use VSHOT (Video Scanning Hartmann Optical Test) and a beam characterization system.
We use VSHOT, developed by the U.S. Department of Energy's SunLab, to characterize the optical performance of point-focus and line-focus optical concentrators. The system uses laser ray tracing combined with fast video imaging to mathematically describe mirror concentrator surfaces and compare them to desired surfaces. It reports slope errors of the actual surface relative to the desired surface and provides plots of error location, magnitude, and direction. The surface slope data and mathematical surface description produced by VSHOT can be input into ray trace models to predict flux distributions on receivers.
And VSHOT is fast. It allows us to thoroughly test a solar thermal concentrator in 2 to 3 minutes or less. When detailed data isn't needed, VSHOT can test mirrors in even less time. SunLab continues to improve the speed and functionality of VSHOT, extending its capabilities as a field instrument for concentrator installation and alignment. The system has been used extensively both in the laboratory and in the field to quantify parabolic dish and parabolic trough optical performance, providing developers with valuable information in their efforts to deploy cost effective, high performance concentrating solar power technology.
Beam Characterization System
We use a beam characterization system to measure the distribution of concentrated sunlight on a target. The portable system acquires and processes images reflected from a diffuse, or Lambertian, target. These images are proportional to the incident flux. The system consists of:
- A 10-bit digital camera with a spatial resolution of 736 x 484 pixels
- A motorized zoom lens
- A laptop computer with docking station housing the frame grabber card and imaging software.
The Beamview Digital Laser Beam Diagnostic System from Coherent, Inc. comprises the camera, frame grabber, and software. The beam characterization system allows us to measure the solar flux incident at the focal plane of thermal or concentrating photovoltaic receiver. The instrument is used extensively at the High-Flux Solar Furnace. However, because the beam characterization system is portable, it is used periodically to support field measurements at the request of our industry partners.
To learn more about NREL's research and development of concentrators, see our information on parabolic trough solar field technology.
Receiver Test Laboratory
With NREL's parabolic trough receiver test stand, researchers can analyze the steady-state off-sun thermal losses of receivers used in solar parabolic trough power plants. First, electric heaters and thermocouples are placed inside the receiver being tested. Then, the heater power use is recorded at a desired absorber temperature. This routine is repeated for several different absorber temperatures, generating heat loss curves for a receiver.
Research continues to help reduce collector optical losses, as well as to further reduce receiver heat loss at elevated temperatures. For more information on receiver heat loss testing, visit TroughNet.
Heat Collection Element (HCE) Temperature Survey
NREL's non-disruptive, automated method records HCE glass temperatures in a parabolic trough power plant solar field. Occasional HCE temperature surveys can document the condition of HCEs over extended periods of time and locate those with unacceptable heat losses.
In this method, a vehicle with an infrared (IR) camera and Global Positioning System (GPS) receiver is driven down each solar field row. A data acquisition system uses the IR camera to photograph HCE glass temperatures and processes them automatically. The glass temperatures of about 6000 HCEs can be determined in one day. During this time, the solar plant operates normally.
The glass temperature indicates how well the HCE is working. The cooler the HCE glass temperature for a given air temperature, wind speed, and internal heat-transfer fluid (HTF) temperature, the less the heat lost to the environment — leaving more heat to increase the temperature of the internal HTF. HCEs that have lost their vacuum or have hydrogen in their annuli show significantly increased glass temperatures (˜300°F) and heat losses relative to evacuated HCEs.