For centuries, the sea route has been used for the transportation of goods. Global trade would not be possible without shipping, as around 90% of goods worldwide are transported by ship. With a current share of around 20%, the transportation sector makes a significant contribution to global CO2 emissions. And the emissions generated during transportation influence the carbon footprint of a product, too.
Green logistics – and in particular green mobility – play a crucial role in the fight against climate change and for the manufacture and distribution of sustainable products. This applies equally to all modes of transport, even if shipping is considered the most environmentally friendly form of freight transportation. Decarbonization is therefore not only being driven forward on the road and in the air, but also on the water. By or around 2050, international shipping should reach net-zero greenhouse gas (GHG) emissions – at least this ambition is included in the latest GHG strategy of the International Maritime Organization IMO.
Alternative drives for ships: The future is electric
Currently, heavy fuel oil is the main fuel used on the high seas. As with all other modes of transportation, alternative drive and energy systems play a central role on the way to climate-friendly ships. Therefore, the trend towards electromobility does not stop at shipping.
The challenges in the electrification of the drive are comparable for all forms of electric mobility. In particular, the efficient operation of battery cells, defined among other things by performance indicators such as service life and cycle stability, requires effective and reliable solutions. This applies both to the maintenance of a constant and uniform temperature distribution and to the safety of the battery, which can be jeopardized, for example, by the consequences of a short circuit or mechanical damage to a cell.
Safe batteries for electric drives: thermal management is key
An optimal thermal management system plays a crucial role in protecting the battery from overheating and safely dissipating the heat from critical temperature-sensitive components. Marine and automotive batteries for electric drives differ considerably in their dimensions. Marine batteries require significantly more storage capacity – ideally several MWh. To provide this much energy, battery units are assembled from individual modules to large container solutions.
In addition to cooling the battery cells during normal operation and during the charging process, solutions must also be available in the event of a thermal runaway, i. e. the temperature of a cell rising uncontrollably: The battery thermal management must be designed for this case as well – to ensure efficient and safe operation of the battery containers.
The transfer of the very rapidly generated thermal energy to other cells should be prevented or at least slowed down. This requires heat spreader materials that can effectively dissipate the suddenly generated heat and withstand even high temperatures. This is exactly where SIGRATHERM flexible graphite foils from SGL Carbon come into play.
Best heat dissipation with SIGRATHERM
SIGRATHERM highly thermally conductive and high-temperature resistant graphite foils are the optimal solution for uniform temperature distribution and heat dissipation in the event of a thermal runaway.
- Excellent in plane thermal and electrical conductivity of several 100 W/mK
- Excellent resistance to heat, oxidation, and corrosion
- Low weight
- Outstanding adaptability due to high compressibility and flexibility
- Easy to process
- Made in Germany and the USA
- 100% natural graphite - without binders and additives
- Low energy costs in production, as no graphitizing is required
- High sustainability aspect: material can be reprocessed into powder and reused
- Wide range of variants: different thicknesses, densities, formats (e.g. die-cuts, sheets, material on rolls)
- Additional adhesive coating on one or both sides possible
Safe electric ferries: SIGRATHERM in practice
In an electric ferry, battery modules with high-performance nickel-manganese-cobalt (NMC) pouch cells with a total battery power of around 1 MWh are equipped with a thermal management solution that uses SIGRATHERM.
The cells are designed for extreme performance requirements and have been developed for continuous operation in marine propulsion batteries. Due to the high charging and discharging rates and continuous operation they are exposed to a constant load, which can lead to considerable heat generation.
The energy flows used during the charging process are enormous. Despite the large capacity of the modules, this only takes a few minutes. If the temperature rises above 150°C during charging or discharging – far above the normal operating temperature of the cells, there is a risk of a thermal runaway and, in the worst case, even a battery fire.
The heart of thermal management
The cell unit design enables the heat spreader, the SIGRATHERM graphite foil, to act as the central component for heat dissipation. Due to its excellent in-plane thermal conductivity of several 100 W/mK, it can distribute and dissipate the heat evenly.
SIGRATHERM graphite foil is flexible, and its density can be adapted to the mechanical requirements in the cell. The material is available with an adhesive coating on one or both sides, which allows stable positioning in the cell even under mechanical loads such as vibrations or the natural movements of the cell via charging and discharging.
Modular and powerful: Structure of the cell unit
The heat directly absorbed and transferred by the SIGRATHERM graphite foil is then absorbed and dissipated by the liquid coolant in stainless steel pipes. The average system temperature is approximately 25 °C, whereby the cooling system in the customer application is designed for larger amounts of energy.
The cell carrier system described is installed in a single battery module. This modular design enables the system to be expanded flexibly, resulting in a total battery power of around 1 MWh in this application.
Schematic structure of a cell unit:
1 aluminum cell carrier (with stainless steel tube for liquid cooling), 2 insulation foil, 3 pouch cell, 4 SIGRATHERM graphite heat spreader, 5 foam plate
Picture source: ©Kerafol
Sources
Navigating towards a greener future, Deutsche Bank
Verteilung der CO2-Emissionen weltweit nach Sektor 2022, Statista