How Off-Grid Solar Power Systems Work?


It's a fact that many households can be converted to off-grid with the help of solar power systems these days. But the only thing that holds many back is the cost of solar panels and batteries. We can eliminate the battery cost by implementing grid-tie solar systems but my focus is on off-grid solar systems. Solar power can provide electricity to households where the grid is not yet reached. 
Off-grid solar power system


That's why we are going to look at the  AC based off-grid solar power systems in detail. Let's go through each and every component of an off-grid solar power system. In an off-grid system, there is no electricity grid. Once solar power is used by the appliances in your property, any excess power will be sent to your battery bank. When your solar system is not working (night time or cloudy days), your appliances will draw power from the batteries.

A solar system can basically be of 3 types: An on-grid solar system,  an off-grid solar system, and a Hybrid System. An off-grid solar system can be further classified as DC-based and AC-based. In a DC system as the name suggests the entire system is DC-based. Its basic components would be a solar panel, solar charge controller, batteries, and DC load. There isn’t any DC to AC conversion here.
The main difference between an on-grid and an off-grid solar system design is just how it sounds like in the name. The off-grid systems rely on a battery to save all the power created just for that one household or building. An on-grid solar system is just the opposite.

Any power that is created by that home or buildings solar panels is sent to an electricity grid where anyone who is also connected to that same grid can use that energy. This can be a good thing to have in cases where there is no solar energy being created for long periods of time.

Components of an Offgrid Solar System (AC)


An off-grid solar system has four main components. A Solar panel, battery pack, charge controller, and an inverter. The diagram below explains how each and components are connected together ina sn off-grid solar power system.
Connection diagram


An off-grid solar system uses the basic principles of solar power. When we say this, we simply mean that with this system there are panels that are used to collect the sun’s energy. Once the initial energy is collected it is then sent to a solar battery which then sends the power to an inverter.

From there it will use energy to power electronics that are in your home. In the end, whatever green energy is created and is not used goes to the battery bank. This is a personal battery that saves power for the home to use at night or on days that are cloudy and overcast.

Solar Panels

Solar panels convert solar energy directly to electricity. The principle behind this conversion is photovoltaics. If you would like to learn how solar cells generate electricity click this link  How Solar Cell Works? There are different types of solar panels in the market. But most common technologies are mono-crystalline and polycrystalline solar panels. To know more about mono and polycrystalline solar panels read this post How Crystalline Silicon Solar Cells are Manufactured? If you are planning to install an off-grid solar power system in your house you have to calculate the power ratings of the solar panel. This calculation is very simple and can be done in minutes. First, you have to calculate the power consumption of your house or office, let's call it property. Read How to Design Solar Powered Inverter?


Battery

The solar battery also is known as solar panel battery, solar power battery, or solar battery storage. It refers to devices that store energy generated from the solar panels for later use. Solar battery designed to connect with a solar charger controller or solar inverter for power backup.

All types of solar systems run the connected load in the day time during sunlight and export the extra electricity to solar batteries with off-grid solar systems and hybrid solar systems. Solar batteries work for energy storage generated from solar panels during the day. They save energy as DC energy and therefore, you will need a power inverter to convert DC energy into AC energy.
There are mainly two types of solar batteries. If you are installing a solar system with a solar battery then you should know about its type and models. It is also important for its evaluation purpose. Let’s have a look over the types of solar batteries.

Tall Tubular Solar Battery

The lead-acid tall tubular solar battery is the upgraded version of normal batteries that used at home and other places. This solar battery is specially designed as per the solar application requirement. Solar tubular batteries are fully tested and reliable solar batteries that have been used in the off-grid solar system, hybrid solar system, solar home lighting system, and solar street lights for decades. A lead-acid tall tubular solar battery requires to top-up with water every 3 to 6 months.

For solar applications, these batteries required to be a charge on low ampere. So, tall tubular solar batteries are C-10 rated batteries for slow charging capabilities. These solar batteries can store more power than any other battery. But if we compare than these solar batteries have a comparatively short life and lower DoD.

