Environmental Engineering Reference
In-Depth Information
Note that high Coulombic efficiency is observed at high flow velocities;
therefore higher current densities may be achieved when operating at these
velocities.
Commercial Application: Cellstrom
Now that the vanadium redox flow battery system has been explained, we
can discuss a current commercial application of this technology. Cellstrom,
a German company, has developed a complete energy storage system (ESS)
utilizing VRB technology.
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The FB 10/100 consists of a vanadium redox flow
battery with a smart controller and configurable power electronics housed
in a weather-proof container. The system can be charged and discharged
up to 10kW and provides 100kWh of energy (10 h discharge at full power).
The battery can be connected to photovoltaic devices, wind turbines, diesel,
petrol, gas, and biogas generators, fuel cells, and water turbines to form dis-
crete autonomous power suppliers or can work as part of a micro-, mini- or
smart grid. The FB 10/100 is divided into fluid, electrical, thermal, and safety
systems.
The fluid system is seen in Figure 6.7, which also provides a layout dia-
gram. Two tanks that house 2500 liters of electrolyte each are located on the
lower level. Chemically resistant pumps provide the pressure to move the
electrolyte into the stacks above. Even if the electrolytes mix, a smart con-
troller automatically compensates for this by opening a rebalance valve to
maintain the desired potential across the electrodes.
The electrical system is configured to meet the demands of the customer.
The stacks are charged via a terminal connection to an outside power source.
During discharge, the dc power of the batteries is converted to ac via invert-
ers on the opposite sides of the stacks. An interface cabinet (Figure 6.8) pro-
vides lightning protection, AC fuses, and connection points for the load.
The operating temperature of the system ranges from 5 to 40°C. The tem-
perature is kept within these parameters via the smart controller. This con-
trol system uses ventilation fans to cool the apparatus using outside air when
the temperature exceeds operational temperature. In addition, the electrolyte
solution acts as a coolant as it is pumped through the stacks to allow better
heat exchange and helps to reduce thermal management problems.
When the temperature falls below the operational level, the smart control-
ler seals the container. The heat generated from the system is then allowed
to keep the cell operating within its temperature range. The temperature of
the electronics side of the FB10/100 is also monitored and regulated by a
separate ventilation system. Thermal separation of the fluid and electrical
components also helps prevent local hotspots.
Finally, safety is built into the unit to protect against lightning, fire, spill-
age, and hydrogen production. The battery and electronics are housed in a
sturdy container fitted with lightning protection for outdoor mounting. Any
electrolyte that spills due to damaged stacks or lines returns to the tank via a
