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what is Difference Between On-Grid and Off-Grid Solar power Systems?
Many people want to install a solar system, but they don't know what is a grid-connected solar system and an off-grid solar system,
So before installing a solar system, we need to know which solar system meets our needs.
The Difference Between On-Grid and Off-Grid Solar power Systems
1. The on-grid solar power system must be connected to the public grid. The solar power system is connected with the home grid and the public grid. The solar system must have the public grid to operate. It is mainly composed of solar panels and grid-connected inverters. The solar panels are directly converted into 220V AC by the inverter and power household appliances. When the power generated by solar energy exceeds the electricity used by household appliances, the excess electricity will be sent to the public power grid; and when the power generated by solar energy cannot meet the needs of household appliances, it will be automatically supplemented from the power grid. And the whole process is intelligently controlled and does not need to be turned on or off by people.
This ON-grid solar system saves costs because it does not use batteries, and the excess electricity can be sold to power companies. From the long-term perspective of investment, the cost can be recovered and there is a possibility of profit in a few years. Therefore, if you want to save electricity bills and stabilize public power, you can choose grid-connected solar power generation systems.
However, grid connection also has disadvantages, that is, when the public grid is out of power, the solar photovoltaic power generation system cannot operate.
2.off-grid solar power generation system, also known as an independent solar power generation solar power system, is a system that operates independently without relying on the grid. The electricity generated by the solar panel directly flows into the battery and is stored. When it is necessary to supply power to electrical appliances, the DC current in the battery is converted into 220V AC by the inverter. This is a repeated cycle of charging and discharging. This kind of power generation system is widely used because it is not restricted by the region. It can be installed and used as long as there is sunshine. Therefore, it is very suitable for remote areas without power grids, isolated islands, fishing boats, outdoor breeding bases, etc. Emergency power generation equipment in the area.
Because this kind of system must be equipped with batteries, the total cost will be more expensive about 30% than grid-connected.
It is also very practical for families in areas without grids or areas with frequent power outages. Especially in order to solve the lighting problem during power failure, DC energy-saving lamps can be used, which is very practical.
Therefore, off-grid solar power generation systems are mainly used in areas without grids or areas with frequent power outages.
How to choose the battery in the off-grid system
At present, most off-grid solar systems use lead-acid batteries or colloidal batteries. The following are the differences between the two batteries we have sorted out for you. You can choose the appropriate battery type according to your budget and needs.
Ordinary battery comparison chart:(If the solar system needs to use lithium batteries, we will have a separate article to introduce)
|
Item |
Lead-acid battery |
Gel battery |
|
Structure and performance are different |
1. The electrolyte is adsorbed in the porous glass fiber separator and must be in an unsaturated state 2. Less electrolyte 3. The electrolyte is liquid, and liquid acid is easy to flow out during use 4. Large self-discharge, shortening life 5.The floating charging voltage is relatively high, the floating charging current is large, and it is easy to heat up 6.Poor cycle performance, sulfuric acid solution is prone to crystallization and short circuit during deep discharge |
1. The electrolyte is fixed in the form of colloid, which can fill all the spaces in the battery. 2. The electrolyte is 10%-20% more than lead-acid batteries 3. Electrolyte gel, no leakage and no atomization 4. Self-discharge is 10% of lead-acid battery, good storage performance 5. Low floating charging voltage, long floating charging life 6. The cycle performance is good, and the deep discharge will not form a crystal short circuit |
|
advantage disadvantage |
1. There is memory in the discharge low-voltage area 2. Short battery life of 4-5 years 3. Relatively high conversion efficiency 4. Cheap price 5. The charging-free storage time is 4-6 months |
1. It can be deeply discharged, and the battery life is long for 6-12 years 2. Strong ability to restore capacity 3. The price is 10% more expensive than lead-acid batteries 4. The storage time without charging is 12 months |
What to pay attention to when connecting the battery
1. Make sure the voltage connected to the solar panel is the same as the rated voltage of the solar controller/solar hybrid inverter
2. Confirm the solar inverter or solar hybrid inverter DC voltage
3. After confirming the above voltage, connect the batteries in series or in parallel
4. Choose a suitable battery connection cable. The battery cable should not be too small, as it will easily generate heat, and it should not be too long to reduce internal resistance.
The selection calculation method of the battery line is as follows:
For example:SWN 48VDC3KW inverter
The power of the inverter/the minimum voltage of the battery=3000W/42VDC (the minimum voltage of a single 12V battery is 10.5V*the number of 4=71.4A
1 square battery line can pass 6A current, so the size of the battery line: 71.4/6=11.9A can be used if you choose a battery line larger than 12 square meters
5. When the battery pack is connected to the solar controller/solar hybrid inverter, a DC switch needs to be added to ensure that the battery system is safer
6. The screws need to be tightened when connecting the battery pack to prevent short circuit or open circuit caused by poor contact.