What is the Role of Hydrogen Fuel in Sustainable Mobility?

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Editorial Team - everything PE

Apr 4, 2024

The conventional fuels such as petrol, diesel, etc used in vehicles produce enormous amounts of pollutants that damage the environment. This has led to a high demand for environment-friendly fuel solutions for mobility. Sustainable mobility refers to the various transportation modes such as automobiles, trucks, trains, etc., that minimize environmental impact, promote social equity, and ensure economic viability for now and in the future. It contributes to the reduction in the emission of greenhouse gases such as carbon dioxide thereby reducing atmospheric pollution, improving air quality, and reducing global warming and ozone layer depletion.

Hydrogen Fuel: The Premier Source of Sustainable Energy

Hydrogen is the simplest and most abundant element in the universe. It is considered to be a renewable energy source for the future. The natural occurrence of hydrogen is in the form of compounds with other elements such as oxygen to form water or carbon to form hydrocarbons. Although the industrial and chemical applications of hydrogen have been widely exploited, its potential as a sustainable energy source is a topic of recent interest. Hydrogen when used as a fuel in engines is preferred in its liquid form. It needs to be produced from renewable or non-renewable sources as it is naturally not found in liquid form.

  • Grey Hydrogen: Grey hydrogen refers to the hydrogen gas that is produced from natural gas through the process of steam methane reforming (SMR) without any means of carbon capture and storage (CCS). It is the most commonly used method of hydrogen production and extracts hydrogen from methane (CH4). Grey hydrogen results in the most carbon-intensive form of hydrogen production releasing carbon dioxide into the atmosphere and affecting climate change.
  • Blue Hydrogen: Blue hydrogen refers to hydrogen gas that is produced from natural gas through the process of steam methane reforming (SMR), with carbon capture and storage (CCS) employed to capture and store the carbon dioxide (CO2) emissions generated during the production process. The captured CO2 is then compressed and transported to suitable geological areas for long-term storage, such as depleted oil and gas reservoirs, saline aquifers, or deep geological formations, where it is stored securely underground.
  • Green Hydrogen: Green hydrogen refers to hydrogen gas that is produced using renewable energy sources, such as wind or solar power. This energy is used to electrolyze water (H2O) into hydrogen (H2) and oxygen (O2). Unlike conventional methods of hydrogen production, which rely on fossil fuels like natural gas, green hydrogen production does not produce greenhouse gas emissions or other pollutants. This makes green hydrogen a clean and renewable energy carrier for sustainable mobility applications.

There are two types of hydrogen vehicles - 

  • Hydrogen Vehicles using Electric Motor
  • Hydrogen Vehicles using IC Engine

Both types of vehicles use hydrogen as fuel. The difference lies in the way they convert the fuel into power. 

A hydrogen vehicle that uses an electric motor is known as a Fuel Cell Electric Vehicle (FCEV). In this type of vehicle, hydrogen gas is fed into the fuel cell stack where it undergoes a chemical reaction with oxygen in the air to produce electricity. 

There are two types of fuel cell stacks: 

  • Proton-Exchange-Membrane Fuel Cell (PEMFC) Stack – A PEMFC stack is a collection of proton exchange membrane fuel cells arranged in series or parallel to generate electrical power. Each fuel cell within the stack consists of various layers, including a proton exchange membrane (PEM), an anode, and a cathode. It is mostly used in applications where high power density, compact size, and quick start-up are essential such as in fuel cell vehicles (FCVs) and small-scale stationary power systems.
  • Solid-Oxide-Fuel-Cells (SOFC) Stack – The SOFC stack is a collection of solid oxide fuel cells arranged in series or parallel to generate electrical power. The individual cells within a SOFC stack are electrically connected to increase the overall voltage and current output. It is ideal for stationary power generation applications such as combined heat and power (CHP) systems for residential, commercial, and industrial use and also for grid-scale power plants.

Working Principle of FCEV

A fuel cell stack consists of multiple fuel cells which are stacked together to increase the amount of electricity produced. Each fuel cell consists of an anode, a cathode, and an electrolyte. When hydrogen gas is introduced to the anode and oxygen is introduced to the cathode, a chemical reaction occurs producing protons and electrons. The protons pass through the electrolyte to the cathode, whereas the electrons are forced through an external circuit, generating an electric current. This electric current powers an electric motor that drives the vehicle’s wheels with water being the only by-product of the reaction. Thus, the fuel cell stack does not burn the hydrogen gas, rather it transforms the chemical energy of hydrogen to electrical energy.

