The Scenario HDF5 File Format

In ARTIST, all simulations are based on a so-called scenario file. This HDF5 (Hierarchical Data Format) file contains the complete configuration of a solar tower power plant. It defines, for example, the type, layout, and orientation of the heliostats in the field, as well as the positions of the receiver and calibration targets.

The HDF5 file format is designed to store and organize large amounts of data in a hierarchical structure. It supports various data types, including numerical arrays, tables, and metadata, and provides efficient compression and chunking mechanisms, making it well-suited for handling large datasets. Structurally, HDF5 files are composed of:

Groups, which act like folders and allow nested organization of data,
Datasets, storing the actual array-like data, and
Attributes to attach metadata to the actual data.

They provide a versatile, scalable, and platform-independent way to store, manage, and access large, complex data structures. That is why they are widely used in research, engineering, and data analysis applications.

Structure of an `ARTIST` Scenario

An ARTIST scenario consists of five main elements:

Power Plant

To provide a realistic geographical context, the power plant location is stored in the scenario file. The coordinates are saved in WGS84 coordinates (latitude, longitude, and altitude).

Target Areas

Every scenario contains at least one target area. A target area is a defined area on the solar tower where reflected light is concentrated. If the target area is a receiver, the concentrated light is converted into thermal energy for electricity generation or industrial processes. If the target area is a calibration target, this area on the tower is used exclusively for calibration tasks, for example in the alignment optimization. There are currently two types of target areas implemented in ARTIST, which differ in their geometry: planar and cylindrical. Planar target areas are commonly used for calibration surfaces, while cylindrical target areas represent receiver geometries. Due to these geometric differences, each target area type requires its own ray-tracing methods. ARTIST handles this automatically by sorting the target areas provided in the scenario HDF5 files into the appropriate classes and applying the correct methods for each type. The scenario structure supports multiple target areas, which is particularly useful for calibration setups or multi-receiver power plants, where different target area types may be used within a single simulation. Each target area includes basic information such as its name, position, and normal vector. In addition, planar target areas store geometric dimensions, while cylindrical target areas include parameters such as radius, axis, height, and opening angle.

Light Sources

Each scenario contains at least one light source, which models how the incoming radiation is generated before being reflected onto a receiver. A light source has a defined type, for example, Sun, and specifies how many rays are to be sampled from this light source for ray tracing. The scenario structure allows multiple light sources, which can be useful in advanced calibration or testing configurations.

Heliostats

A concentrating solar power plant relies on mirrors, the heliostats, to reflect light onto the receiver. Therefore, an ARTIST scenario must contain at least one heliostat (typically many). Each heliostat includes:

A unique ID,
a position in the field,
an aim point it is focusing on,
a surface,
a kinematics model, and
at least one actuator.

The surface is the reflective mirror geometry and composed of multiple facets. As each facet is modeled using Non-Uniform Rational B-Splines, the corresponding NURBS parameters must be stored in the HDF5 file.

The kinematics define how the heliostat can move, i.e., the number and orientation of rotation axes and the permitted movement directions. Each kinematic configuration contains at least one actuator responsible for performing the orientation adjustments.

Prototypes

In realistic CSP plants, almost all heliostats are identical. Operators typically source heliostats from a single manufacturer to reduce maintenance costs and simplify the acquisition process. To avoid redundant storage of identical parameters, an ARTIST scenario includes prototypes for the surface, kinematics, and actuators. If a heliostat does not specify individual configuration parameters, ARTIST automatically loads the corresponding prototype. This significantly reduces file size and improves maintainability.

These five elements result in an ARTIST scenario HDF5 file with the following structure:

.
├── power_plant [1]
│   └── position [1,1]
├── target_areas_planar [1,*]
│   ├── calibration_target1
│   │   ├── position_center [1,1]
│   │   ├── normal_vector [1,1]
│   │   ├── plane_e [1,1]
│   │   └── plane_u [1,1]
│   ├── calibration_target2
│   │   └── ...
│   └── ...
├── target_areas_cylindrical [1,*]
│   ├── receiver1
│   │   ├── cylinder_axis [1,1]
│   │   ├── cylinder_center [1,1]
│   │   ├── cylinder_height [1,1]
│   │   ├── cylinder_opening_angle [1,1]
│   │   ├── cylinder_radius [1,1]
│   │   └── cylinder_normal [1,1]
│   ├── receiver2
│   │   └── ...
├── lightsources [1,*]
│   ├── lightsource1
│   │   ├── type [1,1]
│   │   ├── number_of_rays [1,1]
│   │   └── distribution_parameters [1,1]
│   │       ├── distribution_type [1,1]
│   │       ├── mean [0,1]
│   │       ├── covariance [0,1]
│   │       └── ...
│   ├── lightsource2
│   │   └── ...
│   └── ...
├── heliostats [1,*]
│   ├── heliostat1
│   │   ├── id [1,1]
│   │   ├── position [1,1]
│   │   ├── surface [0,1]
│   │   │   └── facets [1,*]
│   │   │       ├── facet_1
│   │   │       │   ├── control_points [1,1]
│   │   │       │   ├── degrees [1,1]
│   │   │       │   ├── position [1,1]
│   │   │       │   └── canting [1,1]
│   │   │       ├── facet_2
│   │   │       │   └── ...
│   │   │       └── ...
│   │   ├── kinematics [0,1]
│   │   │   ├── type [1,1]
│   │   │   ├── initial_orientation [1,1]
│   │   │   └── deviations [0,1]
│   │   │       ├── first_joint_translation_e [0,1]
│   │   │       ├── first_joint_tilt_n [0,1]
│   │   │       └── ...
│   │   └── actuator [0,*]
│   │       ├── actuator_1
│   │       │   ├── type [1,1]
│   │       │   ├── clockwise_axis_movement [1,1]
│   │       │   ├── min_max_motor_positions [1,1]
│   │       │   └── parameters [0,*]
│   │       │       ├── increment [0,1]
│   │       │       ├── initial_stroke_length [0,1]
│   │       │       ├── offset [0,1]
│   │       │       ├── pivot_radius [0,1]
│   │       │       └── initial_angle [0,1]
│   │       └── actuator_2
│   │           └── ...
├── heliostat2
│   └── ...
└── ...
└── prototypes [1,1]
    ├── surface [1,1]
    │   └── facets [1,*]
    │       ├── facet_1
    │       │   ├── control_points [1,1]
    │       │   ├── degrees [1,1]
    │       │   ├── position [1,1]
    │       │   └── canting [1,1]
    │       ├── facet_2
    │       │   └── ...
    │       └── ...
    ├── kinematics [1,1]
    │   ├── type [1,1]
    │   ├── initial_orientation [1,1]
    │   └── deviations [0,1]
    │       ├── first_joint_translation_e [0,1]
    │       ├── first_joint_tilt_e [0,1]
    │       └── ...
    └── actuator [1,*]
        ├── actuator_1
        │   ├── type [1,1]
        │   ├── clockwise_axis_movement [1,1]
        │   ├── min_max_motor_positions [1,1]
        │   └── parameters [0,1]
        │       ├── increment [0,1]
        │       ├── initial_stroke_length [0,1]
        │       ├── offset [0,1]
        │       ├── pivot_radius [0,1]
        │       └── initial_angle [0,1]
        └── actuator_2
            └── ...

The Scenario HDF5 File Format

Structure of an ARTIST Scenario

Structure of an `ARTIST` Scenario