What is an Inverter?

Have you wondered what is an inverter and how it works? You have come to the right place. The use of inverters has become mainstream with the widespread installations of solar panels. If you have solar panels at home you do have an inverter of some sort. The inverter is a device which main function is to convert DC (direct current) to AC (alternating current) and vice versa. It is because solar panels generate direct current but our home appliances use alternating current.

Conversely, it can convert DC to AC. This is necessary when you have battery storage at home to store your energy from renewable energy sources (solar, wind etc.) for later use. Because battery storage systems can only work with DC, you need an inverter to convert that DC back to AC so that it can be used in your home sockets. It gives constant AC voltage at its output socket when the main power supply of AC is unavailable. Read on to learn how it makes this possible.

How Does an Inverter Work?

An inverter’s job is to provide your house with a constant supply of 110/220V alternating current from your renewable energy source (e.g., solar panels) or batteries. It can also function as a power backup in case of power outage. There are a number of circuits/systems in an inverter that allow it to perform this task.

The DC-AC converter is a key component of a power inverter. When the mains power is available, the battery is charged via the charger circuit and the inverter section stays on standby. The inverter basically consists of an inverter transformer and an oscillator. The inverter transformer generates the alternating current which is then superimposed by the oscillator circuit generating a waveform of around 50Hz.

Diagram of how an inverter works within a solar panel system.

The direct current from the battery is first converted into alternating current via the DC-AC converter. The initially converted alternating current is at low voltage, which is then converted into 230-volt alternating current via a step-up transformer. The efficiency of an inverter depends on the performance of the step-up transformer and the oscillator as the voltage and frequency in the output depend on these two components of the inverter.

Also Read: How Do Solar Panels Work?

Battery Capacity and Inverter Efficiency

The battery that provides direct current for the inverter is the backbone of this entire system as its efficiency directly depends on it. The backup time of an inverter varies depending on the capacity of the battery. In other words, the inverter can supply your home with electricity as long as there is enough energy in the battery.

Most domestic inverters come in different ratings. They are specified in terms of Volt Ampere (VA). The common inverters come in 500 VA, 1000 VA, etc. Battery capacity is represented in Ampere hour (Ah). It is the battery’s ability to deliver the amount of current in Ampere for an hour.

Many inverters feature maintenance-free batteries as they require minimal attention. They do not require water topping as it used to be the case in the past. Battery technology has made great strides in the last decade. Lead batteries used to be in wide use. However, its bulkiness coupled with low capacity and power output, have made them virtually obsolete.

Nowadays, lithium-based batteries have replaced them in today’s energy hungry world. Lithium batteries have a number of benefits including high energy capacity and high-power output while being completely maintenance-free. Their lifespan is also longer compared with the Flat Lead plate batteries.

The Difference Between Pure Sine Wave and Modified Wave Inverter

Now that you know the answer to “what is an inverter?” and “how does it work?”, it’s time to elaborate a bit on inverter categories. Pure Sine Wave and Modified Wave are two main categories of inverters. A pure sine wave inverter offers high-quality supply of electricity that is either better than or equal to the electricity provided by a utility company to a home. Pure sine wave inverters are ideal for powering expensive electrical appliances or medical equipment as they ensure that the appliances do not get damaged and work best for their specific ability.

Modified sine wave inverters, on the other hand, provide a lower form of electricity. It is relatively lower than what you would find at home. These inverters produce a sine wave that is suitable for about 80% of appliances – 18V tool charging, hairdryers, microwaves, vacuums, fridges, laptops/computers, TVs etc., are all suitable loads. In short, modified sine wave inverters are safe to power most electrical equipment and are a good choice when using them for occasional/leisure use.

Inverters are made of transformers and oscillators to convert DC/AC electricity.

Types of Inverters Available on the Market

There are three primary types of inverters available on the market. These include grid-tied, off grid, and hybrid.

Grid-tied Inverters

Grid-tied means your inverter, along with your solar panels, are tied to utility grid (Your energy provider). This is what most homes use because with it you are covered in case your PV solar system under- or over-produces according to your changing energy needs. Simply put, when you use a grid-tied inverter, your utility grid acts as your battery space.

If you generate more energy with your solar panels, the excess energy is sent to your local power company, resulting in a credit that you can cash out at the end of the year. This is commonly known as net metering. Grid-tied inverters are beneficial as you do not have to purchase a battery back-up system to store any excess energy. However, without battery storage to save your energy for later use, you will have to rely on the grid at night and probably on cloudy days as well.

Off Grid Inverters

Being off-grid means you are not connected to your grid’s energy provider in any way. Off-grid inverters are an attractive option as you are fully independent and manage your own energy usage. However, going fully OFF-GRID means there are some important things to think about. First you need to make sure your renewable source of energy produces enough energy to satisfy your needs. That might mean installing a bigger system in case of unfavourable days of energy production.

More importantly, you will also have to purchase a battery storage system to fill in the gaps when you are producing no or little electricity. In case you have PV solar panels, this is on cloudy days and at night. Depending on the manufacturer, battery storage systems can be pricey. You should take into account all the costs before you decide to go fully OFF-GRID.

Hybrid Inverters

Hybrid inverters combine both the concept of grid-tied and off grid inverters together for an easy “plug & play” solution. The goal with this specific type of inverters is to help minimize your peak energy consumption during the day. Hybrid inverters are designed to store excess energy into batteries and whatever is not used either by your property or batteries goes back to the utility grid. The cost efficiency of solar + batteries make sense as more and more utilities are nowadays shifting toward on-demand pricing framework.

Applications

The answer to “what is an inverter?” may imply that these devices are only used in solar systems to provide constant, usable electricity in a home when the main power supply of AC is unavailable. However, that is not the case. There are many applications of inverters in today’s world. These include (but not limited to) the following:

• UPS or Uninterrupted Power Supply uses the combination of a battery and inverter to supply constant AC power.
• Inverters are a key component of a solar power system. Since the solar PV panels generate direct current, an inverter is required to convert it into usable AC electricity.
• Inverters are used to charge batteries from the utility grid at cheaper rates and use the stored energy later when the cost per 1kWh is higher. This is often called peak shaving or grid balancing.
• Inverters are also used in the compressor of air-conditioner and refrigerator. When using an inverter, the compressor is able to utilize the variable frequency drive (VFD) to control the motor speed and hence, how cooling is done.
• Inverters are also used to control the speed of an electric motor. Since inverters generate variable output voltage, controlling that voltage allows you to control the speed of the electric motor.