HTW launches electricity storage initiative with specific household instructions

There are already around 1.8 million solar energy storage units in German households. However, they are far from reaching their full potential. The Berlin University of Applied Sciences (HTW) wants to change this and is launching the initiative “Your electricity storage can do more!” The initiator is Johannes Weniger from the Solar Storage Systems research group. The aim of the initiative is to raise awareness of forecast-based charging strategies. This is because they have clear advantages, not only for system operators, but also for the electricity grid in general.

It is one of the worst-kept secrets that most home storage systems are already full in the morning – before the associated PV system has even reached its maximum feed-in. This is not conducive to the grid. On the contrary: this charging strategy contributes enormously to the feed-in peaks at midday. And that is a challenge.

There are two main problems, as the German Association of Energy and Water Industries (BDEW) points out: grid bottlenecks occur when more electricity is fed into the grid than can be transported away. And it jeopardizes the balance between generation and consumption, which is essential for a stable grid frequency. All of this makes balancing measures necessary, electricity at midday increasingly loses value and hinders the expansion of new plants.

Concrete instructions for activating forecast-based charging

The HTW is convinced that forecast-based charging systems or intelligent energy management systems can provide a remedy. This is because they can use solar power forecasts to shift battery charging to midday, for example. This has several advantages: Firstly, the private systems then primarily feed into the grid in the mornings, when the demand for electricity is higher. Secondly, this approach reduces the downtimes when fully charged. According to the HTW, this can extend the service life of lithium-ion batteries by two years. After all, the longer lithium-ion batteries remain in a fully charged state, the faster they age.

If the battery storage system has not yet been charging based on the forecast, this can be quickly changed in the settings, says Weniger. “With a maximum of six clicks, operators can benefit from the advantages of forecast-based energy management.” HTW has compiled information on how this works for the systems of seven manufacturers on a dedicated website. Here, users select their product and can then scroll through the step-by-step instructions. The manufacturers include E3/DC, Fenecon, Kostal, RCT Power, SMA, Sonnen and Tesvolt.

According to HTW, systems from established manufacturers already frequently work with forecast-based charging strategies. The situation is different with new players from overseas. Here, the focus is not necessarily on intelligence, but on economic efficiency.

Solar peak law with zero remuneration

The topic of forecast-based charging is also relevant regarding the Solar Peak Act that recently came into force. As its name suggests, it is intended to curb solar midday peaks. For new systems, for example, it includes the obligation to control the system if it is to feed in at full power.

According to the law, new PV systems must be in a technical condition from commissioning so that the grid operator can call up the actual feed-in at any time and regulate the feed-in power remotely. If this is not the case, the feed-in capacity (not the quantity) must be limited to 60 percent of the installed capacity. This applies until the system is equipped with an intelligent metering system and a control device. A smart meter is a prerequisite.

On top of this, instead of a flat-rate feed-in tariff, new systems will no longer receive a cent if the electricity exchange price is negative. “The amendment to Section 51 (1) EEG 2023 reduces the subsidy to zero in any period in which the spot market price is negative (…).” This applies to all newly constructed plants with an installed capacity of 2 kilowatts or more. Typically, negative electricity prices occur at midday, when PV systems are feeding into the grid in an uncontrolled manner.

The forecast-based charging strategy prevents precisely this by allowing the systems to feed in the morning and charge at midday. In this way, the system operators ultimately secure a better yield in terms of the feed-in tariff.

(ssi)