All the electricity produced by the solar panels is produced as direct current (DC), which differs from the electricity that is distributed through the grid and we use in our homes, which is alternating current (AC). For this reason most solar photovoltaic systems are now connected up with some type of inverter, which changes the DC to AC, allowing the individual to sell the electricity back to the grid (in grid-tied systems) or to be used easily in homes.
There are 2 major types of inverter that can be installed in your solar photovoltaic system:
These are used in grid-tied systems where the solar panels are wired together in series, which is known as a string of panels. Each string of panels is connected to a string inverter, which converts the DC current to AC for use in the home and selling back to the grid. You can imagine each string as a mini power station, producing electricity.
The main issue with string inverters is that if one of the panels in the string fails or produces less electricity (from things like shading), this impacts the output of all the panels. They will all operate at the output of the worst panel, so a small amount of shading or debris on your solar array can disproportionally reduce the total output of your entire solar photovoltaic system.
They also have relatively short lifespans when compared to micro inverters.
The benefits include simple wiring and that you can use thinner wires within your solar PV system, so less copper is used which makes the system cheaper. Buying one string inverter (which is normally the case of most home solar PV systems) is also considerably cheaper than buying multiple micro inverters.
These are a newer technology and service each solar panel individually, so each panel requires its own micro inverter and acts as an individual power station. As a result, micro inverters do not suffer the same performance reduction as a result of shading because any power reduction in a particular solar panel is handled by one micro inverter, having little effect on the combined power output from the entire solar photovoltaic system.
Micro inverters are much more expensive than the string inverters. However much of this cost is offset by the increased performance (25% more power produced using micro inverters) and the fact that they are more reliable than string inverters (warranties for micro inverters are up to 25 years).
When looking for which inverters to buy, ideally you want your alternating current (AC) to match that provided by the utility companies. Waveform relates to the quality of the AC signal that an inverter produces. Cheaper inverters will provide modified sine wave signal, while the more expensive versions will produce the pure sine wave signal. Some appliances (such as computers) simply don’t work unless they are powered by a pure sine wave signal, so we recommend strongly that you spend a little more to get this type of inverter.
Grid tie inverters differ slightly from your regular inverters in that the AC pure sine wave signal has to be perfectly coordinated with the waveform from the grid. As such, these tend to be more expensive than the typical inverters that you buy. They also have a built-in safety feature to cut off power from the solar array if the electricity grid goes down for any reason.
It is also worth noting that most inverters now also have ‘Maximum Power Point Tracking’ (known as MPPT) installed within them, which helps to maximise the electrical output of your solar photovoltaic array system.
The principle of MPPT is to extract the maximum available power from the photovoltaic module by making them operate at the most efficient voltage (known as the maximum power point voltage). The algorithm included in the MPPT inverter compares the output from the photovoltaic module with grid voltage and then fixes it at the most efficient voltage, to allow you to export the maximum amount of kWh of electricity back to the grid. An MPPT charger in your solar photovoltaic system will improve your power gain by 20-45% in the winter and 10-15% in the summer.
Synergy recommend SolarEdge Micro Inverters as the leading manufacturer of cutting edge solar technology.
If your inverter is out of warranty now is the time to start looking at replacing it, contact us for a no obligation comparison.