What is an inverter?

The inverter is the piece of equipment which lies at the very heart of your solar PV system. It’s an intricate, delicate workhorse. So what exactly does it do and why is it so important?

Simply put, the inverter converts Direct Current (DC) electricity into Alternating Current (AC) electricity. This is necessary because many of the appliances used in our homes run on AC.

AC vs DC

Getting back to basics, you probably know from all those physics classes that electricity is the flow of electrons through a conductor, usually metal wires. 

There are two main types of electrical current that concern householders. DC and AC. The main difference between AC and DC currents is the direction that the electrons move in.

In a DC current, the electrons move from a negatively charged zone to a positive charge area without any change in its direction. The DC current stays at its maximum voltage and continues in a straight line. If examined through an oscilloscope, a DC current would look flat, like this:

©elevise.co.uk

The electricity generated by the solar panels in a PV system is DC. 

Direct current is mostly used for devices which run on batteries. For example, mobile phones, TVs and laptops. Basically anything which has a transformer plug.

Alternating current is the current that is supplied by our mains electricity providers from the grid to our homes. AC means that the electrical current constantly changes direction. Seen through an oscilloscope, the electrical wave of AC looks like this.

©elevise.co.uk

In an AC state, the current constantly switches (or alternates) between positive and negative. This is useful for powering electric motors, which convert electrical energy to mechanical energy. Home appliances which use AC include toasters, hairdryers, washing machines, dishwashers, fans and fridges.

The UK mains supply is about 230 volts and has a frequency of 50Hz (50 hertz). This means the current changes direction and back again 50 times a second. Some of the reasons why AC and not DC is used in our homes are as follows:

• AC is better for transporting current over long distances. DC voltage starts to lose energy fast over even short distances. Therefore DC is not as efficient.
• DC creates more heat due to the greater power loss compared to AC. This can cause fires.
• AC is safer than DC at an equal voltage in case you come into accidental contact with the current.

Therefore, an inverter is an absolutely crucial piece of kit in a solar PV system because without it:

• You could only store your solar energy in a battery, which can only be used to power DC powered devices; and
• Any AC appliances powered using DC solar energy are liable to become damaged because they are not designed to be powered by DC.