As of the end of 2017, nearly 40% or 10.4 GW (GW) of utility-scale photovoltaic (PV) systems operating in the United States were fixed-tilt photovoltaic solar panel mounting racking systems rather than tracking systems. Based on the horizon, 76% of utility-scale fixed-tilt PV solar mounting bracket systems have tilt angles between 20 and 30 degrees.
The amount of electricity generated by a fixed tilt photovoltaic mounting racking system depends on the direction of the photovoltaic panel relative to the sun. When the sun's rays are perpendicular to the panel, the panels of the solar PV system can collect solar radiation more efficiently.
Fixed tilt photovoltaic solar mounting systems use two independent angles to determine their direction relative to the sun: azimuth and tilt.
• Azimuth specifies the direction of the compass facing the sloping panel: North, South, East or West. Most panels in the northern hemisphere are facing south.
• The inclination is the angle to the horizontal ground. A zero tilt means that the panel lies flat on the ground, while a tilt of 90 degrees means that the panel is perpendicular to the ground and looks like a wall standing on one side.
Latitude is usually the main factor determining the slope of the panel, because tilting the panel south to the same angle as its latitude maximizes the annual light rate of direct sunlight. In the United States, systems installed at lower latitudes (more south) typically have shallower photovoltaic slopes, while systems installed at higher latitudes (north) typically have steeper slopes.
Fixed-angle photovoltaic solar racking systems of US utility scale are deployed in areas between 20 degrees north latitude (Hawaii) and 50 degrees north latitude, such as Oregon and Minnesota. Due to other factors such as height restrictions, shadow problems, and system layout, panels are typically mounted at shallower slopes than indicated by latitude. Systems with tilt angles that are less than the tilt angle of the plant position are expected to increase yields in the spring and summer months when the sun is above the sky, but will reduce autumn and winter yields.
In recent years, photovoltaic power plants have increasingly installed tracking systems rather than fixed tilt systems. The tracking system either rotates on a single axis (usually from east to west) or on a double axis. While tracking systems are more expensive than fixed tilt systems, the benefits of tracking the extra power generated by the sun moving the path in the sky often exceed its increased cost. Since the tracking mechanism is designed to track from east to west, many existing single axis tracking systems have a zero degree tilt function.