Why to use satellite-based solar resource data in PV performance assessment

It is widely accepted that high-standard pyranometers operated under rigorously controlled conditions are to be used for bankable performance assessment of photovoltaic (PV) power systems. Asset managers, O&M providers, and owners of PV portfolios are increasingly relying on satellite-derived solar resource data.

Have you ever had doubts about your Performance Ratio (PR) calculations because of gaps in solar data, unrealistic values, or simply because the information did not come from an independent source? Satellite-data provide benefits that help relieve worries.

1. It is beneficial to complement pyranometers by satellite data

Quality control of ground measured data

Maintaining systematic solar resource monitoring at high quality and without gaps is challenging, due to potential issues in data acquisition, storage and transmission. Data from ground-mounted sensors are prone to errors for reasons such as shading, misalignment of instruments, calibration issues, irregular or insufficient cleaning, etc. Use of satellite data allows for quality control, error detection and gap filling of ground measurements.

Independent verification

The satellite-based solar data make it possible to independently confirm validity of PR calculations based on ground measurements. As the satellite data come from an independent service provider, they can also be used for settling contractual arguments relating to doubts about measurements from pyranometers.

Save your time and money

Data supply from the satellite models is very stable and reliable. The satellite-based solar resource is cheap and redundant source of information, which enables implementation of advanced quality control and data analysis, and enables high level of automation.

Accuracy

Independent validation studies show that the Solargis satellite-based model has low uncertainty and stable performance. In many regions the accuracy of monthly and annual totals is comparable to that of data measured by well-maintained pyranometers. Correlating ground measured data and satellite-based model estimates helps reducing the uncertainty even more, and maintaining it in a longer term.

 

FIG. 1: UNCERTAINTY OF SOLARGIS GLOBAL HORIZONTAL IRRADIATION DATA VS. MEASUREMENTS FROM PYRANOMETERS. MODEL VALIDATION AT 190+ SITES, WORLDWIDE, SHOWS THAT ACCURACY OF GHI IS COMPARABLE TO PYRANOMETERS FOR MONTHLY AND ANNUAL SUMMARIES IN MOST REGIONS. EVEN LOWER DATA UNCERTAINTY CAN BE ACHIEVED BY CORRELATION OF SATELLITE AND GROUND-MEASURED 

2. Performance evaluation of residential and commercial projects

Installing and maintaining the pyranometers is relatively expensive and challenging. Therefore it is typically not an option for residential and small commercial PV projects. In a case of portfolio of smaller systems, use of satellite-derived solar resource is the only practical approach for performance evaluation.

3. Yearly variability of solar resource

It is often asked to what extent a particular month or year had received higher or lower solar radiation compared to the long-term average. Satellite-based modelled data are the most suitable for such an exercise as they record stable and map based historical archive of more than 16 years.

FIG. 2: LONG TERM AVERAGE OF YEARLY TOTAL OF GLOBAL HORIZONTAL IRRADIATION REPRESENTING YEARS 1999 TO 2014. SOURCE: SOLARGIS

 

FIG. 3: RELATIVE DIFFERENCE OF YEARLY TOTALS OF GLOBAL HORIZONTAL IRRADIATION IN YEARS 2012, 2013 AND 2014 COMPARED TO THE LONG-TERM AVERAGE (CALCULATED OVER A PERIOD 1999 TO 2014). SOURCE: SOLARGIS

 

Where to start?

Solargis pvSpot service is one of few options to receive solar resource and PV simulated data on a daily basis, for any location in North & Central America. In addition to solar resource, pvSpot supplies also the expected PV power simulation data. Register three PV systems of your choice at solargis.info/pvspot and receive free data, representing last 6 months, for your testing. For large portfolios the data are typically delivered via FTP or Web Service (programmable API).