Not all PV systems are the same. Basically, a distinction can be made between grid-connected and grid-independent (so-called island systems). Find out everything about the differences and the advantages and disadvantages in this guide.
First things first
Grid-connected PV system
Grid-connected PV systems are connected to the power grid. Electricity can be fed in and drawn from.
feed-in systems
Grid-connected systems that supply electricity both feed as well as from the Internet.
PV stand-alone system
island systems have no connection to the power grid. Energy is only obtained through self-generated electricity.
zero-feed systems
The electricity is self-consumed and not fed in. Electricity can still be drawn from the grid.
What is the difference between an off-grid system and a grid-connected PV system?
Both off-grid systems and grid-connected systems are ordinary photovoltaic systems - with small differences.
Grid-connected photovoltaic systems can convert electricity that cannot be consumed directly into the connected power grid. PV island systems, on the other hand, have no connection to the power grid and therefore cannot feed in electricity. Instead, they provide autarky of the respective operator and ensure its entire power supply.
A grid-connected solar system usually requires an inverter that converts the energy generated by the photovoltaic modules direct current to alternating current This is the only way to operate ordinary electrical devices and feed the electricity into the power grid.
Whether the power of an island system needs to be converted using an inverter depends on which devices are to be operated. For small island systems, directly consumes direct current.
To be independent of solar radiation, stand-alone systems require a connected power storage, which is controlled by a charge controller. It is important to ensure that the power storage unit is particularly cycle-resistant. Grid-connected systems do not automatically require a power storage unit.
| feed-in system | zero-feed system | island systems | |
| connection to the public power grid | Yes | Yes | no |
| power supply | Yes | no | no |
| electricity supply | Yes | Yes | no |
| electricity storage | optional | Yes | Yes |
| inverter | Yes | Yes | optional |
Grid-connected systems
Grid-connected photovoltaic systems include all systems that are connected to the power grid. A distinction is made between feed-in systems and zero-feed systems.
The feed-in system
A feed-in system is a photovoltaic system that uses the solar power generated and not directly consumed to the public gridThe house is connected to the public grid and any surplus electricity is fed into it.
Feed-in systems represent the majority of private photovoltaic systems on roofs. These solar systems combine two advantages of generating electricity from sunlight:
- On the one hand reduces self-consumption of the electricity generated energy costs of the household.
- On the other hand, the feed-in of the excess electricity income be generated.
For an average family will be around 30% of the solar power generated is consumed directly. remaining 70% are fed into the grid. With the help of an electricity storage system, the self-consumption up to 75% be increased.
A disadvantage of feed-in systems is the cost, caused by the connection to the networkFurthermore, the network operator must be billed using calibrated meters and the user’s own consumption must be recorded in order to determine the corresponding amount of feed-in tariff per kWh to be able to determine.
The zero feed-in system
A zero feed-in plant is connected to the public power grid, but produces no excess solar powerThis is consumed by the operator himself and not fed into the grid. A zero feed-in system is particularly suitable for homeowners who have a high self-consumption have.
An important prerequisite for zero feed-in is the electricity storageThis stores the excess electricity to at night or to cloudy days to ensure the energy supply. The inverter, on the other hand, continuously adjusts the output of the PV system to the current consumption.
As with a feed-in system there is a connection to the power grid. However, in a zero feed-in system, this is not used to feed in electricity, but only to cover peak consumption with purchased electricity to balance.
Such a system is particularly advantageous when there is high electricity consumption. In addition the costs of feeding in the electricity are eliminated such as calibrated meters etc.
The disadvantage of such a system is the lack of earning opportunities and poorer scalability to name.
The photovoltaic island system
One PV stand-alone system operated independent of the power grid, as it is not connected to it. It therefore ensures the complete power supply of the respective consumer. Island systems are often used when a connection to the power grid not possible or too expensive is.
To a degree of self-sufficiency of 100% To ensure this, the power storage unit must be dimensioned accordingly.
Island systems offer the great advantage that they can ensure power supply even in remote locations. Remote mountain huts, electronic street signs or parking ticket machines are examples of areas where island systems can be used. They can also as an emergency power generator function.
Another advantage is that the costs for the grid connection and electricity meter are saved.
The disadvantages are the lack of earning opportunities, as the feed-in tariff cannot be claimed. In addition, island systems are mostly more expensive than grid-connected systemsThis is due to the larger dimensions of the storage, which results in correspondingly high costs.
Feed-in system, zero feed-in system, island system?
Grid-connected PV systems are connected to the power grid so that the unused electricity can be fed into the grid or consumers can draw electricity from it. Grid-connected photovoltaic systems can be used in feed-in system and zero-feed system be divided into.
feed-in system are photovoltaic systems that can feed the surplus electricity into the public power grid orthe lack of electricity The majority of PV systems on German roofs are feed-in systems.
zero-feed systems are connected to the power grid. However, they do not produce any excess electricity that could be fed into the grid. This is consumed by the energy used. Consumers do not have to feed-in tariff, but also have fewer associated obligations. In case of shortage, electricity can obtained from the network become.
An island system is not connected to the public power grid. The electricity can neither be drawn from the grid nor fed into it. The household is solely dependent on the from the solar modules produced electricity. Island systems absolutely require a solar storage system.
