> ## Documentation Index
> Fetch the complete documentation index at: https://docs.plantpredict.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Fixed-Tilt Arrays

export const AngleOfIncidence = () => <Tooltip tip="Angle between the sun's rays and the perpendicular to a surface; 0° when sun is directly facing the surface.">
    angle of incidence
  </Tooltip>;

## Summary

Fixed-tilt arrays maintain a constant orientation throughout the year. PlantPredict assigns the user-defined tilt ($\beta_m$) and azimuth ($\gamma_m$) angles directly—no calculations or optimizations are performed. These constant values are used for all timesteps in the prediction.

## Inputs / Outputs

| Name                     | Symbol     | Units   | Description                                                                            |
| ------------------------ | ---------- | ------- | -------------------------------------------------------------------------------------- |
| **Module Tilt Angle**    | $\beta_m$  | degrees | Angle of module surface from horizontal (0° = horizontal, 90° = vertical)              |
| **Module Azimuth Angle** | $\gamma_m$ | degrees | Direction the module faces, clockwise from North (0° = N, 90° = E, 180° = S, 270° = W) |

If $\beta_m = 0°$, a small offset of $0.001°$ is applied so that the module surface has a definable azimuth (at exactly 0° the surface is horizontal and its azimuth is undefined).

The <AngleOfIncidence />, which determines how much direct beam irradiance reaches the module surface, is calculated separately (see [Incidence Angle](./incidence_angle)).