Should a larger solar system be installed?
Some people say that the bigger size of solar system we have, the more generation from it. No, it’s not much more correct. This result may be different from what you imagined when you check the PV generation data on your APP or other monitoring software.
When you look at the power generation data, you will find why the curve is not always peaking, but high and low, even sometimes directly to 0.
This phenomenon is commonly referred to as curtailment.
Correctly estimating the power consumption is necessary
At this time, plenty of sunlight outside shouldn’t show the curve like this. Of course, clouds will block it and cause a bit poor power generation. But we’re not talking about the weather, but curtailment.
curtailment means solar power is suspended or stopped exporting to the grid due to overloading. The voltage generated by the solar system is higher than the voltage of the external grid, the excessive solar power has nowhere to go. So your inverter will automatically turns off and on intermittently to balance between PV generation, consumption and export grid.
For example, a three phase household can be allowed maximum 15kW export. And meanwhile, the family has a heated swimming pool that consumes 5kW energy, so a total of 20kW power’s destination has been determined. This customer can choose 10~15kW inverter.
The extent to which your rooftop solar system might be curtailed depends on several variables, including the capacity or strength of your local electricity network and whether your neighbours also have rooftop solar panels. If every house has solar, it’s likely that every house has curtailment, and If you’re in a rural area with a lot of solar, then you have the potential to be curtailed.
But in the end, after the 15kW system is installed, the extra is likely to be wasted. That is, the extra can neither be output nor consumed, so it will be derated. In other words, after disconnecting from the panel, this extra electrical power does not actually exist because no electricity produced. You will see peak power at 15kW instead of more.
Another extreme example is the widespread power outage caused by the storm in South Australia. SA’s grid disconnected from National Energy Market (NEM) and became an island. Excessive solar power generations can easily lead to grid capacity overload, making the grid unstable and at risk. According to the voltage principle, the power generation of your home will also be derated up to zero even if you have not been turned off the inverter in emergency remote disconnect.
