Environmental Engineering Reference
In-Depth Information
acceptable range has settled to about 300mi regardless of vehicle mass or overall
economy (target range is 380 mi). The fuel tank is sized to match the range goal.
The Prius, for example, has a 11.9 US gallons fuel tank and will average
400mi per fill-up (without having the low fuel indicator on). Low fuel annunciation
is prompted when the fuel tank content falls below 2 gallons.
Performance cannot be compromised. A hybrid vehicle must deliver accel-
eration, handling and ride comparable to or exceeding that of its non-hybridized
counterpart. The powertrain is augmented with sufficient electric torque to com-
pensate a downsized engine. In addition to an advanced battery technology, many
manufacturers today are turning to ultra-capacitors for high pulse power delivery
for brisk accelerations and handling, plus for benefits on energy recovery.
3.6 Usage requirements
Vehicle usage statistics are compiled through drive surveys that target diverse geo-
graphical and metropolitan areas. Performance data are obtained from data
acquisition systems installed on the vehicle. Data collected on the vehicle is sent
via telemetry to a central facility where it is analysed [3]. Such data are essential
in order to assess HV performance at remote locations, or if fleets of vehicles
are being tested. The system consists of self-powered telematics instrumentation
that transmits vehicle data over a secure data channel to the programme engi-
neers. In such monitoring systems, GPS time, latitude and longitude, altitude and
other information is collected and transmitted along with vehicle system's per-
formance. Putting a time tag on data permits the usage patterns of the monitored
vehicles to be assessed by location and local conditions.
3.6.1 Customer usage
It is generally far more difficult to characterize vehicle option content usage than it
is to monitor customer's driving habits. Vehicle electrical burden consists of all
key-ON loads (continuous), scheduled loads and customer selectable loads. The
electrical power needed to sustain engine operation (ignition, fuel metering and
delivery, throttle actuation, fuel pump etc.) define the key-ON loads. Scheduled
loads include radiator cooling fan actuation by engine coolant temperature, auto-
matic cabin climate control scheduling of blower motor speed, blend door actuation
and air conditioning compressor clutch engagement. Customer selectable loads
consist of interior and exterior lighting, windshield wipers, electric heating of seats,
mirrors and windows, plus all infotainment features.
3.6.2 Electrical burden
Vehicle fuel economy assessments are performed for an electrical burden of 500-
700W depending on vehicle class. This level of electrical burden represents
all power necessary to support key-ON loads (240-300W) plus scheduled loads
needed to maintain engine operation and hybrid component thermal management
(coolant pumps and radiator fans).
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