Meteorological information is essential for the design, the operation and the qualification of solar plants and their components. The scientists in the working group “Solar Energy Meteorology” determine the meteorological parameters that are relevant for solar energy and analyze their effect on the performance of solar power plants.
The activities are carried out mainly at the Plataforma Solar de Almería (PSA) of the Spanish cooperation partner CIEMAT (Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas). At PSA, DLR’s Institute of Solar Research operates the Meteorological Station for Solar Technologies (METAS) in close collaboration with CIEMAT. Additional measurements are performed on sites in Jülich, Cologne and the Middle East and North Africa to evaluate the conditions in these regions.
A key criterion for the choice of the site and the layout of a solar power plant is the available solar irradiation. For concentrating power plants the direct normal irradiance (DNI) is relevant, for photovoltaics and flat plate collectors the irradiation on a tilted plane is required. The solar irradiation is, therefore, the key parameter of solar energy meteorology and its determination is the central question of our research.
The accuracy of the irradiance measurements is crucial to determine the total efficiency of the collectors of an existing solar power plant. To reduce measurement errors precise sensor calibration has to be performed.
For short-term forecasts of the solar irradiation and studies of the dynamic effects of clouds on the solar resources, and thus on the power plants and the power grid, we operate cloud cameras, shadow cameras, and LiDAR systems. The short-term forecasts for next fifteen minutes can be used to optimize the operation of the power plant and the power grid. The camera-based forecasts are part of a forecasting system which was developed by the Earth Observation Center at the DLR which also covers the next hours and days.
In addition, we study other parameters which influence the efficiency of solar power plants and develop suitable models and measurement techniques:
To study the aerosols an AERONET sun photometer and LiDAR systems are used. The aerosol concentration close to the ground is determined with particle counters, visibility sensors, and transmissiometers. We study the soiling level of solar power plants as it significantly reduces the reflectivity of mirrors and the transmission of covering glass layers which leads to reduction of the efficiency of the solar plant. Based on dedicated measurement methods we develop soiling and dew models to describe this efficiency reduction. We also measure and model the attenuation of the solar radiation in tower plants between the heliostat field and the receiver with various methods.
To improve the data base for project developers we develop standards and guidelines for the generation of bankable solar radiation data. This work is performed as part of the IEA Solar Heating and Cooling Task 46: “Solar Resource Assessment and Forecasting“ and SolarPACES Task V.