Off Grid Inverters

More about off-grid inverters

 The off-grid inverters are made to work in solar installations that do not have a connection to the electrical grid. These facilities usually have solar panels, a bank of solar batteries and sometimes a backup diesel generator. When to use off-grid solar inverters The use of off-grid inverters is common when it is intended to power a house autonomously without grid connection, supply power to a motorhome, power a series of water pumps or any other type of consumption, usually of a small and medium size. that for any reason does not have a permanent electrical network.

What are the off-grid inverters?

Stand-alone inverters, also known as off-grid inverters or stand-alone inverters, are electronic devices used in stand-alone power generation systems that are not connected to the conventional power grid. These systems operate independently and do not rely on the grid for their operation and are therefore referred to as "off-grid systems".

The main characteristics of off-grid solar inverters are:

1 - Energy autonomy: These inverters are part of stand-alone power generation systems, which may include solar photovoltaic panels, wind turbines, diesel generators or other renewable energy sources. The energy generated is used to power devices and appliances directly or to charge batteries for later use.

2 - Energy storage: In many off-grid systems, batteries are used to store excess energy generated during periods of high production. Solar batteries provide a reserve of energy to meet electricity demand when generation is insufficient, such as at night or on cloudy days.

3 - DC-AC conversion: Stand-alone inverters convert the direct current (DC) generated by renewable energy sources and stored in batteries into direct current (DC), and then convert it into alternating current (AC), which is the form of energy used by common devices and appliances.

4 - Charge and discharge regulation: Inverters in off-grid installations usually have regulation and control systems that manage the charging and discharging of the batteries to ensure efficient use of the stored energy. Among some parameters, solar inverters with integrated charge controllers control the charge/discharge current and the level of depth of discharge in order to keep the solar batteries in optimal condition.

5 - Backup system: In some systems, especially those that rely on variable renewable sources such as solar or wind, a diesel generator can be included as a backup for extended periods of low renewable energy production to continue powering the loads. 

Off-grid systems are common in rural or remote areas where there is no access to the conventional power grid, as well as in special applications such as weather stations, cottages, shelters, communication towers and research projects in isolated locations. These systems require careful planning, proper sizing and regular maintenance to ensure a stable and efficient power supply.

How does a stand-alone inverter work?

An isolated inverter, also known as an off-grid inverter or stand-alone inverter, is a device that converts direct current (DC) generated by power sources, such as solar panels, wind turbines or batteries, into alternating current (AC) that can be used to power electrical devices and systems in areas not connected to the public power grid. These inverters are commonly used in stand-alone systems, such as rural homes, remote installations and back-up power systems.

Here's how a stand-alone inverter works:

- Power Generation: Power is generated through sources such as solar panels or wind turbines. These sources generate electricity in the form of direct current (DC).

- Storage (if necessary): In many off-grid systems, batteries are used to store the energy generated during times when generation exceeds demand. This allows the stored energy to be used when generation is insufficient, such as at night or on cloudy days. To determine the storage capacity, it is necessary to determine the hours of supply we expect from the solar batteries on a daily basis. Assuming that the batteries are fully charged and discharged on a daily basis, we can establish the kWh of batteries needed to be installed. In the case that we foresee that the solar batteries cannot be charged every day we can assume that they will be charged every 2 or 3 days and therefore we will have to dimension the charging and discharging of the batteries correctly. 

- Current Inversion: The isolated solar inverter takes direct current (DC) from the power sources and batteries and converts it to alternating current (AC). This is essential for powering electrical devices and systems that operate on alternating current. It is important to match the AC (output) power of the inverter with the total power of the loads to be supplied. Although stand-alone inverters are not usually sized with the maximum power of the loads, it must be at least 50%. We will have to take into account the simultaneity factors of the installation. This will force us to not be able to connect all the loads at the same time. While the simultaneity factor is taken into account in grid-connected electrical installations, in the case of off-grid solar installations, it must be more restrictive in order to keep the critical loads in operation.

