Hydrogen Shipbuilding Glossary

A certification issued by classification societies confirming that a design concept meets regulatory requirements during the preliminary design phase. It is a key milestone before Type Approval and indicates that the technology is safe and compliant for maritime use.

A process used by the IMO to approve ship designs that use new technologies or fuels not covered by existing prescriptive regulations. Currently required for hydrogen-fueled ships until specific IMO regulations are developed (expected by 2028).

A carbon-free fuel that can be used in combustion engines or cracked to produce hydrogen for fuel cells. Easier to store and transport than pure hydrogen, but toxic and requires careful handling. Increasingly considered as a hydrogen carrier for maritime applications.

An evaluation confirming that a technology’s basic design meets safety, performance, and reliability standards. Similar to AiP but focuses on the foundational design elements.

The natural evaporation of cryogenic liquids like liquid hydrogen due to heat ingress into the storage tank. Even with excellent insulation, LH₂ tanks experience boil-off rates typically between 0.1-0.5% per day. This boil-off gas can be captured and used as fuel.

A French classification society providing certification and compliance services for ships and maritime equipment. One of the major organizations granting Type Approval and AiP for hydrogen fuel cell systems.

The process of refueling a ship. For hydrogen vessels, bunkering involves specialized equipment to safely transfer compressed or liquid hydrogen from shore facilities or bunker vessels to the ship’s storage tanks. Infrastructure development is a key challenge for hydrogen adoption.

Independent organizations that establish and maintain technical standards for the design, construction, and operation of ships. They conduct inspections and issue certificates. Major classification societies include DNV, Lloyd’s Register, Bureau Veritas, ABS, and RINA.

Hydrogen stored at high pressure (typically 350-700 bar) at ambient temperature. Simpler technology than liquid hydrogen but has lower energy density per volume. Common in smaller vessels, inland barges, and service vessels where space is less critical.

Storage of liquefied gases at extremely low temperatures. For hydrogen, this means maintaining temperatures at -253°C (-423°F). Requires specialized vacuum-insulated tanks (typically Type C tanks for ships) to minimize boil-off and maintain structural integrity.

Small, fast vessels used to transport crew and equipment to offshore installations, particularly wind farms. The Hydrocat 48 is an example of a hydrogen-powered CTV operating in the offshore wind sector.

A leading Norwegian-German classification society and one of the world’s largest organizations for ship certification and standards. DNV has been at the forefront of developing rules and approvals for hydrogen-powered vessels and fuel cell systems.

An internal combustion engine capable of running on two different fuels, typically diesel/marine gas oil and hydrogen. Allows ships to operate on hydrogen when available and switch to conventional fuel when necessary. The BeHydro V12 used in the Hydrotug 1 is an example.

The amount of energy stored per unit of volume or mass. Hydrogen has high energy density by mass (about 3x that of diesel) but low energy density by volume, which is why storage method (compressed vs. liquid) significantly impacts ship design and range.

A European Union funding program supporting innovative low-carbon technologies. Several hydrogen ship projects have received grants, including Energy Observer 2 (€40 million) and various ferry projects, helping accelerate the development of zero-emission vessels.

An electrochemical device that converts hydrogen and oxygen into electricity, water, and heat through a chemical reaction. Unlike batteries, fuel cells produce electricity as long as hydrogen fuel is supplied. More efficient and quieter than combustion engines, with zero emissions at point of use.

Multiple individual fuel cells connected in series to increase voltage and power output. Maritime fuel cell systems typically consist of multiple stacks arranged in modules. For example, a 200 kW system might use 4-6 stacks of 30-50 kW each.

Hydrogen produced through electrolysis using renewable energy sources (wind, solar, hydro). This production method results in zero carbon emissions. Contrasts with “gray hydrogen” (from natural gas) and “blue hydrogen” (from natural gas with carbon capture). Essential for truly zero-emission shipping.

The lightest and most abundant element in the universe. As a fuel, hydrogen produces only water vapor when burned or used in fuel cells, making it a zero-emission energy carrier. Can be stored as compressed gas, liquid, or in chemical carriers like ammonia or methanol.

