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The first commercially produced prototype H2FCEV is generally accepted to be the 1966
General Motors Electrovan, shown below in Figure 3.7. The Electrovan used 32 alkaline fuel cells and was fuelled with liquid H2 and liquid O2. It had a range of 240km, took 30s to
go from 0-100kph and weighed ~3500kg[112]. The entire cargo bay was occupied by the system and safety concerns saw the van restricted to operation solely on GM property. Nevertheless it was a valid demonstration that fuel cell technology could power a vehicle.
Figure 3.7 - The General Motors Electrovan [112]
Some 45 years later, fuel cell vehicles have progressed substantially. Many major automotive companies have made prototypes and small-scale pre-production models and the H2FCEV has been one of the major focuses of spending on alternative vehicle
technology research and development over the past decade.
A chronological selection of the vehicles produced to date by the major automotive manufacturers is shown in Table 3.3 [108, 113-116].
Vehicle Year Drivetrain Fuel Cell Fuel MPG Speed Range
Mercedes NECAR 1 (180 Van)
1994 FCEV1 50kW PEM CH230MPa2 N/A 90km/h 130km
Mercedes NECAR 2 V- Class
1996 FCEV 50kW PEM CH2 25MPa N/A 110km/h 250km
Toyota RAV4 1996 FCBHEV3 20kW PEM Hydride N/A 100km/h 250km
Mercedes NECAR 3 A- Class
1997 FCEV 50kW PEM Methanol
Reformer N/A 120km/h 400km
Toyota RAV4 1997 FCBHEV 25kW PEM Methanol
Reformer N/A 125km/h 500km
GM Zafira 1998 FCEV 50kW PEM Methanol
Reformer 80mpg 120km/h 483km
Honda FCX-
V2 1999 FCEV 60kW PEM
Methanol
Reformer N/A 130km/h N/A
Honda FCX-
V1 1999 FCBHEV 60kW PEM Hydride N/A 130km/h 177km
BMW 7 Series 2000 H2ICEV N/A LH2 N/A 105km/h 300km
Mercedes NECAR 4 A- Class 2000 FCEV 85kW PEM 1.8kg CH2 35MPa 53mpg 145km/h 200km Mercedes NECAR 5 A- Class
2000 FCEV 85kW PEM Methanol
Reformer N/A 150km/h 450km
Ford Focus
FCV 2000 FCEV 85kW PEM CH2 25MPa N/A 128km/h 160km
Ford TH!NK
FC5 2000 FCEV 85kW PEM
Methanol
Reformer N/A 128km/h N/A
VW HyMotion 2000 FCEV 75kW PEM LH2 60l4 N/A 140km/h 350km
Fiat Seicento 2001 FCBHEV 7kW PEM CH2 N/A 100km/h 140km
Mazda Premacy 2001 FCEV 85kW PEM Methanol
Reformer N/A 124km/h N/A
Ford Adv Focus
FCV 2002 FCBHEV 85kW PEM
10kg CH2
35MPa 50mpg N/A 290km
GM Zafira 2002 FCEV 94kW PEM 3.1kg CH2
70MPa 55mpg 160km/h 270km
Honda FCX 2002 FCUHEV5 85kW PEM CH2 35MPa 50mpg 150km/h 355km
1 FCEV – Fuel Cell Electric Vehicle 2 CH2 – Compressed Hydrogen Tank
3 FCBHEV – Fuel Cell Battery Hybrid Electric Vehicle 4 LH2 – Liquid Hydrogen Tank
Vehicle Year Drivetrain Fuel Cell Fuel MPG Speed Range
Nissan X-Trail 2002 FCBHEV 75kW PEM CH2 35MPa N/A 150km/h N/A
VW HyPower 2002 FCUHEV 40kW PEM CH2 N/A N/A 150km
Fiat Siecento 2003 FCBHEV 7kW PEM CH2 N/A 100km/h N/A
Audi A2 2004 FCBHEV 66kW PEM CH2 N/A 175km/h 220km
GM Sequel 2005 FCBHEV 73kW PEM 8kg CH2
70MPa N/A 145km/h 483km
Ford Explorer 2006 FCBHEV 60kW PEM 10kg CH2
70MPa 35mpg N/A 563km
GM Equinox 2006 FCBHEV 93kW PEM N/A 39mpg 160km/h 320km
Fiat Panda 2007 FCEV 60kW PEM CH2 N/A 130km/h 200km
Honda FCX
Clarity 2007 FCEV 100KW PEM CH2 N/A 160km/h 570km
VW Touran 2007 FCBHEV 80kW PEM CH2 35MPa N/A 140km/h 161km
Renault Scenic
FCV H2 2008 FCBHEV 80kW N/A N/A 161km/h 240km
Toyota FCHV 2008 FCBHEV N/A CH2 70MPa N/A 155km/h 830km
VW Tiguan 2008 FCBHEV 80kW HTFC 3.2kg CH2
70MPa N/A 140km/h 230km
Mercedes B-
Class F-Cell 2009 FCEV 90kW PEM CH2 54mpg 170km/h 385km
Mercedes Blue
Zero F-Cell 2009 FCBHEV N/A N/A 81mpg N/A 400km
Audi Q5 2010 FCBHEV 98kW PEM CH2 70MPa N/A N/A N/A
Table 3.3 - Existing Fuel Cell Vehicles
Further analysis of the material summarised in Table 3.3 reveals several significant trends:
a) Compressed hydrogen storage is the only storage system now used; reformers, liquid hydrogen and hydrides have been tried and discontinued.
