IAIN ROBERTSON 

Toyota-Mirai-Mk2-1

Toyota-Mirai-Mk2

With full government support and a projected 2030 fossil-fuel cut-off date in prospect, reports Iain Robertson, consumers could be gulled into believing that there is no alternative to EVs, except that Toyota plans for a ten-fold growth in its hydrogen demand.

To be fair, Toyota is not alone in developing its alternative fuel portfolio, as Hyundai, Honda, BMW and Mercedes-Benz have also made major investments in the hydrogen fuel scenario. My first drive in the first generation Mirai took place around six years ago. It felt genuinely ground-breaking, the ungainly profile of the car cutting an interesting and spirited dash around North Yorkshire, although it was cut short by a lack of refuelling infrastructure.

Toyota’s vision for a future sustainable hydrogen society recognises the value of the gas as a viable and plentiful resource. It has the potential to deliver zero carbon mobility, not just in road vehicles but equally in trains, ships and planes, while also generating power for industry, businesses and homes.

Toyota-Mirai-Mk2-2

Toyota-Mirai-Mk2

Toyota began development of its hydrogen fuel cell electric vehicle (FCEV) in 1992, drip-feeding Mirai into a worldwide market from 2014. Toyota’s approach recognises that each category of battery-electric vehicle has qualities suited to different mobility demands, with EVs for shorter commutes and urban driving, hybrids and their plug-in alternatives for general and longer distance personal travel, and FCEVs for larger and heavier passenger cars, heavy-duty vehicles and public transport.

Such a broad-brush undertaking can be best described as ‘generous’ but it is familiar ground for Toyota. The latest Mirai hikes FCEV technology onto a higher plane, offering greater appeal in terms of more contemporary styling and accessible performance. A redesigned fuel stack, improved packaging and less radical aerodynamic efficiency combine to extend the driving range to around 400 miles per tankful, with pure water as its only emission.

Relocating the ‘engine’ from beneath the car to beneath the bonnet means that Mirai Mark Two can accommodate five adults, not four, as before. At just shy of 5.0m in length, Mirai is a large car but increased wheel diameters to 20.0-inches give it a more balanced appearance and greater emotional appeal. Three, high-pressure fuel tanks (in a below car T-formation) have a total capacity of 5.6kg of hydrogen. The high-power electric motor and battery pack are positioned above the rear axle, which contributes to a near 50:50 weight distribution and resultant gains in driveability.

Toyota-Mirai-Mk2-5

Toyota-Mirai-Mk2

The fuel cell stack uses a solid polymer, as in the outgoing Mirai, produced with smaller and fewer cells (330 against 370) and an accompanying 50% weight reduction. Yet, it sets a new record for specific power density at 5.4 kW/l (we all need to become more familiar with alternative power rating terminology!), with maximum power rising from 114kW to 128kW (around 174bhp). Cold weather performance, an early problem, has also been improved with start-up now possible at temperatures from as low as -30˚C.

A smaller but energy-dense lithium-ion high-voltage battery replaces the former nickel-metal hydride (NiMh) unit and promises superior environmental performance. Containing 84 cells, it is rated at 310.8V, with a 4.0Ah capacity. The pack’s weight has been reduced to just 44kg.

Structural rigidity of the body has been increased with bracing, strengthening and the wider application of body adhesives and laser screw welding. Adopting multi-link front and rear suspension (which replaces the former McPherson strut type) takes advantage of the stronger architecture, to provide vastly improved levels of stability, controllability and ride comfort. While the original Mirai delivered a significantly less involving experience, improving the dynamic qualities of the Mark Two version was prioritised; thicker anti-roll bars, optimised upper and lower ball-joint locations and greater suspension rigidity yield the much-desired on-road rewards.

Toyota-Mirai-Mk2-3

Toyota-Mirai-Mk2

Further benefits are gained from the use of larger wheels and tyres, the 20.0-inch rims fitted with 245/45 R20 tyres possessing both low noise and low rolling resistance, while contributing to fuel efficiency, handling agility, improved grip and a more refined cabin. Naturally, airflow around the car has been considered judiciously, Toyota’s GA-L platform benefiting from a flat bottom, while air channelling around the front grille, along the flanks and boot area contribute to a much-reduced drag coefficient, which is an essential aid to maximising fuel efficiency.

Control linearity has been improved dramatically, with a more measured throttle response and less tendency for the previously over-assisted brakes to detract from progressive stopping ability. Of course, the car drives through a single gear transmission and, apart from a distant but not distracting ‘whine’, its ‘feel’ is just like most EVs…in other words, clean and brisk acceleration, supported by less aggressive braking. Typical of BEVs, reversing the polarity of the electric drive motor allows it to harvest energy for the battery pack, while also slowing the car through several driver-adjustable stages.

However, another Toyota innovation lies in a catalyst-type filter that is incorporated in the air intake. As air is drawn into the vehicle to supply the fuel cell, an electric charge on the non-woven fabric filter element captures microscopic particles of pollutants, including sulphur dioxide (SO2), nitrous oxides (NOx) and PM 2.5 particulates. The system is effective in removing from 90 to 100% of particulates between 0 and 2.5 microns in diameter from the air, as it passes into the fuel cell system. Inevitability, Toyota seizes a marketing opportunity to describe its new Mirai not as a ‘zero emissions’ but as a ‘negative emissions’ vehicle; one that effectively hoovers up dirty air and cleans the atmosphere, as it is being driven!

Toyota-Mirai-Mk2-4

Toyota-Mirai-Mk2

Toyota is keen to target a changing market with its new Mirai, with a 10-fold expansion in sales volume. This growth will be supported by the new model’s stronger performance and improved customer appeal, notably as a more affordable vehicle with a selling price reduced by around 20%, from £66,000 to a more affordable £52,000. It is still expensive and the government contribution (£3,000) hardly dents it.

Conclusion:     The practicality of a hydrogen fuelled car will also increase as markets improve their sustainable refuelling infrastructure and local authorities introduce fresh incentives and regulations for cleaner mobility. As a significantly cleaner alternative to regular EVs, the hydrogen FCEV will be the innovation the market needs.