Kipp & Zonen Blog

Irradiance measurements for PV plants: satellite or pyranometer?

[fa icon="calendar"] December 08, 2017 / by Jan-Willem Sips

Jan-Willem Sips

That’s not a question: we need both! As a result of a fruitful co-operation, 3E and Kipp & Zonen present a joint white paper, indicating that satellite and pyranometer irradiance data can both co-exist and do even complement each other.

Both 3E and Kipp & Zonen often receive questions about satellite and pyranometer irradiance measurements for PV plants, and their differences. And what to choose?

Why good irradiance measurements matter!

Adequate monitoring of a PV plant is crucial to evaluate its performance and improve the operation and maintenance of it. Irradiation data is the most important environmental factor determining the production of the solar array. Accurate irradiation measurement is essential for determining the overall performance of a solar park, since the energy provided at the earth’s surface by light from the sun and sky has a large variability, both in space and in time.

A few percent error in irradiation measurements, together with small and unnoticed plant under-performance, can easily result in substantial lost annual revenues. In the white paper, we show a case where inaccurate measurements result in a late detection of underperformance. An undetected performance degradation of 2% over 5 years can result in a revenue loss of € 70k for 5 MW plant in Europe. I can imagine this amount of money matters to all stakeholders of a PV plant…

What to measure?

Measurements of irradiance at the same tilt and orientation as the solar panels are most important, since this parameter is a major input for monitoring the expected yield and performance of the solar plant. This measurement takes reflections from plant structures and the ground into account: the reflection of white sand is much higher than that of black soil.

However, to compare sites to each other, and to compare on-site pyranometer data with satellite data, irradiance measurements in the horizontal plane are necessary as well.

Benefits of using both satellite and pyranometers to collect irradiance measurement

Use both satellite AND pyranometer data!

At the last Solar Asset Management Europe conference in Milan, I was asked several times whether one should use satellite or pyranometer data; we always ended whit the conclusion to use both:

    • Satellites and pyranometers are fully independent sources of irradiance data that can be compared, analysed and correlated to determine very reliable irradiance data.
    • For site prospecting, historical satellite data (reprocessed with present state of the art algorithms) provides an excellent base for long-term yield estimates.
    • Well performed pyranometer measurements are very important for fault detection and analysis of the PV plant, which require accurate short term measurements; in longer term measurements (half a year and longer), the data quality of both pyranometers and satellites becomes comparable.

Comparison of long and short term irradiance data by satellite and pyranometers


It is clear that the combination of satellite and pyranometer irradiance data results in very reliable irradiance data: one of the most important inputs to evaluate the performance of your PV plants! So use both!

See what satellite and pyranometer data can do for you: download the joint 3E and Kipp & Zonen whitepaper here.

Download the whitepaper 'Benefits of both pyranometer and satellite irradiance data for utility scale solar energy parks

Topics: satellite, pyranometers, irradiance data

Jan-Willem Sips

by Jan-Willem Sips

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