Could intelligent heat management systems be a new weapon in the battle to reduce fuel consumption and carbon dioxide (CO2) emissions?
BMW discussed the idea during its recent Innovation Days 2009 event and looked at projects including reducing cold starts; using waste heat for different heating applications; and the implementation of a thermoelectric generator for waste heat recovery.
Currently even a highly efficient combustion engine will only convert around one third of the energy in the fuel into traction to propel the car, while the remaining two thirds are lost as waste heat going into the environment. By making some of this waste heat energy available through intelligent heat management there is significant potential to reduce both fuel consumption and CO2 emissions.
Let’s look at each of the projects discussed by BMW:
No more cold starts: Starting the engine from cold will consume the largest amount of fuel due to the greater internal friction and the high viscosity of the engine oil when it is cold. BMW engineers are now working on avoiding cold start conditions with intelligent heat management and by significantly reducing the warm-up period. Potential solutions include improving heat insulation on the engine to retain heat built up in the engine and engine compartment for as long as possible.
Heating with waste heat: By using the thermal energy contained in the car’s exhaust there could be major savings and comfort potential. Implementing this heat to warm the interior, allows fuel consumption to be cut by as much as 10 per cent from a diesel engine depending on the outside temperatures. In the case of a car with a petrol engine, an exhaust gas heat exchanger could effectively warm up the drivetrain and avoid friction; while in a modern direct injection diesel engine hot exhaust emissions could be used via a heat exchanger positioned as close as possible to the catalytic converter and diesel particulates filter, providing an additional source of heat for the interior.
Thermoelectric generator: The BMW Group believes the thermoelectric generator could be used as an integrated component in the exhaust gas recirculation cooler. In this new stage of development it can reduce CO2 and fuel consumption by around two per cent. Exhaust gas recirculation will keep temperatures low during the combustion process minimising the generation of nitric oxides, while to cool the residual gas and recirculate it, the EGR would come with a water cooler and control flap offering ideal conditions for enhanced efficiency. BMW hopes to fit a larger thermoelectric generator in the exhaust system in the future.
