Hydrogen as a Marine Fuel (Part 1 of 3)

Emissions regulations – CO2 emission regulations

The drive towards a low carbon future in the marine industry is gaining momentum with IMO establishing a vision towards a mandatory reduction in greenhouse gas emissions from shipping. The International Maritime Organisation has also come up with a strategy to specifically target the carbon emissions from the marine industry as detailed in IMO Strategy on reduction of greenhouse gas emissions from ships, 2018.

The environmental aspects will continue to drive the adoption of efficiency measures, adoption of alternate fuels or other methods such as carbon capture.

Alternate fuels such as LNG, LPG, Methanol, Ammonia etc are gaining prominence. Hydrogen is also considered as one of the alternates.

Let us look at the basics of this fuel and its possible application in the marine industry as an alternate fuel in this three part article.

What is Hydrogen?

Source - (https://phys.org/news/2019-12-scientists-cheaper-hydrogen-energy.html)


Hydrogen is the most abundant element in this universe – when we consider the oceans and other water bodies. It is available in gaseous form as a colourless, odourless and flammable substance.

Being a flammable gas with energy content, it has been explored as a source of energy in various applications including space rockets.

Hydrogen Production

It is mainly produced by reforming natural gas. There are also ways to produce Hydrogen through electrolysis for water or from renewable energy sources.

Currently, the predominant way of producing Hydrogen is from reforming of natural gas.

Boiling Point	-253C
Density	70.96 kg/m3
Heating value	119.93 (LHV)
Flammability Limits	4.2 – 77% (vol. fraction% - in NTP air)
Ignition Energy	0.017 mJ (for Ignition in air)
Auto-ignition temperature	858K

Some of its properties (Source – ISO 15916:2015)

What do we mean when we say H2 as fuel?

Hydrogen as a source of energy has been used in several applications. It can be used in internal combustion engines as fuel in its gaseous form.

More widely, it has been used in conjunction with fuel cells application.

Using H2 as fuel in internal combustion engines

BMW - Hydrogen Powered IC Engine Car (Source - Wikipedia)

Hydrogen’s application as a fuel in internal combustion engines is widely documented. Several of the automotive companies have developed IC engines using Hydrogen as Fuel.

It includes combustion of Hydrogen directly in the engines as a gas or mixing it with another hydrocarbon based gas.

There are also two different ways to inject Hydrogen as fuel to the internal combustion engines.

(i) Direct injection to the engine cylinder

(ii) Injection of Hydrogen gas to the charge air before entering the cylinder

Both of the above are already been used for LNG fuelled engines. However, these would require considerable modifications to suit for using Hydrogen.

It should be recognised that due to the high self-ignition temperature of Hydrogen, the internal combustion engine would need to be of the spark plug type.

Emissions associated with Internal Combustion Engines

We are using Hydrogen with the intention of reducing any emissions. Let’s examine if that would 100% true.

The products of Hydrogen undergoing a chemical combustion are essentially water vapour.

The Balanced chemical equation would be 2H2 + O2 = 2H2O

However we should take into consideration of emissions from other aspects.

NOx Emissions 

NOx emissions are a function of the combustion temperature and more or less remains the same across similar engine sizes regardless of the fuel. Accordingly, we would still require some means of after treatment (Selective Catalytic Reduction – SCR OR Exhaust Gas Re-circulation – EGR) etc. depending on the engine type.

Other Emissions 

Engines would need lubricating oil to function, i.e. to lubricate the engine components. A small portion of which goes into to cylinder, for sealing the piston rings etc, is designed to be burned in the cylinder. Certainly this would cause some carbon emissions and also particulate matter.

Using Hydrogen in Association with Fuel Cells

Fuel cells placed onboard a ship could produce electricity which then be used to power motors for electric propulsion of a ship. Hydrogen would be used in association with these fuel cells.

Two types of fuel cells has been in service in the marine industry.

The Proton- Exchange Membrane Fuel Cell (PEM-FC) and Solid Oxide Fuel Cell (SOFC). We will look at these fuel cells in detail in another blog post.

These fuel cells in essence would power a battery or battery bank which would feed the electric motor for propulsion. Hydrogen in liquid or compressed form would serve as fuel for these fuel cells.

Advantages

Let’s look at some of the advantages of Fuel Cells 

• There are no NOx emissions as there is no combustion.
• There are also no vibrations or noise as associated with the IC engines

Limitations

However fuel cells have certain limitations. These are expensive, the power density is low and the level of technology available with these systems are still in the development phase.