An inverter buyers guide

CMS inverter

Whether you live off grid or have a grid-interactive generation system, the right inverter can make all the difference. We check out what’s available, where to get them and which one is right for you.

One of the most important components in a 240 volt renewable energy system is the inverter. In stand-alone systems, this is the device that converts the DC electricity from the battery bank into 240 volt AC mains power* to run standard appliances. In grid-interactive systems, this device converts the energy from solar panels into mains power and feeds it into the house’s electrical wiring.

It is important to have a good inverter—if your home relies solely on 240 volt power from a stand-alone inverter and the inverter fails, you will have no power, even though it is still being generated and stored.

Inverters are divided into two main types depending on the type of power they provide—modified squarewave and sinewave.

Modified squarewave inverters (sometimes referred to as modified sinewave to make them sound better!) are the cheaper of the two, but some appliances (such as VCRs, TVs and computers) may not run as efficiently using this type of power, and some may not run at all.

Sinewave inverters, on the other hand, provide the same type of power as the mains grid. Indeed, the power from a good quality sinewave inverter will usually be of higher quality and have better voltage stability than power from the grid.

Modified squarewave inverters are becoming rare in renewable energy systems as the difference in price between the two types steadily reduces, so in this guide we only look at sinewave inverters.

Independent or grid-interactive?

Sinewave inverters themselves can be divided into three broad groups—grid-interactive inverters, stand-alone units, and inverter-chargers. There is also a fourth type—sometimes called a hybrid inverter—that combines both grid-interactivity with the ability to take energy from and put charge into a battery bank.

Grid-interactive inverters are connected to both the power source (usually a solar array but sometimes a wind or hydro turbine) and the mains power grid. Power generated by the energy source is converted to AC mains power of the correct voltage and frequency, and fed directly into the grid. This supplements the power drawn from the grid by the home’s appliances. At times there will be more energy generated than being used and the excess is fed into the mains grid. At these times the power meter may actually run backwards (this will depend on the agreement with your power company and the types of meters they use). In effect, the system is using the mains grid as a battery bank.

Read the full article in ReNew 122

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