knowledge of installing solar panels: install batteries beyond the rated capacity of grid-tied inverters.

Why is it necessary to install a solar panel capacity higher than the rated capacity of the inverter?

– The rated power on the label of the panel is the power under standard conditions (radiation intensity 1000W/m2, panel temperature 25 degrees Celsius). When installed under actual conditions the panel does not achieve rated power due to lower radiation and higher temperatures than reference conditions, or it can be achieved but for a very short time and very rarely at times of the year. achieve. When the temperature increases, the battery capacity is reduced, each battery brand will have this reduction factor, usually from 0.25-0.5% capacity when the temperature is higher than the standard temperature. The lower the coefficient, the better.
– When operating in real conditions, there is a lot of dust hidden in the air, dust on the battery that is not cleaned regularly also causes a decrease in capacity.
In addition, when installing, the mounting direction and tilt angle also affect the output power.
So, when it comes to actual installation, depending on the output power and desired power output and depending on the geographical location, calculate the appropriate amount of oversize. If calculated well, it will optimize the investment rate per unit of capacity.

Calculate the amount of Oversize:

Based on the specifications of each inverter manufacturer, the amount of oversize will be different, this parameter is usually written as “DC power max" or “PV Max"… inverter companies usually allow 10% or more PV excess. In addition, it is also necessary to rely on the maximum allowable open-circuit voltage (Voc Max) to calculate the number of panels connected in series, and the allowed short-circuit current I max to calculate the number of batteries in parallel.

Actual conditions in the installation area are also factors to calculate, equatorial and sub-equatorial areas like in Vietnam need less overpower, low radiation areas like temperate regions need high amounts of over. than.
The power graph of the solar system is shaped like a mountain, the most optimal calculation is that the power at the peak is equivalent to the nominal capacity of the inverter.
In Vietnam, the South is suitable for 5-10% oversize, the North is about 10-30% oversize.

If you install too much oversize, it will be a waste because of the large amount of PV power, the output power is only equivalent to the nominal inverter.

Is it necessary to install an oversize? It is not necessary, depending on the actual conditions needed and the financial situation that allows, planning to upgrade PV in the future to calculate the system. For example, when calculating needs 10kwp battery or less, you can choose to install a 3-phase 10kW Senergy grid-tied inverter without oversize. Or you can oversize by choosing an 8 or 9kw inverter to reduce inverter costs while ensuring the same output as installing a 10kW inverter.

3-phase grid-tied inverter SENERGY SE10KTL

Parameters for your reference to calculate, based on actual installation experience of Gigawatt company:

The maximum capacity of the system in the south at a good noonday is usually about 85% of the PV system's capacity, ie 1kWp (About 3 HT-SAAE Poly haflcell 340Wp panels) the panel will produce 850W of power. The rate at the best time of the day will be lower at other times. Output on a good sunny day is 5.5-5.8kWh/Kwp, the average year-round is about 3.6-4.0kWh/kWp (3.6-4 hours of sunshine).

Graph of January 23 for the system with 3.7 kwp solar panel and 3kW inverter (oversize ratio 23.3%) , southeast direction, fixed staging.

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