Solar Radiation Data for Site Assessment: Free Online Tool

Solar radiation data is the foundation of any solar energy project. Whether you are selecting a site for a photovoltaic (PV) installation, estimating annual energy yield for a solar farm, or comparing candidate locations for a rooftop project, accurate solar irradiance measurements are essential for making informed investment decisions.

Solar Radiation in PixelGust

PixelGust provides solar radiation data from the ERA5 reanalysis dataset, measured as surface downward shortwave radiation in MJ/m². This represents the total solar energy reaching the ground surface, accounting for atmospheric absorption, cloud cover, and seasonal variation.

Available data includes:

• Current solar radiation: Latest GFS model output for real-time conditions.
• 7-day forecast: Predicted daily solar radiation for the coming week.
• Historical monthly data (2015-2025): Min, mean, and max values for every month over 10 years. This is particularly valuable for bankable solar resource assessments.

Why Historical Solar Data Matters for Energy Projects

Reducing Investment Risk

Solar energy projects represent significant capital investments. Using only one or two years of solar data can lead to overestimating or underestimating energy yield. By analyzing 10 years of monthly data, developers can understand the full range of solar variability at a site and make more accurate financial projections.

Seasonal Planning

Historical solar data reveals the seasonal patterns at any location. For example, a site in southern Europe may receive 3x more solar radiation in July than in December. Understanding these patterns is critical for grid connection planning, energy storage sizing, and revenue forecasting.

Inter-Annual Variability

Solar radiation varies from year to year due to weather patterns, volcanic aerosols, and climate cycles. PixelGust's 10-year dataset lets you quantify this variability. A site with low inter-annual variability provides more predictable returns and lower financial risk.

How to Assess Solar Potential on PixelGust

1. Open the dashboard at pixelgust.com/app and click your target location.
2. Check current solar radiation in the Weather panel under "Wind & Energy" section.
3. Switch to Historical mode to see 10 years of monthly solar radiation data with min, mean, and max values.
4. Analyze cloud cover trends. Historical cloud coverage data helps explain solar radiation variations.
5. Check terrain. Enable the Terrain panel to see slope and aspect. South-facing slopes (in the Northern Hemisphere) receive more direct sunlight.
6. Compare sites. Save multiple candidate locations and export data to Excel for side-by-side comparison.

Complementary Data for Solar Site Assessment

A thorough solar site assessment requires more than just irradiance data. PixelGust provides several complementary datasets:

• Temperature: PV panel efficiency decreases at high temperatures. Historical temperature data helps estimate temperature-related losses.
• Wind speed: Higher wind speeds cool PV panels, partially offsetting temperature losses. Wind data is also relevant for structural design.
• Cloud cover: Detailed cloud coverage statistics help explain solar radiation variability.
• Terrain slope and aspect: Ground-mounted PV systems benefit from south-facing (Northern Hemisphere) or north-facing (Southern Hemisphere) slopes.
• Proximity to infrastructure: Distance to roads, power lines, and substations affects project economics.
• Land cover: ESA WorldCover data shows current land use, helping identify suitable areas for solar development.

API Access for Solar Developers

For automated site screening across many locations, use the PixelGust REST API:

GET /v1/weather?lat=37.98&lon=23.73&mode=historical

Response includes monthly solar radiation:
  "solar_radiation_mj": {
    "2024-01": {"mean": 6.2, "min": 5.8, "max": 6.9},
    "2024-07": {"mean": 24.1, "min": 22.5, "max": 25.3}
  }

Data Source

Solar radiation data in PixelGust comes from the ERA5 reanalysis produced by ECMWF at 0.25-degree resolution. ERA5 combines satellite observations, ground station measurements, and atmospheric models to produce the most accurate global solar irradiance dataset available. Monthly averages are pre-computed for fast retrieval.