Solar Analysis Engine
SolarScope's solar analysis engine transforms raw irradiance data from NASA POWER and NREL into actionable production estimates and performance metrics. This page explains the analysis methodology, data sources, and how to interpret the results.
Data Sources
SolarScope integrates three primary data sources for solar analysis:
NASA POWER (Prediction of Worldwide Energy Resources)
NASA POWER provides 20+ years of historical surface solar irradiance data derived from satellite observations and atmospheric modeling. Data is provided at 0.5° × 0.5° spatial resolution globally. SolarScope uses POWER API v2 to retrieve monthly and annual averages for GHI, DNI, DHI, and temperature.
NREL National Solar Radiation Database (NSRDB)
The NREL NSRDB provides high-resolution (4 km) hourly solar resource data for the Americas, India, and other covered regions. SolarScope uses NSRDB for locations within its coverage area to supplement NASA POWER with higher-resolution data.
ArcGIS Geocoding and Mapping
ArcGIS services provide address geocoding (converting addresses to GPS coordinates) and the basemap imagery used in Site Studio.
Analysis Methodology
1. Location Resolution
When you create a project, SolarScope geocodes your address to precise GPS coordinates. These coordinates are used to query NASA POWER and NREL APIs for the nearest grid cell or interpolated data point.
2. Historical Data Retrieval
SolarScope retrieves monthly averages for:
- GHI (kWh/m²/day and kWh/m²/month)
- DNI (kWh/m²/day)
- DHI (kWh/m²/day)
- Surface air temperature (°C)
- Wind speed (m/s)
Data represents the long-term climatological average, typically 20+ years, providing stable estimates that smooth out year-to-year weather variability.
3. Production Calculation
Annual energy production is estimated using:
E = A × r × H × PR
Where:
- E = Energy output (kWh)
- A = System area (m²), derived from rated system size and panel efficiency
- r = Panel efficiency
- H = Annual solar irradiance (kWh/m²)
- PR = Performance ratio (typically 0.75–0.85)
The performance ratio accounts for inverter losses, wiring losses, soiling, mismatch, and temperature derating.
4. Temperature Correction
Panel output is derated based on the temperature coefficient of power (Pmax). For each degree above 25°C (STC conditions), output is reduced by approximately 0.40%. SolarScope uses NASA POWER surface temperature data to calculate monthly temperature corrections.
Accuracy and Limitations
SolarScope's analysis is suitable for pre-feasibility and feasibility-level assessments. For detailed engineering design or bankable energy yield assessments, consider:
- On-site irradiance measurement (pyranometers)
- Hourly time-series modeling with PVsyst or equivalent
- Site-specific shading analysis
- Long-term resource variability (P90 estimates)
Typical accuracy compared to measured production: ±10–15% depending on location data quality and site-specific factors not captured in regional climate models.