Canadian marine energy storage company Sterling PBES has tested its battery system’s ability to withstand catastrophic mechanical damage and demonstrated that thermal runaway did not occur.
The tests validated the integrated liquid cooling, fire stop and ventilation systems when a ferrous metal spike was driven through all plies of a cell in the battery. Typically, damage like this would result in a thermal chain reaction (thermal runaway) where heat from the damaged cell causes the other cells in the battery to also ignite. The release of the energy contained in the battery can result in temperatures of more than 800 degrees Celsius and the release of toxic and flammable gasses that are explosive when contained inside the hull of a vessel.
In the nail test, the damage inflicted upon the cell was compounded, as the metal spike was conductive, creating a dead short to the internal circuits of the cell. In repeated tests, the damaged cell almost instantaneously reached a temperature of over 500 degrees Celsius. Due to the integrated liquid cooling system, the heat of adjacent cells did not reach more than 80 degrees Celsius, well within safe parameters. All gasses were safely released through the company’s patented E-VentTM ventilation system.
“In destructive testing over the last five years, we have been unable to force our liquid cooled batteries into a thermal runaway event,” said CEO Brent Perry.
The Sterling PBES energy system uses lithium nickel manganese cobalt (NMC) batteries – the chemistry used in most consumer electronics and electric vehicles. The system design makes it easy to swap out individual cells if they fail or reach the end of their lifetime; typically they are swapped out on a five-year cycle. This helps reduce waste and enables a more streamlined installation, says the company. The battery doesn’t need to be oversized to compensate for variables like changes in route, duty, heat or even ownership and maintenance intervals. A battery that is designed for a five-year lifespan with CellSwap may be only 30-50 percent of the size of a battery designed for a 10-year life.
If the hypothetical 10-year battery is air-cooled, the size of an alternative liquid cooled system with CellSwap is even smaller. A liquid cooled system doesn’t require large air gaps between components. Ducting and the blowers and compressors for HVAC are also eliminated, and liquid cooling means the battery can work at a higher rate. The result is a far smaller battery in terms of installed kWh, physical size and weight.
Currently, around 0.5 percent of the global marine fleet has energy storage systems installed, including around 20 ferries and tugboats fitted with Sterling PBES technology.