Power up subsea operations with energy storage solution

Online Editor

Stefan Marx and Sören Johannsen delve into the world of subsea energy storage.

In the ever-evolving realm of underwater technology, German firm SubCtech stands out with its innovative approach to ocean monitoring and subsea power solutions. Guided by the expertise of founder and CEO Stefan Marx and COO Sören Johannsen, the company has carved out a significant niche in this highly specialised industry. Both here discuss SubCtech’s products, the challenges of subsea engineering and the sustainability of modern subsea energy storage.

Based in Kiel, Germany, SubCtech has two primary business units: Ocean Monitoring and Ocean Power. The company began by manufacturing products to monitor seawater quality, and, over time, its focus has evolved to meet the increasing demand for battery power underwater.

From its small beginnings, crafting small underwater batteries, the firm now boasts a 1MWh battery storage system set to be in operational use from the beginning of 2024.

SubCtech’s Ocean Power unit manufactures subsea batteries that can be deployed aboard underwater vehicles or as backups for oil and gas industry applications offshore. To ensure its customers are comprehensively serviced, the Ocean Power unit is subdivided into three sectors: offshore energy, underwater vehicles, and standard subsea power products.

Founder and CEO Stefan Marx says SubCtech’s Ocean Power unit offers both standard batteries and bespoke solutions: “We offer solutions that fit into the customer’s available space and within its weight limitations – that’s where our roots lie, and that’s the service that has delivered our growth thus far.”

A boost in Storage

The company’s engineering prowess was on full display in late 2023, with SubCtech’s unveiling of the largest battery that it has ever produced: a 1MWh battery storage system.

The battery is the first subsea MWh battery in the world. But it is also only one among many other batteries in SubCtech’s collection including two perennial off-the-shelf battery solutions dubbed ‘Big Jim’ and ‘Long John’. Both battery units have standard physical dimensions and similar weights, but the innards can be customised according to specific requirements, such as capacity and voltage, both within set limitations.

For vehicle-based solutions, SubCtech offers three different standard battery housing diameters, namely 260mm, 310mm and 416mm internal diameter sizes. Meanwhile bespoke sizes, energy, power, and voltage ranges are available on request.

Quality german engineering

SubCtech was founded in 2010 by Marx, who boasts over 30 years’ experience working in ocean-related industries in various roles. The company was originally headquartered in a small town near Kiel, but soon moved into Kiel, where its staff-count has gradually risen from 20 to 80 to accommodate growing demand for the company’s products.

Following several relocations around the city to accommodate its growing workforce and workload, SubCtech constructed its own production space.

SubCtech’s products are qualified according to military standards, and all are certified by Det Norske Veritas (DNV), an internationally accredited registrar and classification society headquartered in Norway. This DNV certification, which seeks to guarantee the safeguarding of life, property and the environment, ensures comfort for users of the company’s products and is a legal qualification for any equipment fitted to the deck of a vessel.

The importance of materials

SubCtech sources the highest-quality raw materials from around the world for the construction of its products, an important point about the company. “The steps from prototyping to operational use for any material and any product is a long process involving testing and certifications,” says COO Sören Johannsen. “There’s a big difference with the quality of materials used underwater and our task is to sell a fully qualified, 100%-secure product.”

One material is titanium used for every battery’s pressure hull – most of the battery’s internal components are manufactured at SubCtech including battery management systems, hardware, software, testing, control systems.

“While we’d prefer to use existing materials, so many components our products need for deep-sea operations simply aren’t available on the market, and so we have to make them ourselves,” Marx says.

The same applies to its production machinery and even test-bed equipment, all of which is developed and built in-house since it simply doesn’t exist in the market.

Mercifully, then, one of the most important components – lithium battery cells – are sourced from well-known producers with whom SubCtech has supply contracts.

Sustainabnle electric power

While rechargeable lithium-ion batteries have become commonplace in most consumers’ daily lives, it’s a relatively new technology for subsea operations. “These products are a big step forward for the subsea industry and an important topic for us, particularly in terms of the way they improve the industry’s sustainability,” Marx says. “First, because we’re replacing primary batteries with rechargeable batteries, and secondly, because hydraulic systems are being replaced by battery-electric systems which have a design life of 25 years, so they’re very robust and clients don’t have to replace them frequently, this makes them sustainable.”

At the end of one of SubCtech’s battery lives, customers can simply return the batteries to the company, which then forwards them to specialist partners for recycling. Although they are also fully recyclable, the titanium pressure hulls housing SubCtech’s batteries have an endless design life and are reusable.

The recycling process must follow strict legal guidelines to ensure full transparency. “German law requires that every item we recycle be documented so that the flow back to to raw material is also documented,” says Johannsen.

Concluding, Marx explains how the company’s best assets are driving it forward: “We’ve learned over the years that even as a medium-sized company, we’re able to move the world a little bit. We have the best products, a great reputation and a high-quality team. In my 30 years in the industry, that’s been the recipe for success.”

Stefan Marx and Sören Johannsen are with SubCtech.

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