Renault, having operated a 42-volt Scénic demonstrator since 1998, has already acquired expertise in this area. 

For Renault, the cars of years to come will be safer, more comfortable, and more respectful of the environment. These developments will lead to an increase in the number of electrical components in the vehicle, as well as an increase in the consumption of electrical energy. The switch to a 42V standard for the main electrical system (in place of the present 14V) allows this objective to be met, while also further optimising the efficiency of electrical power generation, thus reducing fuel consumption. Following its work in this area, Renault has since 1998 been operating a prototype Scénic equipped with a 42V electrical system with a special alternator. The company's research has also involved the means of supplying this new electrical system. Together with the 42V alternator, two possible alternatives are the ADIVI (Alternateur Demarreur Integre au Volant d'Inertie - flywheel integrated starter-alternator) and the use of an auxiliary power generator built around a fuel cell. While an intermediate 14V-42V "twin voltage" approach will be needed towards 2004, Renault hopes to offer "all-42V" cars on the market by about 2007.  

42-volt systems made necessary by the trend towards an increasing number of electrical components in the car 

To respond to the needs of the market, within a few years the majority of our cars will be equipped as standard with comfort equipment such as electric power assisted steering, a heated windscreen and even electrically powered air conditioning. On-board electronic equipment, navigation and multimedia systems, will also appear in an ever greater number of vehicles. Safety equipment such as ABS, traction control and electric braking systems will be added to these features in consuming more and more electrical energy. In terms of powertrains, the Camless engine could also be a considerable energy consumer. 

These innovations thus make it necessary to increase the generation of electrical power on board (expressed in Watts), this figure being equal to the product of the system voltage and the current (in amperes). Since 1980, vehicle energy requirements have increased by 4% a year. The electrical power requirement of a mid-range Renault car has increased by 50% between 1980 and 2000, and could increase by 300% for a top-range car by 2005. While a top-range car today requires about 1.5kW, by 2005 its consumption could be 5kW. 

It should be noted that electrical power consumption has a direct effect on fuel consumption (for each 100W consumed, fuel consumption increases by 0.17 litres/100km for a petrol-engined car, and 0.15 litres/100km for a diesel). The switch to 42V will however allow the consumption of electrical energy to be optimised through a reduction in conduction losses, thus making possible lower fuel consumption and reduced "greenhouse" CO2 emissions.

The use of lighter wiring, made possible by the reduction in current, is a further factor working towards reduced fuel consumption. 

If 14V electrical systems are retained, the electrical energy available will not be sufficient to meet the demands of this extra equipment. At the same time, conduction losses reduce the efficiency of rotating electrical machinery. Existing alternators and technologies cannot supply the electrical power demanded by tomorrow's cars. 

(June 22, 2000)