Xantrex Technology GT3.0 - Manual (Page 88)

Maintenance and Troubleshooting
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Factors Affecting GT Inverter Performance
This section describes several factors that will affect the amount of power that a
properly installed and operating GT Inverter can produce.
PV Array Factors
PV array ratings PV arrays are rated at ideal factory conditions, such as specified illumination
(1000 W/m
2
), spectrum of the light and specified temperature (25°C / 77°F),
which seldom reflect real-world installations. This is called the STC (Standard
Test Condition) rating and is the figure that appears on the PV module nameplate
label.
Expected
performance Because of several unavoidable environmental factors, you can expect your
PV array to produce around 60% to 70% of its peak STC-rated output for a
properly designed and installed PV system on a typical day.
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 GT Inverter is designed to maximize its energy production in all of the above
situations using its MPPT algorithm.
Important: The GT Inverter 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 GT Inverter in a shaded location with good air flow.