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Extinguishing the safety concerns of electric and hybrid vessels

With an increasing number of vessels becoming electrified or hybridised as part of efforts to decarbonise the shipping industry and protect the environment, the role of lithium-ion (li-ion) batteries in this transition continues to grow. Alongside this growth, safety concerns are increasing around the use of Li-ion batteries, specifically around the fire risk they pose to such vessels and the related challenge of fire suppression at sea.

Here, Government Europa looks at a number of risks that fires can pose to electric and hybrid vessels fitted with li-ion batteries, and how innovation and regulatory efforts are being co-ordinated across Europe to eliminate the challenges of thermal runaway and other complications that new technologies can cause to these new, more environmentally sound ships.

Estimating the effects of fire risks to shipping
Electric and hybrid vessels now range from passenger ferries to offshore supply vessels, which work to ensure the safety of vital oil rig operations. As a result of the electrification and hybridisation of these ships, they are now far more reliant on energy from lithium. Ships consume vast quantities of energy, and some vessels can hold around one thousand modules. Although the technology has proven to be simultaneously reliable and powerful, safety concerns have also caused some hesitation on behalf of vessel operators to convert their ships and adopt the technology.

In 2017, China launched the world’s first electric cargo ship, which quickly became exemplary of the potential for electric power in shipping, highlighting both its feasibility and practicality. In the future, it is predicted that the majority of commercial vessels will soon utilise some form of electric power storage, and lithium-ion has become one of the leading options for ship operators.

Lithium-based batteries offer a wealth of advantages: they are inexpensive, lightweight and powerful, and pose less of a threat to the environment than their alternatives. Despite this, the large amount of energy which they are able to generate creates an increased risk of fire or explosion, which can be disastrous to human life, the vessel itself, or at the very least to its cargo.

The challenge of thermal runaway
As not all battery systems are created equally with the same safety systems, both testing and certification for energy storage on board ships has taken on a more important role. Even in light of this, calls for action to reduce the risk further are being made. One of the largest risks caused by batteries is that of thermal runaway, which can occur when li-ion cells are:

  • Subject to mechanical abuse;
  • Experiencing internal manufacturing defects; or
  • Operating over/under the appropriate voltage or temperature.

As a result, heat is generated within the cells, leading to a reaction between the cathode and electrolyte. Subsequently, the temperature of the cells increases up to a point where the cell begins to excrete toxic and flammable gases.

Should ignition occur, the gases can start a fire which could pose great difficulty in extinguishing, and in the case that a great many batteries are aboard, can also spread very rapidly. For this reason, smart safety solutions are needed to ensure that batteries are not vulnerable to ignition during thermal runaway, or that at the very least, appropriate fire-suppression measures are in place.

Applying energy storage safety solutions on the seas
To date, the solutions available on the market seek to reduce the internal temperature of batteries. These technologies aim to maintain safe operating temperatures for li-ion batteries aboard electric and hybrid vessels, which can prevent the conditions which are conducive to fires on board. To this extent, in March 2018, the classification society DNV GL, based in Oslo, Norway, announced that it would be launching a joint development project in efforts to analyse the use of li-ion batteries throughout the shipping industry and address safety concerns.

As reported by Ship Technology, DNV GL’s Benjamin Gully, senior engineer, said: “Rules have been put in place that cover a lot of the dangers of lithium-ion batteries, but there’s a real opportunity for the industry to benefit both in terms of the total level of safety as well as the efficiency of the approval process, by increasing the level of knowledge in the industry through technical data and answering hard-to-answer questions.”

The project aims towards reaching several goals, and lists among its priorities:

  • Development and assessment of a safety model which is based upon knowledge established prior;
  • Launch and implementation of a lithium-ion battery risk assessment;
  • Establishment of a testing programme which seeks to establish battery safety;
  • Creation of a safety simulator;
  • Introduction and refinement of analysis tools; and
  • Project management and dissemination, which can be input to both requirements and rules.

Despite significant research which has sought to address the risks associated with lithium-ion batteries, thermal runaway is still a prevalent concern. Oliver Chabilan, space product development engineer at Skeleton Technologies, added: “Although there has been significant progress with lithium-ion batteries, it is still possible they can go through a thermal runaway and catch fire.”

As the only safety system which has currently been proven to prevent thermal runaway, liquid cooling works to prevent batteries from entering the state through extracting more heat than the cells are able to produce. The solution sees low pressure, high volume closed loops of cooled water circulated throughout the battery, and has proved largely effective in suppressing the potential flammability of li-ion batteries which remain a vital element of reinforcing safety on electric and hybrid vessels, facilitating the wider electrification of the global shipping industry.
Source: Government Europa

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