For example, window orientation and size can affect heating and cooling of the building. South-facing windows transmit solar energy in the winter that is beneficial in reducing heating requirements. By having access to solar radiation data for their location, engineers and architects can evaluate the effects of window orientation and size on the energy consumption of the building and determine the size of the heating and air-conditioning equipment needed. They can use this information, combined with desired levels of natural lighting and the building aesthetics, to formulate the final building design. Except for concentrator systems, solar radiation data cannot be used without first accounting for the orientation of the solar collector.
Designers employ equations to calculate the total or global radiation on a flat-plate collector.
The equations use values of the direct beam radiation, the diffuse radiation on a horizontal surface, and the orientation of the collector. To maximize the amount of solar radiation received during the year, flat-plate collectors in the Northern Hemisphere face south and tilt from the horizontal at an angle approximately equal to the site's latitude. Solar radiation data combined with computer simulations can define these relationships more precisely. In the initial design stage, designers of cells used in photovoltaic modules can use spectral solar radiation data bases and models to optimize the cells for maximum energy production. Because the spectral content of solar radiation changes throughout the day and season, photovoltaic cells are tailored for a specific range of solar radiation wavelengths that will produce the most energy.