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BMW’s “CO2 Champion” Performance Concept is a Plug-in Diesel Hybrid; 50 km/31 mile All-Electric Range; Thermo-electric Generator for Waste Heat Recovery

30 August 2009

Bmwconcept2
The powertrain of the plug-in hybrid BMW Vision EfficientDynamics. Click to enlarge.

BMW has provided more details on the concept car it will unveil at the upcoming Frankfurt Motor Show—a concept that Dr. Norbert Reithofer, Chairman of the Board of Management of BMW AG, called a “CO2 champion” that will demonstrate “a whole new dimension of driving pleasure with regards to efficiency with performance” during a press conference late in July. (Earlier post.)

The plug-in full hybrid BMW Vision EfficientDynamics all-wheel drive concept car is powered by a 1.5-liter, three-cylinder turbodiesel; two electric motors, one on each axle; and a 10.8 kWh lithium-polymer battery pack. Overall system output is 262 kW (356 hp), with maximum torque of 800 N·m (590 lb-ft).

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The BMW Vision EfficientDynamics. Click to enlarge.

BMW Vision EfficientDynamics is able to run completely under electric power for up to 50 km (31 miles), with the power of the turbodiesel engine alone, or through an infinite combination of the three power sources. Depending on driving conditions and the driver’s particular requirements, the two electric motors may be used both for accelerating and for regenerating energy when applying the brakes and in overrun.

BMW Vision EfficientDynamics is neither a mere variant of a production car built for maximum efficiency nor a purely visionary study completely separated from series development. Rather, all the technologies contributing to the car’s outstanding efficiency come from a development process conceived for regular production. Indeed, some of these technologies are already in use in current BMW models, others are approaching production standard or have already proven their functional benefits in practical tests and in prototypes.

—BMW

Objectives. The purpose of the high-performance concept study was to visualize the dynamic performance typical of a BMW against the backdrop of future demands in sustained mobility, according to the company. The specific development aim was to provide the performance of a BMW M Car and a highly emotional character combined with the fuel economy and emission management of a modern small car in the premium class.

Engine. Through its compact dimensions, the three-cylinder fits neatly in front of the rear axle like in an mid-engined sports car, despite the two seats at the rear. Fuel is injected by the latest generation of common-rail direct injection, and the turbocharger features variable intake geometry for maximum efficiency.

Engine output is 120 kW (163 hp), peak torque 290 N·m (214 lb-ft). The output per liter of 80 kW (109 hp) achieved in this way sets a new record in diesel technology. The power delivered by the turbodiesel is conveyed to the rear axle by means of a newly developed, minimum-consumption version of BMW’s direct-clutch gearbox with six speeds for maximum efficiency and flexibility.

Motors. BMW said the concept’s development engineers followed the principle of “Best of Hybrid”, choosing the optimum combination of a hybrid synchronous motor on the front axle and a full-hybrid system at the rear.

The rear axle comes with a second-generation full-hybrid system corresponding to the technology introduced for the first time in the BMW ActiveHybrid 7 production model. (Earlier post.) Running as an electric motor, the compact electric power unit positioned between the combustion engine and the double-clutch gearbox develops a consistent 25 kW and is able to reach a peak of up to 38 kW.

Maximum torque, again, is 290 N·m or 214 lb-ft, the power developed in this way serving, depending on driving conditions, either to support the combustion engine or for all-electric motoring.

A second electric motor acts on the front axle. This power unit, a hybrid synchronous motor, offers permanent output of 60 kW and peak torque of 220 N·m or 162 lb-ft. Extra power of 84 kW is available for a period of up to 30 seconds; for 10 seconds the electric motor is even able to develop 104 kW. Power is transmitted through a two-stage, single-speed reduced-ratio gearbox.

