ammonit solarresourceassessment
Reliable solar measurement systems
that meet your high requirements
Solar measurement for Solar Site Assessment

The sun irradiation differs from site to site. Thus it is essential to measure the local irradiation to design profitable solar power plants. There are certain methods and technologies to measure the irradiation. Depending on the planed solar power plant, PV (Photovoltaic) or CSP (Concentrated Solar Power) different measurements are necessary:

  • GHI (Global Horizontal Irradiation)
    Measurement instrument: Pyranometer, reference cell
    Application: PV and CSP

  • GTI (Global Tilted Irradiation)
    Measurement instrument: Pyranometer (tilted), reference cell (tilted)
    Application: PV

  • DHI (Diffuse Horizontal Irradiation)
    Measurement instrument: Rotating Shadowband Irradiometer, Pyranometer with shadow ring or ball
    Application: PV

  • DNI (Direct Normal Irradiation)
    Measurement instrument: Pyrheliometer installed on Sun Tracker, Rotating Shadowband Irradiometer
    Application: CSP and large PV power plants

The more precise the measured irradiation data is, the more precise you can evaluate the solar power for the site.

ammonit solarresourceassessment 01

Learn more about our solar resource assessment systems in our brochure: Download (English, PDF)


Soiling Measurement for PV power plants

Soiling significantly affects the energy production of PV power plants. Do you know how much PV module output power is lost due to soiling? In absense of significant rain events or regular cleaning, production losses due to soiling effects increase. Measuring soiling effects provides important details about the PV power plant production, e.g., how much dust can be on the modules before any problem occurs and how does the dust affect transparency and efficiency of the modules.

However, effects of soiling on your PV modules should be assessed site-specific due to variations in soil type, location and weather patterns.


Our soiling measurement systems compare power output and surface temperature of a naturally-soiled PV reference module with the data of a clean PV reference device. The measurement station determines local solar irradiation for power output parameter evaluations. Additionally, several meteorological parameters are measured to give a detailed insight into the local weather conditions.

Use the gathered data for, e.g.;

  • Analysing soiling losses for PV performance guarantees
  • Monitoring soiling losses to enable detection of other system-level issues
  • Optimizing washing schedules for best return-on-investment
  • Determining typical soiling rates for forecasting models

Learn more about our soiling measurement systems in our brochure: Download (English, PDF)
For details about the Ammonit Soiling Measurement Kit Order No. SD2100) refer to our data sheet: Download (English, PDF)
For technical details regarding our I-U Conversion Box (Order No. CM8281) refer to our data sheet: Download (English, PDF)

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Solar Database PVGIS and Global Solar Atlas of the World Bank Group

As part of the SOLAREC action to implement renewable energy in the EU as a long-term energy supply, the European Union introduced the PVGIS (Photovoltaic Geographical Information System). The system provides a map-based inventory of solar energy resource and assessment of the electricity generation from PV power plants in Europe, Africa and South-West Asia.

PVGIS for Europe
PVGIS for Africa and South-West Asia

The World Bank Group provides the Global Solar Atlas. The Global Solar Atlas is an online platform developed as part of the Energy Sector Management Assistance Program (ESMAP). It provides solar measurement data for a number of countries for energy yield analysis.

Global Solar Atlas

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Comparison: Satellite-based data vs. ground-measured data*

Most of the available radiation data is based on satellite data, which is calculated from sun radiation (satellite) as well as temperature and wind speed (weather stations). However, there is a lot of uncertainty in these calculations. Thus there are significant deviations between satellite-based data and ground-measured data, particularly when the sky is cloudy. Another influencing fact is the area, which is considered for the data; satellite-based data refers to large areas of approx. 1km², ground-measured data are exact.

However, the deviation is smaller when GHI is considered instead of DNI. If data for GHI and temperature from both satellite-based data and ground-measured data is correlated, good regression values can be reached: R²=0.92 and R²=0.97. If DNI and wind speed is considered, regression values show huge deviation between both measurements: R²=0.78 and R²=0.5.

ammonit solar correlation

We recommend measuring the sun radiation with ground stations at the location of the planned solar power plant. Only with measurement stations on the ground you get accurate measurement data, which can be used to calculate the annual energy yield at the site.

*The data is based on the case study „Validation of PV Performance Models using Satellite-based Irradiance Measurements“ published by Clean Power Research.

Additionally, the quality of the installed measurement instruments has to be carefully considered to get accurate measurement results, e.g., classification of pyranometers. Benefit from our long-term experience and our know-how from many projects worldwide to get the best measurement system for your solar project.

Our solar measurement systems meet the latest international quality standards. We design your measurement system including suitable radiation sensors, communication and power supply system considering your planned solar installation as well as local weather conditions.

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Components of our solar measurement systems

Our solar measurement systems meet international quality standards. The following components can be part of a solar measurement system.

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Standards and Guidelines for Solar Resource Assessment

NREL "Best Practice Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications" (Feb 2015 / 63112)
The NREL handbook is a comprehensive report, which summarizes important information for all steps of a solar energy project - reaching from required measurements and the design of measurement stations to forecasting the potential solar radiation. Additionally, NREL informs about measurement instruments and its application as well as sources for solar measurement data.
Download: NREL Best Practice Handbook for the Collection and Use of Solar Resource Data for Solar Energy Applications (Feb 2015 / 63112, English, PDF)

ISO 9060 Solar energy – Specification and classification of instruments for measuring hemispherical solar and direct solar radiation
In the ISO 9060 standard pyranometers are classified in three classes: Secondary Standard for scientific measurement quality, First Class for good measurement quality and Second Class for medium measurement quality. The ISO 9060 is accepted by the WMO (World Meteorological Organisation). See also Pyranometer.

IEC 61724-1:2017 Photovoltaic system performance – Guideline for measurement, data exchange and analysis
This standard decribes measurement system components and processes. It focuses on measurement uncertainties and defines accuracy classes. Additionally, the standard defines cleaning and calibration intervals for pyranometers.


Ammonit Solar Resource Assessment Systems (English, PDF)
Ammonit Soiling Measurement Systems (English, PDF)

Contact us or on of our partners to design your solar measurement system: +49 30 6003188-0 or Email住址會使用灌水程式保護機制。你需要啟動Javascript才能觀看它

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Benefit from our online platform AmmonitOR (Ammonit Online Report). AmmonitOR simplifies your data archiving and data management. With AmmonitOR you can access, monitor and analyse your measurement data conveniently at all times, wherever you are. Register today and send us an email at: Email住址會使用灌水程式保護機制。你需要啟動Javascript才能觀看它 . Our service team will set up your personal account.



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