Solar Inverter

Solar Inverters Types & an Affluent Comparison: Which one to buy in 2021?

Solar inverters are one of the most essential devices of a solar power system, either it is for home usage or utility-scale usage.

As the renewable energy demand is increasing, technology is also evolving. Today, several kinds of solar panels are available in the market which vary by their efficiencies. 

In a similar way, solar inverters are available varying with their specifications. These are as important as the solar panels themselves in your solar energy system. 

Why do you need a solar inverter?

The primary function of an inverter is to change the Direct Current output of the solar panels into Alternating Current.

Direct current is used for small appliances or for devices where there is power stored in the battery. Some devices which use direct current are iPod, Mobile Phones, etc. 

While AC (alternative current) is the power that supplies inside the circuit.

This current is used on the grid and in most household appliances. Some are Washing machines, Televisions, etc.

A solar inverter is a device that converts the DC current generated by your solar panels into the type of electricity that can be used by appliances and other electronics in your home.

How does a solar inverter work?

When sunlight falls on the surface of solar panels, it reflects or absorbs. Solar panels convert the absorbed energy into DC electricity. 

And then here comes the use of solar inverters, these convert DC output of solar panels into AC (alternating current) power suitable for our homes usage.

How Solar inverter works?

After the current is converted into AC, Switchboards are used to distribute electricity between electrical sources.

You can also store the electricity in the batteries attached for later usage.

Now Let’s switch to the discussion of types of solar inverters:

How many types of solar inverters are available?

There are three types of inverters that are currently available to you for your solar energy system: 

Grid-Tie Inverters

These inverters are used with a solar PV System that is integrally connected to the utility grid power.

These inverters need to be connected to the grid to function.

The electricity produced by the solar system which is not consumed will automatically transfer to the grid via a Bi-directional meter.

In case of a power cut, the inverter stops to function as a safety feature, called Anti Islanding.

This type of system does not have battery backup. So, during power cuts, you will not have access to power. 

Hence, these systems are used in areas where there are very few power cuts.

On-Grid Inverter
Grid Tie Inverter

Also, it can be alternatively used if you already have a normal inverter battery system at home for power backup during power cuts.

Off-Grid Inverters

These are like the normal inverters used at home. In this, the DC charge generated by the solar panels is used to charge the solar batteries.

When there is a power cut, the inverter will draw stored energy from the battery, converting the DC power of the battery to use AC power for running appliances.

Generally, these systems are used in the area where there are long or frequent power cuts.

Hybrid Inverters

Hybrid inverters are the combination of both on-grid inverter and off-grid inverters.

A hybrid inverter system can be used in both high power cut areas or areas where there is a rare or very little power cut.

Under normal operating conditions, it can supply power to the home, charge the batteries and excess power can be transferred into the grid. 

In case of a power cut, the unit will automatically switch over to battery supply and continue to operate independently from the electricity grid.

Anyone going off-grid or wanting to use a hybrid system that can send solar-generated electricity during the day and store that power for use at night, during an outage, will need a solar charge controller

Mostly, Solar inverters have inbuilt charge controllers in them.

What is a Solar Charge Controller?

Since, in off-grid systems, batteries are used to store power generated from solar panels.

So, in the case of a battery-based system, the solar charge controller is used to prevent batteries from overcharging or excess draining and prevent the current from draining back into the PV array at night.

Also, it regulates the incoming power from the Solar PV Module, thereby providing a regulated DC output. 

Since overcharging can cause heating, and that can result in the reduction of efficiency of the system.

Also, excessive heating can even lead to an explosion. Hence, a solar charge controller is an essential part of the installation. 

Types of Solar Charge Controller

There are two main types of voltage regulators:

  • PWM: Pulse Width Modulation 
  • MPPT: Maximum Power Point Tracking

Both MPPT and PWM are energy control methods used by the charge controllers to regulate the flow of current from the solar panel to the battery. 

PWM inverters

PWM refers to pulse width modulation technology. These types of charge controllers are widely used in battery-based systems. 

PWM Charge Controller
PWM Charge Controller (Image Source: ledsaves.org)

PWM controls the power to the load. They have simultaneous on time and off time. During the charge time, they are on continuous On-time and make sure that the battery is charged quickly. Once the battery is fully charged, it alternates between On time and Off time.

This action helps in maintaining the battery voltage at a constant level and prevents the battery from either over-discharging or overcharging. 

MPPT inverters

MPPT stands for Maximum Power Point Tracker. The main function of an MPPT inverter is to maximize the energy available from the connected solar panel system at any time during its operation.

MPPT Charge Controller
MPPT Charge Controller (Image Source: ledsaves.org)

MPPT charge controllers are widely used in On-Grid inverters, even though it is also used in battery-based systems. 

There is a minimum voltage from the solar PV modules that can be utilized to power the load.

The voltage beyond the minimum level is converted to current at a lower voltage via a DC-DC converter. 

This ensures that the battery is charged quickly in a battery-based system. 

In an on-grid system, where there is no battery, this ensures that the maximum power is being produced. 

Difference between PWM and MPPT

The core difference among these two is: 

In a PWM controller, the current is drawn out of the panel slightly above the battery voltage, whereas, in an MPPT controller the current is drawn out of the panel at the panels’ maximum power voltage.

Below is a comparison table, so you can decide with ease that which solar inverter suits you best:

PWMMPPT
These controllers only control the input voltage to match it with battery voltage MPPT technology is able to sense the optimal input voltage and current rom panels.
These are used in small solar panel systems and have limited capacity for system growth.MPPT units are generally larger in size.
These have less efficiency.These controllers have comparatively high efficiency.
The cost of PWM charge controllers is relatively cheaper.The MPPT charge controllers are a little more expensive when compared to PWM charge controllers.
These cannot be used in applications having sizes above 60 A.These are available in sizes up to 80 A.
Generally, the warranty period of the PWM controller is less as compared to the MPPT controller.These have a comparatively longer warranty period.

In Conclusion

As I have discussed the use of solar inverters and functionalities of solar charge controllers. PWM is cheaper in price and has a 75% conversion rate while MPPT asks for a higher price, but the latest version of it has a conversion rate improvement of up to 99%.

Hope this post helps you to decide which one will be the best buy for you. Also, if you are thinking of installing a solar power system for your home, then, you can read our post on how many solar panels do you need?

Do your research and purchase the best!

Still, If you have any queries, you can ask in the comment section below this post.

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