Battery pack. The energy cells featured in BMW Vision EfficientDynamics are housed in a chassis element running from front to rear through the middle of the car. Overall, BMW Vision EfficientDynamics comes with a total of 98 lithium-polymer cells, each offering a capacity of 30 Ah and developing continuous output of 600 Amps at a voltage of 3.7 V. For a period of 30 seconds, each cell is even able to develop maximum output of 1,200 Amps.

Serial arrangement of the lithium-polymer cells serves to generate nominal voltage of 364 V, and the gross storage capacity of the battery is 10.8 kWh. Offering an unusually high discharge capacity of 80%, the battery delivers 8.6 kWh for driving the car.

Overall weight of the entire energy storage system is 85 kg or 187 lb. Through their optimum dimensions tailored to the specific qualities and features of the car, the lithium-polymer cells, together with the operating strategy chosen with a concept of energy management looking ahead at upcoming requirements, reduces the thermal load acting on the battery to such an extent that there is no need for active cooling.

Connected to the regular European domestic power mains (220 V, 16 Amps), the system requires a maximum of 2½ hours to fully charge the lithium-polymer cells. Wherever a power source with higher voltage and amperage (380 V, 32 Amps) is available, the charge time is an even shorter 44 minutes at the very most.

In addition to the electrical energy storage system, BMW Vision EfficientDynamics comes with a conventional fuel tank at the rear end of the central chassis tunnel, offering a capacity of 25 liters (6.6 gallons US). Running on diesel fuel alone, BMW Vision EfficientDynamics is able to cover a distance of approximately 650 km (400 miles) with the combustion engine. With the extra range of up to 50 kilometers in the all-electric mode, the car offers an overall cruising range of approximately 700 kilometers (435 miles).

Thermo-electric generator. One objective of BMW’s engineers was, wherever possible, to further reduce the loss of energy still quite substantial even on the most efficient combustion engines. A water-cooled Thermo-Electrical Generator (TEG) is integrated in the exhaust system of BMW Vision EfficientDynamics, serving to convert a lot of the thermal energy contained in the exhaust emissions into electric power. (Earlier post.)

This technology uses the Seebeck effect generating a certain voltage through a temperature gradient within metal-based semi-conductors. The Vision EfficientDynamics Thermo-Electrical Generator, which has already proven its practical qualities in a BMW 5 Series test car, develops maximum output of up to 200W.

The pipes and manifolds in the exhaust system are designed in this case to maintain the full power and all the characteristics typical of the combustion engine also when using this generator system.

Forward-looking Energy Management. Having the individual system components on board BMW Vision EfficientDynamics networked with one another enables implementation of a forward-looking system of energy management using information gathered by the sensors of the driver assistance units fitted in the car.

Data provided, for example, by the rain sensor or Active Cruise Control with its Stop & Go function as well as by the navigation system, and subsequently evaluated by the central control unit, offers an overview of current and upcoming driving conditions.

Then, evaluating such data, the on-board computer is able to forecast driving conditions on the stretch of road immediately ahead, such calculations serving to prepare the car for upcoming requirements and make efficient use of the energy available through optimum operation of all systems.

Should the high-performance central computer establish, for example, that the driver is about to take the motorway, the power used for running the cooling system is reduced for a certain period in advance, on the assumption that the short increase in coolant temperature resulting from such an energy-saving measure will quickly be set off by the higher speed of the car on the motorway. Another example of such pre-conditioning is the regeneration of energy from the air conditioning, from EPS Electronic Power Steering and the Brake Assistant.

The management system considers not only data collected within the car, but also data coming from other vehicles (Car 2 Car) or from sensors fitted on buildings or bridges (Car 2 Infrastructure), thus enabling the driver, say, to avoid traffic congestion in good time or find parking space far more quickly.

The services already offered by BMW ConnectedDrive to avoid traffic congestion and speed up the process of finding parking space are therefore being enhanced by further components and features serving above all to provide even greater efficiency.

