Datasets - overview

Below, meta data of the main datasets used to compute the PV potential are summarized. Intermediate files for individual processing steps are described in the subfolders.

Meteological data

*Physical potential*

The outputs of the physical potential processing steps are merged into one netCDF files with the following coordinates:

• x, y: coordiates of the pixel centroids
• timestamp: time identifyier in datetime format, for each hour

and the following variables:

• SIS: global horizontal radiation
• SISDIR: direct horizontal radiation
• DNI: direct normal radiation
• DHI: diffuse horizontal radiation
• DNI_extra: extraterrestrial radiation
• rel_airmass: relative airmass
• apparent_zenith: apparent zenith angle of the sun
• azimuth: apparent azimuth angle of the sun

*Surface albedo*

The monthly-mean-daily surface albedo is saved in a netCDF files with the following coordinates:

• x, y: coordiates of the pixel centroids (identical to the solar radiation file); Swiss CH1903 / LV03 (EPSG:21781)
• month: integer value from 1-12

and the following variable:

• ALB: surface albedo

*Maximum temperature*

The monthly-mean-daily maximum surface temperature, obtained from *Physical_potential/Temperature/max_temperature_MMH.ipynb*.

Coordinates:

• chx, chy: coordiates of the pixel centroids (1x1 km grid by MeteoSwiss, CH1903 / LV03)
• lon, lat: Longitude/latitude, which are functions of chx, chy
• month: integer value from 1-12

Variables:

• TmaxD: Monthly-mean-daily maximum temperature, averaged across 30ish days of each month
• stddev: Standard deviation across 30ish days of each month

Rooftops

*Rooftop characteristics*

From the roof polygons, a csv table has been created, containing one row for each roof. It contains the following columns:

*POLYGON PROPERTIES*

• DF_UID: Unique roof surface identifier
• FLAECHE: Tilted roof area (i.e. A_{polygon} / cos(tilt) )
• AUSRICHTUNG: Aspect angle of the roof, with the convention "clockwise from South", i.e. 0° = south
• NEIGUNG: Tilt angle of the surface (in °)
• XCOORD, YCOORD: Coordinates of the centroid of the roof polygon, in Swiss CH1903 / LV03 (EPSG:21781)

*PANEL PROPERTIES*:

• panel_tilt: Tilt angle of the PANEL (= roof tilt for tilted roofs, and = 30° for flat roofs)
• panel_direction: Aspect angle of the roof (convention: clockwise from north), 180° (south) for flat roofs

Available area

*Estimated available area*

A csv file that combines the predictions and uncertainties for the available area (A_{PV}). It contains the following columns:

*GENERAL PROPERTIES*:

• DF_UID: Unique roof surface identifier
• tilted_area: Tilted roof area (= FLAECHE)
• available_area: Predicted available roof area

*VIRTUAL PANEL PROPERTIES* *FULLY SHADED PROPERTIES*

Hourly shading and SVF

*Hourly unshaded fraction*

This variable represents the hourly unshaded fraction of the roof, referred to as (1 - S_{sh}(t)). It is a netCDF file with the following coordinates:

• DF_UID Unique roof surface identifier
• timestamp time identifyier in datetime format, for each hour

The variable is:

• partly_shading: Hourly unshaded fraction of each roof surface, i.e. (1 - S_{sh}), after bias correction (by 0.0272). Missing values are replaced with the average for its aspect and tilt class (see "Tilted_radiation/Shading" for details).

*Sky view factor*

A csv file with the following columns:

• DF_UID: Unique roof surface identifier
• SVF: Sky view factor, computed from the 2x2 m2 DSM of the entire Switzerland. Missing roofs are replaced with the mean value (0.69)
• SVF_unbiased: Sky view factor after bias correction (SVF - 0.0716)

*Mutual shading*

Output of *Geographic_potential/Flat_roof_simulation/mutual_shading.ipynb*. A netCDF file containing additional factors for S_{sh} and SVF for flat surfaces, arising from mutual shading between adjacent panel rows. The coordinates are:

• timestamp time identifyier in datetime format, for each hour
• tilt: Tilt angles of panels on flat roofs
• distance: Distances between adjacent panel rows (the values represent integer multiples of the panel height)

Variables:

• shading: direct shading from the previous row of panels
• SVF_flat: reduction in SVF due to the previous panel row

Tilted radiation

*POA radiation*

Output of *Geographic_potential/Tilted_radiation/merge_poa_irrad.ipynb*. A netCDF file of the following coordinates:

• DF_UID Unique roof surface identifier
• timestamp time identifyier in datetime format, for each hour

The variables are:

• poa_direct: Tilted beam radiation, later multiplied with the roof shading
• poa_sky_diffuse: Tilted diffuse radiation (Perez), later multiplied with the SVF
• poa_ground_diffuse: Ground reflected radiation, accounting for the surface albedo

*Tilted radiation*

Output of *Geographic_potential/Tilted_radiation/compute_tilted_irrad.py*. A netCDF file of the following coordinates:

• DF_UID Unique roof surface identifier
• timestamp time identifyier in datetime format, for each hour

The variables are:

• tilted_irradiance: Total tilted radiation on each roof, in W/m2
• yearly_kWh_m2: Annual tilted radiation, in kWh/m2/a

Technical potential

*Panel performance*

Output of *Technical_potential/Panel_performance/Efficiency_model.ipynb*. A netCDF file of the following coordinates:

• G_t: Tilted radiation, values spanning the range of tilted radiation values found in the data
• T_amb: Maximum daily ambient temperature, values spanning the range found in the data

Variables:

• T_cell: Cell temperature, computed from *PVSyst*
• module_eff: Module efficiency, computed using *PVWatts* (average 60-cell mono-crystalline panel)
• losses: Product of all system losses
• inverter_eff: Inverter efficiency, computed using *PVWatts* (default inverter model)
• PF: Performance factor, i.e. inverter_eff multiplied with losses
• PF_mean: Performance factor, averaged across T_{amb}

*Panel performance per roof*

Output of *Technical_potential/Panel_performance/efficiency_mapping.py*. A netCDF file of the following coordinates:

• DF_UID Unique roof surface identifier
• timestamp time identifyier in datetime format, for each hour

The variables are:

• module_eff: Module efficiency (computed as a function of ambient temperature and radiation on the tilted panel)
• PF_mean: Performance factor (computed as a function of tilted radiation)
• TmaxD: Maximum daily temperature (monthly-mean-daily, i.e. 12-year average daily value per month)

*PV potential*

Output of *Technical_potential/compute_PV_output.py*. A netCDF file of the following coordinates:

• DF_UID Unique roof surface identifier
• timestamp time identifyier in datetime format, for each hour

The variables are:

• pv_potential: Potential hourly electricity production from PV, in W
• yearly_PV_kWh: Annual electricity potential for each roof, in kWh