Inverters

Inverters are different in reality and common usage!

Definitions

Inverter

An inverter changes DC power to AC power. Literally that is all. The opposite is a rectifier, that changes AC power to DC power. Since all solar power, from panels, is DC, and virtually all appliances are AC, power needs to be inverted.

Transformer

Changes one voltage (e.g. 12V) and amperage to another voltage (e.g. 250V) and amperage. Since most solar panels are 12V or 24V, and all appliance in Zimbabwe are 250V, this also needs to happen.

Usage

However, it has become common in Zimbabwe, and worldwide in solar applications to use the term “inverter” to indicate the whole unit that includes inverter, transformer, and often charge controller.

It is also important to note that DC power does not travel down lines well, while AC power does. The national grid would not work on DC power. Solar panels need to be fairly close (±less than 30 meters, depending on application) to the "inverter" to avoid power loss.

Types

A Grid tie inverter.

This is between the national grid and your solar panels. There are no batteries. It will have a bidirectional meter (so you pay when using, you are paid when producing). It also connects you solar panels to your appliances. When the sun is out, you are running your things, and selling to the national grid. When the sun sets, you are buying from the national grid to run your things. A great way to be ‘green’ and reduce costs.

Oﬀ grid inverters.

Probably the most common solar inverter in Zimbabwe. Your interface between your panels and batteries, and the grid. When there is no grid power, it will use your batteries, which it will charge whenever there is sun. And they (most) can be set to use from the solar panels when they are producing, and not the grid. Settings should be there to say when above XXvolts, use panels/ batteries, when below, used national grid power.

Hybrid inverters.

Connected to the grid, panels and batteries. And they can be set to send excess power back to grid.

Brand

As is true with many to most things, you will get what you pay for. Get as good a brand as you can aﬀord. And you will pay for the better brands. And various installers and salespeople will swear by some and NEVER use others. So get as many opinions as you can. And ask intelligent questions. To use a vehicle analogy, not everyone needs to pay for a Rolls Royce, and some Mahindra brands are very good. Moreover, it is a fast moving industry. In the ‘70s, Renault R4s, Datsuns, and Toyotas were looked down on. But not today.

Size

Inverters are classed by size. How much power they will produce with ‘sufficient’ battery and / or panels charged and attached. They range from 120W (VA) for little things (hair clippers), through 1500VA – and fridge and (sometimes both) or a freezer, to 5kW (5000 Watts, or Volts x Amps = VA) inverter, to 20 and 30kVAs – you will not even notice power cuts.