Further features of intelligent energy management on BMW Vision EfficientDynamics allow the driver to influence the efficiency of the car. By adding an Eco Mode to the existing system of Dynamic Drive Control, for example, this new concept car enables the driver to reduce fuel consumption and emissions through the individual style of motoring.

This is done by a display in the instrument cluster instructing the driver to accelerate, apply the brakes and—in the manual mode—shift gears with maximum efficiency. In the automatic mode, in turn, the electronic control unit adjusts the gearshift map on the double-clutch gearbox and the control map of the electronic gas pedal to current driving conditions also in the interest of enhanced fuel economy.

Aerodynamics. Measuring only 1.24 metres or 48.8" in height and with a sweeping, arch-like roofline, BMW Vision EfficientDynamics offers the slender silhouette of a classic Gran Turismo. With the combustion engine fitted in front of the rear axle, the designers have furthermore succeeded in giving the car a very low and sleek front end, with the flow of air depending on driving conditions being further smoothened by active louvers in the radiator closing completely whenever the need for cooling air is relatively low.

This efficient function follows in the footsteps of the active air flap control already used as a feature of BMW EfficientDynamics in many of BMW’s current production models. And as a further highlight, BMW Vision EfficientDynamics guides air smoothly and exactly as required into the car through an active air intake at the front.

Numerous details in the design of the body are based on the know-how BMW has gained in Formula 1, a number of body elements serving as air deflectors and guide vanes, as on the BMW Sauber F1. Designed as ducts, for example, the A-pillars serve to channel the flow of air in the same way as the rear lights with their wing profile.

The underfloor of the car is fully covered from front to rear and from one side to the other, thus maintaining a smooth surface to avoid any air swirl liable to increase fuel consumption. Slender openings around the front air dam guide the air flowing in specifically into two closed ducts leading inside the front air dam to the wheel arches where the air comes out again through a very slim aperture at high speed, flowing just next to the outer wheel flanks. This air jet rests on the front wheels like a curtain and is therefore referred to most appropriately as the air curtain with its highly stabilizing effect.

To further optimize the aerodynamic qualities of the entire vehicle and keep rolling resistance to a minimum, BMW Vision EfficientDynamics comes with tires and rims of quite unusual size on a sports car. The tires measure 195/55 in their width-to-height ratio, while large 21-inch rims provide a contact surface on the road otherwise offered only by a much wider tire.

In combination with the sophisticated axle kinematics, this ensures particularly agile driving behaviour. The extra-large rim covers extending over part of the tire flanks add to the unique, very different look of BMW Vision EfficientDynamics from the side.

The blade profile integrated in the rims serves furthermore to reduce the negative effect of the turning wheels on the overall aerodynamics of the car. In all, these features optimizing the aerodynamic qualities of the car give the BMW Vision EfficientDynamics concept car a very low drag factor (CX) of 0.22.

Materials. The chassis and suspension of BMW Vision EfficientDynamics are made completely of aluminium, the roof and the outer skin on the large doors are made almost completely of a special polycarbonate glass automatically darkening as a function of the light shining on the car.

Performance and fuel consumption. Anticipated acceleration from a standstill to 100 km/h is 4.8 seconds, with a top speed of 250 km/h (155 mph) (electronically limited). Applying the criteria of the EU test cycle currently prescribed by law, BMW Vision EfficientDynamics offers projected average fuel consumption of 3.76 liters/100 km (62.6 mpg US), with CO2 emissions of 99 grams/kilometer.

These consumption and emission figures are measured on a consistent internal power balance, meaning that the batteries and storage media for electrical energy maintain the same charge level throughout the entire test cycle (with the same level at the beginning and end) and are charged while driving only by the car’s on-board systems.

As a plug-in hybrid, BMW Vision EfficientDynamics is able to cover the entire fuel consumption drive cycle under electric power alone. Then, to subsequently charge the lithium-polymer cells to the same status as when setting off, all the driver has to do is connect the car to an external power grid. To determine the consumption of electric power, the only requirement is to compare the charge level of the battery before and after the test cycle.

