At SUN VALO, we have noticed there is some confusion about Solar systems and what they do, so here is a simple explanation of what each can and cannot do.
GRID CONNECTED SOLAR SYTEMS (ON GRID)
A grid connected solar system is a solar power plant that is connected to the electricity grid. It uses solar panels connected to an inverter, which then feeds into the fuse box in the house. The system by law must be connected AFTER the smart electricity meter, so that the meter can register power in and power out of the house. The solar system feeds power directly into the house and any excess is registered by the smart meter and fed into the grid. It should be noted that you need someone to buy your excess electricity, certainly in Finland.
If there is a power cut, the system automatically shuts down for the safety of any electricity repair engineers. You will lose the power in your house, but when the power is restored, the inverter detects the connection to the grid and switches back on automatically.
We are able to monitor the production of our own system as well the consumption of the house. We choose to use as much of the generated power ourselves by using the dishwasher, washing machine or any other loads while there is power being generated. We also have what is known as “Directing” to the hot water – This is programmable to switch the hot water heater on at peak sunshine hours and above a certain solar power kW level. The directing can also be used to help charge an electric car, or certain other high demand devices.
This is pretty much the most popular system on the market however, Grid connected hybrids (battery ready and full battery systems) are gaining pace.
GRID CONNECTED HYBRIDS (ON GRID)
Now available on the market are “battery ready or battery connected” systems.
Again, solar panels feed an inverter, inverter feeds into fusebox, but the inverter also charges lithium batteries, the charging preferences of which can be controlled by the user through one of the many apps now available.
Á full backup battery system (battery connected) operates like this. In the event of a power cut, the solar system and batteries can carry on powering the house. There must be a fail safe changeover switch that automatically detects a grid failure which shuts down the inverter and restarts it in “island mode” (Island mode means that the system is completely isolated from any grid connection, while still suppling electricity to the house) When the grid is restored, it again shuts down the inverter and changes the system back to the grid connected mode.
A “battery ready” inverter can be installed first, allowing batteries to be added at a later stage. Some battery ready inverters are able to offer the equivalent of a standby power supply for a limited time even without batteries. The inverter can supply a single phase, single power socket with mains up to 3kW. IT IS VITAL that this single socket is completely separated from the mains system of the house and is marked as a Solar power supply and that in order to isolate that socket, the customer must be aware that the solar system needs to be completely shut down.
OFF GRID SOLAR SYSTEMS
As the name implies, these systems do not connect to any mains grid, making them suitable for places where there is no mains electricity available, e.g. summerhouses. The solar panels charge the batteries via the controller/charger/inverter and can provide a limited mains supply to the house. Sizing a system needs quite careful planning and the user must be aware of how much they can load onto the system at the same time. LED lighting is recommended on these installations, as they really do consume the least amount of electricity for the amount of light they give off.
If there has been no sun for several days, the batteries will discharge depending on the loads they have to run so again, quite careful planning is needed to size the system to the household needs.
We hope that this clears up confusion, but do feel free to contact us for more information.