Che cos'è l'inverter off grid? Significato, funzionamento, costo

The off grid inverter is used when you cannot connect your power system to the grid (or do not want to). This can be if you live in a remote location or where grid power is too costly to install or use. Below, we explain what an off-the-grid inverter means, how it works and how much it will likely cost you to install one—how to size it for your system, too.

What is Off Grid Inverter?

In simple terms, an off grid inverter is a type of inverter that works without connecting to the grid. Put another way, it’s an inverter that you use in a stand-alone energy system and that works with a DC power generation or storage system to ensure a constant supply of electricity.

Off Grid Inverter Meaning

Off grid means not connected to the mains power of a utility company’s system. The off the grid inverter is, therefore, the opposite of a grid tie inverter that takes excess power to the main power system, or can draw power from it.

On Grid vs. Off Grid Inverter

The main difference between an on grid and off grid inverter is seen in the way they work in an energy system. Whereas on grid inverters can feed to or draw power from the grid, the off grid type cannot. Instead, its use typically involves power generation and storage systems.

The off grid inverter setup is best suited for remote areas, while grid tie inverters are best used in urban places where grid power is readily available. Additionally, grid tied inverters are mostly used without storage, since they can draw electricity from the mains power system.

Off grid inverter with generator backup
Off grid inverter with generator backup
Resource: https://www.youtube.com/watch?liuy2xD4RTg

How to Off Grid Inverters Work?

An off grid power inverter works like any other type of inverter, converting DC electricity into AC, and ensuring that your DC energy system can power your AC loads. The only difference is that it works independently of the grid. So it comes with fewer features and connections than inverters that are designed to connect the grid.

That being said, you can use your off grid inverter system with or without a storage system. It’s also common practice to include a generator when using the inverter with storage batteries. The generator then acts as backup should the main sources fail, such as when using solar in overcast weather.

Off Grid Inverter with Battery Backup

This is the most popular way of using an off the grid inverter. In this system, the inverter converts the energy stored in the batteries to AC, while the main source supplies the energy to be stored. This is what happens when using an off grid solar inverter with battery storage:

  • During the day when the sun is shining, the panels generate current.
  • The charging system uses this current to juice up the solar battery or batteries.
  • The inverter, on the other hand, draws DC current from the batteries
  • Using inbuilt circuits and electronic components, it, converts the power into usable AC current.
  • This arrangement ensures your home or business is constantly powered, even at night when there’s no sunshine, or during times when the weather is overcast.

Off Grid Inverter without Battery

If you intend to use your inverter to power intermittent loads, such as your home’s water pump or irrigation system, a storage system may not be necessary. For example, you only need power during the day if using solar power to irrigate crops or water your lawn. Here’s how an off grid solar inverter without battery backup works:

  • When the sun is shining, the panels are continually generating energy
  • The inverter takes this energy, which is in the form of DC, and converts it into AC.
  • The AC current powers your intermittent load or loads.
  • At night, the inverter remains inactive.
  • During the day the cycle repeats itself.

Off Grid Inverter with Generator Backup

You can use the off grid inverter with a portable DC generator, or include it in a solar system as a backup power source. Using the off-grid inverter with generator backup makes your energy generation system more reliable when it comes to powering your home or business.

In this setup, the panels generate power to charge a storage system while the inverter converts the DC power from the battery into current electricity for your AC loads. The generator then only comes in when the power generated by your panels is too low, such as in bad weather, or when your storage is depleted.

Off grid solar inverter system
Off grid solar inverter system
Resource: https://www.youtube.com/watch?QiMTdvvmOC4

Off Grid Inverter Sizing

Off grid inverter manufacturers make the product in different ratings. When buying one, therefore, it helps to know how to size it correctly. This is a critical factor when it comes to its reliability and the efficiency of your energy system. The steps below should help you find the best off grid inverter based on your power needs.

1. Add the watt ratings of your equipment or loads to find total power consumption. This is the approximate continuous power rating that you need your inverter rated for. An example calculation is given below:

  • 1 TV x 120 watts = 120 watts
  • 5 light bulbs x 20 watts = 100 watts
  • 2 cell phones x 20 watts = 40 watts
  • 1 laptop x 100 watts =100 watts
  • Total watts = 360 watts

2. Since no inverter can output power at 100% efficiency, divide your total consumption by its estimated efficiency, or what’s called power factor. This is typically between 70% and 80%. Assuming 80% efficiency, we now get 360 watts ÷ 0.80 = 480 watts for your off grid power inverter.

3. Note that if any of your loads require a starting current (AC, refrigerator, etc.), you’ll need to size your off grid inverter that as well. This is normally 3-5 times higher than the normal or continuous wattage we calculated earlier.

4. Finally, industry standards require you to choose an inverter that’s rated 20%-25% higher than your power consumption needs. This applies to both continuous and peak current ratings.

Conclusione

The off grid inverter is meant for energy generation systems that do not connect to the grid, such as stand-alone solar systems. Often best used with storage batteries, this type of inverter is most popular in remote areas, or anywhere where the grid power is not available, such as campsites. It’s also simple to use, in addition to being compatible with different energy setups.

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