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Factors Affecting Sun Tie XR Performance
975-0053-01-01 3–11
Temperature and
reduced output
PV array temperature affects the output of the entire system. As the
temperature on the array surface heats up, its energy output goes down.
Roof-mounted arrays also collect the heat generated by the roof surface
(or trapped under the array) and will produce less output than pole-
mounted arrays, which allow greater air circulation behind the panels.
Angle of the sun The angle of the sun in relation to the PV array surface—the array
orientation—can dramatically affect the PV array output. The array
energy output will vary depending on the time of day and time of year as
the sun’s angle in relation to the array changes. Sunlight output decreases
as the sun approaches the horizons (such as in winter in North America)
due to the greater atmospheric air mass it must penetrate, reducing both
the light intensity that strikes the array’s surface and spectrum of the light.
In general, you can expect only four to six hours of direct sunlight per
day.
Partial shade Shading of only a single module of the array will reduce the output of the
entire system. Such shading can be caused by something as simple as the
shadow of a utility wire or tree branch on part of the array’s surface. This
condition, in effect, acts like a weak battery in a flashlight, reducing the
total output, even though the other batteries are good. However, the
output loss is not proportionate to shading.
The Sun Tie XR is designed to maximize its energy production in all of
the above situations using its MPPT algorithm.
Other Factors
Other factors that contribute to system losses are:
• Dust or dirt on the array
• Fog or smog
• Mismatched PV array modules, with slight inconsistencies in
performance from one module to another.
• Inverter efficiency
• Wire losses
• Utility grid voltage
For additional information and technical notes concerning PV array
performance, please visit our Web site at www.xantrex.com.
Note:
The Sun Tie XR will reduce its energy output to protect its
electronic circuits from overheating and possible damage in high heat
conditions. For maximum output in hot climates, mount the Sun Tie XR
in a shaded location with good air flow.