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Stromspeicher und Nachhaltigkeit | RCT Power


Solar power storage charging strategies:
Play with the weather the clever way

The RCT Power storage system lets you choose between two charging strategies: forecast-based charging and simplified charging. Why are there two charging strategies for solar power storage systems? And which of those strategies should you select for your system?

RCT Power can influence many things: unfortunately, not the weather. Sunshine is unpredictable. Sometimes you get 10 hours a day, sometimes only a few minutes. It is common knowledge. What is not always known, though, is that the daily number and period of sunshine hours have a big influence on the battery, the self-consumption rate and the public electricity grid. It is where charging strategies for solar power storage come into play.

Simplified charging strategy

The operating principle is simple: as soon as the sun shines, your PV system produces energy that at first covers your immediate self-consumption needs. Excess energy is stored in the battery storage until it is fully charged. Every additionally generated kilowatt-hour of energy is fed into the public grid until the active power reduction limitation is reached. However, on sunny days, PV systems often reach this limit by midday. The result: Your storage battery is in a maximum state of charge, and the PV system throttles the feed-in to the grid until the feed-in is eventually switched off.

Forecast-based charging strategy

The forecast-based charging strategy knows about the expected weather and your usual electricity consumption. Dedicated Software in the inverter calculates the yield of your PV system from forecast weather data and stored data from your system control. Depending on the expected yield, the storage battery is charged immediately, delayed or only partially.

What does this mean in specific? On sunny days, part of the generated energy is stored in the battery, and the remainder is fed into the public grid. In contrast to the simplified charging strategy, grid feed-in and storage battery charging run in parallel. The first aim is to feed in as much of the not self-consumed energy as possible, exploiting the active power reduction limitation. The second aim is to ensure that the battery is only fully charged in the evening. This approach reduces the load on the public electricity grid, as not all owners of a PV system feed in their solar power at the same time. Even on sunny days, the active power reduction limit is triggered less often because the time when the storage battery is fully charged is pushed towards the end of the day. It will also help to preserve the storage battery and extend its usable lifetime. On cloudy days, the storage battery is charged directly with the first rays of sunlight, as it is expected that the active power reduction limitation is not triggered during the day.

It is better to know about the weather

The forecast-based charging strategy is the factory default for the RCT Power storage system. It has proved to be efficient and is a frequent prerequisite for receiving subsidies. The annual self-consumption yield of the PV system increases, and the active power reduction limitation is triggered less frequently. So it is good to know the weather and your consumption behaviour. With all our solar energy storage systems, you can, of course, switch to a simplified charging strategy if you wish.

We are happy to advise you on the charging strategy of solar power storage systems.

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