The combination of new and existing technologies in the maritime industry can make a major contribution to cleaner operations of ships but safety issues must be understood and addressed
The concept of integrating hybrid-electric power systems with conventional power sources and the use of energy storage systems such as battery syste[ds_preview]ms, has become more attractive to vessel owners in recent years. However, some demonstration projects using fuel cell technologies in the maritime industry are getting noticed too. The main hybrid power system concepts are the integration of conventional sources (diesel engine generator sets, gas turbine generators, dual-fuel engines with or without shaft generators) and new technologies such as fuel cells, energy storage systems (batteries and supercapacitors) and in the future photovoltaic solar, wind and flywheels. Currently Lithium-ion battery technology still dominates the use of energy storage systems and we expect more applications in the maritime sector, where battery systems based on solid state technology, metal-air, Li-Sulfur (Li-S) will become part of the ecosystem once more research, development and testing take place.
Optimising installations
The power generated from the combination of devices, machinery and systems results in electric and mechanical power required to supply electrical loads and propel vessels. Theoretically, most vessels can be equipped with a combination of technologies, however it is known that there are several limitations such as maturity of technology, availability of bunkering systems, safety constraints, vessel structure, design, layout and operational profiles that may complicate the process.
The operating guidance, maintenance and inspection plans provided by battery system’s vendors are very important to understand the life cycle of the batteries. Procedures are typically based on manufacturer’s own and other recognized standards. This documentation should be considered for all maintenance regimes.
Battery systems such as Lithium-ion types have known safety issues such as thermal runaway and the risk of fire or explosion, potentially causing injuries to personnel. The thermal runaway reaction in the battery cells can lead to battery failure and potential ignition of the electrolyte separator and electrodes, causing a fire in the battery system. Battery management systems and fire protection systems must be in place to prevent this from happening and prevent further damage in the event of thermal runaway.
Some research indicates Li-ion batteries may have nearly reached their theoretical limit in energy and power density. This may limit their potential for maritime applications where higher power and energy levels are needed, and it may accelerate the research and development of other battery chemistry technologies in the mid future. Potential alternatives to Lithium-ion batteries are in different stages of research, but they may show promise for battery systems to become more practical and widespread in maritime applications in the future.
With regards to installation of fuel cell power systems, this will have to go through a rigorous design and risk assessment process prior to their installation on marine assets where personnel or crews are part of the daily operation.
A maintenance and operational plan including emergency response is required and emergency operational procedures are necessary for firefighting and abandon-ship scenarios. In the case of battery charging, procedures necessary for shore power options need to be clearly established and conducted in co-ordination with service providers.
Next generation technologies
In addition to Lithium-ion type batteries, research and development on several other technologies such as solid state, air-metal, Li-S, redox is continuing and will continue to evolve for deployment in the maritime industry in the future. The use of biofuels, their contribution to the development of more dual fuel engine types also will be a big contributor to this process.
While hybrid systems can contribute to the reduction of fuel consumption and greenhouse gas emissions for hybrid systems to be effective, there is a need for efficient and sustainable battery technologies that can provide the required power.
The enhancement of battery systems will also allow for renewable energy to be further implemented, potentially reducing emissions further. As emphasis continues to increase on reducing environmental impact, this may be an essential technology for an eventual shift to more hybrid or even all-electric vessels.
Author: Modesto Lezama Managing Principal Engineer American Bureau of Shipping, ABS
