If you own your own photovoltaic system on the roof, you want to use the electricity you have generated yourself. But the production and consumption times are very different. So that you can use your own solar power even in times when the sun is not shining, it is temporarily stored in solar power storage. In this way, the solar power produced in the midday hours can be used in the evening.
It is important that the system of photovoltaic system and battery storage works optimally. When selecting a solar power storage, the following performance characteristics should be observed so that sufficient solar power is also available.
How big should the solar power storage be dimensioned?
In order to be able to select the suitable size of the solar power storage, one needs the exact electricity demand of the household. In order not to experience any nasty surprises, it is advisable to consult an expert. Because a misjudgment could have far-reaching consequences. Once you have determined the electricity needs of a household, a solar power storage with the corresponding performance characteristics can be selected. The performance of the photovoltaic system is not relevant for the size of the solar power storage.
What does the storage capacity say?
The storage capacity is given in kWh (kilowatt hours). A distinction is made between the nominal and the usable storage capacity. The decisive factor is the actual usable storage capacity, because the solar power storage can never be completely discharged. It always requires a certain remaining capacity and is therefore limited to a certain depth of discharge. This is given in percent. The energy remaining in the power storage is used for faster charging and ensures a long lifespan for the solar power storage.
Tip: The usable storage capacity is usually less than the nominal one, since the electricity storage always needs a residual energy.
What lifespan can be expected?
The longer a solar power storage can be used, the more economical it is for homeowners. The lifespan of a solar power storage does not only depend on the years of operation, but on the number of charge and discharge cycles. These are influenced by the type of battery technology, but also by factors such as deep discharge, overcharging and charging speed.
Basically, one speaks of the cycle and calendar life. While the former indicates the expected number of charge and discharge cycles, the calendar life describes the aging process of the material. So it may be that the calendar life is reached before the cyclical one.
Tip: Buyers should ensure a lifespan of at least ten years guaranteed by the manufacturer.
How much electricity must a solar energy storage device be able to store?
The efficiency and performance of the solar power storage are crucial. Efficiency is the electricity that can actually be used. Energy is lost during storage in the system, which is then no longer available to the consumer. The buyer should also ask about standby losses. The efficiency is given in percent and describes the relationship between the electricity available for extraction in relation to the previously loaded quantity. The difference to 100 percent indicates the loss.
But it is not only interesting how much electricity the solar power storage can store, but also how often and how quickly I can access it. If, for example, double the capacity can be removed from a solar power store with a capacity of 5 kWh in one hour, this would be a maximum of 10 kWh.
Tip: With 90 to 95 percent, lithium-ion batteries are more efficient than lead-acid battery stores with 80 to 85 percent.