Solar Exposure Thermal Model

SWITCH TO API

Description

The Solar Exposure Thermal Model is a Thermal Model that computes solar heating power for any Physical Object based on sun direction, exposed area, and surface properties. When attached to a Solar Panel, it automatically calculates waste heat from absorbed solar energy not converted to electricity.

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Example Use Cases

• Surface Heating Analysis: Calculate solar heat input on spacecraft surfaces for thermal budget analysis.
• Solar Panel Thermal Modeling: Determine waste heat generated by solar panels during power generation.
• Attitude-Dependent Heating: Evaluate how spacecraft orientation affects thermal loading.

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Module Implementation

The model computes solar heating based on the projected area facing the sun and surface absorption properties.

Generic Object Heating

For general physical objects, the solar heating power is:

$$P={\alpha }_s(1-\sigma )A_{\text{proj}}\Phi$$

where ${\alpha }_s$ is the solar absorbance, $\sigma$ is the shadow factor, $A_{\text{proj}}$ is the projected area, and $\Phi$ is the solar flux.

Projected Area

The projected area is computed from the exposed surface area and the angle between the sun direction and surface normal:

$$A_{\text{proj}}=A_{\text{exp}}(\hat{s}\cdot \hat{n})$$

where $A_{\text{exp}}$ is the exposed area, $\hat{s}$ is the unit vector toward the sun in body frame, and $\hat{n}$ is the surface normal in body frame. Negative values (sun behind surface) are clamped to zero.

Solar Panel Waste Heat

When attached to a Solar Panel, the model calculates waste heat as the absorbed energy not converted to electricity:

$$P={\alpha }_s(1-\eta )A_{\text{proj}}\Phi$$

where $\eta$ is the solar panel electrical conversion efficiency.

Albedo Contribution

If an Albedo Model is attached to the parent object, the reflected flux from nearby celestial bodies is added to the direct solar flux.

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Assumptions/Limitations

• The sun direction is computed from the root object’s transform; all child objects share the same solar geometry.
• The shadow factor represents external shadowing and must be set manually; self-shadowing is not automatically computed.
• The model assumes a flat surface with uniform absorbance properties.