Regulator: Private storage should participate in the energy market

Contents

German households have over 17 gigawatt hours of battery storage capacity, which is used almost exclusively in one way: during the day, they store surplus energy, and at night, they supply energy to consumers in the home. Large-scale battery storage systems, of which there are currently less than 3 gigawatt hours in Germany, work very differently. Among other things, they are used for arbitrage trading, i.e., they charge when electricity prices are low (or negative) and discharge back into the grid when prices are high. On the one hand, the operator earns money, and on the other hand, this shift in energy quantities serves the grid – This is why there is an exemption from grid charges, which would otherwise apply for every kilowatt hour. This was previously not permitted for private operators, who usually operate battery storage systems together with a PV system. The following principle applies: under no circumstances may non-green electricity (i.e. electricity not generated by the PV system) flow into the public grid.

This regulation could soon be abolished if the Federal Network Agency has its way, having published a so-called specification entitled "Market integration of storage and charging points" (MiSpeL) for consultation. This is therefore a proposal, not yet a finished regulation. If MiSpeL comes into force as proposed, it would open up new options for storage owners and also e-car drivers. "With this regulation, we are laying the foundation for making small and large electricity storage systems more flexible: in future, they can both actively participate in the electricity market and continue to be used to optimize their own consumption. Until now, only one of the two was possible," BNetzA President Klaus Müller is quoted as saying.

Dynamic procurement and dynamic feed-in

In order for a private operator to be able to use the scenarios described, a number of prerequisites are required: digital electricity meters are needed that can record imports and exports separately in 15-minute intervals. This is crucial for the evaluation at the end of the year. It also requires a dynamic electricity tariff for procurement and dynamic feed-in tariffs via a direct marketer, both according to the day-ahead exchange price on a quarter-hourly basis.

The Federal Network Agency is proposing two options for the specific metering concept, which are to be offered in parallel: the demarcation option and the flat-rate option. The former requires a much more complex meter construct consisting of two bidirectional meters, with one meter only demarcating the battery. For systems with a hybrid inverter that supplies the PV strings and battery, this is unlikely to be feasible – and requires greater intervention in the meter cabinet for all other systems. In return, it is possible to determine for each quarter of an hour in which direction and how much energy has flowed, enabling precise billing based on the respective electricity exchange prices.

The flat-rate option, which only requires one meter, is simpler and presumably more attractive for private operators. It counts how much energy has flowed into the house or from the house into the grid per quarter hour, but it cannot determine where it came from. Therefore, a few assumptions are made to determine how much market premium must be paid for energy fed into the grid from the PV system: For each kilowatt peak installed, it is assumed that 500 kilowatt hours per year can flow into the grid (and about 300 are consumed in the house). For a 10 kW system, 5000 kWh per year is therefore assumed.

This amount is considered eligible for subsidy and the market premium that is already paid today for direct marketing is distributed – but only at times when the exchange price is not negative. There is also a simple assumption for electricity trading (arbitrage trading), i.e. buying when electricity prices are low and selling when they are high, so that the private operator does not have to pay grid charges on energy that it has purchased for the purpose of selling later: If, at the end of the year, the feed-in is higher than the amount of energy expected from the PV system, it is assumed that this electricity has been purchased and temporarily stored for energy trading. Example: In a system with 10 kW, 5000 kWh are expected, but on 31.12. there are 8000 kWh on the meter. It is then assumed that 3000 kWh have been purchased for trading –. No grid fee is charged for this amount.

Bidirectional charging

The BNetzA also takes electric cars in combination with bidirectional wall boxes into account in its proposal. They are to be treated like other battery storage systems. This means that if the car manufacturer releases battery capacity for storage, the car can also be used as a storage facility for electricity trading in the future.

Conclusion

With its draft, the BNetzA is opening up new opportunities for storage owners and, in future, electric car drivers to use their storage more economically and is creating incentives to shift feed-in to times of high prices. This is also likely to change the business model for storage and inverter manufacturers – because arbitrage trading only works effectively if the energy management system of the storage unit or inverter decides when to feed in and feed out based on forecasts and electricity exchange prices.

In any case, the prerequisite for implementation is intelligent metering systems with smart meter gateways that can transmit their measurements in quarter-hourly intervals. And, as is well known, their expansion has been stalling in Germany for years.

(jam)