Reducing fuel consumption

Recovering wasted energy
Typically more than 80 % of the energy produced in a vehicle engine goes to waste; lost as for instance heat in the exhaust gases or as frictional losses when the vehicle is braking. At the same time many auxiliary units, e.g. the oil pump, are driven directly by the engine. Volvo researchers are therefore looking into how the wasted energy can be recovered as electric energy and stored in a battery.

This electrical energy can then be utilised to for instance drive auxiliary units with electrical machines instead of driving them directly by the engine. Another way to use this recovered electrical energy is to supply some or all of the power needed by an electrical machine which assists the engine, this type of vehicle is then called a hybrid.

Alternative energy sources
An interesting alternative energy source under study is solar power. The electrical energy that could be produced by covering the whole roof of a truck or a bus with solar panels is substantial although it is far from enough to completely propel the vehicle. The energy could be used to for instance supply some of the power needed by an electrical machine which assists the vehicle engine.

Energy management
In today’s vehicles, mainly the engine drives the electrical generator. However, during long periods of time, the output current needed by the loads (e.g. lights, radio, etc) is relatively low. This means that the energy losses are high compared to the

electrical energy generated. The total losses can be lowered by turning off the generator and let the battery supply the loads. Thereafter the generator is turned on again, and the output current becomes higher since the loads and the battery needs to be supplied.

One way to lower the generator losses is to let the battery supply the electricity when the power need is low. The generator can then be run during shorter periods of time when there is a greater need for power.

In hybrid vehicles, however, it must be decided when to run only the engine, the electrical machine or both. There are many different input parameters to consider, for example how much energy is left in the battery, in order to get optimal use of the electrical energy in the hybrid vehicle.

EE-VERT, an EC funded project
Many of the electrical system improvements are investigated in a European Commission funded project, EE-VERT (Energy Efficient Vehicles for Road Transport). Volvo is one of a total of nine partners from seven different countries. The partners represent universities, vehicle manufacturers and subcontractors. More information about this project can be found on the web site: http://www.ee-vert.net/