Green hydrogen is hydrogen produced by the electrolysis of water using electricity generated from renewable energy sources like solar or wind power. This production method results in zero or near-zero greenhouse gas emissions on a lifecycle basis, making it a critical component of efforts to achieve net-zero economies and transition to sustainable energy. 

How Hydrogen Energy and Fuel Stacks Work?

Hydrogen energy works by using a fuel cell to convert the chemical energy of hydrogen and oxygen into electrical energy without combustion. 

A fuel cell stack is an assembly of many individual fuel cells connected in series to achieve a useful level of power output, as a single cell typically produces less than one volt. 

The process within a fuel stack:

Hydrogen is fed into the negative electrode (anode) side of the cell, and oxygen (from the air) is fed into the positive electrode (cathode) side.

At the anode, a catalyst splits the hydrogen molecules into positively charged protons and negatively charged electrons.

The protons pass through a special electrolyte membrane to the cathode.

The electrons are forced through an external circuit to reach the cathode, creating a flow of electrical current that can power a device.

At the cathode, the protons, electrons, and oxygen combine to produce water (H₂O) and heat, which are the only byproducts. 

Features of Fuel Cell Stacks

Zero Emissions: When using pure hydrogen, fuel cell stacks emit only water vapor and warm air at the point of use, making them an environmentally friendly power source.

High Efficiency: They convert chemical energy to electricity through an electrochemical reaction, which is typically more efficient than traditional combustion engines.

Continuous Power: Unlike batteries that store a finite amount of energy and require recharging, fuel cells produce electricity as long as fuel (hydrogen) and air are supplied.

Scalability: Individual cells can be stacked together to meet diverse power requirements, from a few watts for portable electronics to megawatts for utility-scale power plants.

Quiet Operation: They have few or no moving parts and generate electricity silently.

Modularity: Stacks are housed within fuel cell modules that include balance-of-plant components like cooling systems, control software, and power electronics to manage operation and output. 

Applications of Hydrogen Fuel Stacks

Fuel cell stacks are used across a diverse range of applications: 

Transportation: Powering vehicles such as passenger cars, buses, heavy-duty trucks, forklifts, drones, and potentially aviation and shipping.

Stationary Power Generation: Providing primary or backup power for critical facilities like hospitals, data centers, and telecommunications hubs.

Portable Power: Used in small electronics like laptops or remote sensors.

Industrial Processes: Providing process heat or acting as a feedstock for industries such as steelmaking, petroleum refining, and ammonia production.

Energy Storage: Storing excess renewable energy (as hydrogen) for later use, providing long-duration or seasonal energy resilience. 

How to Select Fuel Cell Stacks?

Selecting a fuel cell stack depends heavily on the specific application requirements: 

Power Output: Determine the required electrical power (voltage and current) and the number of cells needed to achieve it.

Fuel Cell Type: The type (e.g., Proton Exchange Membrane (PEM), Solid Oxide (SOFC), Alkaline (AFC)) dictates operating temperature, required fuel purity, and efficiency, influencing suitability for a given use case.

Operating Conditions: Consider the operational environment, including temperature range (e.g., low temp for automotive, high temp for stationary power where waste heat can be utilized), pressure requirements, and physical space constraints.

Durability and Lifespan: Different applications have different lifespan requirements (e.g., 5,000 hours for cars vs. 20,000+ hours for buses).

Cost vs. Performance Trade-off: Balance initial capital investment with long-term operational costs, efficiency needs, and maintenance requirements. 

Price of Fuel Cell Stacks

The price of fuel cell stacks is currently a significant barrier to widespread adoption. Producing clean hydrogen and the associated fuel cell technology is often more expensive than conventional power sources and even some other clean energy options like battery-electric vehicles in certain applications. 

Cost Factors: Prices are influenced by the type of fuel cell, material costs (e.g., platinum catalysts are common in PEM cells), power output, and scale of production.

Current Trends: While costs remain high, significant global investment, research, and development in an expanding electrolyzer and fuel cell pipeline are aimed at reducing costs and achieving market competitiveness in the coming years. The ultimate goal is to make clean hydrogen and fuel cells cost-competitive to help meet climate goals