Class societies approve next-generation batteries

Classification societies are type-approving new maritime energy storage system (ESS) designs as the industry passes the milestone of 1,000 vessels with batteries on board. Corvus Energy is the latest manufacturer of battery modules for tugs, workboats and other vessel types to secure class-approval for its latest storage units.

The Bergen, Norway-headquartered manufacturer secured type-approval from Lloyd’s Register for its Dolphin NxtGen Energy marine battery system in March 2025, confirming this energy-dense ESS complies with the stringent rules, regulations and safety requirements of the maritime industry.

Corvus used its experience with its Orca ESS, which is widely used on board vessels for all-electric and hybrid propulsion, in developing Dolphin NxtGen Energy ESS and its safety systems.

Corvus says its advanced safety measures include passive single-cell isolation in case of a thermal runaway (TR) occurring and a TR gas exhaust system. Dolphin NxtGen Energy has an advanced battery management system and proprietary digital solutions, including continuous remote monitoring and digital-twin technology, to enhance operational safety throughout the battery system’s life.

“Receiving Lloyd’s Register’s type-approval confirms Dolphin NxtGen Energy meets the high safety standards required in the maritime industry,” says Corvus Energy chief executive Fredrik Witte. “This is a major milestone in our work to power a clean future in segments where the adoption of hybrid and electric solutions are high.”

Classification societies Bureau Veritas and DNV have also type-approved Dolphin NxtGen Energy and Corvus says it is pursuing type-approval certification from additional maritime classification societies for this product.

Corvus has sold more than 1,000 MWh of total battery capacity in around 1,300 projects and its ESS modules have recorded over 10M running hours combined, according to Corvus Energy vice president of sales, Pål Ove Husøy.

He says there has been a “rapid pace of development in battery cell technology and increased uptake by vessel owners” while the annual increase in cell-level energy density is 10-15%.

Other trends include lower costs, higher charging rates and a longer shelf life and lifecycle​ of batteries with lithium-iron phosphate, nickel manganese cobalt oxides and nickel cobalt aluminium oxides.

New chemistries are being developed, but Mr Husøy thinks these are “currently not suitable for marine applications as energy densities are low​”. They are better suited for non-marine applications and “technology improvements are needed​”.

Mr Husøy highlights safety issues and risk mitigation solutions for marine ESS installations. “Safety must be on all levels, from design to the end of life,” he says. In the design phase, batteries should be sized according to the operational profile​ of the vessel. For tugs, this could include sizing to meet high bollard pull, or zero-emissions transits between jobs. 

Other design considerations include installing cooling, monitoring, gas detection and fire extinguishing systems in battery rooms. There needs to be passive single-cell TR insulation and battery management systems, and crew need safety and maintenance training, while an emergency response team is a must, says Mr Husøy.