Key Components of FCEV 

  • Fuel Cell Stack: It is the heart of a FCEV and contains an assembly of multiple fuel cells that use hydrogen and oxygen to produce electricity.
  • Fuel Filler: It is an access point through which fuel is added to the vehicle’s fuel tank.
  • Fuel Tank (Hydrogen): Hydrogen FCEVs store hydrogen gas on board in high-pressure tanks or liquid form, depending on the vehicle design. Safe and efficient storage of inflammable hydrogen is a technically challenging task and every vehicle manufacturer adopts different storage methods to address the issue.
  • Battery (Auxiliary): This low-voltage auxiliary battery supplies electricity to start the vehicle before the traction battery is engaged and also powers vehicle accessories.
  • Battery Pack: This high-voltage battery stores energy generated from regenerative braking and provides additional power to the electric traction motor.
  • DC-DC Converter: These converters convert high-voltage DC power from the traction battery pack to the low-voltage DC power needed to run vehicle accessories and recharge the auxiliary battery.
  • Electric Traction Motor: This motor drives the vehicle by utilizing power from the fuel cell and the traction battery pack. Hydrogen FCEVs are typically electric vehicles (EVs) in terms of their propulsion system, but instead of depending on batteries for energy storage, they use hydrogen fuel cells to generate electricity on demand.
  • Power Electronics Controller: This unit manages the flow of electrical energy delivered by the fuel cell and the traction battery and controls the speed and torque of the electric traction motor. 
  • Thermal Management System: This system maintains a proper operating temperature range of the fuel cell, electric motor, power electronics, and other components.
  • Transmission (Electric): The transmission transfers mechanical power from the electric traction motor to drive the wheels.

A hydrogen vehicle that uses a combustion engine is known as a Hydrogen Internal Combustion Engine Vehicle (H2ICE). In this type of vehicle, hydrogen gas is fed into an engine, where it is mixed with air and ignited. The resulting explosion drives a piston which turns a crankshaft and powers the car’s wheels. However, hydrogen internal combustion engines emit pollutants such as nitrogen oxide and other pollutants similar to gasoline-powered engines.  FCEVs have an efficiency of up to 60% which is two times higher than the efficiency of H2ICE. This implies that FCEVs require less hydrogen to travel the same distance making them cost-effective in the long run.

Key Advantages of Hydrogen as a Fuel

  • Zero Emission: The use of hydrogen in a fuel cell vehicle produces zero tailpipe emissions. The only derivative of the reaction between hydrogen and oxygen in the fuel cell is water vapor. This makes a hydrogen fuel cell vehicle (FCV) a clean and environmentally friendly transportation option.
  • Energy Efficiency: Hydrogen fuel cells are highly efficient energy converters compared to traditional internal combustion engines. Its higher energy conversion efficiency leads to reduced energy consumption per mile traveled.
  • Fast Refuelling: The fuelling time needed for hydrogen fuel cells is comparable to that of gasoline or diesel vehicles, typically taking a few minutes to fill a tank. This fast refueling capability eliminates the range anxiety often associated with battery electric vehicles (BEVs) and makes hydrogen FCVs more suitable for long-distance travel.
  • Longer Range: Hydrogen FCVs offer longer driving ranges compared to battery electric vehicles (BEVs). This is because hydrogen has a higher energy density by weight compared to batteries, allowing for more energy to be stored onboard and providing a greater driving range per tank.
  • Versatility: Hydrogen can be produced from a variety of renewable and non-renewable such as water electrolysis using renewable electricity, natural gas reforming with carbon capture and storage (CCS), biomass gasification, and wastewater treatment. This versatility allows hydrogen to be integrated into existing energy systems and enables a transition to renewable hydrogen production over time.
  • Diverse Applications: Hydrogen fuel cell technology is not limited to passenger cars but can also be applied to other vehicle types such as buses, trucks, trains, and maritime vessels. This versatility allows hydrogen to play a significant role in decarbonizing various sectors of the transportation industry.
  • Minimize Dependency on Fossil Fuels: The usage of hydrogen reduces dependency on fossil fuels and enhances energy security. This is very crucial in this era of climate change, air pollution, and the finite nature of fossil fuel resources.

Limitations of Hydrogen Fuel in Mobility

While hydrogen technology offers many advantages for sustainable mobility, it also has several technical shortcomings that limit its widespread adoption. Some of the key limitations include:

  • Infrastructure: The greatest challenge faced by this technology is the lack of infrastructure for hydrogen production, distribution, and refueling. Huge infrastructural investment in terms of hydrogen production facilities, transportation, storage, and dispensing stations is necessary to build a hydrogen refueling network. 
  • Cost of Production: The revenue required to produce hydrogen is relatively high compared to traditional fossil fuels. Most hydrogen is currently produced through steam methane reforming (SMR) or electrolysis, both of which require energy inputs. While renewable energy sources can be used to produce green hydrogen through electrolysis, the technology remains more expensive compared to fossil fuel-based hydrogen production methods.
  • Storage and Distribution: Specialized tanks or storage systems are needed to store hydrogen compactly and safely, which adds weight and cost to the vehicle. Also, the transportation of hydrogen from production facilities to refueling stations is energy-intensive, especially for long distances.
  • Fueling Time and Range: The fueling time for hydrogen vehicles is comparable to gasoline refueling. The driving range of hydrogen fuel cell vehicles is limited compared to conventional internal combustion vehicles or battery electric vehicles. This is due to the need for large onboard hydrogen storage tanks, which impacts the vehicle design and payload capacity.
  • Safety: The highly flammable nature of hydrogen necessitates careful handling to ensure vehicle safety. Though hydrogen fuel cell vehicles are designed with various safety features, including robust hydrogen storage tanks and leak detection systems, anxiety about hydrogen safety remains a limitation to the widespread adoption of hydrogen technology. 

Thus, hydrogen fuel offers a promising pathway to clean and sustainable mobility, particularly for applications where long driving ranges and fast refueling are essential, such as heavy-duty trucks and buses.

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