There are Pwm and MPPT two kinds solar controller in the market, the solar controller MPPT (Maximum Power Point Tracking) provide in comparison to conventional solar controller PWM (Pulse With Modulation) to a minimum 15% load power and more.
PWM Load :
By using the traditional solar controllers, the solar panel is directly connected to the battery to charge. The battery defines the operating voltage of the module. Therefore, the power of load is still lower than if the regulator was directly connected with the module. The rated power of a solar panel is always the result of the product voltage and current to the point of optimal work at 25 °C.
In the framework of a 12V system, the voltage of the battery is located between 10-15V. The conventional solar panels have a maximum voltage of approximately 17V. Therefore, in the voltage range 10-15V, the available power is reduced.
Depending on the charge state of the battery, the conventional systems are not able to use the power available. On average, this represents the loss of approximately 20 %.
MPPT :
The MPPT solar controller determine of uninterrupted and with a great accuracy the point of optimal work on the output curve on which the voltage and the current UMPP IMPP reach a maximum (Product UMPP * IMPP = PMPP ). The energy resulting from the point of optimal work is electronically converted to battery voltage the more low to charge the battery with the higher current possible.
Example:
A module of 100W ( UMPP = 17V) loaded using the regulator Tristar- MPPT a battery of 12V. In the ideal case, 5.88A of current flows in the solar regulator MPPT (17V * 5.88A = 100W) as the output voltage of only amounts to 12V (battery voltage), the output current will rise to 8.33A (8.33A * 12V = 100W). More than the difference between Umpp and voltage of the battery is great, the more current with which the battery will be charged will increase. More than the state of charge of the battery is low, more than the load current from the battery is high.
Changes in the surrounding environment:
The changes of the surrounding environment (temperature, radiation) lead to a fluctuation in values Umpp . Partial shadows or a change in temperature of the module are causing the greatest differences. While the MPPT is continuously adapted to the respective conditions, the performance remains to a large extent the same. The difference between conventional regulator and MPPT tracker is very easy to see when low temperatures. The Umpp value shifts to the top and the power of the module as well as the load current increases in function. A conventional regulator would benefit in nothing in the case of low temperature.
Sizing of the MPPT controller modules for:
For optimum operation it is very important that the regulator specifications are respected. Thus the voltage to empty during low temperature must not exceed in any case the maximum input voltage permitted by the regulator. A no-load voltage too high (Uoc) can damage the electronic components in the regulator. For a battery voltage and a MPP voltage of a module, it is essential not to exceed the recommended solar power.
Attention: The load current from the battery is in all cases higher than the current of the module. The specifications for the current maximum MPPT, multiplied by the voltage of the battery decide to the maximum power of the module to use.
Example 1:
A MPPT controller 15A is used with a 12V system (field of battery voltage: 10-15V). The " rating" current multiplied with the voltage of the battery gives about 200W (15A * 13.3V= 200W). The maximum power of the module should not exceed 200W.
Example 2:
A MPPT controller 15A is used with a 24V system (field of battery voltage: 10-15V). The maximum power of the module should not exceed 400W (15A * 26.6" FOR V= 400W).
An overrun of the solar power allowed (within the limits of the currents allowed) does not lead to a damage to the regulator. The higher power that the limits calculated in examples 1 and 2 simply cannot be converted and will be lost. The MPPT controllers can be used with all types of modules. By contrast, the PWM solar controller cannot only be used with modules which are tailored to the batteries.
Optimization of the performance:
The performance of a regulator Mppt may vary slightly with the different voltages of battery voltages, modules, and powers.
As you'll read in the previous lines, the use of the MPPT regulator has many advantages. The most relevant argument is certainly that it is more difficult to find suitable solar panels to recharge battery. Because of this, it was more and more use of modules for "network injection" which are best markets but which due to their higher voltage cannot be used with a conventional regulator. The price difference between a conventional and a regulator regulator MPPT is nothing compared to the savings that are achievable by purchasing a classic module.
The regulator has a optimal behavior when a low solar radiation or when a part is shaded. The MPPT regulator allows also to lengthen the life of the battery through its a technique of load.For standalone installations of 100W and less, a traditional regulator is recommended.