Hydro smart Electric vehicle with Fuel Cell Range Extender

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1 Hydro smart Electric vehicle with Fuel Cell Range Extender Prof. Dr.-Ing. Hugo Gabele, Institut für Brennstoffzellentechnik (IBZ) Hochschule Esslingen Prof. Dr.-Ing. Ferdinand Panik, Institut für Brennstoffzellentechnik (IBZ) Hochschule Esslingen Dipl.-Ing. Christian Wilk, Fa. Euro Engineering Dipl.-Ing. Martin Ziegler, Fa. Hyliontec Overarching aims One important aim was to provide students with experience in the field of Alternative Engineering by means of an F&E project, Electric Smart with Fuel Cell Range Extender. The project, which went several semesters, had a special focus on practical skills and was particularly concerned with costs, function, engineering sophistication and customer satisfaction and use. The final aim was to present a full functional prototype. Informations about the Institute for Fuel Cells Technology The Institute for Fuel Cells Technology was founded in 2005 in cooperation with the Faculties of Automotive Engineering, Housing Services, Mechanical Engineering and Basic Sciences as well as industrial partners such as Daimler, Ballard, Nucellsys, etc. Since then, it has become established as an important institution for research into mobile and stationary fuel cells. The lesson module Alternative Engineering, offered by the Faculty of Automotive Engineering, includes practical laboratory work using testing equipment and educationally sound teaching methods. System Integration and the integration of fuel cells are an important component of hybrid drive systems with electrical energy storages and intelligent energy management. On average over 40 students are actively engaged in fuel cell projects per semester, whether in the context of the lecture course Simultaneous Engineering or within the scope of student projects. Some of these projects have already won prizes, for example the Ergolite Glider 2, which was awarded the prize for the best overall technical achievement for a vehicle using alternative engineering at the international Challenge Bibendum in Paris. Students from the Institute were also involved in building the record-breaking vehicle Hysun 3000 (world record: 3000 km with only 3 kg of Hydrogen). In November 2007 the Institute successfully took part in the Michelin Challenge Bibendum Shanghai with the fuel cell scooter HydroFight, achieving four times the first place in individual disciplines and the second place overall in the field of environmentally friendly two-wheeled vehicles against 15 other teams, mostly from China. Exceptional achievements in membrane research for PEM fuel cells must also be mentioned. In cooperation with the University of Stuttgart, Prof. Renate Hiesgen, a member of the Institute for Fuel Cells Technology, has developed a new procedure that, among other things, makes it possible to measure the proton conductivity of a PEM, thereby enabling an important insight into processes which take place within fuel cells. Her work received the special f-cell Award in Product conception and development With the support of renowned sponsors such as Daimler, Ballard, Brusa und Euro Engineering, the Institute for Fuel Cells Technology has been able to convert a standard production series smart into an electric vehicle with notable performance in less than one year (fig. 1). The vehicle has been equipped with a total number of 704 lithium-polymer-consumercells with a capacity of 22 kwh and a weight of 135 kg, which allow a range of approx. 130 km. To extend the range, a small 2.5 kw is included in the front. A carbon-fibre bottle with a capacity of 39 litres and a pressure of 350 bars is installed in the back. This allows the range to be extended up to 250 km, depending on driving style.

2 Fig. 1: The Hydrosmart of the Institute for Fuel Cell Technology Project aims The Hydro Smart project was conceived with the ambitious aim of developing a vehicle for the future which exceeds the performance and range of all other existing vehicles in its class. Preliminary studies had shown that over 90% of all trips in this class of car are less than 100 km. For such cases, the vehicle can be recharged at any standard household electrical socket by the integrated 3kW charging device. The relatively small fuel cell comes into use for longer journeys and works as a range extender. Procedure Based on an early market study (fig. 2), the wellknown smart production car with internal combustion engine was analysed according to performance, weight, price and driver impressions. Overview Smart car with internal combustion engine Smart Pure 45kW/61HP - 3-cyl. petrol motor 999cm³ - torque 89Nm - empty weight 750 kg - price from EURO Smart Pulse 52kW/71HP - 3-cyl. petrol motor 999cm³ - torque 92 Nm - empty weight 760 kg - price from EURO Smart Brabus 72kW/98HP - 3-cyl. petrol motor 999cm³ - torque 140Nm - empty weight 780 kg - price from EURO Driver impressions : slightly low performance Driver impressions : ideal performance Driver impressions : sportive Fig. 2: Market study of available Smart models

