New concept för battery fire safety ventilation developed
During thermal surge, batteries can produce gases that are toxic, flammable or explosive. Therefore, completely new ventilation concepts are needed for battery rooms on electric ships of the future. An innovation project from the Swedish Transport Administration and Lighthouse has taken the first step in developing a concept for it.
There are two types of ventilation for a battery room. One, the room ventilation, must manage the room's temperature and humidity and conducts gases out of the room and the ship. The second type is to manage gases from the battery modules if there is a thermal rush, so-called off-gas ventilation.
“The concept we worked on is based on different levels of emergency scenarios and provides ventilation rates that can be calculated on a case-by-case basis. For room ventilation, we have developed an equation that takes into account the volume of the room and the gases produced during thermal rush. The issue that was also discussed is when the system should go from normal to forced ventilation and then to the final step with full exhaust”, says Anna Karlsson, researcher at Rise who led the innovation project Battery Fire Safety Ventilation for Fully Electrical Vessel.
“We have also looked at the ship design itself and how to draw the ventilation ducts so that no dangerous gas is released in inappropriate places.”
The project is a follow-up project to the previous project Electric Light and both have been carried out within the Swedish Transport Administration's industry program Hållbar sjöfart (Sustainable shipping). In addition to developing a ventilation concept, the aim has also been to investigate concepts for action strategies after a fire or other incident in the battery room.
“Here we didn't get as far, but a first step today is the importance of the battery supplier together with the operator having a dialogue and through risk assessment defining routines for handling after an incident.”
The report points out that today's standard design, regulation and operation of battery room ventilation needs to be discussed from a safety perspective.
“When batteries are tested today, one battery cell is tested. The ventilation must therefore be able to handle thermal rush in a cell and the gas that is then formed. But a battery room consists of several modules with many battery cells. Therefore, the question is whether it is enough to test at the cellular level. The risk in a battery room is that several cells, depending on how they sit and are connected, start to produce gases and thus produce a larger amount of gas than the ventilation can handle.”
Fires are dynamic and how they spread is difficult to predict. Add gases to that and it becomes even more complex to understand how ventilation works best.
“How gases move depends on how a room is shaped, where fans are placed, whether the gases are light or heavy and so on. Such cannot be predicted with an equation but must also be tested when the battery compartment is installed.”
There is a lot to do in the area, says Anna Karlsson.
“We want to look further into explosion risks, both in battery rooms and cargo spaces. What risks exist, for example, when batteries have stopped burning but still produce gas?”
The report Battery Fire Safety Ventilation for Fully Electrical Vessel was authored by:
Vasudev Ramachandra, Anna Karlsson, Ola Willstrand and Mikael Hägg at RISE Research Institutes of Sweden AB and Martin Schreuder at Chalmers University of Technology
In collaboration with: Corvus, ABB, Echandia, Trident BMC, Consilium Safety, Stena Teknik, ForSea, Wallenius Marine, Destination Gotland, the Swedish Transport Agency and DNV.
