Home' Australian Automotive Aftermarket Magazine : Australian Auto Aftermarket E-zine December Contents AUTOMOTIVE AFTERMARKET MAGAZINE DECEMBER 2012 47
while reducing power consumption.
Using sensors, it determines if the front
passenger seat is occupied and automatically
closes all vents serving this seat.
The same happens to the rear seats when the
S-flow button is switched on to maximise the
HVAC system efficiency.
The system also measures the ambient air
temperature, interior air temperature and
insolation to determine the optimal level of air
The target airflow volume is customised for
each seat through Temperature Airflow Output
Upper and lower independent, multilayer air
mix technology has been adopted to achieve an
environment tailored for driver, front and rear
The new system also introduces a two-tier
interior/exterior air control which prevents
In addition, the air conditioning system
incorporates a new odour and purification
This air cleaning technology operates
automatically when the air conditioning is turned
on. It releases 20 to 50Nm diameter particles -
negatively charged ions wrapped in water
molecules - into the cabin via the driver's side
dashboard air vent.
By attaching themselves to airborne particles
these ions have a purifying and odour eliminating
They also deodorise vehicle seats and roof
lining to create a cleaner cabin environment.
And because the moisture content of these
ions is about 1000 times that of conventional
ions, this system has a moisturising effect on
skin and hair, acting to enhance occupant well-
Phase change materials
To reduce emissions and improve fuel
economy, start-stop engines are expected to be
commonplace in the market in the not too
A number of HVAC OE suppliers have
recently announced that they are developing air
conditioning that saves energy without
compromising cabin comfort.
The new Phase Change Material (PCM)
evaporator will keep the cabin of start-stop
vehicles cooler longer and is also ideal for
extending the electric range of hybrid and
This system integrates a reservoir of PCM
within the air conditioning evaporator.
During normal operation, thermal energy is
removed from the material which solidifies or
When the air conditioning system is stopped,
the PCM gradually liquefies or melts, drawing
heat from the air to keep passengers cool and
The system can typically maintain target air
temperature at the cabin vents for one to two
minutes, depending on the volume of PCM
specified, keeping occupants comfortable
throughout periods of stop-start driving.
Traditional air conditioning can account for
more than five percent of a vehicle's average fuel
usage in a hot climate and consequently a
similar proportion of CO2 emissions.
According to Delphi, this technology can
reduce air conditioner system fuel use by 50
percent and extend the zero emissions range for
hybrid and electric vehicles while reducing or
eliminating the associated compromise in cabin
The introduction of the new refrigerant
R1234yf entails some system redesign including
the evaporator, so the likely roll-out of PSM is
expected in the 2015 model year.
The current major drawback to the
marketability of electric cars is range.
The impact of HVAC systems in an electric
vehicle is to reduce the maximum range by
around 35 percent in extreme temperature
In providing more efficient HVAC systems,
not only will the zero emission range of electric
and hybrid vehicles be extended, but these
efficiencies, when used in a conventional
vehicle, will also save fuel and reduce emissions.
The major heat loads on a vehicle are roughly
30 percent for solar irradiation through glass, 15
percent through metal body surfaces and up to
20 percent by heat released from vehicle
The reduction of solar heat load can be
mitigated by glass tinting and more efficient heat
In the USA, California has just mandated the
use of infrared (IR) reflective glass in all vehicles
sold in 2014.
Although the new glass is mandated in
California, automakers are likely to adopt this
technology nationwide to meet the federal fuel
Lightweight and more efficient insulation
materials, non-metallic body panels and solar-
reflective paint can be used to reduce heat load
ingression into the passenger compartments.
A proposal for California regulators to
mandate solar reflective paint at the same time
as the introduction of heat reflective glass has
Solar powered ventilation used in the Toyota
Prius, which cools the car while parked, was also
considered but not mandated.
According to US Department of Energy
testing, the combination of IR glass, solar
reflective paint and solar powered ventilation can
reduce the air conditioning cooling capacity from
5.7kW to 4.0kW while maintaining the same
cool down performance of 30 minutes.
The other significant, but uncontrollable,
component of heat load is that generated by the
To minimise air conditioner power
consumption while providing comfort, zoned or
spot cooling and heating is expected to be the
Current vehicle HVAC cools and heats the
whole interior of the vehicle and the power
consumption to do this is more than 5kW.
To reduce this load, heating or cooling can
be plumbed directly into the seats.
These seats are called climate controlled
seats and feature individual ducting and blowers
used in conjunction with perforated seat
As the occupant is in direct contact with the
seat, the thermal conductivity is higher
compared to air which is a poor conductor.
With this arrangement the power per
occupant could be reduced to around 700 watts
Climate controlled seating (heating and
cooling) is already available as an option in some
European, Asian and American built cars.
The HVAC system in electric and hybrid
vehicles become even more complicated when
you consider that lithium-ion batteries require
similar temperature conditions as the vehicle
occupants to operate efficiently and durably.
Lithium-ion batteries can only be used
efficiently within a specific temperature range
and at operating temperatures of 40°C and
above, the battery life span is reduced.
At very low temperatures under --10°C,
battery performance declines and efficiency
To achieve these conditions, thermal
management of the battery is mandatory.
The approaches taken by vehicle
manufacturers vary, but the most common is to
integrate thermal management of the battery
with the occupant HVAC system.
But this is a whole new subject in itself
which will be left for another day.
Acknowledgement of assistance in
preparation of this article to Waeco,
Delphi, Lexus, US Dept. of Energy.
Links Archive Australian Automotive Aftermarket E-zine - Annual Performance Guide Navigation Previous Page Next Page