Sonnen: Intelligent battery charging vital for home solar arrays

Since the end of February, the Solar Peak Act has stipulated all new solar arrays will not receive EEG payments when electricity prices are negative. Negative-price hours will be added on at the end of 20-year EEG subsidy periods, extending the time during which payments will be made – provided smart meters are in place – but solar owners are nevertheless losing income in the short term.

Storage company Sonnen has calculated homes with a 10 kW solar array and a 10 kWh storage system, which feed 6 MWh into the grid annually, and which don’t have smart meters would have lost around €120 last year, when 460 negative electricity price hours occurred.

Sonnen estimated around 14% of the solar electricity generated last year was fed into the grid during negative electricity price hours. As such events mostly occurred around midday, grid electricity consumption was low and home batteries would have been fully charged, equating to losses of around 25% of payments for home solar owners, according to Sonnen.

Making the case for batteries equipped with intelligent charging, Fermin Bustamante, vice president for sales and marketing DACH at Sonnen, said, “The negative prices occur precisely at the time when simple storage systems are already full or the photovoltaic system simply exceeds the storage system’s capacity. The losses hit precisely when the system is feeding in a lot of power. This is immediately noticeable in terms of revenue.”

If the almost-390 negative electricity price hours recorded in the first half of this year are extrapolated over 12 months, losses for solar owners could rise to more than 40%, around €250.

Sonnen is advocating intelligent battery charging configured to charge storage units when electricity prices are negative and to either discharge it to specific consumers or to engage in intraday or balancing power markets.

Allgäu-based Sonnen offers customers access to direct marketing, which it says eliminates the restrictions of the Solar Peak Act. Use of a smart meter, and intelligent charging, means stored electricity can be directed to electric car charging or can follow market signals in Sonnen’s virtual power plant.

“The solar peak tariff package is fundamentally changing the economic calculations of the last 25 years,” said Bustamante. “Anyone without an intelligent system today will lose revenues that were firmly planned and that solar system owners will now have to wait two decades for. However, those with an intelligent and powerful storage system can generate more revenue than was previously possible. This allows households to respond to signals from the electricity market and charge selectively when the feed-in tariff is no longer available. The additional periods of the tariff period, under the Solar Peak Tariff Act, will be added to the end of the tariff period.”

From pv magazine Deutschland.