Defining weather data and location data of a system

One of the first steps in setting up the project is to select the weather data. In Polysun, you can access weather data for a specific location directly from the Meteonorm web service. Polysun also enables you to import meteorological data from external monthly values and profile files.

The dialogue box for selecting weather data opens in the top-left corner of the project window, under ‘System Location’. There are five weather data options.

• Web service (recommended if an internet connection is available): Meteonorm version 9.
• From location (according to Meteonorm Version 8): offline and only for locations on the list.
• From location (1 hour and 1 minute, according to Meteonorm Version 6) — offline, older database.
• Profile: custom or measured weather data from a CSV file.
• External monthly values — hourly values calculated from monthly values.

The right option depends primarily on whether an internet connection is available. The following sections provide a detailed explanation of each option.

Video explaining how to set the location and choose the weather data.

Recommended: Web Service (Meteonorm 9)

If an internet connection is available, the ‘Web Service’ option is recommended, as it provides the most up-to-date weather data. This option is available whether the location is selected from the map or the list. The Web Service uses Meteonorm Version 9 to retrieve weather data directly from the Meteonorm website.

The reference period for Meteonorm 9 is from 2001 to 2020, and includes data on solar radiation, temperature and other meteorological parameters.

For more detailed information, visit the Meteonorm website.

Offline Weather Data (No Internet Connection Required)

Even if an internet connection is unavailable, you can still access weather data. Select a location from either the map or the list.

Meteonorm 8 (Offline):

The “Location” option uses the offline weather data stored by Meteonorm 8. The underlying reference periods are:

• Solar Radiation Parameters: 1996–2015
• Temperature, dew point temperature, wind, and precipitation: 2000–2019

This option is only available for locations selected from the list and not for map selections.

Important: Are the Meteonorm 8 data grayed out? The standard Polysun installation does not include Meteonorm 8 weather data. To access Meteonorm 8’s offline weather data, reinstall Polysun and select the desired region.

Meteonorm 6 (offline, older data):

You can define the weather data for the selected location using the “From location (1 hour, according to Meteonorm Version 6)” or “From location (1 minute, according to Meteonorm Version 6)” options. Time resolutions of one hour or one minute are available.

The underlying weather data covers the period from 1986 to 2005.

• The solar radiation parameters are from 1986 to 2005.
• The remaining parameters are from 1996 to 2005.

We recommend using either Meteonorm Version 8 or the web service (Version 9) because they offer newer weather data

Importing weather data using a profile

The “Profile” option allows you to import your own weather data from a CSV file. For example values that were measured at the location. The CSV file must contain the following weather data in the form of columns:

Gh Global radiation [Wh/m²]

Dh Diffuse radiation [Wh/m²]

Lh Long-wave radiation [Wh/m²]

Tamb Ambient temperature [°C]

Vwnd Wind [m/s]

Hrel Humidity [%]

Select one of the available profiles. Note that you may need to adjust the system location to match the location of the imported dataset. The software uses this information to calculate the sun’s path.

You can also save one of the provided meteorological data profiles under a new name using the “Copy” button, open it, and adjust it using the actual measured values.

Importing weather data using monthly values

The “External Monthly Values” option allows you to modify imported monthly values. When selected, the hourly values are calculated from the monthly values using the Meteonorm method included in the software.

Horizon and shading

In order to calculate the energy yield of a photovoltaic (PV) or solar thermal system as accurately as possible, potential obstacles such as neighboring houses, trees, and mountains must be taken into account. These obstacles affect the system’s yield, especially in the winter when the sun is lower in the sky. For this reason, the software allows users to select December 21 of each year—the shortest day of the year in the Northern Hemisphere—as a “worst-case scenario” for shading calculations.

The horizon profile, as well as neighboring obstacles and self-shading, can be simulated using the “Horizon Editor,” which takes the surrounding topography into account. The objects are recorded with their distance and height. The dimensions of the objects are then displayed on the horizon line, which allows for greater precision in the location data and yield calculation.

To define the horizon of the system, “Location of the system” is clicked at the top left of the project window, followed by the “Edit” button under “Horizon.” The Horizon Editor that then opens is divided into four parts. In the upper left corner is a horizon line, shown as a red line, along with the sun’s path, shown as a yellow line. By moving the sliders in the upper right field, the sun’s path on individual days and the position of the sun at specific hours can be set. Obstacles and self-shading can be entered via the form in the lower left field. Via the “Obstacles” button, buildings or other shading objects near the PV modules or solar collectors can be entered. Existing horizon data can also be imported in the field at the very bottom right, for example the horizon of the selected location from Meteonorm. In addition, new shading objects can be entered via the obstacle button with distance, height, and azimuth angle. Via the self-shading button, the exact arrangement of the PV modules or solar collectors can be specified. For this, the distance between the rows, the tilt angle, and the self-shading causing the shadows are entered. Self-shading depends on the deviation of the roof orientation from due south (a), the distance between the rows (d), the tilt angle (α), and the height of the solar collectors or PV modules causing the self-shading (w).

Clicking “Add” adds the respective obstacle or self-shading to the horizon line. The horizon profile can also be further modified by manually adjusting the azimuth and tilt angles in the lower right window. Clicking “Reset” at the very bottom right undoes all changes.

The horizon profile can also be imported from a file, which may possibly be generated from other programs.

Video: Horizon line and near shading