Sunday, May 22, 2011
Mercedes hydrogen car mission
Mercedes is on something of a mission to raise awareness about hydrogen as a viable, alternative future fuel. And how: by taking a brace of B-Class cars on a world tour – all 19,000 miles of it.
Electric power might be the flavour of the month but it’s not for everyone. Range, battery weight, charging issues and cost – government grants notwithstanding – are just a few considerations. Hydrogen fuel cell-powered cars offer, in principal, greater flexibility and range, petrol car-like performance plus supermini levels of economy. And don’t forget, the only tailpipe emission is water.
Unlike an electric car, you can’t buy a fuel cell model. Until now, anything that showed potential was little more than a prototype. The B-Class is different; it is a regular car destined for low scale production and real world trials. Its clever ‘sandwich’ floor allows the hydrogen tanks and fuel cell to fill the gap, with the electric motor in the nose and the car’s lithium-ion battery pack, used for the start up and initial running, located aft below the boot space.
The test location was the coastal town of Ceduna, west of Adelaide, Australia. The 1,200-mile, four-day journey to Perth on Outback roads included dodging the legendary roadtrains, snakes, flies, 36-degree heat and plenty of dust. If a high-tech fuel cell car could survive here it could survive anywhere.
There was never any need to worry. The cars had already travelled close to 9,000 miles without a hitch. Sure, the dozen or so support vehicles were never far away. Having started in January the group had already experienced a mild European winter and travelled East-West across North America before flying to Sydney for the start of the Australian leg.
To date, the exercise has shown that the cars work. No fuss, no glitches, no performance worries. With the maximum 3.7kg of compressed hydrogen on board, the car’s range is approximately 250 miles of mixed motoring. Regular running at 60 mph on Outback roads saw that drop to around 200 miles. Overall, though, conventional fuel consumption is said to be around 85 mpg – much better than your average family hatchback.
Passing through typically Australian places such as Ecula, Balladonia and Boondi Rock en route to Perth, the B-Class was straightforward to drive. Due to how the fuel cell works – a chemical reaction between the onboard hydrogen and oxygen from the passing air produces electricity, which powers an electric motor – you’re really driving an electric car. And with the B-Class that translates roughly into a 130 bhp equivalent experience from the 70kW motor (100kW peak output) and single speed transmission.
The B-Class might be eerily quiet but you don’t quite get the same ‘instant on’ acceleration of a true electric car. With a fuel cell, energy is being made on demand and not stored in a big battery. It’s a little like old school turbo lag, but only for a fraction of a second. The upside is that if you’re not requesting power you’re not consuming the raw fuel.
After four days behind the wheel you soon learnt to keep the electric motor spinning between 10 and 20kW for maximum efficiency. It proved best to ‘prime’ the system before any determined acceleration – winding the motor up to 50kW before applying full throttle worked best.
The regenerative effect of the electric motor in lieu of conventional braking provided ample retardation in most cases, and helped recharge the onboard lithium-ion battery. On start up the B-Class is powered directly by the battery for the few metres it takes the fuel cell to power up. Depending on its capacity, if you exhaust the hydrogen supply the battery could get you out of trouble – but we’re talking a lot less than a mile, not a true ‘get you home’ backup.
Which brings us to the subject of refueling. The two hydrogen fuel tankers accompanying the cars acted as mobile filling stations, as locally sourced fuel has been the backbone of the tour.
In the real world, however, it’s the scarcity of bricks and mortar filling stations that is proving to be the real bottleneck to progress.
This is a significant factor behind Mercedes’ efforts as, by raising awareness, it is hoped more can be done by governments and other agencies to speed up the process of building a refuelling infrastructure. Sure, Mercedes and others are also developing electric vehicles.
However, the B-Class boasts more than twice the range of Nissan’s Leaf. Not everyone is happy to be restricted to urban motoring or has easy access to a garage or power socket. Fuel cell cars could be a more versatile one-car solution for a family or business. We just need the infrastructure to catch up – and fast.
Mercedes engineers calculate an electric car-beating three-minute refuelling time for something with the B-Class’ 3.7kg tank capacity.
On the day it took longer thanks to the high ambient temperatures and the simple fact that the mobile rigs can’t cool the hydrogen down to the levels of a fixed refuelling station.
After four days and 1,200 miles what lessons have been learnt? Simply put, the B-Class works and is ready for the real world; the driving experience is conventional and overall performance is good. The recent developmental gains have been significant – double digit for performance and economy.
What’s needed now is a similar effort from those responsible for building a refuelling infrastructure. It will take time and money, two things the world appears to be lacking, but the technology must not be allowed to go to waste.
At a glance
70kW electric motor (100kW at overboost)
Single speed transmission as standard, driving the front wheels