How much capacity is solar panels?

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Because of its outstanding economic and environmentally friendly values, solar energy is increasingly popular and becoming more widely used. We need to calculate solar power capacity to bring the highest efficiency in solar PV system installation. At the same time, it ensures the voltage of the whole system, provides adequate electricity for the entire load consumption, saves costs and brings economic values.

Today's G7Solar article wants a guide on how to calculate the solar PV system's capacity to match your project.

On average, 1kwp will generate 4-5 kilograms of electricity a day, with current panels falling at about 450Wp, the capacity of a solar panel is about 2 kilograms of electricity a day.

How much total energy consumption (watt-hour) is all solar-powered appliances?

Total energy consumption

Total Watt-hours consumed in 1 day of full load = The number of Watt-hours of each equipment consumed per day combined.

For example, the load is a television with 80W power consumption, using an average of 8 hours per day, the number of watts per hour used per day is 80 x 8 = 640 wh.

The solar panels must provide the full load for how many Watt-hours per day

The Watt-hour of solar panels providing about 1.3 times higher than the total Watt-hour of the full load. The reason is due to system loss.

Calculation: Number of Watt-hours of solar panels (PV modules) = 1.3 x total Watt-hours of full load used.

In the example above, the watt-hour for solar panels is 640 x 1.3 = 832 wh

How to calculate the size of solar panels

Size of solar panels to use

We calculate the maximum (Wp) needed by solar panels when calculating the usable size of solar panels. Depending on the gas of each region in the world, the amount of Wp solar cells generated. When placing the solar panel in different places, the level of energy absorption is also different even though the panel is completely the same.

In order to design correctly, one must measure and measure the absorbance of solar radiation in each region during the month and give an average coefficient called the “panel generation factor”, roughly translated as the radiation absorption coefficient. of the solar cell.

The panel generation factor, also known as the radiation absorption coefficient of the solar cell. This factor is used to design the panels correctly.

The "panel generation factor" = collection efficiency multiplies by solar radiation, its unit is (kWh / m2 / day).

For example, the solar energy absorption in a place in Vietnam is 5 kWh / m2 / day, we take the total watt-hours of solar panels divided by 5, we will get the total Wp of the solar panel.

According to the above example, the watt-peak of solar panels: 832/5 = 166 Wp

Number of solar panels needed = total Wp needed for a solar panel divided by its Wp parameter will be received.

For example if using 85 wp solar panel, number of panels required = 166/85 # 2 panels.

The above example is just the minimum required number of panels. The system will work longer and better if the number of solar cells is more. In the case of a few solar cells, on cool days, the battery easily depletes energy, greatly affecting the battery's life. In contrast, designing multiple batteries is expensive, sometimes not necessary. Therefore, how much battery is needed depends on the system redundancy.

We can daisy-chain all solar cells together, or combine them into series and parallel combinations, handled by one or more solar controllers.

These things have mutual interactions on the design of the battery system and the solar charger system below:

Calculating the battery (Battery)


Deep-cycle is the type of Battery used for the solar power system. This type has a high durability and longevity, they allow for very low discharge and fast refilling. Besides, they are capable of charging and discharging many times (many cycles) without being damaged inside.

How to calculate the battery capacity:

Battery capacity (Ah) = (Total Wh consumption per day / (0.85 x 0.6 x battery voltage)) x number of days of backup

The efficiency of the battery is only about 85%, so divide the Wh of the load consumed by 0.85 to get the Wh of the battery. With a deep discharge (Deep of Discharge DOD) of 0.6, we divide the Wh number of the battery by 0.6 to have the battery capacity.

A battery can be selected after calculating the battery voltage V and the capacity Ah of the battery, and calculating how to best fit them together, taking into account the redundancy of the whole system.

For example, a 12V / 1000AH ac-battery system with 5 pairs of 12V / 200AH in parallel will have a higher safety level than 1 row of 12V / 1000AH, if some of the batteries are damaged, we still have other ranges working well in repair timeout.

Battery capacity (Ah) = Total Wh consumed per day / (battery performance x DOD level x battery voltage)

Battery capacity (Ah) = Total Wh consumption per day / (0.85 x 0.6 x battery voltage)

Because calculating solar energy is extremely time consuming and requires a certain understanding. Then calculate the most accurate system capacity. We should seek the advice of experts experienced in the renewable energy industry to calculate the most accurate solar capacity.

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