Applying this measurement process, the BMW Vision EfficientDynamics concept car consumes 17.5 kWh per 100 kilometers, equal to a CO2 emission rating of 50 grams per kilometer in the EU test cycle based on the EU electricity mix.

To determine the total volume of CO2 emissions when driving in the all-electric mode, new standards for measuring the level of fuel consumption are currently being prepared for hybrid and electric cars with a plug-in power supply. Applying this calculation method, the CO2 emission ratings generated by BMW Vision EfficientDynamics are reduced further to just one-third of the original figure of 99 grams per kilometer.

August 30, 2009 in Diesel, Hybrids, Plug-ins | Permalink | Comments (23) | TrackBack (0)

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Comments

Wow. Verycool. I want one :)

The battery is a huge improvement over the Volt’s battery. Same size in terms of available kWh but the BMW battery weights 187 lb versus 375 lb for the volt. Also amazing power of the BMW battery 435 kW in peak power (98*1200*3.7). Now if it were not just a concept.

This is a lot more than just a concept.
See the BMW comment above:
'Rather, all the technologies contributing to the car’s outstanding efficiency come from a development process conceived for regular production. Indeed, some of these technologies are already in use in current BMW models, others are approaching production standard or have already proven their functional benefits in practical tests and in prototypes.'

Most of the weight loss in the battery compared to the Volt is due to their ability to drain it down by 80% vs 50%, but we can't be sure that BMW have specified as long a cycle life as the 150,000 miles that GM has gone for.
Perhaps Mitsubishi who have said that the iMiEV in production will get more miles than the prototype are counting on reaching a higher level of battery drain by the time it hits production.

Now ... If they can just get the price below $10,000. I might consider buying one.

BMW must have intended this PHEV to be a super-duper sport car, trying to wring out the last ounce of torque from the engine, that they are using a 6-speed transmission. Otherwise, a family sedan version of this vehicle would do well with just a two-speed transmission, due to the tremendous torque of the electric motors at low speeds, and the relatively-large battery pack.

A two-wheel drive version of this vehicle would have one electric motor directly attached to the engine, acting as a starter/generator/motor, and a second electric motor attached to the 2-speed single-gear stage transmission, thereby allowing a smaller electric motor, since the transmission can multiply the torque of the motor at slow speeds, and reducing the cost of the vehicle. A clutch separates the engine from the transmission, allowing serial-hybrid transmission at slow speed when battery power is depleted, thereby eliminating the torque converter, and allowing infinitely-variable transmission during the serial-hybrid power transmission mode.

A parallel-hybrid like this arrangement, minus the 6-speed gear box and minus the 4-wheel drive capability, is what I would like to see on the GM Volt.

Henrik, for the maximum 30 seconds 1200AMP peak current battery voltage is not 3.7V but 3.7V/2. Because power equation for a battery is:
P = (Eo - rI)I then
dP/dI =Eo- 2rI
The parabol curve maximum occurs for I=Eo/2r or V= Eo/2
Then Pmax= 217.5 kW . It's a pretty good value with a battery internal resistance around 16 mOhms.
In fact 1200AMPS is a 40C rate of discharge. This type of value, for 30 secons pulse, is usual in aircraft Ni-Cd batteries to start the APU.

Raymond I believe you as I am an economist of education I tend to understand technical issues in a more superficial manner. I am surprised that you can lose half the voltage when pulse discharging a battery. Just a few clarifying questions. 1) Does this mean that if you pulse discharge a 10kWh battery you may only get 5 kWh out of the battery? 2) If 1) is affirmative where does the lost energy go? Is it lost in heat because of battery resistance? 3) If 2) is affirmative does it imply that if you could lower the battery resistance you would also lose less of the voltage?

