Subsea Power Solutions

Online Editor

A variety of subsea applications require power. Stefan Marx introduces a range of advanced power technologies based on Li-Ion batteries

For many years, SubCtech has recognised the ever-increasing demands for power and capacity within the subsea sector. It recently responded by introducing a new Li-ion battery series particularly aimed at large subsea storage, vehicle propulsion and also for the electrification of oil & gas production facilities (which plays a crucial role within the transition from electrohydraulic to “all-electric” systems).

The special requirements of the offshore oil & gas industry have triggered the development of extremely reliable batteries with a lifetime of up to 25 years. With the UN T38.3, MIL-STD, DNV-GL or API17F standards and qualifications, depending on the target market, batteries have to withstand rapid temperature changes as well as extensive shock and vibration tests. Such qualifications as well as highest reliability are compulsory for operations in the sea, as service or failure would cost millions.

At present, SubCtech is supporting the future revision 5 of the API17F on the subject of fully electric production facilities (all-electric systems) containing batteries. With this standardisation along with consideration and integration of functional safety according to IEC 61508, the safety of future electrical underwater systems is significantly increased.

The energy of the batteries is easily scalable by stacking SmartPowerBlock (SPB) battery modules. Power distribution units (PDU) and voltage conversion as well as data interface can be added to the single titanium or duplex steel housing completing a battery system. Combining these functions in a single pressure housing reduces the number of subsea connectors and simplifies system integration.

The Li-ion cell technology that is used offers enormous advantages in terms of safety, energy and power density at moderate costs. Due to the flexible design, the charger can be external or can be integrated into the pressure housing, e.g. for AUV/ROV docking stations or subsea storage solutions. SubCtech has developed DC and AC converter technology that allows high charge power and therefore short charging times without complex cooling.

The transformation into an all-electric system technology protects the oceans and enables a sustainable, careful use of our limited resources. Here, the innovative, modular SubCtech battery system plays an elementary, almost indispensable role and offers new, equally innovative all-electric systems a wider range of options.

Economic Value Of Li-ion Batteries

All oil & gas applications have in common that the use of the oceans is advancing, but must be more sustainable and safer. With the aim of making technologies more efficient and using ocean resources cost-effectively, future solutions must always consider protection and sustainability.

With its standardised, safe and reliable Li-ion batteries with a long design life, SubCtech aims to make underwater energy reliable and cost-effective. The high level of safety and the elimination of maintenance reduces OPEX significantly.

Another part to optimise OPEX costs and increase sustainability is the pressure housing. Unlike traditional duplex and 316L steel canisters, SubCtech specialises in titanium. A coating and corrosion protection (CP) is not required and thus reduces the possible entry of pollutants into the water. In contrast to regular expensive maintenance at subsea structures with ROV support, titanium housings are 100% maintenance-free over their design life. The same applies to the Li-ion batteries used. These also have a service life of up to 25 years, so that here, too, no maintenance or even replacement is necessary, which reduces cost significantly.           

Since the company also produces large titanium housings, battery systems can also be easily scaled to different water depths and form-factors. This, as well as the battery itself – through innovative and modular engineering and construction methods and processes with little effort – is extremely cost-efficient.

The ability to adjust operating parameters during operation without retrieving and service on board enables simple testing at significantly reduced costs.

Industry Impact

The benefit of this all-electric technology is obvious for the offshore oil & gas industry. A large energy storage system (ESS) is currently being built that will offer enormous added value through the installation of an electrical backup system for a large gas extraction system. The all-electric systems offer cost advantages compared with conventional systems, which are more expensive to maintain and purchase. With this product, an industrial standard could be created that would add considerable value for many other oil & gas production platforms.

Furthermore, SubCtech develops standards for safe operation, maintenance and obsolescence, commissioning, decommissioning and disposal, but also data exchange with major companies. The firm therefore also supports the further development, standardisation and implementation of the framework of Subsea Instrumentation Interface Standardisation (SIIS). With its long-term focus on safety-critical applications, the company is ideally positioned to meet the current and forthcoming industrial requirements.

Stefan Marx is CEO of SubCtech

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