Forecasts Overview
Proximal forecasts hourly weather and solar power production for utility-scale solar projects. Each forecast combines project configuration, weather data from the Integrated Forecasting System (IFS), and the Proximal PV performance model.
Weather forecast
The forecast service requests the ECMWF Integrated Forecasting System (IFS) at the project's latitude and longitude. The request is aligned to the most recent available IFS model run. The current request returns 240 hourly forecast points, covering 10 days.
All forecast timestamps are stored in UTC:
time_forecast_runidentifies the IFS model run used by the forecast.time_forecastedidentifies the valid time of each weather and PV value.
The weather input contains:
| Field | Unit | Description |
|---|---|---|
ghi | W/m² | Global horizontal irradiance |
dni | W/m² | Direct normal irradiance |
dhi | W/m² | Diffuse horizontal irradiance |
ambient_temperature | °C | Air temperature |
wind_speed | m/s | Wind speed |
PV simulation
The forecast adapter passes the IFS weather series and project configuration to the Proximal PV performance model. See the PV model overview for the model chain and individual calculation steps.
The simulation runs one step for each weather timestamp. For the current IFS request, this is 240 hourly steps; the forecast does not add sub-hourly interpolation. Each step uses the weather values for that timestamp to calculate:
- Tracker position, using the project's true-tracking or backtracking configuration and rotation limits
- Plane-of-array and effective irradiance
- Module temperature and DC power
- Inverter and other electrical losses
- AC power at the point of interconnection
The simulation uses the project's DC capacity, module temperature coefficient, geometry, and interconnection limit. PV power is clipped at the interconnection limit before export.
p_mp is instantaneous AC power at the point of interconnection, stored in watts. It is not an energy value. To estimate energy for an hourly interval, multiply the power by one hour and convert watts to the desired energy unit.
Forecast outputs
The service stores both weather and PV results in two forms:
- Forecast history: Each run is retained with its
time_forecast_run, allowing forecasts to be compared with later runs and observations. - Latest forecast: The most recent run is retained for each
time_forecastedvalue for applications and dashboards.