PWM technology vs MPPT technology

After reading the article, understanding the importance of the solar charge controller, you must have realized the significance of the charge controller. The solar charge controller is the integrated and vital part of any solar power system .Here we will learn the two  different types of solar charge controllers and their performance under different set of conditions.

(1) Types of charge controller

The solar charge controllers which are commonly used in the solar power systems are:

• PWM (Pulse Width Modulation) solar charge controller.
• MPPT (Maximum Power Point Tracking) solar charge controller.

Both of these charge controllers are based on the sophisticated technologies and they adjust their charging rate based on the charging level of the battery .They match power source voltage with the battery voltage.

(2) The working of two charge controllers

The PWM solar charge controller works by adjusting the charge from the solar panels according the battery’s condition and its recharging requirements. The charging rate is higher and pulses are wider when the battery is nearly discharged and the charging rate and the width of the pulses keeps on decreasing as the battery reaches its maximum charging level .It can keep the battery fully charged state for an indefinite period of time. This helps in avoiding heating and gassing of the battery and results in high charging efficiency with healthy battery life. When sizing the system the voltage specification of the PWM charge controller must match the voltage of the battery.
Whereas the normal solar charge controller also called shunt controller, stops charging the battery when it is fully charged and re-charges again when battery drops to the certain level.

• What is the difference?

The main difference between the two is that the PWM charge controller is unable to capture the voltage difference between the panel voltage and the battery voltage while the MPPT charge controller has the ability to detect the voltage difference and convert the excess voltage from the solar panel into the equivalent amount of the amperage so that the same amount of power reaches the battery which is being generated by the solar panel.
However each technology has its own advantages which are based on the site location, temperature, and size of the array with respect to the load, size and the cost of system.
Let us understand their efficiency and the advantages under different set of conditions:

Change in location

The angle at which sun rays striking at the solar panels depends on the location and the season. The less amount of energy is absorbed by the solar panel when the sun rays coming at the shallow angle and hence resulted in less output power from the solar panel. Here the MPPT technology is suitable for harvesting the maximum amount of the solar energy.

Change in temperature

As the temperature drops the Vmp of the solar module increases causes more differential between the battery voltage and the panel voltage. As MPPT charge controller has the ability to track or detect the excess voltage and covert the difference into the equivalent amperage. Therefore in lower temperature conditions the MPPT technology has better harvesting power than that of PWM technology.

Increase in the size of the array with respect to the load

In a situation where the size of the panels are large enough relative to the power drawn by the load, the battery will remain in the full charge state almost all the time. Here the PWM charge controller is suitable and economical as compared to the MPPT charge controller.

When the size of the system is small

Small power solar system is better suited to the PWM controller because it operates at the constant harvesting efficiency irrespective of the size of the solar system. Whereas, the harvesting efficiency of the MPPT charge controller is low with small solar power system. So, in low power applications PWM charge controller is better and economical option.

Cost of the system

PWM charge controllers are less expensive than the MPPT charge controllers. So PWM charge controllers have cost advantage over their counterpart.
So, you can decide which type of the solar charge controller is suitable for your solar system by analyzing the above mentioned parameters.

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