[Lots more information about this interesting project has surfaced since our original post. Thanks to Alex over at noonzwheels.com for the tip! Click any pic for a high rez version]

After nearly three years of development, the U.K.-based team led by specialist engineering company Ricardo has delivered a full-hybrid diesel version of the Citroen Berlingo minivan. Built in response to the U.K. Department of Transport's Ultra Low Carbon Car Challenge, the fully-equipped van emits just 99 grams/km CO2 (equivalent to more than 75 mpg), while meeting or exceeding the Euro IV emissions standards for NOx, PM, HC and CO.

The $5.6 million project started in early 2004, with the goal of producing a prototype of a viable ultra-low carbon car with uncompromised comfort and convenience features, that could be affordably mass-produced. Ricardo's partners in the project include PSA Peugeot Citroen and U.K. aerospace company QinetiQ.

Lots more details, and pics, after the jump...
The Lithium-ion battery pack is just visible beneath the Berlingo's capacious storage area, just to the right of the tailpipe.


Tightly packed, but it all fits!


Detail of the battery pack beneath the rear floor.



The team's solution is a diesel full-hybrid, based on the diesel-powered Berlingo MPV. In keeping with the Challenge's mandate, the various hybrid subsystems are neatly tucked away without cutting into the people mover's interior space. The mix of technologies in the project vehicle includes:

• PSA Peugeot Citroen's 90 hp 1.6-liter turbo diesel
• a 23 kW 288 volt DC electric motor, fitted between the engine and the transmission, for torque assist, power generation, regenerative braking and low-speed all-electric operation
• a starter-alternator that allows engine shut-down and rapid restart for smooth transition to and from all-electric driving modes
• a 5-speed automated manual transmission that automatically selects the most efficient gear ratio
• a 288 volt Lithium-ion battery pack and battery management system
• a supervisory control system to coordinate vehicle systems to meet driver demands while optimizing fuel economy

Automated manual gearshift.


Driver display, here showing the vehicle operating in mode 5.
To optimize performance and minimize emissions at all times, the car operates in six distinct modes:

• Mode 1: highway cruising, powered by the diesel engine through the clutch and gearbox
• Mode 2: generation mode, in which the electric motor absorbs power from the engine to generate electricity for storage in the Lithium-ion battery pack.
• Mode 3: acceleration - using the electric motor, powered by the batteries, to augment the diesel engine to boost acceleration
• Mode 4: all-electric operation, used to pull away from a stop or in low-load conditions
• Mode 5: regenerative braking - with the diesel engine off, the vehicle's kinetic energy is captured by the motor and stored in the batteries
• Mode 6: stationary operation, using the diesel engine to drive the electric motor to charge the batteries and/or operate electrical equipment, such as the air conditioning system

But wait, there's more! In order to support normal operation of the car in all modes, systems which are normally mechanically driven (like power steering) are replaced by electrically driven equipment, for seamless operation whether the diesel engine is running or not. This includes a DC-DC converter to provide 12 volt power from the 288 volt battery system, 12 volt electro-hydraulic power steering, an electric vacuum pump for brake assist, and electric air conditioning.

All this complexity is managed by a control system incorporating no fewer than 10 microprocessor controllers, running 70 megabytes of custom control code.

The full-hybrid Berlingo gives a 30 percent improvement in fuel economy and CO2 emissions over the same vehicle powered only by the 1.6-liter turbodiesel. In a lighter sedan-style vehicle, Ricardo predicts the same powertrain will deliver over 80 mpg-equivalent fuel economy. Best of all, the hybrid Berlingo will beat the pants off its diesel-only sibling, cutting 1.4 seconds off its (admittedly leisurely) sprint from 0-62 mph.

Interestingly, the chart of powertrain efficiency (shown as tailpipe CO2 versus energy requirement), while showing the diesel hybrid to be the most efficient powertrain, shows the straight diesel solution running a close second, well ahead of gasoline hybrids.



The team estimates that a production version of their full-hybrid MPV would sell at about a $5,600 premium over the diesel-only version.

[Source: Ricardo, PSA Peugeot Citroen]