What Are Vital Aspects That Impact The Outputs Of A Solar Installation?
There are industry standards for all types of PV modules which are rated and compared. The standards are known as STC or Standard Test Conditions. The STC is defined in set laboratory condition which is considered appropriate for solar panels. The condition is defined ideal for understanding the environ at which the PV panels can be optimally used. STC is known to be the universal standard for installation of solar panels.
However, STC includes 3 distinct factors which are as follows:
Irradiance
(Sunlight intensity/power)
This is described in terms of wattage per square meter, which falls on the flat surface of a PV panel. The standard measurement is 1kW/sq m.
Air mass
It is referred to the thickness or clarity of air through which sunlight is able to pass through and reach a panel. The standard is considered to be 1.5.
Cell temperature
Cell temperature differs from the ambient temperature. According to STC the cell testing temperature is considered as 25 degrees Celsius.
Optimum power point
Solar panels are not alike. They have a different model and each model will display a set of distinct characteristics. Basically, the characteristics differ based on a module’s output relation which is defined between the current and the voltage output that is again calculated based on a given condition signifying the temperature and sunlight availability.
Considering theories, every PV panel is supposed to have multiple I-V curves. Every I-V curve is set for different combinations of temperature and sunlight conditions, which further affect the STC ratings which include air mass, temperature and irradiance. A module will lose its voltage when the cell temperature increases. However, such kind of an impact is common among all types of crystalline modules. According to Ohm’s Law the output of decreased level of voltage is, low power output.
The Moving Target
There is basically a couple of temperature conditions which boost the level of voltage in PV panels/solar systems which solar installers in South East Queensland need to consider during an installation process. These include:
- Over-irradiance
- Temperature effects
Over-irradiance is another term for sunlight with the intensity standard that goes above the 1000watts/square meter value.
Over irradiance occurs in different ways. Let’s have a look:
Decreased air mass
This is referred to a lesser energy-consuming atmosphere for the sunlight to pass easily. The condition is applicable in higher altitudes.
Edge-of-cloud impact
According to professionals working for a solar company in South East Queensland the impact rises when a cloud passes away from incoming sunlight that hits straight on the panels. Under a scenario like this, refraction will concentrate sunlight allowing the edge of shadow to pass by. The results are a complete boost in the “module voltage output”.
Ambient sunlight reflection
Stronger reflections from nearby water bodies or a layer of snow on bright winter days generally boost solar intensity which further affects the voltage.
Colder it is, the better the results
Temperature impacts are outcomes of inherent features of the crystalline silicon modules. They will produce higher voltage with every fall in temperature and vice versa.
Any derating calculation of a solar panel is dependent on the adjustment of temperature effects. The derating is measured while calculating sizes of any related system component which includes the grid-tied inverters or charge controllers. They should ideally be sized for handling chances of current spikes resulting from the PV arrays brought upon by over-irradiance or temperature impact.
The size of the grid-tied inverters relies mostly when the lowest temperature is identified and recorded at a particular site.
While designing PV systems for a solar installation, these are key aspects which propose the planning and size of the solar system.
Author-bio: the author runs a solar company in South East Queensland. In recent times the author has been shedding light on key aspects concerning the subject.