b) The trend in compressed hydrogen storage is towards the use of high-pressure 70Mpa composite fuel tanks.
c) Most recent fuel cell vehicles are hybridised with a nickel metal hydride (NiMH) or lithium ion/polymer (Li-Ion/LiPo) battery pack.
d) Ballard was the pre-eminent supplier of fuel cell stacks though today Toyota, General Motors, Honda and VW now produce their own stacks.
e) Significant amounts of data about the existing prototype vehicles is not publically disclosed and what is, often has to be collated from multiple sources.
Reviewing these trends, a) and b) are in line with this study. c) is a direct result of the slow reaction rate of the fuel cell discussed in 3.4. The fuel cell system can not instantaneously meet the power demands of acceleration and the response times seen in the literature vary between 1s and 10s depending on both the fuel cell and size of the power demand change as a percentage of the cells power rating. To avoid a sluggish response, poor performance and negative driving experience an additional power source is needed to hybridise the power drive train and provide the transient power to fill the gap between the power demand and the actual fuel cell output. Three methods exist in the literature for doing this, batteries, ultra/super-capacitors and flywheels. The predominant approach is to use batteries as although ultra-capacitors have significantly higher power density than batteries they also have significantly lower energy density and can be exhausted before the fuel cell has caught up with demand. Batteries can also capture more energy from regenerative braking and in certain configurations provide all electric range (AER), usually in a fuel cell plug-in hybrid electric vehicle (FCPHEV).
The lack of data highlighted in e) and f) is the single largest driving force behind this study. In order to evaluate and develop the FCHEV power drivetrain it is critical that the existing approaches can be analysed in detail both qualitatively and quantitatively. Even on the qualitative side this is incredibly difficult and starkly highlights the difference and conflict between academic research and commercial research and development. Quite prudently and understandably, manufacturers gloss over research failures and rigorously protect the intellectual property and patents their R&D investment yields. Breakthroughs in fuel cell membranes, catalysts, power converters, drive train control strategies, gas cylinders or any of the other critical components in the fuel cell vehicle could ultimately be worth billions of pounds. With these potential windfalls and due to the substantial sums invested, published information is often incomplete, cursory or too high level to be of any real scientific use.
Take two vehicles for instance, the published information tells us that both drive trains are fuel cell battery hybrid drive trains, and that the rating of the fuel cell and battery is identical in each. The performance figures however, are completely different. We know nothing about the energy management strategy of each vehicle, the power converters used, whether they both use the same motor or whether one is including all electric range on remaining charge in the battery as part of the range once the hydrogen fuel has been expended or a host of other necessary parameters we need to perform proper critical
analysis. In many cases the vehicles are tested against different benchmarks yet the headline efficiency figures are published in a manner that suggests equivalence.
From an academic point of view, it is impossible to completely describe or quantify the current state of the art without significant caveats that all but make the comparison useless for anything other than establishing what is currently said to be possible. Different methods of arranging the same components may yield gains or losses. Configurations may be suited to one type of driving or automotive market more than another, a fuel cell system may be better suited to a different vehicle or a highly efficient drive train may be let down by the type of motor being used. The constraints that commercial research places on companies, often using single chassis types, component sets and following a single development pathway targeted towards their existing markets, prohibits this useful and direct comparison. The costs involved would be significant and in the current economic climate it is unlikely that such projects will be funded. Yet this sort of research is vital to achieving the step developments needed to realise advanced alternative fuel vehicles in the near term. Incremental change will be useful, but it is not in itself a guarantee that vehicles can become sustainable or that they will be available before substantial adverse economic impacts arise from increasing oil prices.
There is a wealth of information in peer-reviewed publications about the fuel cell power drive trains, subsystems, control and associated subjects. A small fraction relates to the development programs of major automotive manufacturers but the overwhelming majority is academic research aimed at developing various aspects of the drive train. Comparison between much of this literature is also very difficult as different aspects of subsystems are often analysed which makes drawing conclusions about the overall system difficult. Where similarities exist or where whole systems are analysed, different tests and metrics are applied.
In order to fully establish the performance of current fuel cell vehicle drive train systems a detailed study of existing drive trains that can be qualitatively and quantitatively studied is needed. An extensive search of the literature revealed that some limited studies have been carried out but a comprehensive review and analysis of all current and proposed topologies did not exist and the decision was therefore taken to undertake one. Building on the methodologies discovered in the literature a multi-stage review process was developed and the results used to highlight the most optimal systems and possibly identify opportunities
to further develop and optimise systems into more efficient, higher performance, less complex and cheaper drive trains.