In the last years, energy market is transforming towards a decentralized system where consumers generate energy they need and feed the surplus into the grid. Driven by this trend, energy storage is becoming a key technology, especially associated with renewable energy sources like solar or wind power, which are not always available when there is demand from grid users.
For this reason, storage systems will play a key role in the development of renewables. Currently, the most efficient and mature technology for large-scale energy storage is BESS (Battery Energy Storage Systems) which are based on batteries. These systems are typically represented by containers full of batteries that need to be uniformly cooled at constant temperature of about 23°C during charging and discharging. This is where the work done by STULZ, a leader in customized air conditioning, together with Westrafo comes into play, serving the customer SMA Altenso (Altenso).
SMA Altenso (Altenso) is an international system integrator of complex large-scale battery storage systems, hydrogen applications, and off-grid & hybrid solutions based in Germany. As a young, diverse, and dynamic company, Altenso is working towards the goal of implementing innovative power projects as a contribution to the energy transition. The company commissioned Westrafo to build battery containers for multiple BESS projects.
The company commissioned Westrafo to build battery containers for following BESS projects:
In each of these projects, Altenso developed the complete BESS project, Westrafo designed the containers in close collaboration with Altenso and built the battery containers, and STULZ took care of the sophisticated environmental control system to cool 38 battery racks inside each container.
Focusing on the thermodynamic project, it has been asked STULZ to maintain a constant and uniform temperature of 25°C inside a 40” container totally filled with batteries, except for a narrow central aisle.
After some initial proposals, the WXUC5 was developed based on the WallAir series: 35kW monoblock air conditioner installed on each short side of the container.
Blowing cold air in a double duct placed above the batteries, it was possible to cool and heat the entire 12 meters of the container consistently. Heating, necessary during the battery’s standby phase when external temperatures are particularly cold, such as in Prague, has been achieved using 13kW multi-stage electric heaters.
Meanwhile, an “uneven” dual-compressor solution provided the modulating cooling needed to handle load variations during battery charging, standby, and discharging.
Since the solution has been designed for hot as well as cold environments, oversized heat exchangers and winter kit allowed air conditioner to operate in external temperature range of -40°C/+50°C.
Finally, the entire system has been simulated using CFD analysis to optimize the air distribution system via supply vents, ensuring the required airflow and temperatures and maximizing battery life.
The partnership between Altenso, Westrafo, and STULZ worked closely together, starting from initial meetings to on-site commissioning, including preliminary design and engineering phases, system integration, and the success of FAT.
WXUC5 represents the perfect solution to cool containers used for BESS, and these three projects: ENERPAC, JUWI, and DECCI acted as springboard. Now 3+2+7 containers with 24 units installed have been realized, but the unit is ready and tested to be an important piece of energy storage systems.
Photo below represents DECCI power plant, detail of WXUC5 installed and indoor view of container full of batteries, respectively.
With WXUC5, STULZ developed a unit dedicated to BESS applications, with following features: