Just little over an hour's drive from Berlin in a southeast direction lands you dead in the middle of Eastern Germany's lignite mining area.

With roughly a quarter of the reunited nation's required electricity coming from coal, the open-cast mines here still have a vital role to play in the national energy mix, although environmentalists would argue the transition to more renewables is not happening fast enough.

People at the Schwarze Pumpe [Black Pump] power station here in Eastern Germany's Lusatia region know that the days of coal-fired plants may be numbered, but sober-minded experts say they seem safe for the next 10 to 15 years.

New-generation plant

Schwarze Pumpe is a very modern coal-fired plant which started operating in 1997 to eventually boast two 800 megawatt blocks of installed power, raising the bar both in terms of efficiency and low emissions for new generation coal-fired power stations.

It achieves an energy conversion efficiency of 40 degrees, meaning less coal has to be used to produce the same amount of electricity, and hence lower CO2 emissions.

But the rise of renewables seems unstoppable in a nation that has made the transition to greener energy a major policy goal and made the phasing out of nuclear energy irrevocable.

The trend is clear. Back in 2009, just 16 percent of all electricity generated in the country came from renewables. Just five years later, they already accounted for 27.3 percent, while in 2017 their share of total electricity output amounted to 33 percent.

There's a snag

One of the downsides of relying a lot more on renewables — with the focus in Germany being on wind — is that dependence on weather conditions increases. When, say, there's less wind and less sun for that matter, resulting fluctuations in electricity supplies to the national grid have to be compensated in some way to head off power outages.

German transmission system operators are responsible for maintaining the balance between electricity generation and actual demand (consumption) around the clock.

Registered imbalances on a lower scale are first compensated between the various operators in a process that's come to be known as imbalance netting. But oftentimes, that may not suffice.

What kicks in then is a sophisticated system of additional control power procurement and more often than not the activation of the so-called primary control reserve, meaning that additional electricity is fed into the grid by power stations and other market actors, with procurement ensured and rewarded through a competitive bidding process among potential suppliers.

Primary load balancing in focus

This brings us back to the Schwarze Pumpe power plant in Lusatia. Its operator, LEAG, has announced that Czech contractor EGEM and local service companies are planning to build a huge battery storage facility hooked up the coal-fired plant to reach a storage capacity of 53 megawatts, making it the biggest of its kind in Europe and helping to ensure smooth grid operation.

"The combination of existing power plant infrastructure and battery storage technology is unique in Europe, and so will be its start-of-life capacity," LEAG spokesperson Kathi Gerstner told DW.

"I'm not aware of any other comparable project of that size in Europe," she added.

LEAG is investing €25 million ($28.8 million) in the lithium-ion storage facility comprising 13 containers full of battery racks and spreading across an area the size of a soccer pitch.

The German state of Brandenburg, where LEAG is headquartered, takes €4 million of total investments. The storage facility will be operational by the summer of 2020.

Australia leading the way

LEAG CEO Hubertus Altmann said BigBattery Lusatia, as the project is called, was an investment in the future. "In order to stabilize the grid, we'll be using the facility on days where electricity generation fluctuations are high due to renewables."

Gerstner confirmed that "the main use of the facility would be to provide primary load balancing electricity which the market pays for."

By the way, the 100 megawatt/129 megawatt per hour Hornsdale Power Reserve in Australia is currently the world's largest lithium-ion battery storage facility. It covers about 1 hectare of land and is located at the Hornsdale Wind Farm, South Australia's largest generator of renewable energy.