The companies Ricardo, QinetiQ and PSA Peugeot Citroën presented, on June 2, 2006, their prototype: a Citroën Berlingo Multispace diesel hybrid which should emit only 99 g / km of CO2 (ie a consumption of 3,75 liters per hundred). Its CO2 emissions are therefore 30% lower than those of standard diesel vehicles. This project, Efficient-C, is the first result of the “Ultra-Low Carbon Car Challenge” program of the Department for Transport (DfT, Ministry of Transport). This £ 10 million (approximately € 15 million) program was created in April 2003 and is administered by the Energy Savings Trust.
Its aim is to encourage the development of practical “clean” vehicles: it only concerns family-sized five-door cars. The Efficient-C project, which cost 3 million pounds (about 4,4 million euros) over 2 years, received 1,5 million pounds (about 2,2 million euros) from the DfT . Two other projects were funded under this program: one has been blocked since the feasibility study and the other, led by the company Zytek, should be completed next year.
Ricardo, an engineering and consulting company for the automotive industry, responsible for the project, supplied the control systems for the hybrid engine and was involved in the integration of this into the vehicle. PSA Peugeot Citroën, for its part, supplied the base vehicle, the components for the hybrid engine and the vehicle control systems. QinetiQ, a partially privatized company transformed from the military DERA, provided its skills for energy storage, in particular for the battery and power cable networks.
The choice of the Citroën Berlingo may seem strange for a contest concerning familliales car with five doors. Its aerodynamic characteristics are quite different from those of standard C-class vehicles. However, its interior is more spacious, making it more functional for testing control equipment. The prototype presented in June 2 2006 is compatible with European regulations Euro IV and is equipped with the following technologies:
- PSA Peugeot Citroën 1,6-liter HDi diesel engine;
- a compact 23 kW and 288 V direct current electric motor mounted between the diesel engine and the transmission shaft; it can provide up to 130 Nm of additional torque;
- a 5-speed manual gearbox;
- a 288 V Lithium-Ion battery.
The hybrid system has six different operating modes:
- conventional propulsion using the diesel engine;
- the electric motor recharges on the diesel engine, producing electricity thus stored in the battery for future use;
- when the car requires significant acceleration, the energy stored in the battery is transmitted to the electric motor which provides additional torque;
- at low speed, the electric motor operates alone, powered by the battery (saving fuel and therefore CO2 emissions); the vehicle can travel 10 km in electric mode;
- when the vehicle is braking, the electric motor absorbs the kinetic energy of the vehicle and stores it in the battery (retroactive braking);
- when the vehicle is stationary, the diesel engine produces electricity which is stored in the battery, unlike the Toyota Prius, a hybrid vehicle currently on the market, which stops its electric motor when the vehicle is stationary.
Considering the number of modes, the control systems are very important and the software which manages the transitions between the diesel and electric engine has a size of 70 MB against 30-40 MB for software controlling only a diesel engine. The pedal of the right foot is connected to the hybrid engine control system and no longer to the accelerator.
In addition, many additional systems are necessary to ensure the proper functioning of the vehicle in its 6 operating modes:
- a low temperature cooling system protecting the electronic parts of the engine;
- a DC-DC converter, transforming the current produced from 288 V into 12 V (more efficient direct production of 12 V);
- electrical auxiliary systems: power steering, vacuum pump for assisted braking and air conditioning system.
This prototype is not yet ready to be marketed: the current cost of equipment and manufacturing means that this Berlingo costs 3 pounds (approximately 000 euros) more than the model currently on sale. The industrialists of PSA estimate that the additional cost of the car should be at most 4 pounds (approximately 400 euros) to allow its mass production.