Solar Panel Thermal Model

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Description

The Solar Panel Thermal Model represents the thermal behavior of a solar panel component. It extends the base Thermal Model and provides a thermal representation of power losses due to solar absorption and conversion inefficiency.

This model couples electrical and thermal subsystems, allowing the simulation of temperature variations as a function of:

• Incident solar flux
• Optical properties (absorptivity, emissivity)
• Conversion efficiency
• Panel orientation and projected area

The class operates as a child model of the Solar Panel component.

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Module Implementation

Core Calculation

The thermal power generation $(P_{\mathrm{thermal}})$ is computed each simulation step as:

$$P_{\mathrm{thermal}}=(\alpha -\eta )\times A_{\mathrm{proj}}\times {\Phi }_{\mathrm{solar}}$$

Where:

• $\alpha$ : Solar absorbance
• $\eta$ : Power conversion efficiency
• $A_{\mathrm{proj}}$ : Projected area [m2]
• ${\Phi }_{\mathrm{solar}}$ : Solar flux [W/m2]

To ensure the model never introduced non-physical cooling from solar illumination, negative results are clamped to zero

$$P_{\mathrm{thermal}}=\max (0,P_{\mathrm{thermal}})$$

Integration with Thermal System

After computing the power absorbed as heat, base Thermal Model, which handles:

• Thermal capacitance and temperature update
• Radiative and conductive exchanges with connected nodes
• Steady-state and transient heat transfer resolution

The coupling enables coherent temperature evolution within the spacecraft’s overall thermal network.

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Assumptions/Limitations

• Uniform Illumination – The entire projected area receives a uniform solar flux.
• Constant Optical Properties – Absorptance and emissivity are assumed constant over temperature and time.
• Instantaneous Power Conversion – Electrical conversion losses are immediately manifested as heat.
• Negligible Shadowing – No partial shadow or inter-panel occlusion effects are modelled.
• Steady Solar Spectrum – Uses the standard Earth solar constant $({\Phi }_{\mathrm{solar}}=1361W/m^2)$ when not defined.
• No Angular Dependence – Does not consider the cosine of the incidence angle between the Sun vector and panel normal.
• No Thermal Degradation – Material degradation or optical aging is not simulated.
• Simplified Heat Transfer Coupling – Radiative view factors are not explicitly computed; handled generically by the parent Thermal Model.
• Single-Node Representation – Each solar panel is treated as a single lumped-parameter thermal node rather than a distributed surface.

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References

[1] Bergman, Theodore et al. Fundamentals of Heat and Mass Transfer. 8th ed. Wiley, 2017. Web. 29 Oct. 2025.

[2] Howell, J.R., Mengüc, M.P., Daun, K., & Siegel, R. (2020). Thermal Radiation Heat Transfer (7th ed.). CRC Press. https://doi.org/10.1201/9780429327308

[3] 3. Wertz, J. R., Everett, D. F., & Puschell, J. J. (2011). Space Mission Engineering: The New SMAD (2nd ed.). Microcosm Press.