Solar Maps

Solar maps provide monthly average daily total solar resource information on grid cells of approximately 40 km by 40 km in size. The insolation values represent the resource available to a flat plate collector, such as a photovoltaic panel, oriented due south at an angle from horizontal to equal to the latitude of the collector location. This is typical practice for PV system installation, although other orientations are also used.

• Types of Maps
• How the Maps Were Made
• Solar Resources for Flat Plate Collectors
• Solar Resources for Concentrating Systems

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Types of Maps

United States Solar Atlas—Dynamic Map

This map interface accesses monthly average PVWatts Version 2 - Dynamic Maps solar resource information for any given location in the United States. It also provides access to spreadsheets giving average monthly radiation for 14 different types of solar collectors. Data for individual collectors are also available for fixed, flat-plate (photovoltaic) collectors on five different orientations. Added features include a zoom tool, which allows the user to zoom to zip codes and latitude/longitude locations. Learn how to use the U.S. Solar Atlas (MS Word 2.7 MB). (If you have pop-up blockers enabled, the PVWATTS Version 2 application on this Web site will not work properly. To fix this, you can go to your tool menu and allow popups from the mapserve2.nrel.gov site.) Note: Pop ups must be enabled to view maps.

PVWATTS Version 2—Dynamic Map

PVWATTS calculates electrical energy produced by a grid-connected photovoltaic (PV) system. Researchers at the National Renewable Energy Laboratory developed PVWATTS to permit non-experts to quickly obtain performance estimates for grid-connected PV systems within the United States. To access this calculator, go to PVWATTS Version 2. Learn more about the PVWATTS calculator. Note: Pop ups must be enabled to view maps.

Map of U.S. Solar Measurement Station Locations - Dynamic Map

This U.S. Solar Measurement Station Locations map shows the spatial distribution of measurement stations across the U.S. This site displays stations that are monitored by the following programs and agencies: DOE's Atmospheric Radiation Measurement (ARM) Program, NREL's Cooperative Network for Renewable Resource Measurements (CONFRRM), National Oceanic and Atmospheric Administration's (NOAA) that includes: Central UV Calibration Facility (CUCF), Climate Monitoring and Diagnostics Laboratory (CMDL), Integrated Surface Irradiance Study (ISIS), SURFace RADiation Budget Measurement Network (SURFRAD), the University of Oregons' Solar Radiation Monitoring Laboratory, and the University of Texas' Texas Solar Radiation Database. Each of the measurement station locations has a hyperlink that will take the user to the web site of that particular station or associated agency or program. Note: Pop ups must be enabled to view maps.

To allow the user to pinpoint their area of interest, reference information such as counties, major roads, major rivers, places (cities), and zip codes have been added. In addition, we have added a tool called PVWatts V2. This tool allows the user to calculate the energy production and cost savings for grid-connected photovoltaic (PV) systems located throughout the United States.

Notes: First time users, please click on the icon for the help document for detailed instructions on how to navigate the site.

PV Solar Radiation (Flat Plate, Facing South, Latitude Tilt)—Static Maps

(.jpeg images ranging in size from 260-273kb)

These maps provide monthly average daily total solar resource information on grid cells of approximately 40 km by 40 km in size. The insolation values represent the resource available to a flat plate collector, such as a photovoltaic panel, oriented due south at an angle from horizontal to equal to the latitude of the collector location. Learn more about Solar Resources for Flat Plate Collectors.

Direct Normal Solar Radiation (Two-Axis Tracking Concentrator)—Static Maps

(.jpeg images ranging in size from 268-299kb)

These maps provide monthly average daily total solar resource information on grid cells of approximately 40 km by 40 km in size. The insolation values represent the resource available to concentrating systems that track the sun throughout the day.

How the Maps Were Made

These maps were developed from the Climatological Solar Radiation (CSR) Model. The National Renewable Energy Laboratory for the U.S. Department of Energy developed the CSR model. Specific information about this model can be found in Maxwell, George, and Wilcox (1998) and George and Maxwell (1999). This model uses information on cloud cover, atmospheric water vapor and trace gases, and the amount of aerosols in the atmosphere, to calculate the monthly average daily total insolation (sun and sky) falling on a horizontal surface. The cloud cover data used as input to the CSR model are an 8-year histogram (1985 - 1992) of monthly average cloud fraction provided for grid cells of approximately 40 km x 40 km in size. Thus, the spatial resolution of the CSR model output is defined by this database. The data were obtained from the National Climatic Data Center in Asheville, North Carolina, and were developed from the U.S. Air Force Real Time Nephanalysis (RTNEPH) program. Atmospheric water vapor, trace gases, and aerosols are derived from a variety of sources, as summarized in the references. The procedures for converting the modeled global horizontal insolation into the insolation received by a flat plate collector at latitude tilt are described in Marion and Wilcox (1994).

Where possible, existing ground measurement stations are used to validate the model. Nevertheless, there is uncertainty associated with the meteorological input to the model, since some of the input parameters are not available at a 40km resolution. As a result, it is believed that the modeled values are accurate to approximately 10% of a true measured value within the grid cell. Due to terrain effects and other microclimate influences, the local cloud cover can vary significantly even within a single grid cell. Furthermore, the uncertainty of the modeled estimates increases with distance from reliable measurement sources and with the complexity of the terrain.

References:

George, R, and E. Maxwell, 1999: "High-Resolution Maps of Solar Collector Performance Using A Climatological Solar Radiation Model," Proceedings of the 1999 Annual Conference, American Solar Energy Society, Portland, ME. (PDF 868 KB) Download Adobe Reader.

