Autumn 2017 EN

English Issue
Biogas Journal
| Autumn_2017
Hall with battery
storage unit inside, by
WEMAG in Schwerin.
Photos: Thomas Gau
A typical battery stack,
which fills an entire
hall in Schwerin.
are particularly high, however: The power demanded
must be supplied within 30 seconds. But that’s not a
problem for the battery storage unit.
The first large battery storage unit has also been participating
in the market for balancing power since September
2014. In a building similar to a gymnasium at
the edge of the old town of Schwerin, a total of 25,600
lithium-manganese oxide cells store electricity in milliseconds.
At the end of 2016, WEMAG, the operator,
decided to expand the battery unit by mid-2017. With
the expansion, the battery park’s power will double from
5 to 10 MW and the capacity will nearly triple from
5 to 14.5 MWh. After participating in the market for
balancing power, there is a plan to be able to provide
reactive power.
Alternative to expanding networks
at the local level
In the course of its research project “Smart Power
Flow”, the Reiner Lemoine Institute (RLI) demonstrated
that large storage units are a real economic alternative
to expanding the grid at the local level. The inverters
and control systemy of the vanadium redox flow
battery were independent developments by SMA and
Younicos. “From our perspective, increasing network
expansion does not make sense from an economic point
of view because the grids are designed for a load that is
only achieved on a few days per year – that is unnecessarily
expensive and complex”, explains project manager
Jochen Bühler, a research associate in the area of
transformation of energy systems at the RLI, regarding
the current situation. The researchers tested alternatives,
he said. Large batteries proved to be an economic
alternative to local gried expansion, he continued.
In the project, the RLI researchers used a prototype
of a vanadium redox flow battery, for which they had
developed an inverter and control system especially
for this project. It was integrated into the electricity
network of LEW Verteilnetz GmbH (LVN) in Bavarian
Swabia and was checked in a one-year test phase. The
scientists noted that its operation is both cost-effective
and provides support for the grid. An RLI analysis of
the business models for large-scale batteries indicated
that under the current, relevant conditions in Germany,
using batteries on the balancing power market is by far
the most lucrative application area. For this reason, the
scientists had also focused the project on this business
model, he continued.
However, when providing the balancing power, the batteries’
behaviour was initially not conducive to the distributor
grid. The grid frequency determined the charging
and discharging of the storage unit. For this reason,
the RLI developed an intelligent battery control system
that regulates the voltage in the local grid and, as a
result, increases the ability for renewable energies to
be incorporated.
“The critical and new thing about our approach is the
combination of a battery application at the distributor
grid level that is market driven and, at the same time,
can service the grid”, continues Bühler. From his perspective,
the use of large-scale batteries is worthwhile
in many cases for local grid operators as well. The prerequisite
here is that the storage units are established
by external investors based on sustainable business
models and that the batteries be equipped with a control
system that allows them to service the grid. Then
it is even more economical than expanding the grid for
local network operators, even after making any compensation
payments for using large-scale batteries. At
the same time, this could reduce electricity costs and
advance the energy transition more quickly, according
to comments on the results.
A second life for automobile batteries
In Hanover, the local energy provider enercity has also
started building a large battery storage unit. The spe-
10