Improved hydrogen tanks for fuel cell cars of the future
Hydrogen cars generate zero emissions but up until now have been too expensive to become the car of choice for the majority. The EU-funded COPERNIC project, supported by the Fuel Cells and Hydrogen Joint undertaking (FCH JU), improved the quality of materials, the overall design and the manufacturing process for hydrogen storage tanks, cutting costs and making hydrogen cars a viable and competitive option.
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Vehicles on our roads produce 14 % of the C02 charged with causing climate change. Scientists have developed different alternatives to the internal combustion engine that runs on fossil fuels, but battery vehicles have limited range.
Hydrogen cars could be the ideal solution, but until now the storage of hydrogen as a fuel in cars has been too costly, priced at around € 15 000. Even with government incentives, this takes the cost of a hydrogen fuel cell car to as much as EUR 80 000, says COPERNIC project coordinator Stephane Villalonga.
The COPERNIC project spent over three years improving existing technology to reduce the cost of a hydrogen fuel tank for a car to as little as EUR 3 000. Thats five times less than it costs today, reports Villalonga. The project has been so successful in cutting costs and improving performance that consortium members have already started the process of proposing prototype tanks to vehicle manufacturers.
How engineers create the hydrogen tanks
To manufacture the tank, Villalonga explains, we first create a plastic liner by putting a polymer powder in a mould, before rotating it and then heating it. The heat melts the polymer powder, which then sticks to the wall of the mould. The engineers then allow the heated material to cool down before removing the liner from the mould.
The next step involves placing a mixture of polymer resin and carbon fibre around the liner. This mixture forms black composite layers that are wound around the liner of the tank. At this point, the resin is still quasi-liquid.
To harden the resin, engineers put the vessel into an oven and increase the temperature. This results in a solid matrix of carbon composite material around the liner.
How they improved the tanks from optimised components to robots
When producing hydrogen storage tanks, manufacturers had used more carbon fibre than they needed due to a lack of knowledge about the properties, and tolerance levels of the materials, explains Villalonga. They erred on the side of caution to ensure that the tank passed the stringent safety tests, he adds.
The COPERNIC team tested and selected several carbon fibres to achieve the best performance for the price. They then optimised, thanks to computers and numerical calculations, the structure of the composite for high-pressure vessels, effectively reducing the mass of the composite by 20 %.
Even with this improvement, the hydrogen tanks were still costly. So the COPERNIC team set to work on increasing the productivity of the manufacturing process. We needed to reduce the time it takes to manufacture one tank. We also wanted this to be a repeatable and reliable process, he says. The solution was a robot to replace the traditional classic filament winding process.
The robot improves the quality and reliability of the composite, enabling operators to position the material where and how they want it. In fact, the robot halves the duration of the winding process, reports Villalonga. Mass-producing the tanks also reduces the price; the COPERNIC project has demonstrated this.
More than a tank
Another key to reducing the price is the volume of the tank. The COPERNIC project has shown than it is cheaper to manufacture a bigger tank than to manufacture and use several smaller ones.
The hydrogen storage is, however, more than a tank. It also includes pressure safety valves and protective equipment for fire and refilling. To reduce the number of components in the system, the COPERNIC project tested and certified an on-tank valve that connects the hydrogen tank to the car fuel cell. The valve simplifies the system and reduces the price of managing the pressure tank manufacturers have already expressed an interest.
COPERNIC engineers didnt stop there, however. They also developed a way to monitor the health of the tank in real time during manufacturing and over its lifecycle. By placing optical fibres and sensors into the tank at the start of the manufacturing process, they have helped to optimise the safety of the tank and enabled the car calculator to receive feedback on the safety of the vessel.
The next step is to commercialise the tanks for use in the automotive industry a process that has already begun as part of the EU-funded HIPHONE (HIgh Pressure tank for HydrOgeN storage). And within the next year, the COPERNIC consortium plans to propose a 75-litre tank to car manufacturers, Villalonga reveals.