3 The Smart Pulse was chosen, bought at the end of 2007 and from the summer semester of 2008 onwards converted into an electric vehicle. Motor configuration Research into the motor led to 2 promising configurations which are compared in fig. 3. Because the motor built by the Brusa company seemed to offer a particularly sporty driving performance, it was decided to use this in combination with the original Smart gearbox. Simulations had shown that with a fixed gear selection it is possible to achieve excellent acceleration values as well as an acceptable top speed (second gear, 8.4:1). The advantages and disadvantages of this solution are summarised in fig. 4. Conversion to electric vehicle - 2 motor configurations Getrag motor 624 with 2-gear gearbox 20kW - asynchronous motor - torque up to 40Nm - weight approx. 50 kg Electric Smart with fuel cell - top speed > 120 km/h - range > 200 km - unladen weight approx. 960 kg Brusa motor with standard Smart gearbox 50kW - hybrid motor synchr./asynchr. - torque up to 230Nm - weight approx. 85 kg Expected driving performance: extremely low performance Desired driver impressions: ideal motor performance Expected driving performance: very sporty Fig. 3: Comparison of the most suitable motor configurations Pros and cons - Brusa motor with Smart gearbox Brusa motor with standard Smart gearbox 50kW - hybrid motor synchr./asynchr. - torque max. 230Nm - weight approx. 85 kg PROS + electic BRUSA motor HSM fits exactly to a standard Smart gearbox + BRUSA motor and compatible Drehzahlsteller available as a set; no additional development work required + gearbox is already available (no extra costs) + all replacement parts are available (in case of defects) + perfect adaptation, minimal time requirements + fast software development (no switching procedures) + driving performance would be surprisingly sporty + motor rpm drehzahl not quite so high, thus probably more pleasant noise than high rpm asynchronous motor CONS - standard Smart gearbox is slightly heavier (approx. 35kg) - later reconstruction of gearbox with fixed transmission is necessary Fig. 4: Pros and cons Brusa motor with Smart gearbox

4 The performance of the Brusa motor is impressively illustrated in fig. 5. The maximum torque of the Hydrosmart is greater than the most sporty internal combustion model, the smart Brabus (fig. 2) and is available from zero rpm, i.e. practically from the start (no turbo lag). The engine efficiency is also striking: the maximum power is available between 3000 and RPM. The Brusa HSM (Hybrid Synchronous Motor): technical data Brusa Motor HSM rpm /min nominal power 35 kw at rpm /min power 320V 70 kw power 400V 90 kw nominal torque 85 Nm torque max. 230 Nm weight 55 Kg efficiency incl. controller 96% at rpm /min Fig. 5: The Brusa motor - technical data Tests show that mounting the Brusa motor in the car engine presents no problems as it fits perfectly (fig. 6). The motor is flanged onto the original gearbox using a specially constructed mounting plate. mounting plate gearbox e-motor Fig. 6: Packaging the motor with CATIA V5

5 Alongside the machined aluminium mounting plate, a number of new components were necessary to complete the installation of the motor hardware. These include several brackets, a power converter as well as a new clutch between motor and gearbox. Fig. 7 shows the dismounted rear axle with the new motor. Blocked 2nd gear Speed controller New brackets Mounting plate Clutch Fig. 7: Rear chassis with the new motor configuration Description of the traction battery Following numerous measurement series and comparisons of commercially available lithium-ion cells, the following traction battery was developed, taking into consideration factors such as weight, costs, energy density, robustness, etc. (fig. 8). The Battery pack 704 lithium-polymer cells 3,7V/8Ah were integrated Each group of 64 cells were connected in an 8x8 pack 11 of these packs were connected to the traction battery 704 cells yield 339V/64Ah nominal Energy content approx. 21 kwh nominal The traction battery can provide a nominal power of 60kW (3C) 100 kw (5C) are possible for 10 seconds Fig. 8: Single cell and battery pack configuration

6 For each group of 8 cells, connected in parallel, the capacity was increased to 64 Ah. 8 of these basic units were then connected in series so that the voltage increased to 31 V. Finally, a further 11 of these modules were connected in series to give the desired voltage of 339 V (fig. 9). Connection Series connection; Voltage increases to 31 V Series connection; Voltage increases to 339 V Parallel connection; Capacity increases to 64 Ah Single cell; 3,7 V / 8 Ah Fig 9: Connection of the 704 single batteries The greatest challenge lies in the packaging. In the Smart, one of the smallest street cars, now must contain the electric motor and batteries, but also the space must be reserved for the range extender, fuel cells and the hydrogen bottle. For this, a package-test was carried out (fig. 10). The study shows that the batteries fit extremely well into the undercarriage of the Smart; they are optimally protected there and provide a low centre of gravity for the vehicle; the hydrogen tank has enough room above the motor. The over-dimensional cooler had to move out for the fuel cell. Fig. 10: Chassis package study

7 The exact configuration of the battery-pack as well as the integration and anchor points for the various components is also determined by CAD (Catia V5) (fig. 11). Energy storage: 704 lithium-polymer cells capacity : 21 kwh voltage : 339 V current : 200A/350A (10sec) weight : approx. 135 Kg Fig. 11: CAD construction: undercarriage Finally, the supporting undercarriage plate was manufactured from hand, using GFK/CFK in a positive moulding procedure (Fig. 12). Battery mounting plate / undercarriage Fig. 12: Undercarriage out of GFK/CFK, hand manufactured Glossary: befestigungspunkte = anchor points; Akkufach = battery compartment; Heck = rear; Kabelkanäle = channels for cables

