The National Solar Thermal Testing Facility’s Concentrating Solar Optics Laboratory aims to deliver excellent optical metrology and analysis solutions to support concentrating solar industry, research and education worldwide.
Our optical metrology work focuses on developing precise and reliable solutions for challenging issues such as accelerated tracking calibration, high-resolution optical surface mapping, in-situ optical assessment, heliostat field health monitoring, and dynamic assessment of wind impacts on optics. We seek solutions designed to be easily accessible to the concentrated solar power industry, spanning development stages from prototype development to factory calibration, field calibration, and operation.
Current and emerging capabilities include:
- OpenCSP
- Beam Characterization System (BCS) image analysis
- High-resolution mapping of optical surface slope
- Characterization of optical variation with temperature
- Ground truth checks of measurement accuracy
OpenCSP is a collaborative development environment intended to accelerate the transfer of high-quality optical metrology and analysis tools, and also to provide an effective environment to enable cross-institution team collaboration. OpenCSP includes code, computer-aided design information, and data.
Beam Characterization System (BCS) image analysis
SpotAnalysis is the generalized analysis of a beam of light on an optical target. This issue occurs in several situations in CSP metrology; the Beam Characterization System is one example. Other examples include returned-spot ground truth analysis and laser measurement methods. In BCS, a single heliostat reflects sunlight onto the BCS target at the top of the tower. A camera captures the image, and the SpotAnalysis code identifies both the ideal target point and the actual maximum flux point. The difference between these is the pointing error.
High-resolution mapping of optical surface slope
SOFAST 2.0 is a system for measuring high-resolution maps of mirror slope. It produces a variety of analytic output products, including absolute slope, slope error magnitude, and built-in ray tracing analysis. It is flexible and can be applied to a wide variety of physical layouts.
Characterization of optical variation with temperature
We interfaced SOFAST with a temperature chamber at CFV Labs in Albuquerque, New Mexico. This enabled us to vary mirror temperature to commanded values, and measure the change in optical shape as a function of temperature. Some mirrors show significant sensitivity to temperature variation, which makes this an important measurement.
Ground truth checks of measurement accuracy
Measurement of concentrating solar power systems is often performed using sophisticated tools which include optical and mechanical elements and complex software. One important question is: How accurate are these systems? We are developing a set of ground truth physical standards and measurement methods which may be used to check the accuracy of various CSP metrology systems, developed both at Sandia National Laboratories and elsewhere.
Both photovoltaic and concentrating solar systems can produce large swaths of reflected light. This raises the questions: Will the resulting glare cause visual hazards? Will it be objectionable? The NSTTF-developed software tool, SGHAT, provides analysis to predict glint and glare impacts for proposed solar projects and has been licensed by industry leaders such as ForgeSolar.
Mobile metrology to take capabilities to remote sites
CSP developers wanting to utilize Sandia CSP metrology capabilities have several options. They may obtain direct access to design information, code, and documentation via OpenCSP; seek Sandia support to implement these tools on their site; and bring prototypes to Sandia for testing. A mobile system currently under development will enable us to take our metrology capabilities to a customer site for measurement and training. We anticipate this capability will be available in 2026.
In-situ assessment of heliostat optical performance
One of the most difficult issues in CSP metrology is measurement of heliostat optical performance parameters in the field. This is made more complex during field operation. At Sandia, we are pursuing high-fidelity, high-speed, high-resolution, non-intrusive methods to efficiently measure many heliostats.
Our Team
The Concentrating Solar Optics Laboratory (CSOL) Team:
- Randy Brost
- Braden Smith
- Ben Bean
- Evan Harvey
- Felicia Brimigion
- Madeline Hwang
- Dimitri Madden
- The NSTTF Technologist Team