SolarAnywhere® average year summary files provide a quick summary into the solar resource, weather, and estimated losses due to snow and soiling at your site. They can be downloaded with both SolarAnywhere Typical Year and Sites licenses. These files contain long term monthly sums or averages for each of the selected irradiance or weather data fields. The years included in calculating the long-term monthly sums/averages are dependent upon the geographic data region:
To download average year summary files:
- Select a tile location for download
- Click “Edit Settings”
- Check the box next to “Avg. Year Summary” under “Typical year options”
Figure 1. Selecting the Average Year Summary file option in the SolarAnywhere Data website
Users can demo average year files with SolarAnywhere Public.
Average Year Albedo
The 12 monthly, long-term average-albedo values provided in the average-year summary file are useful in PV performance modeling. These values are calculated from the full available time series of SolarAnywhere albedo at each location, meaning they account for long-term snow conditions.
The long-term average monthly albedos can be input directly into the project settings of your PVsyst simulations.
Figure 2. Example Average Year Summary file
Figure 3. PVsyst project settings
Average Year Snow and Soiling Losses
The 12-month, average snow and soiling loss values provided in the average-year summary file are useful in PV performance modeling. These values are calculated using open-source pvlib snow and soiling loss models with the full historical time-series SolarAnywhere weather data such as precipitation and particulate matter at the project location.
The years included in calculating the average snow and soiling loss estimates are dependent upon the geographic region:
The NREL snow loss model (commonly referred to as the ‘Marion’ model) is used to generate average snow losses and the Humboldt State University (HSU) soiling model is used to generate average soiling losses. SolarAnywhere uses the latest version of these pvlib PV performance models available at the time of Average Year Summary file generation.
To include soiling and snow loss estimates in your Average Year Summary file, select the Average Snow Losses and Average Soiling Losses checkboxes under Datasets as shown in Figure 4. SolarAnywhere users can specify PV array configuration parameters such as the mounting type (horizontal single-axis tracker vs. fixed-tilt) and the tilt for fixed-tilt systems to make average snow and soiling loss estimates more project-specific. For trackers, a horizontal single-axis tracking system (axis tilt = 0) with a tracking rotation limit of ± 60 degrees is used for estimating snow/soiling losses. Item h. in the notes section of the file, shown in Figure 6, displays the PV array configuration parameters that you specified for the simulation.
Figure 4: Selecting Average Snow and Soiling Losses in the SolarAnywhere Data website
The accumulation of snow and particulate matter is cumulative and time-dependent by nature. Using full historical time-series data can improve the reliability of average snow and soiling loss estimates, and account for the effect of inter-annual variability on losses. In addition to local weather data and the PV system’s configuration (such as tracking and tilt), site-specific loss parameters (such as amount of rain that is enough to clean PV panels of accumulated soiling completely, also known as cleaning_threshold) can further affect the magnitude of losses. Average loss estimates included in the SolarAnywhere average year summary file are generated using default values for loss parameters such as cleaning_threshold. The complete list of loss parameters and default values used in SolarAnywhere can be found in the SolarAnywhere API Documentation for snow and soiling losses.
To learn more about the SolarAnywhere loss methodology, validation and applicability of the data , visit these support center pages:
Average monthly snow and soiling loss estimates can be input into third-party PV performance models such as PVsyst and PlantPredict to make PV production estimates more site-specific.
Figure 5: Example Snow and Soiling Loss data in the Average Year Summary file
Figure 6: Example Average Year Summary file notes section
Average Plane of Array Irradiance (POAI)
Long-term average monthly total plane of array Irradiance (POAI) can be useful in solar prospecting, making it easy for solar developers and owners to quickly assess the PV project potential of any location across the globe.
Plane of array irradiance is defined as the irradiance incident on the plane of the PV array and is dependent on the sun position, array orientation (fixed vs. tracking), irradiance components, albedo and shading from near and far obstructions. SolarAnywhere uses community-trusted pvlib models in combination with the full historical time-series of SolarAnywhere irradiance and weather data to estimate POAI at each time step. Monthly totals are calculated from the historical time-series, then averaged for inclusion in the Average Year Summary file. The pvlib models use the Perez transposition model to determine the diffuse irradiance component.
To include long-term average monthly total plane of array irradiance in your average year summary file, select the “Plane of Array Irradiance” checkbox under Datasets as shown in Figure 7. PV array configuration parameters such as azimuth, tilt, relative row spacing (inverse of ground coverage ratio) and number of parallel strings along row height can be specified in the Array Configuration section. Parameter default values are as follows:
- If azimuth is left blank, a default of 180 degrees is used if the PV system is in the Northern Hemisphere and a value of 0 degrees is used for PV systems in the Southern Hemisphere.
- For relative row spacing, a default of 3 (GCR= 0.33) is used.
- For albedo, a static value of 0.17 is used.
- For parallel strings, a default value of 2 is input for the number of parallel strings along row height, but may otherwise be specified. Number of strings is a unitless value representing the number of parallel-connected strings along a row slant height, and is only available for snow loss datasets.
Item h in the notes section of the file, shown in Figure 7, displays the PV array configuration parameters that you specified for the simulation.
Figure 7. Selecting Average Plane of Array Irradiance (POAI) in the SolarAnywhere Data website
How to Video: Project-specific Snow and Soiling Loss Estimates and Plane of Array Irradiance
Watch this short instructional video to learn how to configure a PV array within your SolarAnywhere account to obtain project-specific snow and soiling loss estimates, and plane-of-array irradiance.