40C discharge rate is not good for the longevity of the battery. The best Lithium polymer battery these days rated at 30C. But, don't count on frequently reaching this rate of discharge often, because battery will puff up and lose capacity prematurely. Count on discharging at 1/3 the C rating, or 10C, to prevent premature battery deterioration.

I agree fundamentally with Roger, in terms of how such a vehicle could be modified to another, more efficient class of PHEV;

- 2 wheel drive instead
- 1 liter motor instead

Having a low Coefficient of Drag (Cd) and small cross sectional area (A) proportionally reduces drag;

Force (drag) = - 0.5 * air density * velocity**2 * Cd * A

The Ford Probe prototype achieved a Cd of .15, though amazingly seated 4 people. Mass transit and cycling aside, vehicle aerodynamic performance such as this will need to be the wave of the future.

I have questions concerning the TEG:

Does anyone know what kind of efficiencies modern TEG materials fetch? And what is the cost?
Don't you find 200W rather low, when the TEG materials cost a lot AND you have to add the water-cooling(more cost and weight)?

My opinion is that TEG isn't ripe for automotive applications yet, because of low efficiency and high cost, but I'd be really happy to be proven wrong.

And why not recoup the energy lost via the regular radiator? Much lower kWh in comparison?

Will S,

TEG's depend on high temperature difference to produce an amount of power worth the effort. The radioactive material used in TEG's for space applications are red-hot. Btw. TEG's struggle to achieve more than 10% efficiency.

BMW has also researched steam generators which should be able to produce more power but at vastly increased weight, complexity and cost. Besides, TEG's from the exhaust produce DC power, which the car can use readily.

Roger,

Too bad you didn't read the whole article. The six-speed gearbox is just for the diesel engine.

Btw, it is quite remarkable that they get 163 from a 1.5 litre 3-cylinder engine. Exactly the same power as from the 2.0 litre 4-cylinder engine mentioned in an article about the new EfficientDynamics BMW 320d last week.

Couldn't they use ultracapacitors to deliver the high battery pulse power so you don't reduce the battery's life?

But can the engine charge the batteries? The Volt cannot. The system is 2-3 times more powerful than is needed for a minimalist and lightweight 4 seater; but this is a deluxe sports car concept.

@Thomas,

Too bad, you didn't read my entire posting. I was well awared that the six-speed gear box is for the engine only, driving the rear wheels, while the front wheels are driven by a separate and independent second electric motor at only one gear speed. Ergo, I postulated that if the 4-wheel-drive feature is not required, then the second electric motor can go to the rear, just in front of the transmission, so that a motor of 1/2 the size, at 30 kw instead of 60 kw, can be used, to take advantage of the torque multiplying effect of the transmission at low speeds. The transmission needs be only of a single planetary gear stage for a two-speed transmission, since the combination of a diesel engine and both electric motors will offer a lot of torque, much more than any single ICE can deliver at low speeds.

@JC,
Of course, the engine can charge the batteries in ANY ICE vehicle, Volt is no exception. But, in a PHEV, this question is moot, since you would rather charge the batteries at home and by braking energy recuperation, instead of using engine power to recharge the batteries, in order to conserve petroleum. Unless, of course, you have a power outage at your home after a snow storm that may last for weeks...Then, if you have a PHEV, you can theoretically start up the engine and power up your home and charging the batteries at the same time, provided that the car is designed with a Plug Out feature designed just for that purpose. Since the engine is way too powerful for household electrical demand, the battery can supply base load, and the engine needs to only come on occasionally to charge up the battery.

Unfortunately this is A) only a concept and B) from BMW which is not exactly used to, much less interested in building cars for the masses. BMW is also, unlike Toyota, not proven to be interested or capable of subsidizing the cost of this technology toward affordable vehicles a la Prius. So yes, you’ll see some of this stuff eventually incorporated in a 7 series or M car but that will probably be about it. Unless this foments competition among other manufacturers to reach such extremes of efficiency, I’m afraid this won’t make too much of a dent in the world situation.