Maxwell, E, R. George, and S. Wilcox, "A Climatological Solar Radiation Model," Proceedings of the 1998 Annual Conference, American Solar Energy Society, Albuquerque NM. (PDF 688 KB) Download Adobe Reader.

Marion, William and Stephen Wilcox, 1994: "Solar Radiation Data Manual for Flat-plate and Concentrating Collectors." NREL/TP-463-5607, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401.

Solar Resources for Flat Plate Collectors

These maps provide monthly average daily total solar resource information on grid cells of approximately 40 km by 40 km in size. The insolation values represent the resource available to a flat plate collector, such as a photovoltaic panel, oriented due south at an angle from horizontal equal to the latitude of the collector location. This is typical practice for PV system installation, although other orientations are also used.

These maps were developed from the Climatological Solar Radiation (CSR) Model. The U.S. Department of Energy's National Renewable Energy Laboratory developed the CSR model. Specific information about this model can be found in Maxwell, George, and Wilcox (1998) and George and Maxwell (1999). This model uses information on cloud cover, atmospheric water vapor and trace gases, and the amount of aerosols in the atmosphere, to calculate the monthly average daily total insolation (sun and sky) falling on a horizontal surface. The cloud cover data used as input to the CSR model are an 8-year histogram (1985 - 1992) of monthly average cloud fraction provided for grid cells of approximately 40 km x 40 km in size. Thus, the spatial resolution of the CSR model output is defined by this database. The data were obtained from the National Climatic Data Center in Asheville, North Carolina, and were developed from the U.S. Air Force Real Time Nephanalysis (RTNEPH) program. Atmospheric water vapor, trace gases, and aerosols are derived from a variety of sources, as summarized in the references. The procedures for converting the modeled global horizontal insolation into the insolation received by a flat plate collector at latitude tilt are described in Marion and Wilcox (1994).

Where possible, existing ground measurement stations are used to validate the model. Nevertheless, there is uncertainty associated with the meteorological input to the model, since some of the input parameters are not available at a 40 km resolution. As a result, it is believed that the modeled values are accurate to approximately 10% of a true measured value within the grid cell. Due to terrain effects and other microclimate influences, the local cloud cover can vary significantly even within a single grid cell. Furthermore, the uncertainty of the modeled estimates increases with distance from reliable measurement sources and with the complexity of the terrain.

References:

George, R, and E. Maxwell, 1999: "High-Resolution Maps of Solar Collector Performance Using A Climatological Solar Radiation Model," Proceedings of the 1999 Annual Conference, American Solar Energy Society, Portland, ME. (PDF 868 KB) Download Adobe Reader.

Maxwell, E, R. George, and S. Wilcox, "A Climatological Solar Radiation Model," Proceedings of the 1998 Annual Conference, American Solar Energy Society, Albuquerque NM. (PDF 688 KB) Download Adobe Reader.

Marion, William and Stephen Wilcox, 1994: "Solar Radiation Data Manual for Flat-plate and Concentrating Collectors." NREL/TP-463-5607, National Renewable Energy Laboratory, 1617 Cole Boulevard, Golden, CO 80401.

Solar Resources for Concentrating Systems

These maps provide monthly average daily total solar resource information on grid cells of approximately 40 km by 40 km in size. The insolation values represent the resource available to concentrating systems that track the sun throughout the day. Such systems include concentrating solar power stations such as trough collectors or dishes. The values are also useful for assessing the resource available to solar hot water systems.

These maps were developed from the Climatological Solar Radiation (CSR) Model. The U.S. Department of Energy's National Renewable Energy Laboratory developed the CSR model. Specific information about this model can be found in Maxwell, George, and Wilcox (1998) and George and Maxwell (1999). This model uses information on cloud cover, atmospheric water vapor and trace gases, and the amount of aerosols in the atmosphere, to calculate the monthly average daily total insolation (sun and sky) falling on a horizontal surface. The cloud cover data used as input to the CSR model are an 8-year histogram (1985 - 1992) of monthly average cloud fraction provided for grid cells of approximately 40 km x 40 km in size. Thus, the spatial resolution of the CSR model output is defined by this database. The data were obtained from the National Climatic Data Center in Asheville, North Carolina, and were developed from the U.S. Air Force Real Time Nephanalysis (RTNEPH) program. Atmospheric water vapor, trace gases, and aerosols are derived from a variety of sources, as summarized in the references.

Where possible, existing ground measurement stations are used to validate the model. Nevertheless, there is uncertainty associated with the meteorological input to the model, since some of the input parameters are not available at a 40 km resolution. As a result, it is believed that the modeled values are accurate to approximately 10% of a true measured value within the grid cell. Due to terrain effects and other microclimate influences, the local cloud cover can vary significantly even within a single grid cell. Furthermore, the uncertainty of the modeled estimates increases with distance from reliable measurement sources and with the complexity of the terrain. Concentrating solar collectors are much more sensitive to solar resource characteristics than flat plate collectors, so these sources of uncertainty are more important to concentrator applications.

References:

George, R, and E. Maxwell, 1999: "High-Resolution Maps of Solar Collector Performance Using A Climatological Solar Radiation Model," Proceedings of the 1999 Annual Conference, American Solar Energy Society, Portland, ME. (PDF 868 KB) Download Adobe Reader.

Maxwell, E, R. George, and S. Wilcox, "A Climatological Solar Radiation Model," Proceedings of the 1998 Annual Conference, American Solar Energy Society, Albuquerque NM. (PDF 688 KB) Download Adobe Reader.