Future for use batteries in shipping

Battery technology is rapidly increasing worldwide. Battery powered ships in various segments need validation of economy, safety and reliability.

Battery hybrids have several advantages too, since they enable the vessel engine to run at more favorable loads. This reduces fuel consumption and therefore emissions to air. Further benefits include an improved response time in safety-critical operations, an extended engine lifetime, less maintenance and less noise and vibrations.

Battery cells are today produced to a high-quality standard and it is very seldom that cells from quality producers experience any problems. The electronic control system that is required has also matured and the industry knows how to install large battery systems in a safe and reliable way on board ships.

Onboard ships, there is traditionally an electrical power system for the “hotel load” and the auxiliary systems. The propulsion power is taken care of by a combustion engine, called the main engine. The power for the electrical load is produced by generator sets consisting of an electrical generator driven by a combustion engine. These engines are called auxiliary engines.

Ships that also use the electrical power for propulsion are becoming more and more common today. Ships with operations that require variable power demand (such as offshore supply vessels) or flexible spaces (such as cruise vessels) are typical ships that use electrical propulsion [6].

Mechanical propulsion with battery hybrid electrical power plant.

Figure 97. Mechanical propulsion with battery hybrid electrical power plant

The figure shows a battery integrated into the electrical system of a vessel with traditional mechanical propulsion. In this case, the battery will be effective for smoothing the connected electrical load and helping to handle large load steps. When the large load steps are reduced, the number of auxiliary engines may also be reduced. In cases where the load can regenerate power, such as in cranes, the battery can be used to harvest this energy [6].

Hybrid battery propulsion.

Figure 98. Hybrid battery propulsion

The figure shows batteries integrated into a power system for electrical propulsion. In this case, the battery will provide power to the large propulsion motors. The vessel may run on just batteries, just generator sets or in parallel operation using both batteries and generators. In addition to being a source of energy for propulsion, the batteries will smooth the load variations on the generator sets. The introduction of such a battery hybrid system will reduce the noise and vibration levels on the ship. The topology can also facilitate the use of zero emission operation when entering a harbour.

Hybrid battery propulsion, with distributed batteries.

One challenge involved in the electrical propulsion concept is its efficiency. As seen in the previous figure, the system has several power converters and each of them typically represents a 2% power loss. If the batteries are distributed into the propulsion converters, the losses are reduced, see the next figure [6].

Figure 99. Hybrid battery propulsion, with distributed batteries

Another benefit with the distributed battery concept is that each propulsion unit is independent of a common source of energy. This might be a smart solution for vessels that require a highly reliable propulsion thrust, such as redundant dynamic positioning vessels (DP2 and DP3) [6].