Solar Data Questions
Where does SolarScope's solar data come from?
SolarScope integrates data from three authoritative sources:
NASA POWER: The primary source for global solar irradiance data. NASA POWER (Prediction of Worldwide Energy Resources) is derived from satellite observations and NASA GEOS atmospheric modeling, covering the full globe at 0.5° × 0.5° resolution with 20+ years of historical data.
NREL NSRDB: The National Solar Radiation Database provides hourly solar resource data at 4 km resolution for the Americas, India, and select other regions. Used to supplement NASA POWER where higher spatial resolution adds value.
ArcGIS: Provides address geocoding and satellite basemap imagery for Site Studio.
How often is the solar data updated?
NASA POWER releases annual data updates as satellite observations are processed. Long-term climatological averages used by SolarScope are highly stable — the 20-year mean GHI for any location changes very slowly as new years of data are added.
Solar resource data does not change significantly year-over-year for most locations. Year-to-year variability in actual production (P50 vs. P90) is typically ±5–10% due to weather patterns.
Does SolarScope account for local shading?
NASA POWER and NREL NSRDB data represent regional average sky conditions — they do not capture site-specific shading from trees, adjacent buildings, roof features, or local topography.
To assess local shading:
1. Use Site Studio satellite imagery to visually identify shading obstacles
2. Apply a shading derating factor to SolarScope's production estimate (a heavily shaded site might use a 0.80–0.90 shading factor; an unshaded site uses 1.0)
3. For precise shading analysis, use specialized shade analysis tools (SunEye, Solmetric, or 3D modeling)
What is the difference between GHI, DNI, and DHI?
GHI (Global Horizontal Irradiance): Total solar radiation on a flat horizontal surface. The standard metric for evaluating PV sites.
DNI (Direct Normal Irradiance): Direct sunlight on a surface perpendicular to the sun's rays. Most relevant for concentrating solar and single-axis tracking systems.
DHI (Diffuse Horizontal Irradiance): Scattered solar radiation arriving from all sky directions. Dominant on cloudy days; important for understanding performance in cloudy climates.
GHI = DNI × cos(solar zenith angle) + DHI
What is TMY data?
Typical Meteorological Year (TMY) data is a synthetic dataset representing a "typical" year of weather at a location, constructed by selecting the most statistically representative month from a multi-year historical dataset. TMY data is used by energy modeling tools (PVsyst, EnergyPlus) to run annual simulations.
SolarScope uses long-term monthly averages rather than TMY data directly, which provides equivalent accuracy for preliminary analysis.
Does SolarScope provide hourly solar data?
SolarScope currently provides monthly and annual average irradiance values, which are standard for pre-feasibility analysis. Hourly time-series data is available through NREL's NSRDB Viewer directly for locations within NSRDB coverage. Pro users can access the AI assistant to get guidance on working with hourly data for detailed modeling.
What geographic areas have the best solar data quality?
Data quality is highest for well-instrumented regions:
- United States, Europe, Australia: Excellent — dense ground measurement networks for validation
- Middle East, North Africa: Very good — high irradiance with good satellite coverage
- Sub-Saharan Africa, South America: Good, though ground validation is less dense
- High latitudes (>60°N or S): Lower accuracy due to challenging satellite geometry and limited ground data
Can SolarScope analyze offshore locations?
Yes — NASA POWER provides data for ocean locations, which is useful for offshore solar feasibility or floating PV (floatovoltaics) assessments. Enter GPS coordinates directly for offshore locations.