Compact battery-electric cars (BEV) for the city; mid-sized plug-in hybrids (PHEV) to cover all bases; fuel-cell hydrogen technology (FCEV) for larger cars and long-range cruising… that’s how BMW pitches its alternative fuel strategy.
Munich’s BEVs and PHEVs are already among us, but hydrogen fuel cells like the 5-series GT we’re driving haven’t yet progressed beyond the prototype stage; that’s despite BMW experimenting with the most abundant chemical element in the universe for three decades, and fuel cells – which convert hydrogen into electrical energy and water vapour – for 15 years.
That should be about to change: BMW expects to have ‘production-ready components’ by 2020 and it’s already partnering with Toyota to share expertise, cut costs and speed fuel cell development. Toyota, of course, recently put the hydrogen-fuelled Toyota Mirai on sale.
What’s this particular car all about, then?
The 5-series GT prototype demonstrates the depth of collaboration between Germany and Japan. The fuel-cell stack is produced by Toyota, the fuel-cell housing, hydrogen tank, electric drive and high-voltage battery BMW, and both companies contribute to fuel-cell auxiliaries.
The fuel-cell stack sits under the bonnet, and hydrogen is stored in a ‘tunnel tank’, an aluminium pressure vessel encased in 5cm carbonfibre-reinforced plastic with an aluminium outer casing. It sits where a propshaft would in the rear-drive 5GT. The tank is said to be bulletproof and be at least as safe as petrol or diesel fuel tanks.
Hydrogen from the tunnel tank is fed on demand to the fuel-cell stack, where a chemical reaction takes place with oxygen drawn in via the front of the car. This creates electricity to drive the rear wheels via a 199bhp electric motor. There’s also a small 1kWh battery positioned above the rear axle.
Why should we care?
The advantages of hydrogen are compelling. Hydrogen offers zero tailpipe emissions and very high levels of energy storage, so it’s ideal for longer ranges of up to 440 miles and larger vehicles; nothing but water is emitted from the exhaust. The disadvantages remain: so far, Britain has only five hydrogen refuelling stations compared with 8000 petrol stations. But worldwide, things are changing: Germany plans to up its 50 hydrogen refuelling stations to 400 by 2023; Japan’s 100 stations are scheduled to swell to 800 by 2025.
BMW has even engineered its own twist on refuelling. It’s developed a cryogenic hydrogen storage system, where 7.1kg of gaseous hydrogen stored at -220deg C and a pressure of 350 bar gives up to 440 miles of range in three-to-four minutes of refuelling. That compares with 4.5kg stored at 700 bar for 280 miles’ range. Currently, hydrogen costs around £7.60 per kilo.
What’s it like to fill up?
You refuel much like a regular piston-powered car but the hose is insulated so you don’t feel the cold. The first Total station with both hydrogen refuelling methods opened in Munich last year but your hydrogen car must be compatible with cryogenic refuelling, and, of course, only BMW engineers currently get to use it. BMW expects to offer buyers the option of either cryogenic or regular hydrogen refuelling methods in the future; they’ll have to tick an option box at the time of purchase.
While the hydrogen-powered 5-series GT is based on an existing production car, Toyota’s Mirai uses a bespoke platform, freed as it is from the constraints of combustion-engine requirements. BMW states that future applications will ‘benefit from extensive freedom in the development of innovative design and space-related solutions’, similar to the carbon chassis/aluminium top hat put into production for the BMW i3.
The 5-series GT prototype’s structure has been altered compared with the production car for crash standards, and to house fuel cell components.
How does it feel behind the wheel?
This is a distinctive and impressive car to drive. Press the accelerator and the 5-series GT leaps forward with impressive urgency. Unlike electric cars, it is not silent save for road- and wind-noise: you notice a busy, high-pitched whining, although this is subdued and does not overly intrude. The odd, spacey soundtrack underlines the impression of driving something futuristic but Matthias Klietz, vice president of research, powertrain – and ex of the BMW F1 team – says they need to work on the soundtrack.
The GT features a two-speed dual-clutch automatic transmission, which is also different from the setup found in the electric cars. The steps between the two ratios are very subtle but you can feel the light thunk of engagement at 56mph.
Currently, the FCEV prototype is around 100kg heavier than a production 5-series GT with a combustion engine, but BMW expects substantial savings as development progresses. So while it is not the last word in agility or entertainment, this early prototype was still perfectly capable of lapping a twisty handling course at BMW’s Miramas test facility at very high speed with impressive composure: good front-end grip, contained body roll, excellent traction and a huge punch of straight line speed.
In fact, the long, linear lunge of acceleration makes this eco-friendly 5 GT more exhilarating than any other variant we’ve driven. It’s difficult to judge ride comfort on a relatively smooth test track, but the 5 GT certainly felt comfortable.
Verdict
If this is the future, it’s coming slowly. Klietz says it’s hard to imagine the total changeover to hydrogen-powered cars from fossil-fuel happening within the next two decades at the very earliest.
[“source-carmagazine”]
