Environmental Engineering Reference
In-Depth Information
Table 4.21 ISA switched architecture
Switch S1
Switch S2 Mode
On
Off
Engine Cranking. UC can be precharged from 12 V
vehicle battery. UC delivers
6 kW to ISA for starting.
42 V battery supplies all vehicle loads.
>
On
Off
Boosting. UC power is delivered to the ISA in motoring mode
to augment engine torque. UC power
>
10 kW to engine.
42 V battery supplies all vehicle loads.
On
Off
Regeneration. ISA captures braking energy and routes it to
UC via the ISA at power levels
>
10 kW.
Off
On
Alternator mode, engine supplies average power via ISA to
42 V battery and connected loads.
4.4.7 Flywheels
Sometimes called a 'mechanical' capacitor, flywheels have presented major
materials engineering challenges to ESS designers because of the high angular
speeds involved and the need to provide containment. During the 1990s there was
much development work in the US, especially at the US national laboratory at Oak
Ridge near Knoxville, TN. During those programmes, flywheels that were very
light weight, with composite or glass fibre rotors spinning in vacuum or hydrogen
atmosphere, were constructed. Spin losses, the main self-discharge mechanism,
were minimized by use of magnetic bearings. Power conversion into and out of the
flywheel is via an ac electric drive.
This in fact is the issue that continues to challenge flywheel energy storage,
and that the energy is not stored in the form it will be used in. Unlike ultra-
capacitors where energy is stored in the same form it is used in, mechanical fly-
wheels require the electrical-mechanical-electrical conversion process and hence
incur significant efficiency loss.
4.5 Electrical overlay harness
In most hybrid vehicles, an integrated starter generator (ISG) is used to work in
conjunction with engine to supply power and torque to the vehicle. The ISG helps
start the engine as well as generate required electrical energy and replaces the
engine flywheel. The hybrid system could work on 42 V or 300 V and is connected
to a corresponding battery pack. Various controllers, such as engine controller
module (ECM), transmission control module (TCM), vehicle systems controller
(VSC), ISG and battery controllers are used to control respective subsystems in the
vehicle. Figure 4.43 shows the general layout of major HEV subsystems required
for hybridization.
Some of the systems are replaced to support the hybrid functionality. For
regenerative braking, an electrohydraulic brake (EHB) system is added to the
