Understanding Your Solar Simulation Results

How We Calculate Your Solar Energy

The app uses the NREL PVWatts® v5 model – the same industry-standard method used by professional solar installers worldwide and validated by the U.S. National Renewable Energy Laboratory.

What the model considers:

• Temperature matters: Solar panels lose efficiency as they heat up (about 0.3-0.5% per degree Celsius above 25°C). Our calculation uses your panel's NOCT (Nominal Operating Cell Temperature) rating – typically 45-47°C – to estimate real-world operating temperatures. A panel rated 20% efficient at STC (Standard Test Conditions: 25°C, 1000 W/m²) might only achieve 17-18% on a hot Australian summer day.

• Low-light performance: Panels produce less at dawn, dusk, and under clouds. We apply an exponential correction factor for irradiance below 200 W/m², based on published module performance data.

• Real-world losses: Inverters, wiring, and dust on panels typically reduce output by 14%. This is built into our calculations following IEC 61724 guidelines for PV system performance monitoring.

• Dual-sided orientation: Solar Waves panels are angled east-west. Our model automatically splits panels between two orientations (e.g., 180° and 0°) following the ASHRAE standard for incidence angle modifiers.

How We Calculate Water Savings

When you place solar panels over water, two mechanisms reduce evaporation, following methods published in the Journal of Hydrology and validated against FAO (UN Food and Agriculture Organization) standards:

1. Radiation Blocking (Shading)

Panels block sunlight that would otherwise provide energy for evaporation. A panel at 12.5° tilt shades approximately 97% of the water beneath it. The remaining 3% accounts for gaps and diffuse light penetration.

2. Wind Speed Reduction

The array structure reduces wind velocity at the water surface, decreasing evaporative transfer. Our height-dependent wind block factors are derived from boundary layer theory and validated against field studies of floating solar installations:

• At 0.6m height: 90% wind reduction

• At 2m height: 60% wind reduction

• At 5m+ height: 40% wind reduction (approaching open water conditions)

The FAO-56 Penman-Monteith equation is the international standard for evapotranspiration calculations, used by hydrologists and irrigation engineers worldwide. It combines:

• Radiation balance (net solar energy)

• Aerodynamic resistance (wind effects)

• Vapor pressure deficit (humidity effects)

Sky View Factor (SVF)

For accurate diffuse radiation under arrays, we use Hammersley sequence sampling – a quasi-Monte Carlo method that provides deterministic, reproducible results. This follows best practices in radiative transfer modeling and ensures consistent audit trails.

Where Your Data Comes From

All weather and location data comes from authoritative scientific sources:

• Open-Meteo: Provides ERA5 reanalysis data (European Centre for Medium-Range Weather Forecasts) – the same data used by climate researchers worldwide. Includes:

  GHI, DNI, DHI (Global, Direct, Diffuse radiation)

  Temperature at 2m height (WMO standard)

  Wind speed at 10m height (WMO standard)

  Relative humidity

• OpenStreetMap Nominatim: For reverse geocoding when you click the map

Validation & References

Our models are validated against:

• PVGIS (European Commission's Photovoltaic Geographical Information System)

• ASHRAE standards for incidence angle modifiers

• IEC 61724-1 for PV system performance classification