Understanding risk to DP’s green ambitions

By Dr Julius Partridge, Snr Electrical Engineering Consultant, AqualisBraemar LOC, IUMI Professional Partner,

Recent years have seen a rapid increase in both interest and deployment of battery electric hybrid power systems in dynamic positioning (‘DP’) vessels.  The technology’s significant benefits in reducing emissions and fuel consumption, whilst increasing stability and flexibility in comparison to traditional DP power systems, are widely reported. However, unlocking those benefits is not as straightforward as at first thought.

Recent deployment indicates that the benefits derived from battery electric hybrid systems are dependent on the battery’s specific characteristics and their suitability to the vessel type. Characteristics include the connection points in the power system, size and type of a battery implemented. As such, the battery system’s performance of key functions such as peak shaving, spinning reserve, load levelling, redundancy support and battery only operation, and the flexibility the system offers to these operations, can vary, meaning the rewards in moving to battery electric hybrid power are not always so readily reaped.

Why is this the case? The issue can stem from a knowledge gap between stakeholders in the integration process of the battery system into the vessel’s power system. More often than not, the battery manufacturer understands the battery system, whilst the vessel designer understands the vessel. This is understandable given that the operation of these systems in the maritime sector is still developing. Another contributing factor is likely to be that such systems would be analysed and inspected with a different approach to that for a traditional DP power system. The cycling of the battery requires a more dynamic analysis of the power system’s operation.

There are other associated risks to the use of battery electric hybrid systems in DP vessels. For instance, it is widely understood that battery systems present a fire risk stemming from thermal run away in the battery cells. Battery manufacturers have dedicated significant work to mitigate this risk through both prevention and containment measures in commercially available systems.

So what does this mean for the technology, which could potentially unlock a more sustainable DP sector, therefore supporting a greener overall offshore construction and production space?  

In short, the knowledge gap reported could potentially lead to safety issues if a crew were to overestimate the battery’s abilities in assisting the power system. Furthermore, if the battery is poorly integrated into the power management system it could lead to risk of fire or increase battery degradation through excess power demand from batteries. However, these risks can be mitigated through better understanding of the operational characteristics of battery electric hybrid power systems and their suitability to a given vessel type. The solutions lie ahead, but at present the risks here remain an area of concern, and as with the wider alternative fuel picture, more research and development is often required.