Validation of environmental factors

In this document

We will introduce the importance of incorporating accurate, site-specific environmental factors in PV simulations, particularly focusing on ground albedo, which plays a significant role in influencing the amount of reflected irradiance.

Overview

Accurate albedo modeling is crucial for determining the total irradiance reaching PV modules, making it indispensable for reliable energy yield predictions. Seasonal variations in albedo are particularly significant, and the shift from using a single constant value to twelve monthly values in current industry standards provides a more detailed and precise representation for advanced PV modeling.

To validate Solargis' monthly albedo data, comparisons were conducted using ground-based measurements collected with albedometers. However, the availability of such measurements was limited to stations in North America.

Geographical scope

North America

Data parameters

ALB (monthly values)

Calculated indicators

Bias, MAD, RMSD

Reference period

2006 to 2015

Reference source

AMERIFLUX, SURFRAD

ALB validation statistics

The growing adoption of bifacial modules has heightened the importance of accurate albedo data for design decisions, such as module height, tilt angle, and row spacing, to optimize the capture of reflected light. Therefore, the use of validated monthly albedo data has become increasingly vital for optimizing PV system performance. See results of the validation of Solargis albedo in the following table:

ALB

Number of validation sites

8

Mean bias for all sites

-0.01

The validation exercise demonstrated a very low mean bias of -0.01, indicating excellent agreement between Solargis albedo data and ground measurements.

Details of the ground measurements used for validation purposes are given in the map and table below.


Station name

Latitude, Longitude

Data source

Metolius Mature Pine

44.452, -121.557

AMERIFLUX

Morgan Monroe State Forest

39.323, -86.413

AMERIFLUX

Willow Creek

45.806, -90.08

AMERIFLUX

Walnut Gulch Kendall Grasslands

31.737, -109.942

AMERIFLUX

Fort Peck

48.308, -105.102

SURFRAD

Desert Rock

36.624, -116.019

SURFRAD

Table Mountain

40.125, -105.237

SURFRAD

Bondville

40.052, -88.373

SURFRAD

Conclusions

  • The validation results confirm the high accuracy of Solargis albedo data for PV simulations, even with limited ground-based measurements. Although this validation exercise is limited to a relatively small set of locations, they represent a reasonably broad climatic diversity.

  • The use of monthly albedo values, rather than constant values, aligns with current industry standards and provides a solid foundation for advanced PV modeling. This supports reliable energy yield predictions and optimized system design, particularly for bifacial systems and configurations sensitive to reflected light.

  • Differences between the field of view (FOV) of albedometers and the larger area covered by satellite imagery pixels can impact validation. Satellite imagery often captures non-homogeneous land cover surrounding albedometers, introducing some variability in the comparison of ground-based and satellite-derived albedo data.