The challenge
Unlike grid energy, fuel cells require an upfront investment from the user. Manufacturers therefore need to demonstrate efficiency and durability to give confidence that the cell will offset this initial investment over its lifetime. To understand durability, cells are tested under accelerated degradation conditions to simulate how they will degrade over their lifetime.
Bramble Energy’s fuel cell uses a passivation layer to increase durability – a thin coating which protects the copper components from the corrosive environment of the fuel cell.
Bramble discovered that the passivation layer was not performing as expected. To understand why, they approached NPL through the Analysis for Innovators Programme (A4I), a £4M Innovate UK programme which helps companies access measurement and analysis expertise, in order to solve a problem which could improve their productivity or competitiveness.
The solution
NPL has world-leading capabilities in fuel cell measurements, as well as corrosion testing. Combining these areas of expertise, NPL carried out a range of analyses of Bramble's materials to help them understand their degradation mechanisms, and recommend areas for improvement.
During the nine-month project, Bramble was able to access NPL's state-of-the-art imaging and electrochemical testing facilities, including electron microscopy and electrochemical analysis, as well as its expertise in fuel cell degradation mechanisms.
The most important finding was the unexpected presence of silicon rods scattered around the surface, causing localised stresses. Bramble worked with their manufacturer to identify the source of these rods – an innocuous skimming process – and developed a new manufacturing approach which will eliminate the problem.
Rigorous analyses of samples by NPL before and after degradation testing, and subsequent recommendations, provided Bramble with insight into degradation mechanisms, and helped them tailor their materials selection to improve durability. Testing to date on the new passivation layer suggests these changes have slowed the degradation and will significantly improve durability.
The impact
Bramble has to date been developing products for the low power portable power market. However, the scalability of their innovative new design, which can be produced cheaply using manufacturing methods and materials from the printed circuit board (PCB) industry, offers more lucrative opportunities in higher power applications, such as automotive and combined heat and power (CHP).
For these industries, Bramble must demonstrate durability of tens of thousands of hours in use. This project helped them identify and resolve an issue which was leading the product to degrade too quickly, and so limiting commercial viability. The resulting improvements to durability extended the product lifetime and therefore the competitiveness of their fuel cell, whilst also speeding time to market.
This work was done as part of the Analysis for Innovators programme.
