Function accumulation_model 

pub fn accumulation_model(
    rainfall: f64,
    cleaning_threshold: f64,
    tilt: f64,
    pm2_5: f64,
    pm10: f64,
) -> f64

Simplified soiling loss mass accumulation model (inspired by Hsu et al).

Estimates daily soiling accumulation based on particulate matter concentrations, assuming natural rain washing.

Arguments

• rainfall - Daily rainfall in mm.
• cleaning_threshold - Rainfall threshold to clean the panels (e.g., 5.0 mm).
• tilt - Surface tilt in degrees.
• pm2_5 - PM 2.5 concentration in ug/m^3.
• pm10 - PM 10 concentration in ug/m^3.

Returns

Soiling mass accumulation fraction for the day.