X hits on this document

PDF document

Hybrid Electric Vehicle with Flywheel Energy Storage System - page 2 / 11

22 views

0 shares

0 downloads

0 comments

2 / 11

WSEAS TRANSACTIONS on SYSTEMS

2 HEV with flywheel system

2.1 Comparison between energy storage systems

HEV taking ICE as the main power source usually adopts chemical battery as assistant power. Compared with ultra-capacitor and chemical batteries such as lead-acid battery or nickel metal hydride (NIMH) battery, FESS has advantages of the longest use-life, the highest energy storage density, the shortest charging time and also the easiest maintenance. Moreover it has the least demand for working environment and will cause no pollution. The Comparisons between them are shown in Table 1. Table 1 Comparison between chemical battery, Ultra-capacitors and FESS [1]

Storage Mechanism Use-life

Temperature Range Environmental Concerns Relative mass (Equivalent energy) Practical time To hold a charge

Serious

Less

Slight

serious

Large

Middle

Small

months

Days

Hours

Chemical

Ultra-

Flywheel

Battery

Capacitors

System

Chemical

Electric

Mechanical

3~5 years Limited

12~18years

>20 years

Limited

Less limited

The key point of energy storage with flywheel is to reduce the loss of mechanical energy, namely the loss of kinetic energy that consists of air friction resistance and rotary resistance. According to different means for the reduction of energy loss, FESS can be divided into low-speed flywheel system and high-speed flywheel system. The first reduces air friction by

increasing the is to reduce environment

mass of flywheel while the second the air pressure of operating

of

flywheel.

The

high-speed

ISSN: 1109-2777

Jianhui He, Guoqiang Ao, Jinsheng Guo, Ziqiang Chen, Lin Yang

flywheel system benefits from the use of high strength compound material (carbonic fibre). It has characteristics of small mass, low volume and high speed. Thus it is fit for vehicle using.

The high-speed flywheel system consists mainly of a flywheel, a motor and a generator. It is connected with exterior electrical systems through input or output electronic equipments and the power transported from exterior systems is converted from electric energy into mechanical energy by raising rotary speed of flywheel. When it is needed to output power, mechanical energy is converted back into electric energy through generator and meantime the rotary speed of flywheel is reduced [2]. The motor and generator are usually integrated together and magnetic suspension bearings are adopted by flywheel system, through the support of which the flywheel is fixed in a vacuum container (Fig.2).

Excessive high cost is the main cause preventing FESS from popularizing. Its cost is about 1.5 times that of ultra-capacitor and is about 6 ~ 7 times that of chemical battery. But the use-life of flywheel system is 10 times or more than that of chemical battery and needs no recalling. Moreover the cost for installation and maintenance is also much lower than chemical battery and ultra-capacitor. So if the use-life of each vehicle were accounted for ten years, the annual expenditure consumed on FESS would be slightly higher than that consumed on chemical battery (Fig.1). Furthermore, the FESS will have greater potential of developing after industrialization.

Cost

Fig.1 Cost comparison between chemical battery and flywheel system

639

Issue 5, Volume 8, May 2009

Document info
Document views22
Page views22
Page last viewedMon Dec 05 06:52:03 UTC 2016
Pages11
Paragraphs412
Words5029

Comments