Objective and Background Information

Objective of using battery storage-systems

The objective of using battery storage systems is to not feed excess PV energy that cannot currently be self-consumed into the utility grid, but instead to store it temporarily in batteries. It is then available and can be used when the self-generated PV energy is not sufficient, e.g. on a gloomy day, in the evening or at night.

The duration of use can be set to 24 h or 48 h.

System operators are less dependent on the electricity purchased from the utility grid and increase their self-sufficiency quota.

Background information on forecast-based battery charging

Without forecast-based battery charging

• If the battery is perhaps already fully charged by noon and can no longer take in any excess PV energy.
  This then leads to the fact that the PV feed-in power at the point of interconnection has to be "derated" if the nominal PV system power exceeds the maximum feed-in power specified by the grid provider at the point of interconnection (see Limitation of active power feed-in).

The following features of the Sunny Home Manager play an essential role for the forecast-based battery charging:

• PV yield forecast
  By using a weather forecast based on Internet data and by specifically adapting this to the local conditions, the Sunny Home Manager can accurately predict solar irradiation for a few hours to a few days (48h).

• Consumption forecast
  The Sunny Home Manager creates an individual load profile on the consumption behavior of the system.

• PV curtailment forecast
  From generation and consumption data the Sunny Home Manager identifies when the PV nominal system power would exceed the specified feed-in power at the point of interconnection. Without forecast-based battery charging this PV energy would have to be derated or would not be generated – and thus would get lost.

• Prioritization of loads
  A preferred consideration of the battery charging ensures sufficient availability of energy e.g. in the evening and night-time hours.

• Specifying a minimum load capacity of the battery
  Since a purely forecast-based charging of the battery can lead to a lack of sufficient stored energy available when required, a percentage value can be set for the forecast-based charging of the battery. The battery is definitely charged up to this value before the Sunny Home Manager enables the forecast-controlled battery charging.

Ideally

• all loads are controlled so as to avoid derating losses and to be able to cover the houshold's energy demand exclusively with self-produced PV energy.

The result is that the battery

• always has sufficient PV energy stored to satisfy the current demand.

• still has capacities to absorb PV energy even at the midday peak.