Introduction
A hindcast is a time series of simulated forecasts for historical periods. Hindcasts simulate the site-specific solar forecast that would have been available at the time for operational decision-making.
PV plant developers can use hindcasts to evaluate how solar forecasts can improve dispatch algorithms and reduce hardware requirements to deliver firm power. Hindcasts also make it easy to estimate forecast accuracy for any location.
Methodology
With hindcasting, the forecast for each time step is generated using only the information that would have been available at that time, including operational delays. As with SolarAnywhere forecasts for time-horizons beyond 5 hours, SolarAnywhere hindcasts are created using a blend of Numerical Weather Prediction (NWP) models.
SolarAnywhere operational forecasts may be more accurate than the hindcast simulation. Operational forecasts may also leverage satellite images and cloud motion vector (CMV) processing to increase solar forecast accuracy for short horizons. Due to technical reasons, the CMV has not been incorporated into the hindcast at this time.
In addition, users may note that since solar forecasting technology is constantly improving. Hindcast time series are not versioned.
Applications
Solar forecasts may be used in plant operation to inform energy trading, scheduling and the control of energy storage. Considering the operational strategy of a solar PV plant during the pre-construction phase can reduce capital costs and project risk. The use of hindcasts makes this possible.
Specifically, hindcasts can be used to:
- Understand the value of forecasts in operational decision-making
- Assess site- and condition-specific forecast performance
- Optimize PV and storage plant design to deliver firm power
Using SolarAnywhere hindcasts
Hindcasts are included with any SolarAnywhere Sites license. Customers that do not yet have Sites access can obtain hindcasts for more than 30 locations around the globe for no cost with SolarAnywhere Public.
Hindcast GHI data can be accessed through the SolarAnywhere data website or API. Using the API, you can also request additional hindcast solar and PV output data fields. Availabilities are outlined in the below table
Getting hindcast data through the SolarAnywhere website
Hindcast is available as one of the data types in the settings menu when downloading SolarAnywhere data in the Sites or Public tabs. Hindcast data are output in a custom format designed to support data comparison and analysis.
Download Hindcast Data Sample (CSV File)Customers can select one or more forecast horizons per download. Each file also includes the latest version of SolarAnywhere historical timeseries (Global Horizontal Irradiance (GHI) W/m2, column B). These data are an effective reference for evaluating forecast performance.
Figure 1. Hindcast data type in settings menu.
Getting hindcast data through the SolarAnywhere API
Hindcast data can also be requested through the SolarAnywhere API. Visit the following pages of our developers’ website for example hindcast irradiance, weather and PV production requests: