ABSTRACT
The earth's position related to the sun changes throughout the day and seasons. How much sunlight reaches the ground is dependent on where you are in the world and what the weather conditions are. The amount of sun available is called insolation. Shading happens because at a particular location there may be elements blocking the sun: geography, trees, or nearby buildings. The success of a solar hot water collector or photovoltaic (PV) module is dependent on having access to sunlight during the majority of strong sunlight hours. These occur 3–4 hours on either side of solar noon (when the sun is directly overhead). Because collectors are most efficient when oriented 90° to the sun's rays, it is important to understand the best tilt angle for collection. It is important to be able to determine shading at a site that could impact your design.
