Toyota Motor Corp showed "Sora," a new fuel-cell (FCV) bus, to the press April 20, 2018, in Tokyo.
While using the same fuel-cell technology as the "Mirai" passenger FCV, which the company released in 2014, Toyota focused on the improvement of durability, which is crucial to commercial vehicles. As a result, the bus can travel 1,200,000km (approx 745,645 miles), which is 500% longer, compared with the passenger FCV, until the replacement of the vehicle.
"The key to the durability improvement of FCVs is to prevent the deterioration of FC stack, which is used for power generation," said Kenji Gondo, CVZ (project general manager), CV Company, who led the development of the new FCV bus.
Especially, in the case of FCV buses, which have a large mass and require a large torque for driving, the fluctuation of electric potential in the FC stack tends to be large. When the fluctuation increases, the catalyst that promotes the activation of hydrogen and oxygen in the stack can easily deteriorate. As a result, the response of the catalyst becomes dull, leading to a decrease in output.
To improve durability, Toyota renovated the control method for FC stack, compared with the Mirai. To make electric potential fluctuation as constant as possible, the company employed a method that enables to supplement the output by using an in-vehicle nickel-metal-hydride battery.
For the catalyst, platinum (Pt), which has a high cost-performance, is used. But the company is currently researching and developing a catalyst technology that does not use Pt, in the aim of further reducing costs.