Weather stations or satellites?
Weather stations with well-maintained good quality instruments still provide the most accurate data for solar irradiation. They represent the ground truth, which is the relevant parameter for solar energy applications. But weather stations are not always located in the vicinity of the project site and time series may be incomplete.
In this context, satellites have become a valuable source for solar irradiation data, in particular in areas with sparse distribution of met stations. However, this approach also includes disadvantages such as lack of other meteorological parameters, uncertainties in aerosol values, detection of multiple cloud layers, inaccuracies in areas with snow or no data north of 62°.
There is no standard rule which option is the best one. We always recommend combining multiple data sources of ground and satellite data to achieve the lowest uncertainty for resource assessment. Meteonorm includes weather stations and satellite data
Meteonorm offers unique access to the Global Energy Balance Archive Data (GEBA). The GEBA data is provided from national weather services and fulfils the quality criteria of the World Meteorological Organisation WMO. It also includes high quality measurement networks such as the Baseline Surface Radiation Network BSRN or the networks of MeteoSwiss and the German Weather Service.
The periods 1981-1990 and 1991-2010 are available for solar irradiation on a global scale (1996-2015 for CH, D and UK), the periods 1961-1990 and 2000-2009 for other meteorological parameters. Meteonorm offers the possibility to download of current monthly temperature and irradiation data.
The database of ground stations is extended with data from five geostationary satellites to fill gaps in areas where no weather stations are available. The satellite data is available on a global grid. The data was correlated with long term ground measurements to obtain homogenous long term averages.
All data is quality checked by Meteotest. The uncertainty of the data base and the generated typical years is transparently shown directly in the software and in the documentation.
Global, direct and diffuse irradiation on horizontal and inclined surface, temperature, relative humidity, wind speed, cloud cover, illuminance, UVA/UV radiation, mixing ratio, snow depth, atmospheric pressure, precipitation, days with precipitation, sunshine duration, dew point temperature, wet bulb temperature, surface temperature, Linke turbidity factor and many more.
From the monthly values (station data, interpolated data or imported data), Meteonorm calculates hourly values of all parameters using a stochastic model. The resulting time series correspond to “typical years” used for system design.
Additionally, the following parameters are derived:
The generation of humidity values is optimized to fit building and climate system simulations (including extreme hourly values).
In order to accurately simulate large PV plants or energy management & battery systems, reliable time series of solar irradiation with minute time resolution are essential. There is a huge difference between hourly data and minute data: with minute data, the variation is higher, ramps are steeper and overshootings are more frequent.
Unfortunately, the measurement of minute values is difficult and costly with ground sensors and even impossible with satellite data. In order to meet the requirements of the industry, we decided to implement two new minute models in Meteonorm.
The first new minute model is the "Hofmann" model, as it is already implemented in the simulation software PVSol. Thanks to an agreement with the developer of this model, we have been able to include the code in Meteonorm and thus make the model accessible to everyone.
The second new minute model is an own development by Meteotest: It is based on real measurement data with minute resolution from all over the world. One-minute time series of 15 stations of the Baseline Surface Radiation Network (BSRN) were corrected for clearsky radiation and classified by type of cloud situation, wind speed and solar elevation. Based on this data source we have developed a stochastic generator which is able to generate robust time series with minute resolution.
If you prefer to rely on your own, site specific data (third party satellite data or local measurements), you can import your data set into Meteonorm and still profit from the included models to create reliable minute values.
36 different predefined export formats are available. They cover most of the established simulation software in solar energy applications and building design, including TMY2 and TMY3, EPW, TRNSYS as well as output formats for TRY (German test reference years), POLYSUN, TSOL/PVSOL, PVSyst and PHPP. All export formats are available for hourly as well as monthly values. Data is written to ASCII files.
Alternatively, the parameters and the desired units can be defined in a user-defined export format.
Usually, measurement data can only be used in the vicinity of a weather station. Elsewhere, the data has to be interpolated between different stations. The sophisticated interpolation models inside Meteonorm allow a reliable calculation of solar radiation, temperature and additional parameters at any site in the world.
The intuitive GUI in Meteonorm 7 allows you to easily manage and select your weather stations and sites.
Meteonorm offers dynamic web downloads of current monthly temperature and radiation data (for Europe available data from 2007 onwards). With one mouse click, current data is imported from the internet and displayed. This allows solar energy calculations and performance checks of energy systems based on current data sets.
You can import your own monthly or hourly radiation and temperature data into Meteonorm with a specific import interface. Subsequently, you can apply the Meteonorm models and procedures to this data to gene rate random time series.
Meteonorm calculates reduced global radiation caused by a high horizon. The horizon line can easily be entered either graphically (drag line) or numerically. For most regions of the world, the horizon line is calculated automatically, based on a digital terrain mode (accessed over the internet).
Any rectified picture of the horizon can be imported and used as a background for digitizing the horizon. Images taken with the Horicatcher can be imported and processed directly inside Meteonorm.
The horizon pictures can be use to determine easily the areas where glare effects exist.
The Horicatcher is an add-on for Meteonorm. It is an accurate and fast tool to determine the real horizon line at your specific site. Horicatcher allows you to take into account the reduced solar energy input, the sunshine duration and sun exposure by obstacles like trees, houses or mountains at your site.
Meteonorm includes free and personal customer support by e-mail or by phone.