Green Hydrogen as Marine Fuel
• Green Hydrogen is a completely zero emission, particulate free fuel made by electrolysis of water using renewable energy.
• Hydrogen is stored as a compressed gas (CH2) or a liquid (LH2) below -252C.
• H2 also ignites more easily than natural gas and has a wider flammability range making handling it a complicated task.
• It can either be used in a fuel cell or a internal combustion engine.
• Current cost of green hydrogen is more than twice that of conventional fuels.
• Hydrogen is stored as a compressed gas (CH2) or a liquid (LH2) below -252C.
• H2 also ignites more easily than natural gas and has a wider flammability range making handling it a complicated task.
• It can either be used in a fuel cell or a internal combustion engine.
• Current cost of green hydrogen is more than twice that of conventional fuels.
At standard conditions, hydrogen is a colorless, odorless, tasteless, non-toxic, relatively nonreactive and highly combustible gas. Hydrogen has the highest energy content per mass amongst all the chemical fuels making it highly desirable to increase the efficiency of the engine. However, due to its lower volumetric energy density, LH2 may require four times more space than gas oil or about two times more space than liquefied natural gas (LNG) for an equivalent amount of carried energy.
Hydrogen is commonly produced by converting natural gas or coal into hydrogen gas and CO2, but for making it a truly green fuel it must be produced by the electrolysis of water using renewable electricity like wind or solar. This process is highly energy intensive and substantial quantities of renewable power must be available.
Green Hydrogen is a type of e-fuel or electrofuel.
Hydrogen requires low temperatures below -253° C (-423.4° F) to liquefy. The required volume to store liquid hydrogen could be even higher when considering the necessary layers of materials or vacuum insulation for cryogenic storage and other structural arrangements. There are also associated boil off losses and the necessary cooling requirements for the cryogenic tanks.
GH2 is stored in high pressure tanks (700bar) making it a major safety issue.
Hydrogen has been used as fuel most notably in space programs as rocket fuel. More recently, hydrogen has been used to power cars, buses, trucks, and ferries.
It can be burned in a specialised internal combustion engine or gas turbine with modifications to the fuel injection system and blended with LNG/diesel for a dual fuel operation reducing, but not completely eliminating emissions. It can be used in fuel cells (PEM/SOFC) to produce electricity with zero emissions. Proton Exchange Membrane (PEM) fuel cells have reported advantages of lower operating temperatures and superior gravimetric and volumetric power specifications compared to other types of fuel cells.
There are currently so regulations governing the use of hydrogen as a marine fuel. The crew will have to be trained correctly to deal with the specific risks of a hydrogen fire and the highly explosive nature in case its stored in compressed form at high pressure.
New SOPs will have to be developed before hydrogen can be used as a fuel safely in large quantities.