- Power Distribution: The alternating current generated by the inverter is distributed to the electrical devices and systems connected to the off-grid system. You can use the power to power appliances, lighting, tools and other electrical equipment. The distribution of this power is done through the inverter's AC bus output. The output of the off-grid solar inverter is connected to the power grid of the house/industry or point of energy consumption. The frequency and voltage of the consumption grid will be generated by the inverter itself. Remember that our installation does not have a grid connection. This is why sometimes, in order to minimise consumption and maximise solar production, 12 or 24V "mini-grids" are set up with the corresponding appliances/appliances at this voltage. However, the most common is to have a 220V i 50Hz consumption network with the same loads that we would use in an installation with grid connection. 

- Control and Regulation: Isolated inverters often come with control and regulation features. They may have charging functions to manage the flow of power to and from the batteries, overcharge and undervoltage protection, and monitoring systems to check system status and charging conditions. Depending on the type of solar inverter and the batteries it is compatible with, it will communicate with the BMS (Battery Management System) to control all the above mentioned parameters. In the case that lead batteries are used, the inverter will be in charge of controlling these previously introduced parameters by means of the regulator. This function will be done in open loop (without receiving information from the batteries). There is no real communication between batteries and inverter. 

- Backup Systems: In some cases, an isolated inverter may have an automatic switching system that allows switching from the main power source to a backup source, such as a diesel generator, when renewable energy generation is not sufficient. Depending on the inverter this switching to the back-up system will be done automatically or manually.

In short, a stand-alone solar inverter plays a critical role in stand-alone power systems by converting the energy generated into a usable form to power electrical devices and systems. It can also manage energy storage in batteries while controlling all of its electrical parameters and managing the flow of energy within the system.

When to use off-grid solar inverters?

It is common to use off-grid inverters when the intention is to power an autonomous off-grid home, supply energy to a motorhome, power a series of water pumps or any other type of consumption usually of a small and medium size that for whatever reason does not have a permanent power grid.

What types of off-grid inverters can we find?

The first classification we can find when we talk about off-grid solar inverters is the one that refers to its voltage or working voltage. As explained in the general description of the category, we can find three common voltage ranges:

- 12V Solar Inverter: 12V off-grid solar inverter. For solar panels and solar batteries in this voltage range. Usually for low power installations (less than 3000W, e.g. 12V 2000W inverter).

- Solar Inverter 24V: 24V off-grid solar inverter. For combinations of solar panels and solar batteries in this voltage range. Usually for medium-low power installations (no more than 5000W, e.g. solar inverter 3000W).

- Solar Inverter 48V: 48V off-grid solar inverter. For combinations of solar panels and solar batteries in this voltage range. Usually for medium power installations (from 3000W, being common, for example, inverter 48V 3000W, inverter 48V 4000W or inverter 48V 5000W).

On the other hand, we can find in the market types of inverters of isolation of each of the mentioned voltage ranges that are chargers. Inverters capable of managing the flow from DC to AC and from AC to DC are called charger inverters.

This dual functionality allows the batteries to be charged either from the generation of the panels or through a diesel generator connected to the solar installation. They are also often referred to by their battery voltages as 12V inverter charger, 24V inverter charger or 48V inverter charger. The inverter chargers of isolated allow better management of different energy sources allowing its management and always ensuring the power supply.

In Tienda Solar you can find very competitive cheap inverters of isolated very competitive for any use and application.

Where are the inverters placed?

The location of inverters in a solar power system depends on the type of inverter, system design and site-specific considerations. Below are some common options for inverter placement:

- Inside the home or building: In smaller residential systems, it is common to install inverters indoors, such as in the garage, basement, utility room, or even in a designated wardrobe. This location protects the inverters from the weather and facilitates monitoring and maintenance access. It is important to provide the inverter with good ventilation to allow the heat generated by the inverter to escape. Poor ventilation can cause the inverter to overheat, resulting in temporary shutdown of the inverter or, if this situation persists, total failure.

