Photovoltaic (PV) power cells produce continuous direct current (DC) power, so when a photovoltaic solar system is required to connect to the mains electricity grid, or contains an alternating current (AC) load, a DC to AC conversion of the electrical power is needed. Solar power inverters provide DC to AC conversion using electronic switching techniques. A solar power inverter is an electronic device that converts the electrical power generated by the PV solar array into AC power supply that feeds directly into the power grid. The purpose of using a solar inverter is that it converts the low input voltage into a higher conventional household AC mains power supply of the right voltage and frequency, so you can use your electrical appliances when an AC mains electricity supply is not available.
When it comes to renewable energy, solar inverters convert DC battery/solar panel voltage into mains type AC power, perfect for use in your home or business. Without this conversion, special appliances or adapters will need to be purchased, and DC appliances are usually more expensive than their AC counterparts. A solar inverter is an integral part of the system, and you can have the best solar panels out there, but if the solar inverter is not a high quality one, it can have an impact on the system performance.
To put it simply, the inverter allows you to run computers, mains lighting, vacuum cleaners, and other electrical appliances that can be plugged into wall sockets. If you buy a solar power inverter big enough, then you can use it to run refrigerators, freezers, washing machines and other large appliances. All the standard 120- or 240-volt AC appliances can be powered directly from the PV solar array, or by converting the power stored in the batteries using the correct size power solar inverter. The output power of an inverter is available at any time and allows the stand-alone battery systems to function 24/7.
Types of Solar Inverters
The following are the three main types of solar inverters and their characteristics. Some differences may be subtle, but they’re significant in the way they function.
Square Wave Solar Power Inverters
These are the cheapest inverters on the market as they run just simple things like tools with universal motors. They’re less produced lately, and there are very few available.
Modified Sine Wave Solar Power Inverters
A modified sine wave has a waveform like a square wave, but with an extra step. A modified sine inverter can power most types of electrical and electronic loads, but may present certain compromises when it comes to computers, laser printers, digital clocks, cordless tool chargers, microwave ovens and more. Refrigerator motor, pumps, or fans will use more power from this type of inverter due to lower efficiency. Also, some fluorescent lights may not operate quite as bright, and even make a noise or a low frequency background buzz. The same can happen with some audio amplifiers and radios. The modified sine wave is noisier and rougher than a true sine wave.
True Sine Wave Solar Power Inverters
This type of inverters produces a high quality AC voltage waveform with low total harmonic distortion (THD). These are known as digital inverters, too, and are designed to replicate and improve the quality of electricity supplied by utility companies. For electronic equipment, stereos, printers, copiers and more, experts recommend a sine wave inverter. They’re required as standard by most electrical utility companies as of a grid connected PV solar system. Sine wave solar power inverters have a higher cost than other types of inverters, mainly due to their better internal electronic circuits. They can operate almost anything that can be connected to the local grid and are very efficient.
For off-grid applications, look for a high quality solar inverter that includes an auto-start system that will allow the inverter to switch to a low power consumption standby state when there is no appliance connected or turned on. That will save you from manual switching all the time, but will save you wasted power as well. Then check if it’s able to adjust parameters such as auto-start and battery depth of discharge, which is quite helpful for off-grid systems. Also, it needs to have a high efficiency transformer.
Solar Inverter Ratings
Depending on the type, there are a few different solar inverter ratings, such as the following.
Continuous Power – That’s the amount of power you can use continuously, and will not cause overheating and shutting down of the invertor.
Half Hour Rating – In case the continuous power is too low to run a high energy consumption appliance, it can use the half house rating, especially if the appliance is for occasional use only.
Surge Rating – To start some appliances, a high surge is needed and once they start running, they may need less power to keep working. Such items are TV and refrigerator, they require a high surge to start, but low power when they’re functioning. The inverter should be able to hold the surge rating for minimum of 5 seconds.
IP Rating – This stands for the ability of the inverter seals to prevent water and dust ingress. Some IP ratings are suitable for outdoor installation, but keep in mind that the quality and location of the seals, as well as ventilation, can affect the longevity of the inverter.
Peak Efficiency – This is the highest efficiency of the inverter.
Benefits of Using True Sine Wave Solar Inverters
A true sine wave solar inverter gives ‘clean power’, the same as the pure AC you receive from your electric utility company. Most of the appliances that you use at your home are designed to function this type of power coming from power stations, so a sine wave inverter makes a great fit.
Sine wave inverters have a very low or no distortion at all. Simply put, that means there is no waste energy. They provide high efficiency and help in reducing electricity bills.
Safe Levels of Voltage
A pure sine wave inverter maintains voltage levels around 230V, which is perfect. That way it prevents crashes and your sensitive appliances are safe.
Higher distortions cause humming noises and buzzes in running appliances. Since there are fewer distortions in pure sine wave inverters, your appliances will be running without any noise.