A concentrating solar power field in standby, with reflected sunlight forming a canopy of high-irradiance voxels above the heliostats

Sandia National Laboratories Delivered · open source

FFIAM

Full-Field Irradiance Analysis Model

A concentrating solar power field in standby still reflects sunlight. That energy collects in the airspace above the field, where it's a hazard to aircraft and birds.

FFIAM shows where it collects, how intense it is, and how it moves with the sun and the aim strategy. It divides the airspace into a 3D grid of voxels and computes the irradiance in each one, tracing reflected sunlight facet by facet from every heliostat.

We built it for Sandia as a C++/CUDA library with a parallel CPU fallback, packaged in Docker with a one-command quickstart. On top are two workflows: a Python analysis module and a real-time Unreal Engine renderer. Every image on this page is FFIAM output.

Seeing the Airspace

Colored voxels mark reflected-sunlight irradiance above the reporting threshold. Brighter means more intense.

Voxelized irradiance plume rising above the receiver tower at the National Solar Thermal Test Facility — National Solar Thermal Test Facility

Standby irradiance at Sandia's NSTTF. The highest flux forms a plume above the receiver tower.

Single-point standby strategy producing a dense concentrated layer of irradiance above the field — Single-point standby

Every heliostat aimed at one location. The reflected flux converges into a concentrated high-irradiance column.

Close-up of the voxelized irradiance field, each cell colored by intensity

300 million cubes

Each cube holds the computed irradiance at that point in the airspace. A full-scale V3.0 analysis evaluates about 300 million of them.

FFIAM V3.0

1.6 km

maximum field radius

300 m

airspace height

11,000+

heliostats

~300M

voxels at 2 m resolution

Smaller fields can run at 1 m resolution. FFIAM uses an NVIDIA GPU when there is one and a CPU backend with the same features when there isn't, so it runs on any machine with Docker.

Two Workflows

Data workflow

The pyffiam Python module, run from the command line or a script. It produces voxel-scatter heatmaps in each cardinal plane, time-resolved animations, flight-path irradiance and radiant-exposure plots, and an Excel summary ready for a report.

Visualization workflow

An interactive Unreal Engine scene rendering the field and its high-irradiance voxels, navigable in real time with adjustable site, date and time, aim strategy, and reporting threshold.

Validation

Results were checked against ray tracing and against UAS measurement campaigns flown at the National Solar Thermal Test Facility. The project ran for three years and concluded in June 2026 with the open-source release of FFIAM V3.0 through Sandia's OpenCSP ecosystem.

Released through Sandia OpenCSP

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