Competence E
Stationary Energy Storage System – an Innovative
Pilot System in DC-Coupling
Mastering the challenges of the
energy turnaround
The further expansion of the share of electricity produced
from renewables is one of the core elements of the energy
turnaround. However, especially power generation from
wind turbines and photovoltaic systems is subject to natural
intermittency due to weather conditions and the time of
the day. With energy storage as a link, temporal congruence of demand and load can be achieved and grid stability
can be ensured. Apart from suitable storage technologies
such as high-performance batteries, this requires solutions
for load management and innovative power electronics.
The Karlsruhe Institute of Technology (KIT) and the Siemens
Sector Industry have jointly developed an overall solution
that stores, distributes and equalizes power from renewable
energy resources and hence compensates fluctuations. The
single components of the energy storage system such as
battery and energy generation units are linked with a DC
intermediate circuit.
Storage system of KIT for solar energy
KIT – University of the State of Baden-Wuerttemberg and
National Research Center of the Helmholtz Association
www.kit.edu
Energy system with renewable
energy sources and storage systems
in DC coupling
A pilot system of the newly developed energy storage system
is installed at KIT Campus North and has started its operation in March 2013. The system consists of a 36.5 kWp PV
system, two li-ion batteries with 25 and 50 kWh storage
capacity, the central control unit (CCU) as well as the
DC/AC (250 kW) and the DC/DC (25 kW each) converters.
While the latter originate from Siemens, the overall system
and the CCU were developed by KIT.
DC RSB – Renewable Storage Backbone
Energy system with renewable energy sources and storage systems
in DC coupling
The DC RSB is the link to equalize the energy flow from sun,
battery, grid and other energy sources and drains on the one
hand and the power grid on the other hand according to
grid operator demands. As combination of reliable and proven standard components from the portfolio of the Siemens
Industry Sector, the DC RSB brings together the energy flows
of the connected systems through a DC intermediate circuit.
For instance, the battery units of the DC RSB system are
connected to the intermediate circuit via DC/DC converters.
well as highly complex energy distribution requirements.
Within this context, the CCU is capable of controlling the
system autonomously and solely in dependence of the
measured data by the system and the transferred data
according to the requirement profile of the operator.
Li-ion battery
Control and regulation within the DC RSB system is performed by a real-time capable local grid controller (LGC).
Central Control Unit
The KIT central control unit (CCU) represents the superordinate automation level for long-term and strategic energy
flow control, also taking into account external variables, such
as specifications of the grid operator or weather forecasts.
The CCU provides the LGC with setpoint values according to
the particular requirement profile. The requirement profiles
of the energy storage system can be of different mode and
can reach from synchronized charging and discharging
scenarios to covering times of high tariff and peak load as
Karlsruhe Institute of Technology (KIT)
Hermann-von-Helmholtz-Platz 1
76344 Eggenstein-Leopoldshafen, Germany
Nina Munzke
Project Competence E
Phone: + 49 721 608-28283
E-mail: nina.munzke@kit.edu
www.competence-e.kit.edu
Karlsruhe © KIT 2013
The li-ion battery of the stationary store consists in a first
stage of 8 battery modules adding up to 48.4 kWh battery
capacity. The system voltage is between 500 – 700 V. Every
battery module consists of 48 lithium ceramics cells with a
nominal capacity of 40 Ah. The control of the entire system
is regulated by a redundant control electronics that monitors
all security-related aspects as well. The battery management
system (BMS), which monitors and controls the individual
cells, measures currents, voltages and temperatures for each
cell.
Due to its modular design the capacity of the storage system
is expandable up to 2 MWh. This application represents
another milestone in dealing with renewable energies.