Electricity types
There are two types of electricity – alternating current (AC) and direct current (DC). These two terms describe the way in which the current flows in a circuit. In a DC circuit, the current only flows in one direction, meaning that they have a constant positive (+) and negative (-). This relationship of positive to negative charge is referred to as polarity. In an alternating current circuit, current flow changes direction regularly, switching the polarity (positive (+) and negative (-)) each time. This back and forth switching of polarity in an alternating current circuit is reffered to as frequency and is measured in Hertz (Hz).
Each one has different characterstics that make it useful for certain applications. Nearly all electronic devices run on DC as does anything that uses a battery without an inverter as batteries can only store energy in DC form. Cell phones, radios, televisions all run on TV internally, meaning that if they are connected to the grid or an inverter, they will use electronics to convert the AC to DC. Why not just use direct current for every circuit then? AC has important properties that make it useful in the electrical grid. It is cheaper to transmit AC over long distances as it is easier to change between high and low voltages. High voltages are ideal for long distance transmission as they require less current, which means you can use smaller wires.
All PV systems include DC as PV modules can only produce DC. Many small scall systems are DC only and work well for lightning and the charging of small electronic devices like cell phones. Larger systems require an inverter to convert from DC to AC. In any electrical system, whether AC or DC, the different components must be capable of handling the vol
The two have different characteristics and are therefore useful for different purposes. All systems with storage will use direct current because that is the form in which batteries store energy. If a PV system will operate will provide alternating current for appliances or lights, than an inverter will have to be installed. For all components of a PV, whether appliances, lights or system components - they must be compatible in terms of type of electricity, voltage and frequency. Improperly matched or rated equipment can fail causing injury to users or property.