Lithium-ion Solar Battery

There are different types of lithium-ion solar batteries.  The best type of lithium-ion battery for your solar power application is lithium iron phosphate (LiFePO4). LiFePO4 batteries are completely safe, not burnable, stable for 15 to 20 years, and maintenance-free. It has good electrical performance with low resistance.

A lithium-ion solar battery is generally used in all in one solar street light, solar power vehicles, and mobile battery banks.  The main advantage of this battery is the good thermal stability, increased safety, in addition to the high current rating and long cycle life if misused. Solar batteries for a home with solar panels are increasingly focused on lithium-based batteries, which have seen a steady reduction in costs in recent years.

The biggest benefit of lithium-ion batteries is it’s extremely high life-cycle (up to 5000 cycles) and its high charge and discharge capabilities that help harvest more energy from your solar panel. They also lose less capacity at idle, which is useful in solar installations where energy is rarely used. For these reasons, lithium-ion batteries are a good choice for any solar system whether it is a small or large, off-grid system or on-grid system. The biggest disadvantage is its high price tag. A lithium-ion solar battery can cost 4 times more than a flooded solar battery system.

Charge Controllers

PWM Charge Controller


A solar charge controller manages the power going into the battery bank from the solar array.  It ensures that the deep cycle batteries are not overcharged during the day and that the power doesn’t run back to the solar panels overnight and drain the batteries. Some charge controllers are available with additional capabilities, like lighting and load control, but managing the power is its primary job.

A solar charge controller is available in two different technologies, PWM and MPPT. How they perform in a system is very different from each other. An MPPT charge controller is more expensive than a PWM charge controller, and it is often worth it to pay the extra money. We will discuss the difference between a PWM and MPPT charge controllers in detail in another article. 

Inverter

Most homes use alternating current (AC) energy, not DC, so the energy produced by your solar panels isn’t useful on its own. When your solar panels collect sunlight and turn it into energy, it gets sent to the inverter, which takes the DC energy and turns it into AC energy. At that point, your solar electricity can power your appliances and electronics or, if you’re producing more electricity than you need, it can feedback into the grid. is is called a grid-tie system. But in an Offgrid solar power system doesn't send electricity to the grid. An off-grid solar inverter's only purpose is to convert the DC output of the battery/solar panel to 230 V AC. But in a hybrid solar system, an inverter is also used to charge the battery using the current from the grid. We will soon Discuss both hybrid and grid-tie systems in detail here at New Physicist. So kindly bookmark this page.

How Do an OFFgrid solar power system components are connected?


off-grid solar power system diagram

An off-grid solar power system (AC Based) has the above-mentioned components. Now let's have a look at how these components are connected and how do they work during day and night. There will be multiple solar modules fixed on the rooftop or where solar energy is brightly available in your property. the sizing of the solar module can be calculated based on your daily power consumption. These solar panels convert solar energy directly to DC electricity. the effective output of all solar panel may vary based on your off-grid system size, that is 12V/24V/48V.

The output of the solar panel will be connected to the charge controllers. Charge controllers are used to protecting the battery from getting overcharged or over-discharged. This setup will increase the efficiency and life of the battery. During the day time power from the solar panel will pass through an inverter and get directly converted to 230v AC which is the ideal working voltage of almost all the electrical applications. But in a DC-based solar system, there's no need to convert the DC voltage to AC. 

The excess energy will be used to charge the battery during day time. But where there is a cloud or during the night, there will not we any power coming in from the solar panel. Then the inverter will draw power from the battery pack. This is how an off-grid solar power system (DC-based) works. 

Hope you Clearly understood the off-grid solar power system working and it's components. In the next article, we will discuss different types of solar power systems. They are an On-grid solar system, and Off-grid solar system,  Hybrid System. An off-grid solar system can be further classified as DC-based and AC based. 

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