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Measuring Solar Insolation
This page contains archived content and is no longer being updated. At the time of publication, it represented the best available science. However, more recent observations and studies may have rendered some content obsolete.
These false-color images show the average solar insolation, or rate of
incoming sunlight at the Earth's surface, over the entire globe for the
months of January and April. The colors correspond to values (kilowatt
hours per square meter per day) measured every day by a variety of Earth-observing satellites and integrated by the International Satellite Cloud Climatology Project (ISCCP). NASA's Surface Meteorology and Solar Energy (SSE)
Project compiled these data--collected from July 1983 to June 1993--into a 10-year average for that period.
Such images are particularly useful to engineers and entrepreneurs who
develop new technologies for converting solar energy into electricity.
To attain best results, most devices for harvesting sunlight require an
insolation of greater than 3 to 4 kilowatt hours per square meter per
day. Luckily, insolation is quite high year round near the equator,
where roughly a billion people around the world must spend more money on
fuel for cooking than they have to spend on food itself. Natural renewable
energy resources is a particularly relevant topic in the United States
today as there are rolling blackouts across the state of California
while other U.S. city and state governments grapple with energy
To facilitate development of new technologies for harvesting natural
renewable energy sources, the SSE
Project at NASA's Langley Research Center has made available a wealth of
global-scale data on a variety of meteorological topics, including
insolation, cloud cover, air temperature, and wind speed and direction.
These data are freely available at the SSE Project Web Page.
For more details on the SSE Project, refer to the April 19, 2001, press release issued by NASA LaRC.
Image courtesy Roberta DiPasquale, Surface Meteorology and Solar Energy
Project, NASA Langley Research Center, and the ISCCP Project