Two European utilities have separately announced plans to invest in battery technology in a sign of the growing need for energy storage capacity in Europe.

RWE Innogy, the renewable energy arm of the German utility group RWE, has bought a minority stake in Norwegian technology company Revolt Technology for EUR5.5 million. Meanwhile, Danish utility Dong Energy says it has joined a group of investors backing Lithium Balance, a developer and producer of battery systems.

RWE’s investment in Revolt, which has developed proprietary technology that allows the development of rechargeable zinc-air storage systems, is in line with the company’s aim to expand in the renewable energy sector. The technology could be used in a variety of applications, says RWE, including energy storage and electric vehicles.

The need for energy storage in Europe’s power system is being driven largely by the rapid growth in renewable energy generation, which operates intermittently rather than according to electricity demand.

Dong Energy says that the expected increase in wind power production in Denmark was an important driver behind its investment in Lithium Balance, which has expertise in battery control systems. It also sees the electric and hybrid vehicle market as important.

“[The] efficient use of wind power is very dependent on our ability to flexibly adapt to electricity demand according to how much wind power we have at our disposal,” said Knud Pedersen, Vice President of Research and Development for Dong. “This effective management of charging and discharging of batteries can shift electricity consumption to night-time, when there is often ample wind power.”

“The promotion of renewable energies and the development of high-capacity storage technologies are inseparably linked. If we succeed in storing electricity from renewable sources during off-peak times to make it available during peak times, we will have made a quantum leap in terms of supply reliability,” said Prof. Fritz Vahrenholt, CEO of RWE Innogy.

RWE hopes that its investment will enable the development of zinc-air battery technology for small- and large-scale applications. Until now, high energy density zinc-air technology has been limited to non-rechargeable applications.

“Due to their high energy density, zinc-air batteries could be used not only for electricity storage from wind and solar power, but also for electric vehicles,” explained Crispin Leick, responsible director of RWE Innogy’s venture capital arm. “In contrast to lithium-ion rechargeable batteries commonly used today, zinc-air batteries are more powerful, cheaper to produce, safer and more benign to the environment.”

Dong has previously partnered with American firm Better Place to introduce electric cars to Denmark. It says that development of lithium batteries is important to this market as they are more compact and weigh less than other battery types.

Lithium batteries require an advanced control system to work, however.

“You can compare it with the so-called memory effect in cell phones and laptops, that means that the battery stays charged for an ever shorter time between each recharge, until after one or two years you have to replace it. And in an electric car this would be a catastrophe,” said Lars Barkler, Director at Lithium Balance. “Our battery management system eliminates the memory effect and gets batteries to last longer.”

The investment in Revolt Technology is RWE’s third venture capital deal following investments in a British micro-wind turbine company and a Dutch company developing a biocoal pellet production technology. Revolt Technology is backed by six other capital venture firms.