Design of an Automatic Control Algorithm for Energy-Efficient ...

2 Control objectives 13
Figure 2.6: The perceived air quality (% dissatisfied) as a function of the carbon dioxide
concentration. [14]
do not take much power.
The fan is spinning nearly all the time to provide the passengers with fresh air.
This is necessary as seen in Section 2.2.4. Depending on the model its power consumption
can be as high as ��� � [1]. Although this will be needed rarely. An average consumption
below ��� � is realistic for normal car.
A typical cooling power in a car is around ��� [2]. The installed and maximum
power may be higher. In the refrigeration circuit the only powered unit is the compressor.
The refrigerant is compressed and enters the condenser to transfer heat to the ambient air.
It is then liquefied and expanded into the evaporator cooling the inlet-air. The vaporised
gas returns to the compressor and the cycle starts again. In this way heat is transferred
from the interior to the outside and the car is cooled. The compressor only consumes the
electric power to compress the gas. This corresponds to around 33%-50% of the cooling
power. The energy is mostly taken mechanically from the (fuel-)engine and is replaced
by a separate motor in an electric car.
A typical heating power for a car is around ��� and thus of the same magnitude
as the cooling power [2]. In today’s fuel-run cars most of this is provided by the engines’
waste heat. Only if this it not sufficient, electrically heated PTC-elements are used.
Taking away the combustion process as main heat source other solutions have to be found
for the electric car. Using electricity directly with PTC-elements is not economical. Heat