With modern battery technology the roadmap for total battery powered submarines seems feasible. Simulations with a created concept design show that with current battery technology local to medium range missions are already feasible. This makes a total battery powered submarine an interesting option for navies who want to use their submarine mainly for homeland defence. Changing the conventional diesel-electric powered submarine to a total battery powered submarine could enable more benefits than one might think.
For example, the implementation of a total battery powered system will make the propulsion of the submarine air in dependent and will reduce the signature of the submarine. This contributes to an improvement in covertness of the submarine, which is an important tactical advantage. Other advantages are: reduced amount of installed systems, less maintenance, reduced workload for the crew, and with respect to safety, the creation of total battery powered submarine has advantages and disadvantages compared to diesel-electric submarines. The use of large amounts of lithium based batteries will increase the risks of battery fires and explosions. On the other hand, the absence of the lead-acid batteries and diesel-generator sets will reduce the risk of fires and explosions as well. Furthermore, the amount of pressure hull penetrations will be reduced. This will reduce the risks of water intake and leakages.
With modern battery technology, submarines can sail fully electrically on batteries in the future. The submarines are not only getting quieter, they are less likely to be traced, but are also easier to maintain, cheaper and safer. It is expected that the battery technology will be ready within ten years to be able to realize a completely submersible submarine.
Research by naval engineering firm Nevesbu revealed that the switch from conventional diesel-electric to fully battery-powered submarines could have more advantages than is often thought. Simulations with a concept design have shown that according to the engineering firm.
Nevesbu has been designing submarines since the founding year in 1935 and also regularly conducts research on submarines to keep knowledge up to standard. For example, the agency was involved in the design of the Walrus class of the Dutch navy and various foreign submarines.
Up to three weeks
Sven Los researched the use of lithium batteries in submarines as a graduation project for his master at TU Delft. He was working on the last nine months of his studies. For the study, Los assumed a submarine with a water displacement of 1800 tons. "In an existing design of a conventional submarine I stripped everything that had to do with the diesels and put in extra batteries. With a software simulation, we then looked, among other things, at how much energy is needed and how quickly the batteries discharge. In addition, two things were important. First the balance. The submarine must be just as heavy as the buoyant force. That was quite difficult to achieve. For this we have had to adjust the layout of the design. And because there is no possibility to charge the batteries on the way, you have to manage the energy balance well. You should not use too much energy on board. "
'Submarine can sail for three weeks without having to return to the base to recharge the batteries'
The investigation showed that a submarine can sail up to three weeks without having to return to the base to recharge the batteries. Los has done an example calculation for sailing in the Baltic Sea. "That means that at that time a submarine can do a round of the Baltic Sea."
One of the starting points for Los in the study of fully electric sailing submarines was that the onboard system should be as simple as possible. Complex systems that are necessary for, for example, sailing on hydrogen were not at issue. "Sailing on batteries makes the design less complex than sailing on diesel. Less systems are needed compared to diesel-electric submarines. You do not need these systems when you are sailing on batteries. That also means that you have less maintenance. Lithium-based batteries do not have any maintenance requirements. All this ensures that the availability of the submarine is increased and the operating costs are reduced. "
Thanks to the smaller number of systems, the workload for the crew also decreases. Not only the operation of the drive is simpler, the same applies to the underwater systems. The trim and weight disturbances, for example, are expected to drop sharply because fewer consumables and no fuel are needed. This makes it easier to control the trim and weight compensation. All this means that less crew on board is needed. Calculated separately in his research that the number of people on board can reduce from 34 to 25. As a result, less energy is consumed on board.
In addition to advantages in the technical field, sailing on batteries also has tactical advantages. With a fully battery-driven system, the propulsion of the submarine becomes air-independent. "A conventional submarine of, for example, the Walrus class sails on diesel generators and batteries. If the batteries are low in energy, the submarine has to go to the surface to charge the batteries; the submarine then goes into the so-called snorkel trip. After all, the diesel engine needs oxygen. You do not have that when you are fully powered by batteries. You can then stay under water for a longer period of time. "
'I think submarines can fully run on batteries within ten years'
"The signature of the submarine is also reduced. When charging the batteries in a conventional submarine, the diesel generator must be switched on. This causes a lot of noise, vibrations, heat and acoustic noise. You do not have that any more if you are traveling with batteries. All of this contributes to improving the unobtrusiveness of the submarine and that is an important tactical advantage. "
For safety, the development of fully battery powered submarines has advantages and disadvantages. Nevertheless, Los expects that in the future it will be at least as safe as sailing on diesel. "You have a lot of hot parts when sailing on diesel and hydrogen gas can also be released from the lead batteries. This is not the case with lithium, but these batteries can fall into a fault mode where all energy is released. You must therefore prevent a chain reaction from occurring. "
In the meantime, according to Los in the world, big steps are already being made, including in Japan and South Korea. The challenge is mainly in making the batteries safer. "Lithium batteries consist of certain chemical compounds. You can vary in this. What you still see is that increasing safety is at the expense of energy density. But this goes with steps every year. I think that submarines can fully run on batteries within ten years. "