A modified internal combustion engine that burns hydrogen instead of conventional fuels. Produces water vapor and minimal NOx emissions. Less efficient than fuel cells (typically 35-40% vs. 50-60%) but more familiar technology for ship operators and can provide high power output. Used in vessels like the Hydrotug 1.

A type of fuel cell operating at higher temperatures (150-200°C) compared to LT-PEM. Better tolerance for fuel impurities and can utilize waste heat more effectively, but requires more complex materials and longer startup times. Less common in current maritime applications than LT-PEM.

An IMO regulation providing mandatory international standards for ships using low-flashpoint fuels. Currently covers natural gas in detail. Hydrogen-specific regulations are under development, expected by 2028. Until then, hydrogen ships require Alternative Design Approval.

The United Nations specialized agency responsible for regulating shipping. Sets international standards for safety, security, and environmental performance. Currently developing specific regulations for hydrogen as a marine fuel, expected to be finalized by 2028.

Ships designed for operation on rivers, canals, and inland waterways. Often among the first to adopt hydrogen due to shorter routes, predictable schedules, and proximity to refueling infrastructure. Examples include H₂ Barge 1 and Antonie.

Hydrogen cooled to -253°C (-423°F), turning it into a liquid state. Provides much higher energy density per volume than compressed hydrogen (about 800 times denser than gaseous H₂ at atmospheric pressure), making it suitable for larger vessels and longer voyages. Requires sophisticated cryogenic storage systems.

A British classification society and one of the world’s oldest (founded 1760). Provides certification and technical standards for maritime vessels and equipment. Active in hydrogen technology approval, including the Hydrocat 48 and Ballard fuel cells.

The most common type of fuel cell for maritime applications, operating at 60-80°C. Compact, quick to start, and well-suited for variable loads. Requires high-purity hydrogen. Systems from Ballard, PowerCell, Nedstack, and others use LT-PEM technology.

A unit of power equal to one million watts or 1,000 kilowatts. Used to describe the power output of fuel cell systems, engines, and overall propulsion systems. Small vessels might use 0.4-2 MW, while larger ships may require 4-10 MW or more.

Ships designed to operate in offshore environments, including crew transfer vessels (CTVs), service operation vessels (SOVs), platform supply vessels (PSVs), and offshore support vessels (OSVs). Many are exploring hydrogen propulsion due to emissions regulations in offshore wind farm areas.

A type of fuel cell using a polymer membrane to conduct protons from anode to cathode while blocking electrons, generating electricity. The dominant technology for maritime hydrogen applications due to its compact size, quick startup, and good power-to-weight ratio. Available in low-temperature (LT-PEM) and high-temperature (HT-PEM) variants.

The amount of power produced per unit of weight or volume. Higher power density means more compact systems. Critical for maritime applications where space is limited. Modern maritime fuel cells achieve 0.6-1.0 kW/kg and 0.8-1.5 kW/liter.

An Italian classification society providing certification services for ships and marine technology. Has granted type approval and AiP for several hydrogen fuel cell systems, including Vinssen’s 60 kW stack.

Ships designed to carry wheeled cargo that can be driven on and off. The Wilhelmsen Topeka is an example of a hydrogen-powered ro-ro vessel design under development.

Specialized ships that serve as floating bases for offshore wind farm maintenance crews. They provide accommodation, workspace, and equipment storage, staying on location for weeks at a time. Ideal candidates for hydrogen propulsion due to predictable routes and long periods of stationary operation.

A standard measure of cargo capacity based on a 20-foot (6.1 m) shipping container. Used to describe the capacity of container ships. Energy Observer 2, for example, is designed as a 1,100 TEU containership.

A certification from a classification society confirming that a product design meets all applicable rules and standards for series production and commercial use. More comprehensive than AiP and allows the product to be sold and installed on ships. The final regulatory step before commercialization.

An advanced insulation method using a vacuum between inner and outer walls to minimize heat transfer. Essential for cryogenic liquid hydrogen storage to reduce boil-off rates. The MF Hydra’s LH₂ tank uses vacuum insulation to maintain -253°C temperatures.

A ship that produces no greenhouse gases or pollutants during operation. When powered by green hydrogen (produced from renewable energy), vessels achieve true zero emissions across their entire energy chain. The ultimate goal for sustainable maritime transportation.