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Sonnenbatterie adds ‘very long lifetime’ to residential battery systems

Sonnenbatterie Eco 4. Residential storage systems sales in Germany are thought to have picked up in recent months. Image: Sonnenbatterie.
Sonnenbatterie, considered to be one of the market leaders in Germany’s emerging solar-plus-storage sector, claims the new version of its Sonnenbatterie Eco battery storage system has more than double the potential lifespan of previous models.

The company says the lithium-ion based system now has a lifetime of 10,000 charge cycles, whereas previous versions could manage up to 5,000. Company spokesman Mathias Bloch told PV Tech that additionally, while the previous models could cycle at a depth of discharge (DoD) of 80%, the new version can manage 100% DoD cycling.

“So Sonnenbatteri Eco 4 (the new model) has a usable capacity of 4kWh,” Bloch said.

According to Sonnenbatterie, the new model’s increased lifespan lowers the cost of stored electricity. The system’s pricing ranges from €0.17 (US$0.18) to €0.24 per kWh depending on the system size. While the price remains the same, Bloch said, the economics improve over time.  

“The range of pricing stays equal. But people get now a system with much more cycles. That means that the cost for a stored kWh reduces a lot. If you divide the cost over the capacity and the cycles you get a much lower result now than with 5.000 cycles,” he said.

"With the new version of our most popular model, we add a very long lifetime to the package," company CEO Christoph Ostermann said.

According to a release announcing Eco 4, the new system is a “grid friendly storage system” that will be able to cope with new applications for energy storage, including combining solar and storage with micro CHP (combine heat and power) systems and integrating the system into a “virtual power plant” for residential electricity sales.

The company’s systems are supplied with batteries from Sony’s Fortelion range, with Sonnenbatterie’s proprietary software installed. With a 10-year warranty, it is also scalable in 2kWh steps from 4kWh up to 16kWh.  

Bloch claims the company has sold around 4,000 systems to date in Germany and a handful of other key markets, a significant figure in the relatively immature industry. According to various sources, only around 15,000 residential solar storage systems had been sold in Germany in total by late 2014.

While there is a definite trend of falling PV system sales to German households, the portion of those installed with energy storage options attached is growing, providing something of a lifeline to the market. Germany Trade & Invest, the Federal government agency which promotes and advises on inward investment from overseas companies into Germany and vice versa, quotes figures from research firm EU PD that forecast PV-battery systems sales to hit 100,000 by 2018 in the country.

In a previous interview with PV Tech Storage, conducted last year as Sonnenbatterie closed a funding round worth around US$10 million, the company said it saw “high growth potential” for its products in markets including the UK, Australia and Italy, in addition to a US launch, which was already underway at the time.

According to Bloch, circumstances in the UK market at present have made it a little more of a long term objective than previously implied. The company is likely to attempt a 2016 launch in Britain, spending this year focusing on its homeland in Germany and on its efforts in the US. During this year, Bloch said, Italy will be the most likely fresh market for the company to target, where government support for solar has been diminished, making on-site self-consumption of PV power more attractive, in the same way as has been seen in Germany. Bloch said Sonnenbatterie is currently manufacturing around 100 systems a week.

This article has been amended to clarify Germany Trade & Invest's role as an advisory agency to foreign and German companies, not as a lending institution, as was incorrecty written originally.

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