Solar radiation intensity
The efficiency and performance of solar water heating systems depend on a site’s solar energy resource. Solar resource is measured by the solar radiation intensity of an area, but cloud cover and latitude must also be factored into the system purchase decision. The amount of solar energy available for heating water varies by geographical location. Figures 2.1 and 2.2 show that tilted flat plate collectors located in the United States at an angle equal to the latitude receive the most sunlight in the desert Southwest and the least sunlight in the Pacific Northwest and states in the Northeast. Table 2.1 lists the maximum daily solar radiation and average daily solar radiation for selected US locations. Detailed monthly solar radiation information for a multitude of locations in the United States is available from the National Renewable Energy Laboratory at:
