SWERA/Solar Resource Information

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Solar and Wind Energy Resource Assessment (SWERA)

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Solar Resource Information

SWERA solar products provide information on the solar resource at a specific location that is available for use by solar technologies. These products include maps and data of available solar resource, as well as documentation on the methodology employed to generate these solar resource estimates. The data products and resource maps are derived from models and satellite and global weather observations and do not contain site-specific measurement information. SWERA solar products are classified by the radiation components they describe. Applicability of the different radiation components to the relevant technologies is described below.

Solar Resource Maps

The solar resource map products provide visual presentations of the solar resource. These maps can be used to visually identify areas rich in solar resources within a country or region, and allow an easy look at the data without the need to navigate through large data sets or to apply GIS software.

Solar Data Products

The solar data products can help users estimate the size of a system that would be needed to meet specified loads and whether projects that incorporate these components are economically feasible. The data serve as a screening tool to eliminate areas or applications that are not suitable for solar technologies, and to guide developers to promising regions and applications. Although the majority of the solar data are presented as monthly or annual averages, site-specific data with much finer temporal resolution are also available (see Typical Meteorologic Year (TMY) data). Most data products available through SWERA are in GIS format, and when available can also be found in a spreadsheet format.

SWERA products for Flat Plate Solar Collectors

Flat plate solar collectors (photovoltaic (PV), solar hot water heating systems, etc.) can use all radiation that reaches the collector. This usable solar radiation includes the direct, diffuse and ground-reflected components. SWERA solar data products for flat plate collectors are available for two orientations of collectors on fixed mounts.

Tilted Flat-Plate Collectors
Example of Solar Tilt Map
Flat-plate tilted at latitude (Tilt) products represent the solar resource available to a flat plate collector oriented due south at an angle from horizontal equal to the latitude of the collector location. This collector orientation is typical practice for PV system installation, although other orientations are also used.
Horizontal Flat Plate Collectors
Example Solar GHI Map
Global Horizontal Irradiance (GHI) products describe the solar resource available to a flat-plate collector oriented horizontal to the earth’s surface.
In some locations a latitude tilt orientation will not be optimal due to local weather conditions, such as morning fog or afternoon showers, or diurnal and seasonal load profiles. Some analytical tools, such as HOMER, use GHI data as inputs, which are adjusted for latitude tilt differences within the model.

SWERA Products for Concentrating Solar Collectors

Example Solar DNI Map

The Direct Normal Irradiance (DNI) products are relevant concentrating solar applications. They describe the solar resource available to concentrating solar power (CSP) systems that track the sun throughout the day. Concentrating solar power (CSP) systems are a technology that uses concentrating solar collectors to provide high temperatures for running steam turbine generators.

Other Solar Applications

Diffuse Radiation Example

The diffuse data sets are equal to the global horizontal radiation minus the direct component. If only one of either the GHI or DNI data sets are available, the diffuse data set can be used to estimate the missing data. Diffuse radiation data are also useful for validating radiative transfer models, and have applications in building design where daylighting is a consideration.