What is a hydrogen fuel cell stack and what are the applications?

Fuel cells are increasing the range and efficiency of drones, cars, planes and material handling equipment. With hydrogen in tow, they are paving the way for zero-emission technology in those hard-to-abate sectors. But what sits at the heart of this technology? What are fuel cells made of and how do they support these applications?

What is a hydrogen fuel cell stack and how does it work?

The function of a hydrogen powered fuel cell is to convert chemical energy to electrical energy through an electrochemical reaction between hydrogen and oxygen, with the only by-products of such a reaction being water and heat (read our blog on hydrogen fuel cell technology here).

A single fuel cell is made up of very few parts; two plates (negative anode and positive cathode) to fulfil structural function and provide electrical and thermal properties, gaskets to help provide gas seal under operation, gas diffusion layers (GDL) to aid with gas distribution and water management within the fuel cell, and an MEA (membrane electrode assembly).

The MEA

The MEA is split up into three layers; an anode electrode, a cathode electrode and a middle membrane layer. The electrode layers are generally comprised of a porous material combined with a catalyst and the electrolyte membrane is made of polymers providing chemical and mechanical support. It is important that the membrane layer of the MEA is electronically insulating and should only facilitate the transportation of protons through the membrane to the cathode side.

The reaction within a hydrogen fuel cell stack

Below are the steps involved during a reaction within a hydrogen fuel cell stack, summarised:

1. The single fuel cell parts are appropriately compressed to ensure that they are sealed, and no gas leaks are present.
2. The hydrogen is fed into the anode side and, with the help of the GDLs and plate flow fields, it flows onto the anode side of the MEA.
3. It is here that the hydrogen is catalytically split into protons and electrons and the protons are conducted through electrolyte membrane to the cathode side.
4. The electrons pass along an external circuit (via the anode plate) to the cathode side of the MEA (via the cathode plate) which generates the DC load output of the fuel cell.
5. Whilst this is happening, oxygen from the ambient air is fed into the cathode side of the MEA.
6. Here, oxygen molecules react with the protons that have transported through the membrane and the external electrons to create water molecules.

Stacks

Single fuel cells are then loaded on top of one another to create a fuel cell stack of any number of fuel cells based on the power requirements needed by the system. Stack endplates (positive and negative) surround the base and top of the stack providing current take-offs and sound structural support.

Types of hydrogen fuel cell stacks

There are many different types of fuel cells, ranging from solid oxide to alkaline, however here at Intelligent Energy Ltd we produce proton-exchange membrane (PEM) fuel cells due to the advantageous high-power densities, low weight and volume compared to other fuel cells. Other benefits include comparably lower running temperatures, allowing for much more rapid start-ups and less wear on system components.

Learn more about the different types of fuel cells available in our guide here.

Fuel cell stacks and fuel cell modules

Fuel cell stacks are housed within a system called a fuel cell module. These modules contain a fuel cell stack with required components to operate and manage generation of power, e.g. control software, electronics, hydrogen valves and fans. The communication between a fuel cell and system is essential to the ongoing running of the fuel cell and the generation of usable power.

Applications of hydrogen fuel cell stacks

When incorporating fuel cells into products, it is important to understand the requirements of the product.

For example, in the UAV/drone product range, it is vital to ensure the mass of the fuel cell is a low as possible and is able to output a high-power density for short periods of time.

Alternatively, stationary power applications have less onerous mass requirements but rely on a robust structure and long durability to operate in the environments they are used it.

Automotive applications such as cars, trucks and buses rely on both; mass impacts the range and robustness impacts reliability, so engineering trade-offs are carried out to provide the best possible the outcome.

Hydrogen fuel cell stacks offer a number of benefits across a range of industries in comparison to traditional fuel or batteries. Applications are diverse, and hydrogen fuel cell stacks can be found in systems across the automotive, aviation, materials handling equipment, micro-grid, telecoms and UAV sectors.

If you’d like to find out more about our capabilities and how we can help your business with its renewable energy requirements, please get in touch with us today. Complete our contact form or send us an email at sales@intelligent-energy.com.