8 The hydrogen bottle which is normally used in the F-cell A-class fits neatly into the smart Fortwo between the rear axle suspension domes. The boot floor had to be raised by about 10 cm (fig. 13). Fig. 13: Hydrogen bottle at the rear of the Smart Alongside the mechanical work, simulations were also carried out to enable predictions. Various driving cycles and operating modes can be fed into the simulation tool. Glossary: Längsträger = longitudinal support A Matlab/Simulink model which was especially designed for this purpose was used as platform for these simulations (fig. 14). Fig. 14: Schematic representation of the simulation model

9 Fig. 15 shows the results of the simulation. The energy consumption has been converted into petrol equivalents to facilitate comparison. The highway driving cycle and the new European driving cycle (NEDC) were investigated. The simulated fuel consumption of the ice production car was validated with 4.7 l/100 km, which is close to the manufacturer s specifications. The consumption of the Hydro Smart was predicted between 1,6 and 2,4 litres per 100 km, depending on how intensively the fuel cell was used (with approx. 40% total efficiency) and depending on the driver cycle. Given the max. el. storage capacity of 22 kwh and the calculated consumption 14 kwh/100 km, driving using purely electrical power from the battery produces a theoretical range of 157 km. In actual tests, using a reasonable strategy (SOC from 95% to 10%), a range of 130km was verified. In the near future, the fuel cell will enable ranges to be significantly extended: the compressed hydrogen (compressed to 350 bars) has a chemical energy content of approx. 40 kwh which means that further 16 kwh of electrical energy could be delivered (average fuel cell efficiency is 40%). This means a theoretical range extension of 113 km. Such range extensions can be expected, not only on the highway, but at the average speed typical for street traffic or with the stop-and-go phases typical for commuters because the complete conversion of the hydrogen by the fuel cell requires about 7 hours. Thus, a range of up to 250 km is available, spread out over the day, before the hydrogen container has to be refilled or the battery recharged Vehicle Fuel Economy (gasoline equivalent) NEDC Fuel Economy (L/100km) Highw ay 5 4,5 4 3,5 3 2,5 2 1,5 1 0,5 0 Conventional Smart Fortw o HydroSmart (FC on) HydroSmart (FC off) Fig. 15: Comparison of energy consumption of the production series Smart with the Hydro Smart with and without fuel cell. Fig.16 compares conventional motors with the new system. It show that the HydroSmart delivers an impressive performance due to its sporty driving behaviour, low energy consumption as well as its low CO 2 emissions which, if regenerative energy sources are used, can almost be lowered to zero. And even if it s not possible, there will be zero driving emissions locally, such as hydrocarbons, nitrogen oxides, carbon monoxide and harmful particles. The range is more than acceptable for a city car; prototype costs were also relatively low. They are higher than the costs for the standard production model because of the necessity of integrating only high quality components which are only produced in small numbers. It s possible in the future, that costs for a half-series model could be halved or even fall to as low as a third. This could make the price acceptable for car fleets, car-sharing or for a small group of customers who are concerned about environmental issues.

10 Smart Pulse - motor 3-cyl. 4-stroke 999 ccm water cooled - torque 92 Nm - empty weight 860 kg - range > 500 km - consumption 5l/100km - harmful emissions: Euro 5 - price from EURO Hydro Smart - e-motor Brusa HSM water cooled - torque max. 230 Nm - empty weight ca. 940 kg - range 250 km - consumption 1,5l/100km - harmful emissions: locally zero - prototype costs EURO Fig. 16: Comparison of the production series smart and Hydrosmart Finally, we would like to thank our partners and sponsors. Without the support of Daimler, Ballard, Euro Engineering, HSE-Drive, Brusa, K&W Suspensions and many other suppliers, this project could not have been realised. We would also like to thank the faculty of Automotive Engineering for their active support, especially for making equipment and work space available. The dynamic Institute for Fuel Cells Technology team, as well as staff and students of the University of Applied Sciences also made a significant contribution to the success of the project. Publications on the topic of light vehicles with alternative engineering: /1/ Gabele, H.; Panik, F.; Ziegler, M.: Leichtfahrzeuge mit Brennstoffzellenantrieb, 6th international colloquium fuels, , TAE Esslingen /2/ Gabele, H.; Panik, F.; Ziegler, M.: Ergolite Glider siegreich in Paris, VDI-Tagung "Innovative Fahrzeugantriebe" am 9. und 10. November in Dresden /3/ Gabele, H.; Panik, F; Ziegler, M.: Brennstoffzellenscooter Hydrofight, FUELS, 7th Int. Colloquium, 2009 January 14-15, TAE Esslingen