Henrik,
1) Energy lost as usual gives heat (your battery is warmer after pulse)due to battery resistance.
2) The game to get the minimum resistance in a battery is to reduce electronic and ionic resistance. Electronic resistance is reduced by using larger or thicker current collectors (Aluminum for positive electrode and Copper for negative electrode). Ionic résistance is generally obtained by increasing surface of electrodes and reducing thickness. Larger is the surface lower is the current density in the electrolyte, where ionic charge transfer occurs.
Generally a battery design is a compromise between energy and power. Higher power performance reduces energy density and increases cost.
For a big and compact EV battery, a low internal resistance reduces heat generation and battery average temperature. It's a good way to increase cycle life.

Thank you Raymond.

All in all this BMW is an impressive collection of new technology. The only thing they seem to miss is carbon fiber for lower weight, better acceleration and better fuel economy. This announcement from BMW taken together with the other recent announcement of the new 7 Series ActiveHybrid, the BMW X6 hybrid and the 500 EV Mini’s shows that BMW is very serious about reducing the CO2 emissions of their future vehicles.

@Roger,

If I understood properly, you propose a two-motor solution, separated by a clutch, and a two-speed transmission between secong e-motor and differential/wheels.
So you can use it as a series hybrid at low speeds (first motor used as generator), and at higher speeds (say 30+ mph) you close the clutch and use it as parallel hybrid. Shifting to second gear may be around 45 mph.
I agree it would be very efficient on flat roads.

But what about going long steep uphill roads. In that case it won't be possible to use gears, as the car speed would be too low, and it would have to work as series hybrid. It means that both motors would need to be quite powerful (and expensive).

Another option is to use gearbox with 5-6 gears and smaller motors, where the first motor (a generator one) can be significantly smaller.
It's now a question of price - which architecture is cheaper. Currently I think that the option with powerful motors is more expensive than the one with 5-6 speed transmission (vs 2-speed one).
I may be missing something.
Could you please comment.

"But what about going long steep uphill roads. In that case it won't be possible to use gears, as the car speed would be too low, and it would have to work as series hybrid. It means that both motors would need to be quite powerful (and expensive)."

Use lower gear (of the two speed) for climbing steep hills, once the battery is exhausted. With battery suppplementing power, the car can continue to stay on high gear at all times, except during very hard acceleration, and the battery and the motors will do the load-leveling function...just as in a serial hybrid. Size the engine and the gear ratio in order to allow you to do that effortlessly. Steep slopes are usually of short distance, in which the engine supplies power mechanically via the gear, and the battery supplies power to both motors. The example of this is San Francisco or Colorado. Longer slopes are no more than 7 degrees of incline, in which a typical modern car should have no problem whatsoever climbing in either high gear or low gear, such that, even if the battery is exhausted after a long climb, the engine still should have no problem making 60 mph speed in high gear, or if pulling trailers such as a boat or U-haul, in low gear at somewhat lesser speeds.

Gears are cheaper than electric motors, ergo I have been proposing a serial-parallel hybrid solution, instead of a purely serial hybrid like that of the Volt, thereby allowing you to reduce the size of the generator and of the motor and the expensive power electronics by 1/2, and even the battery, too, can be downsized.
However, there is a practical limit of how much you can downsize the generator and motor, since you will need to provide effective braking energy recuperation, which is a very important energy saving means for city driving. Otherwise, you'll end up with having a mild hybrid instead of a full hybrid, which will seriously undermine your Green Credential or bragging rights!

When you have the motors and batteries big enough for good braking energy recuperation, a two-speed transmission is all you'll need for a family sedan, unless you wanna have an all-out sport car with 0-60 mph in under 4 seconds, then you'll need the 6-speed gear box like this BMW.

Are this concept car's electronics based on the infamous BMW iDrive?

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