Autumn 2017 EN

Biogas Journal | Autumn_2017 English Issue
What kinds of stationary batteries are there?
more electricity than it uses due to the expansion of
wind and solar power, and which is approaching the
limits of network compatibility.
“Only by doing rigorous work in the area of storage technologies
can we succeed in future in providing electricity
from renewable energies that is always meeting the
needs of current demand”, explained Albrecht Gerber, an
economic minister who belongs to the Social Democratic
Party of Germany, on the commissioning of the facility.
He emphasized that the state of Brandenburg is working
on other storage projects, including the hybrid power
plant by Enertrag near Prenzlau, the Power-to-Gas pilot
facility by Uniper at the biogas plant in Falkenhagen, and
a battery storage unit at the Alt-Daber solar park.
The project received 376,000 euros in subsidies. The
storage unit, with lead-acid batteries, consists of two
containers, each with a capacity of 1 MW. The battery
storage containers already provide frequency support
in the high-voltage grid. It was already approved for 50
Hertz by the transmission grid provider for the balancing
market; it is “pre-qualified”, as experts say. Now
Vattenfall GmbH can offer the capacity of the storage
unit in its weekly pool of tenders.
Battery storage units and biogas plants
Not far away, the city district of Feldheim von Treuenbrietzen
has supplied its own electricity since 2010.
Installed is a biogas plant with an installed capacity
of 526 kW. It is operated by the local agricultural cooperative.
Now there’s another attraction: Since mid-
September, the largest battery storage unit in Europe
has been installed here and connected to the grid. The
building is about as large as a gymnasium, measuring
30 m x 17 m.
The battery has 10 MW of power and a capacity of 10
MWh. Up to now, the top position was held by a storage
facility in Leighton Buzzard, England, with 6 MW of
power and a capacity of 10 MWh. Therefore, the energy
density of the storage unit in Feldheim is greater.
“The system’s degree of efficiency is at 85 percent”,
says Michael Raschemann, Managing Director of Energiequelle,
the project developer. The company built the
storage unit in one year.
Its storage modules, about 3,360 of them, come from
LG Chem, a South Korean company. At the rear of the
hall, 35 air conditioning units keep the temperature
at 23 degrees Celsius for the batteries. The project is
being financed by an investment company, which includes
partners such as Energiequelle, the wind farm
construction company Enercon and others. In addition,
the project receives subsidies from the state of
Brandenburg and the European Union. Albrecht Gerber,
the economic and energy minister of Brandenburg,
talks about “a milestone for the system integration of
renewable energies”. The Ministry of Economic Affairs
for Brandenburg supports the battery storage unit with
about 5 million euros from the RENplus programme.
Lead-acid batteries: Electricity is converted electrochemically in the batteries before it is
stored. This process uses electrodes made of lead and sulphuric acid. Due to the chemical
process, the capacity is lowered with each cycle. This means that the intensity and speed of
charging determine the service life of the battery.
Lithium-ion batteries: These batteries are well-known based on many mobile applications.
The voltage and service life can be improved with various material combinations, primarily
those used for the electrodes.
The advantage of redox flow batteries is that the material which stores the energy is located
outside of the cell. Separating energy conversion from the storage medium allows the amount
of energy that can be stored to be metered out in a flexible manner. To do so, two different
electrolytes are used to supply energy and to store it. During the charging and discharging
process, electrolytes that store energy flow in separate circuits from the tanks into the cell,
where a membrane is used to facilitate ion exchange.
Depending on the design, a great deal of power can be generated for a short period or a low
amount of power over a longer total period. That costs for lithium-ion batteries continue to fall
will trigger a real boom in the expansion of large storage applications. And other technologies,
such as lithium-sulphur, vanadium redox flow and metal-air batteries are more competitive
due to cost reductions. This also increases demand for these storage media which, in turn,
drives costs even lower. Up until a couple years ago, all battery technologies had just about
the same starting conditions, but Sauer, a battery expert, now sees one technology ahead of
the rest: “Lithium-ion batteries are totally dominating the current market”. For this reason,
large lithium-ion batteries for stabilizing the network are already less expensive than some
redox flow batteries.
Contributing to system integration
The state government in Brandenburg placed battery
storage units at the top of its agenda: The subsidy programme
RENplus underwent further development for
this reason. It advances model projects with storage
technology as well as regional and community-based
energy concepts. “The coalition will provide at least
10 million euros per year for this”, according to the
coalition agreement. These resources come from both
the European Regional Development Fund (ERDF) and
state resources.
The Feldheim power plant, part of the reserve power
grid, is the biggest individual recipient, says Gerber.
He is convinced that this is a good investment. “When
the expansion of renewable energies moves forward in
seven-league boots, but system integration takes only
tiny steps, the energy transition will never happen”.
The battery storage unit in Feldheim provides balancing
power to stabilize the electricity grid. This means
that it compensates for fluctuations between supply
and demand.
If there is an excess supply of electricity, power can be
removed from the grid in just seconds, and when electricity
production is insufficient, power can be transferred
to the grid to keep the frequency of 50 Hertz
stable in the grid. By the end of the year, the storage
unit is to be approved for the balancing power market
because the four transmission grid providers need this
system service. The requirements for balancing power
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