Hydrogen is one of the most abundant elements available on the planet. It is increasingly recognized in the transportation industry as a critical source for fuel cells. Fuel cells convert the chemical energy of a fuel directly into usable energy – electricity and heat – without combustion. They have recently penetrated the electric vehicle market due to their efficiency, quick refueling, and longevity. Many of today’s larger truck manufacturers are looking to fuel cells as a long-haul goods transport solution that can also reduce harmful emissions.

How Do Hydrogen Fuel Cells Work?

A fuel cell is made up of an anode, cathode, and an electrolyte membrane. The hydrogen is fed through the negatively charged anode of a fuel cell and oxygen is fed through the positively charged cathode. Protons flow across the porous electrolyte membrane, while the electrons flow from the anode to cathode in an external circuit―generating an electric current and excess heat.  At the cathode, the protons, electrons, and oxygen combine to produce water molecules. As there are no moving parts, fuel cells operate silently and with extremely high reliability.

Fuel cell manufacturers must rely on innovative manufacturing techniques to consistently deliver quality bipolar plates and membranes with tight specifications. For bipolar plates, quality characteristics such as channel straightness, shape, and texture can hinder the flow of oxygen or hydrogen, diminishing the overall efficacy of the electrochemical process. Channel straightness and shape impact the efficient flow of gases or liquid through the fuel cell. Additionally, any deviation from the design could lead to a pressure change, impeding the flow rate of the materials and gradually diminishing energy output.

Characterizing Fuel Cell Surfaces

For fuel cells, surface properties impact their efficiency and must be kept within specified target parameters. To address these challenges, manufacturers rely on non-contact optical metrology inspection. Traditionally, manufacturers used CMMs (coordinate measuring system) to review plate flatness or channel depth. But this only provides tens to hundreds of points to capture the surface under examination, consuming considerable time.  Manufacturers which employ 3D non-contact optical profilers achieve quick and repeatable bipolar plate channel inspection with millions of data points, capturing the entire surface with high lateral resolution.

One instance of plate inspection can be conducted with the Zygo 0.5x ZWF objective; with its large field of view (>30mm). By area stitching an entire plate, it is possible to determine channel depth, channel straightness, and overall sealing flatness. Determining channel depth with high accuracy also allows fuel cell plate designers to minimize plate thickness — consequently optimizing the entire fuel cell stack and reducing overall mass.

As fuel cells move to the forefront of innovation for electric vehicles, tight manufacturing specifications must be met for their production. Optical surface topography measuring instruments, such as Zygo’s 3D non-contact optical profilers, provide in-process surface texture and form measurements — a significantly more comprehensive, faster, and cost-efficient inspection than CMM inspections. As automotive engineers and designers continue to push the boundaries of efficient and clean energy systems, Zygo will continue to partner with manufacturers to facilitate precise measurements of their surfaces and deliver knowledgeable insights.