- Outside the house or building: Inverters designed for outdoor use can be installed on the outside wall of the house or on a structure specially designed to protect them. This can be useful if you do not have enough indoor space or if you prefer to keep the inverters outside the house. Outdoor inverters should have at least an IP65 protection rating.

- Machine room or equipment room: In commercial or industrial applications, inverters can be placed in an equipment room or dedicated machine room. This allows easy access for maintenance and can be more effectively protected from dust, moisture and other elements. As discussed for indoor inverters, good ventilation must be ensured. 

- Poles or supports/legs: In larger systems, especially in industrial or large-scale installations, inverters are sometimes mounted on elevated poles or supports to minimise floor space and to facilitate heat dissipation. Depending on whether these structures are indoors or outdoors, the appropriate degree of protection (IP) must be selected. 

- Inverters integrated into panels: Some solar systems may include inverters integrated into the solar panels themselves. These inverters are smaller and are placed on the back of each panel. They are common in systems with micro inverters. These micro inverters should always have a higher protection rating of IP65 and a corrosion resistance corresponding to the location where they are to be installed. 

Regardless of the location chosen, as mentioned above, it is important to consider adequate ventilation and access for maintenance. In addition, solar inverters should be installed in areas where they are not exposed to extreme temperatures, excessive humidity or dust accumulation that can affect their performance and lifespan.

Working with a solar professional or certified installer is recommended to ensure that inverters are installed optimally and safely. If you have any questions please do not hesitate to contact the experts at Tienda Solar. 

How do I know what type of inverter I need?

Choosing the right type of solar inverter for your PV system involves considering several factors. Here are some steps you can take to determine what type of inverter you need:

- System size: Consider the number of solar panels you plan to install. In some cases, two or more inverters may be paralleled depending on the needs and size of the installation. As mentioned before, it is important to size the inverter power according to the power consumption and the expected use of appliances or equipment. 

- Panel configuration: If the solar panels are subject to partial shading or are oriented in different directions, power optimisers may be more efficient by optimising the individual performance of each panel. It is important to check the data sheet of the solar inverter, specifically the part referring to Input / Solar/ PV. This section indicates the maximum power of panels to be connected, the maximum MPPT voltage as well as the maximum panel/string current that each MPPT input can accept. In off-grid systems it is important to have sufficient solar capacity/power, especially for winter. With less solar resource we will need more panels to charge the same batteries in the same period of time. That is why when sizing a stand-alone solar system we should consider winter as the worst-case scenario and adjust the panel power and solar battery capacity accordingly. 

- Energy targets: Are you looking for the solar system to cover part or all of the consumption of the residence or house? Do you need an autonomy of 1, 2 or more days? If you have a back-up generator, the most usual thing to do is to reduce fuel costs and design an installation that provides the house with a relatively long autonomy. The autonomy will also depend to a large extent on the solar resource available at the location.  

- Budget: There are many types and brands of isolation inverters. It is important to be well informed about each one of them as it is a critical component. In the case of off-grid installations, it is even more critical because in the event of a breakdown we will be left without electricity supply as there is no back-up network.

- Monitoring and control: In the past, off-grid inverters did not have very sophisticated monitoring systems. However, more and more off-grid solar inverters have systems (via App) that allow you to control the state of charge of the batteries, the amount generated by solar energy and thus know when we can or cannot consume more energy. It is highly recommended to buy inverters that have the ability to monitor at least the basic parameters of battery charge status and solar generation. 

- Professional advice: Consult with a solar installer or an expert in the field. They can assess your specific situation and recommend the type of inverter that best suits your needs and conditions.

Remember that each system is unique, and the choice of inverter type should be based on your goals, installation conditions and specific requirements. A solar professional can provide you with accurate guidance and help you make an informed decision.

Again, the Tienda SolarTeam is at your disposal for any questions you may have.