Battery (power storage system)
Optimization in details
Self-consumption optimization: Forecast based battery charging
The Energy Management increases self consumption of the electrical energy produced by the photovoltaic system by shifting the battery charging (power storage system). It also covers the use case where the DC power produced by the photovoltaic system is higher than the maximum amount of AC (feed-in) limitation, e.g. due to a lower peak power of the inverter or due to regulatory restrictions.
Without optimization
Due to the sunny weather conditions, the battery is charged as a priority and is fully charged before midday. The photovoltaic system can produce even more energy and the system could now start feeding into the public power grid. However, it is only able to do it to a limited extent, for example, due to regulatory restrictions and due to limited AC inverter power. The dark marked area in graph 1, above the grid feed-in limitation line, displays the amount of energy that the system could have produced but was not feasible to the limitation. This amount of energy can be considered as lost potential.
With self-consumption optimization
The “Forecast based battery charging” optimization feature ensures that the battery is charged and discharged in a way that maximizes the amount of the PV energy produced and at the same time the earnings from the feed-in. The Energy Management has predicted that the peak load will occur around midday and is above the grid feed-in limitation. Therefore, the battery charging pauses at 10:00 a.m. so that the battery still has sufficient storage capacity available at midday when PV energy production peaks. Once the feed-in power reaches the limit, the battery charging is continued, allowing for the maximum possible PV earning to be achieved.
Tariff-based optimization
In addition to self-consumption optimization, tariff-based optimization can be activated in the ViCare app. These optimization features work hand in hand. Tariff-based optimization ensures that the energy stored in the battery is preferably made available to the system when the consumption costs for electricity from the power grid are high. This leads to a shift in consumption from the power grid to times when the price is low and to an overall reduction in electricity costs.
In order to save costs with tariff-based optimization, an active dynamic or time-based electricity tariff must be stored and the “Dynamic Assistant” subscription must be activated in the ViCare app.
With self-consumption and tariff-based optimization
This case shows a dynamic tariff on a mostly cloudy day. The “Forecast-based battery charging” optimization feature has predicted that the peak load will occur around midday and that a smaller amount of PV energy will be produced. This produced PV energy is used to cover the household consumption and the battery is charged with the remaining PV excess. From 6:00 p.m. onwards, insufficient PV energy is produced and the household consumption is covered by discharging the battery. However, the battery is not completely discharged, as it would be without tariff-based optimization, but only at times when the electricity price is high. At times when the electricity price is low, the household is supplied with energy from the power grid. Therefore, the household consumption in the late evening can be covered by the energy stored in the battery when the electricity price is high. As a result, electricity costs are reduced overall.
In systems with a separate heating electricity tariff, which is generally cheaper than the normal electricity tariff, the battery is preferably discharged for consumers on the normal electricity tariff, thus reducing the overall costs.
Battery charging from the grid
To reduce electricity costs even more, energy can be consumed from the power grid to charge the battery in addition to the PV energy produced when the electricity price is low. This stored energy can then be discharged at times of low electricity price to cover the energy demands in the house instead of consuming energy from the power grid at a high electricity price. The system works intelligently and only charges energy from the power grid when it is needed at a later time. This is particularly useful in times of low PV excess, when a large part of the battery capacity remains unused. The “Battery charging from the grid” function can be activated in the optimization settings of the Energy Management in the ViCare app.
