Solar battery storage for photovoltaic

For both environmental and economic reasons, PV systems enjoy great popularity, even though the feed-in tariffs for solar power have fallen drastically over the past years. For this exact reason, it is worth thinking about purchasing a storage system for the solar power generated by PV. Storage systems for PV enable efficient storing of solar power produced. This enables inexpensive own consumption at any time of day or night and increases energy autonomy from the public grid. In addition to our own PV mounting system, we stock PV components from leading manufacturers such as AEG Industrial Solar, SMA, KOSTAL, FRONIUS, SAJ or BYD.

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What is the purpose of a solar power storage system?

This component of the photovoltaic system is used to store the solar electricity. Without the storage, the solar power produced must be consumed directly or fed into the public grid – otherwise it is lost. Direct use is often not or only partially possible because PV produces most of the electricity during the day. However, experience shows that demand typically increases towards evening times. The feed-in tariff for solar electricity is much lower than the purchase price, however. Economically speaking, it doesn’t make sense to feed electricity into the grid during the day and draw it from the grid in the evening. A storage solution therefore considerably increases the economic efficiency of the photovoltaic system.

The system types of solar power storage

The following classifications are available for storage devices:

  • AC storage system

    AC stands for Alternating Current. This is the current that’s typically used in public grids worldwide with frequencies of 50 and 60 Hz. Most electrical appliances require alternating current. However, the photovoltaic system produces direct current (DC). An inverter turns this direct current into alternating current.
    The AC storage system is connected separately to the local grid, which also contains the inverter of the solar system. It has a built-in inverter that turns the AC voltage back into DC voltage, which is then stored. Due to double conversion of current, this results in higher losses than with a DC storage system. The advantage is, however, that these systems can be easily retrofitted into PV systems.

  • DC storage system

    The DC stands for Direct Currrent. These systems are installed before the inverter. They have the advantage of lower conversion losses because the current is only converted once when it is released from storage.

  • PV battery storage

    If you want to buy a solar power storage solution, you can choose between lead-gel, lead-acid and lithium-ion batteries. Lead accumulators have the advantage of very low self-discharge. Due to these low charge losses, lead batteries achieve an efficiency of up to 80%. However, they are being replaced by lithium-ion batteries increasingly.

Advantages of lithium-ion technology for solar power battery storage:

  • They last anywhere from 15 to 20 years, which is longer than lead acid batteries.
  • They have a very high cycle stability. This means that they can withstand up to 10,000 charging and discharging cycles.
  • Lithium-ion battery storages have a discharge depth of 100%, while lead batteries can only tolerate about 50%.
  • Their system efficiency of 90% allows a smaller dimensioning of the solar system, as only little electricity is lost.
  • In contrast to lead accumulators, they do not emit gases. Therefore, they do not have to be placed in a ventilated room.

Installation of the power storage for photovoltaics

Most storage systems can be easily integrated into existing PV systems. It may be necessary to replace the inverter. It should be kept in mind, however, that most storage systems are relatively large.

Evaluation of storage capacities needed

To determine the appropriate storage capacity, daily power consumption has to be calculated. You can calculate the annual power consumption as an average of the last five years.

For example, if it amounts to 6,000 kWh, continue to calculate:

6,000 kWh / 365 days = 16.44 kWh/day.

If we assume that about 2/3 of this consumption should come from the storage, the result is:

16.44 kWh * 0.66 = 10.8 kWh

In this case, a storage with the capacity of 10 kWh should be sufficient.