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Hydrogen fuel and its applications, particularly in the context of clean energy and sustainable transportation.
Why hydrogen Fuel?
Let us explore the key reasons behind using Hydrogen as a fuel in Transportation.
The global transport sector’s contribution to total CO2 emissions is close to 25%. Hence need to de-carbonize the transport sector as quickly as possible to arrest the global warming which is accelerating.
Decarbonizing transport refers to the process of reducing and eventually eliminating greenhouse gas emissions (GHG) associated with the transportation sector. This is crucial for combating climate change, as transportation is a major contributor to global CO2 and NOx emissions.
Hydrogen reacts or burns in air (with oxygen) releasing heat and water vapor only. This reaction highlights that no carbon containing products or CO/CO2 emissions at the point of use. No other green house gases (GHG). Here it is assumed complete burn or complete oxidation at normal temperature and pressure. Burning hydrogen at high pressure, high temperature in closed chamber results in production of NOx gases. However no CO/CO2 is produced.
Similarly when hydrogen is used in a fuel cell, hydrogen generates only electricity, water, and heat when it reacts with oxygen, through an electro chemical reaction. No carbon dioxide (CO2) or no other GH gas is produced when using hydrogen in a fuel cell because no combustion happens. Thus hydrogen as a clean fuel, no harm to environment, good for the climate to sustain. This makes hydrogen a very attractive option for transportation and power generation.
Hydrogen has highest gravimetric energy density (see the table) being the primary reason for considering hydrogen as a strong contender, as an alternative among all types of fuels. In simple terms, by weight, hydrogen holds a highest amount of energy. Approximately 3 kilograms of gasoline required to provide the same amount of energy as 1 kilogram of hydrogen. This physical aspect makes hydrogen as an energy carrier as well. This makes it extremely attractive for both transportation and stationary power applications.
Challenges:
Under normal pressure and temperature conditions, 1 kg of hydrogen occupies approximately 12,000 Litres where as 1 kg of gasoline = 1.34 Litres.
You can now imagine!
Due to its extremely low density, hydrogen in gaseous form takes up huge volume at normal atmospheric pressure. That is by volumetric energy density, hydrogen is the lowest among all. Hence for all practical purposes of hydrogen use, it has to be compressed or liquefied, this is the major roadblock in using hydrogen in transportation other than hydrogen is highly flammable and can ignite easily in normal conditions.
Hence in mobility applications like heavy duty, long haul transport, hydrogen storage requirements can significantly limit passenger and cargo space. Similarly, in passenger vehicles, there’s a trade-off between passenger space, comfort and range.
Reasons for considering Hydrogen as an alternative fuel, comparing with Battery electric vehicles (BEV):
It’s suitable for larger vehicles where battery weight could be prohibitive.
Heavy-duty transport is the ideal use case for hydrogen. The long-range capabilities and fast refueling mean they can match and exceed the performance of diesel trucks, while producing zero emissions at the tailpipe.
For long haul trucking, hydrogen provide a potential answer that could balance distance coverage, weight, and refueling duration. They have the capability to offer a range similar to that of diesel trucks and can be refueled less than 15 minutes. (using Liquid Hydrogen).
There are only two approaches for utilizing hydrogen fuel in transportation.
Hydrogen internal combustion engine (H2ICE or HICE):
This method involves burning hydrogen directly in an internal combustion engine, same like gasoline or diesel vehicles. This combustion generates power to drive the wheels. While emissions are cleaner, near zero CO2 than fossil fuel engines, they still produce NOx (nitrogen oxides), requiring additional exhaust control technologies. We must note that no CO/CO2 emissions are produced in the combustion of hydrogen directly in the engine (except some traces of CO2 from the burned lubricants). No solid particles are produced from the combustion exhaust.
The efficiency of H2ICE is approximately in the range of 38-40% inline with that of conventional gasoline, diesel counterparts.
Hydrogen engines are entirely mechanical, same like gasoline, diesel powered vehicles today.
Hydrogen Fuel Cell based Electric Vehicle (H2FC):
Here, hydrogen from onboard storage tank is converted back into electricity via a fuel cell onboard the vehicle. This generated electricity then powers the electric motor. However, due to energy losses during the conversion process (assuming green hydrogen is used), FCEVs require roughly 2.3 times more electricity to operate compared to battery electric vehicles. No mechanical or combustion process is involved as fuel cell, produces electricity through an electrochemical reaction.
Fuel cell based vehicles are pure zero emission vehicles (ZEV) as no CO2, NOx, unburnt fuels or solid particles are emitted, because there is no combustion or burning at all!
Onboard hydrogen storage challenges remains the same as that of H2ICE powered. There’s a trade-off between space and range.
Relative strengths of H2ICE and H2FC:
Heavy Commercial vehicles (HCV) of significant weight are often required to have extensive range and high-power capabilities. As such, HCVs, including long-haul trucks (LH), are prime candidates for hydrogen based. The hydrogen combustion engine (Hydrogen engines) presents a promising alternative to battery electric and fuel cell electric vehicles, contributing to the goal of a carbon dioxide-free commercial vehicle industry.
Potential Cost Advantage: H2ICE vehicles are cost-effective alternative to fuel cell vehicles, due to their simpler technology and adaptation of existing (gasoline) engine infrastructure.
H2ICEs could leverage the existing network of gas stations, thus easing the smooth transition to hydrogen fuel.
H2FC boast high efficiency (in terms of Fuel Tank Hydrogen to electricity), strictly zero emissions in par with a battery electric vehicle (BEV). However the cost is very high, and a very complex system, however intensive R&D is happening across to overcome the issues and huge cost associated.
.Hydrogen fuel in transportation is still in its infancy. However both H2FCV and H2ICE, have the potential to revolutionize the automotive industry by providing sustainable and eco-friendly transportation solutions.
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