Safe working and string vs micro-inverters
Working on PV installations and safety
As mentioned earlier, we strongly recommend having a basic knowledge of electrical installations or getting assistance from someone who has that knowledge if you are a self-installer. It is not rocket science, but after all, you are working with high voltages and DC currents, solar panels do not have an on or off switch. You will also need to have your installation inspected; we ourselves work with OCB for inspections.
Some important safety matters:
-Currents can only flow when the circuit is closed. So never work on a PV installation or the wiring with a closed circuit. Always switch off the inverter.
-Never just unplug connectors on a working installation to avoid an arc and damage.
-Ensure that the connections are technically sound, so use quality materials.
-Don't forget to set the country setting of your inverter correctly.
A brief explanation about PV systems:
Series connection or string system: keep it simple, stupid?
A series-connected system is also called a string system. A series-connected system has traditionally been the most used system. Most solar panels provide only a limited voltage (about 30 to 40 volts). That is not enough to start a large inverter. On the other hand, the same panels provide a fairly high current. This high current combined with the low voltage causes a lot of loss in the cabling or requires much thicker cables. A simple solution was to connect the panels in series. The voltage adds up, the current remains the same.
The simplicity and relatively low purchase price can be a big advantage regarding the profitability of your installation. The inverter is usually the weakest technical point but is easy to replace if defective.
The main disadvantage is that in a series connection, the weakest link affects the entire string. This means that if one solar panel produces less power than the others or fails, they all suffer from it. When part or even just one of the panels is in the shade for part of the day, a series-connected system may not be the best choice.
With optimizers and/or an inverter with multiple MPPTs, this problem can also be addressed, but this obviously results in a higher cost.
Parallel-connected system
A parallel-connected system is a system with micro-inverters such as those from the brand Enphase.
Behind each solar panel, you place a micro-inverter that converts the approximately 40 volts from the solar panel directly into 230 volts AC. These micro-inverters are connected in parallel on a collection cable carrying 230 volts. The voltage remains the same, the current adds up with each new micro-inverter you connect.
The advantage is that each panel can independently deliver its power. Shade, dirt, or defects do not affect the rest of the system. If one panel breaks, the other panels continue to deliver maximum output. If one inverter breaks, the others continue to do their work.
The yield is typically higher than that of a series-connected system. Additionally, micro-inverters turn on at a lower voltage. In the morning, the system starts up earlier and in the evening it turns off later.
In the monitoring app, you have insight into the system's performance, but also into the performance of each individual solar panel. A defect or problem is quickly found.
Useful links:
-Enphase calculation module to determine if and with which micro-inverter your PV panel is compatible:
https://enphase.com/en-in/installers/microinverters/calculator?_ga=2.66158695.872681191.1696105335-875767476.1696105335
-Calculation of profitability, cable losses, etc. of your PV project:
https://www.sunnydesignweb.com/sdweb#/
