Stacking up: making hydrogen fuel-cell manufacturing viable
The world’s first automated robot for industrial alkaline fuel-cell assembly could trigger renewed interest in the technology.
It seems like the ideal solution. Hydrogen — the most abundant element in the universe — has the potential to fuel our cities, leaving behind nothing but water and heat as a by-product. But while it appears to be a promising technology, this vision of widespread hydrogen-fuelled homes has always been just out of reach.
For decades, the problem has been the high cost of fuel cells required to drive the process. This is now beginning to change as material prices fall and automated systems drive down production costs. In Japan, for instance, large firms such as Toshiba and Panasonic are using fuel cells in industrial boilers to create both heat and energy. In the US, companies such as Wal-Mart are using fuel cells to power fork-lift trucks.
Industry experts believe the UK could also be on the brink of embracing the technology. AFC Energy, for instance, is planning to capitalise on lower material costs by focusing on much larger fuel cells for industrial applications. The Surrey-based group is currently working on a four-year €6.1m (£4.9m) European Union project to develop commercial-scale energy-generation plants using hydrogen as a fuel source.
As part of this, AFC will provide hydrogen fuel cells to Air Products’ industrial gas processing facility in Stade, north Germany. The first of two systems is due to be installed later this year and the plant will generate a total of 500kW of electricity when fully operational. To power the plant, the group has come up with a larger fuel-cell design that has hundreds of components stacked together. The challenge now is to scale up its manufacturing process.
Manually assembling these stacks is impossible given the speed needed. The group looked at existing automation solutions but many proved to be unwieldy for these delicate components. To come up with an alternative, AFC teamed up with Cambridgeshire-based Innomech to create the world’s first automated manufacturing system for industrial alkaline fuel cells. Together, they have come up with a system that they claim can assemble many thousands of fuel-cell layers per day.
‘The project has proved more challenging that we anticipated,’ said Tim Mead, commercial director at Innomech. ‘The components are difficult to work with because they are reasonably large and delicate. There are lots of parts that are built up into each stack and there are fractions of a millimetre difference between one batch of components and another.’
Each batch contains individual fuel cells that have an anode, a cathode and an electrolyte layer. When a hydrogen-rich fuel, such as a biogas, enters the fuel-cell stack, it reacts electrochemically with oxygen to produce electric current, heat and water. Alkaline fuel cells are chemically comparable to a battery that provides electricity as long as it is topped up.
AFC’s fuel-cell stack is made up of layers of these anodes, cathodes and spacer components that form channels to carry hydrogen, air or potassium hydroxide electrolyte. The surfaces of the electrodes are extremely sensitive to damage, so the plates need to be interwoven with protective plastic spacers when stored. The anodes and cathodes also need to be correctly placed face up or face down within the stack.
The assembly system uses an ABB IRB 2600 industrial robot, with a 1.65m arm and a 20kg payload capacity surrounded by fuel-cell components. A similar system, said Mead, had previously been used to put together and test delicate medical equipment. ‘We’ve learned from different industries, but this really was a unique challenge because of the large number of components we were dealing with,’ he added.
An engineer starts the process by manually adding one component to the build frame. The machine then visits the frame, scans it to identify its position and then picks up different components to build the cell in a set sequence. ‘The robot has sensors that will detect the level of the accumulating stack to compensate for these fractions of millimetre build-up of tolerance,’ said Mead.
A specific pattern of holes is punched into each component. The robot presents the component to two SensoPart smart cameras that can read 2D matrix codes and track the life of the part. When all the layers have been added by the robot, the operator instructs the system to rotate the frame to a horizontal position so that rods can be added to hold the stack together.
The final stage of fuel-cell stack assembly is to make the necessary electrical connections between the individual cells. To achieve this, Innomech has combined the robot’s sensor-based guidance system with a passive spring-loaded gripper tool. ‘The robot also needs to compress the gasket materials, which are fitted to ensure a gas-tight seal. So there is a servo-controlled system to compress that to a known force,’ Mead added.
The second phase of work, due to start later this year, is for the company’s automation specialists to develop equipment that can disassemble a fuel cell. ‘The materials used still have a lot of value,’ said Mead. ‘There are some elements of the fuel-cell stack that can be used and fed back round the system again. Some of the other materials are not able to be reused directly but can reprocessed as useful chemicals for other purposes.’
While the technology is being developed in the UK, the end product will find its way to Germany. ‘I know AFC did consider a couple of potential UK sites for installing the fuel cells and using hydrogen. I think was mostly a commercial decision,’ said Mead. However, he is certain that fuel-cell technology has a future, both on the continent and the UK. ‘The whole idea of using fuel cells for industrial power generation is gaining momentum — the time is now right and the technology is coming together.’