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One storage unit for all eventualities

  • 1. June 2016
  • Connectivity
  • Photos: Daimler
  • Text: Walther Wuttke

Stationary energy storage unit with lithium-ion batteries from Mercedes-Benz allows industrial businesses and households to be independent of public energy providers.

At first glance, the latest development from the Daimler subsidiary Deutsche Accumotive appears to be a classic contradiction. After all, Daimler has been working to ensure mobility for more than 125 years. The company has now surprised everyone with a stationary energy storage unit that can be used by industrial businesses and private households alike. To store energy, the unit uses lithium-ion batteries which have already proven effective for supplying energy in mobile applications. The system enables energy generated through photovoltaics or wind power to be fed into the power circuit of the business or household as required.

A stationary device from a company that specialises in mobility – how does that work? “Quite simply,” says Harald Kröger, Vice President Electric/Electronic & e-Drive at Mercedes-Benz Cars, “because the technology that we use in our cars is the safest in the world and is therefore also suitable for stationary operations. Furthermore, we have now achieved a very low cost position, enabling us to offer customers an extremely safe, yet cost-effective solution.”

Turning radiant sunshine into noiseless energy

EXPERIENCE FROM MOBILE STORAGE PUT TO USE IN STATIONARY APPLICATIONS

The new storage unit makes use of the experiences gained by Daimler in the development and use of lithium-ion storage systems. “Mercedes-Benz,” explains Harald Kröger, “was the first automotive manufacturer to incorporate lithium-ion batteries into its cars. When we first started this back in 2008 with the S 400 Blue Hybrid, the rest of the world was still relying on nickel-metal hydride storage.” The knowledge acquired since then about the properties and management of lithium-ion cells is now being channelled into the new technology.

The batteries used by the stationary energy storage unit are the same as those produced for automotive manufacturing by Deutsche Accumotive, and this represents a whole new business field for the Daimler subsidiary. Each individual module delivers 2.5 kilowatt hours. According to Harald Kröger, the average home owner would probably need two of these modules. The storage unit can be scaled up to several megawatts. Compared with the loads encountered in a car, a stationary operation is a bit like a spa break for batteries as they do not have to withstand adverse weather conditions or mechanical stress. To date, the batteries have proven effective in all models and have led to scarcely any failures. Above all, the technology requires a dry room in order to work perfectly.

The storage modules can be used virtually anywhere, whether in a terraced house on the outskirts of town or on a tropical island, where the unit can be used to convert radiant sunshine during the day into noiseless power for the night. “Anyone who installs a photovoltaics system on their roof should really also take the next logical step and install a suitable storage device in their cellar,” explains Kröger. Now that feed-in tariffs for solar energy are being squeezed, home owners can benefit by storing energy independently of public providers and drawing on this as and when required. In fact, initial trial runs have already shown that home owners in and around Stuttgart are interested in this technology.

Lithium-ion battery: during charging, the electrons are delivered via the external circuit and positively charged lithium ions pass through an electrolyte from the positive electrode to the negative.

CHARGE MANAGEMENT

An appropriate charge management system is vitally important to ensuring optimum use of the lithium-ion batteries.

•Lithium-ion batteries are extremely sensitive to environmental influences such as fluctuations in temperature and voltage, as well as mechanical and atmospheric factors. Lithium-ion batteries that are connected in series also need to be precisely controlled to ensure optimum functionality in terms of charging characteristics.

•Optimum charge management enhances both energy efficiency and the service life of the battery.

•Daimler has acquired a great deal of knowledge about battery charge management as, for a while, the Group was the only manufacturer to have its own cell production facility in Kamenz. This knowledge is now being channelled into the management of the stationary energy storage unit, making a significant contribution to battery optimisation.

Harald Kröger, Vice President Electric/Electronic & e-Drive at Mercedes-Benz Cars

GREATER INDEPENDENCE WITH A STATIONARY STORAGE UNIT

Development work on the stationary battery storage unit began back in 2010. The mass storage system known as Lessy (Lithium Electricity Storage System) has been operating since then without any problems. Finally, in November 2014 – long before any of its competitors – Daimler announced the development of a stationary storage unit. In addition to private households, Kröger also anticipates potential customers in trade and industrial businesses. The stationary storage technology will enable businesses to smooth out peak loads and make their production operations independent of the public grid. This, in turn, relieves the burden on the grid because any sudden increases in the demand for energy can be covered by the stationary storage unit.

Today, businesses still depend on expensive services to supply the need of sudden, high demand for energy . The system from Deutsche Accumotive, on the other hand, requires minimum maintenance and, thanks to the use of regenerative energy sources, has no negative impact on the environment. “Our storage unit is much easier to manage than a diesel generator. We’ve succeeded in creating a largely maintenance-free system that places minimum demands on the installation site,” explains Kröger.

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POTENTIAL USE IN THIRD WORLD COUNTRIES

The storage unit is therefore ideal for third world countries where unstable power grids go down several times a day, production is crippled and the supply of diesel fuel for generators cannot always be guaranteed. “We’re unlikely to experience these conditions on our doorstep but, thanks to the global Daimler sales network, there’s hardly a place in the world where we are not represented.” The first concrete enquiries about distributing the technology have already come from South Africa. Despite probably being the most highly industrialised country in Africa, it now has an unreliable public grid which goes down several times a day for an indefinite period due to its infrastructure being neglected over many years.

Daimler has concluded initial distribution agreements with the Baden-Württemberg energy company EnBW. It is also in talks with trade associations with regard to installing the systems. According to the plans, which have not yet been finalised, the systems may also be sold on the internet – in addition, however, a conventional sales network is also being set up and installation of the first units is scheduled to start in the autumn. The modules are built in the Saxon town of Kamenz, where the lithium-ion batteries for electric vehicles from Mercedes-Benz are also made. Feedback from the first test customers – house builders and trade businesses who expressed an interest after the initial announcement was made – has been extremely positive. Looking ahead to the future, Kröger says, “Our biggest problem is likely to be high demand.”

Deutsche Accumotive

  • Founded

    in April 2009 as a subsidiary of Daimler AG
  • Goal

    to drive the industrialisation of vehicle-focused lithium-ion technology
  • Sites

    Kamenz, Saxony: manufacture of energy storage units since 2010

    Kirchheim unter Teck/Nabern, Baden-Württemberg: further development of the lithium-ion batteries

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