PhD Thesis - Cranfield University

Chapter 2
insights to the problem description. As discussed, the problem is sometimes addressed solely
as a ‘power’ management issue and sometimes as a topic of ‘energy’ management. Both
problem descriptors are valid since energy is simply the time integral of power. However,
when multiple energy storage systems that have very different specific power (kW/kg) to
specific energy (kWh/kg) ratios and also different peak power handling capabilities are
combined, the problem is best addressed jointly as power and energy management issue. The
problem of designing a complete power and energy management system could be stated as a
problem encompassing energy resource planning, power delivery and an effective
architecture design for a real-time system
On a rather theoretical level, several researchers have developed energy management and
power management techniques that apply priory information regarding the vehicle
propulsion power demands. These methods do provide a means to identify the maximum
obtainable improvements in terms of energy efficiency and performance benefits. The
findings also clearly support the grounds for further research in this area. However, in spite
of significant contributions, there have not been many attempts to address the complete
implementation process of a working system.
2.4 EV Enabling Technology – The Ultracapacitor
Extensive development has been achieved in recent years in the field of high capacitance
Electrochemical Double-Layer Capacitors (EDLC) [40]. More commonly refereed to as
‘Supercapacitors’ or ‘Ultracapacitors’, these devices are able to operate at power levels high
above that of conventional batteries and can store a considerable amount of energy above
the energy capacity of conventional capacitors. These devices represent one of the latest
innovations in the field of electrical energy storage [41], and lends itself as a significant
technology enabler for future electric and hybrid electric vehicles.
As a relatively new energy storage device, EDLC technology warrants a brief historical
introduction. The first high capacity electrochemical capacitor device was patented in 1957
(US Patent 2800616) [42]. Developed by Howard Becker of General Electric Company, the
device was of a basic construction consisting of porous carbon electrodes. Becker described
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