5.1  Introduction

• A supercapacitor is a device that, unlike the standard capacitor, can store relative to its size a high level of energy (referred to as high energy density).
  
  
• It has a significantly higher capacitance rating than the standard capacitor (in excess of 1,000 times greater). Comparison farad figures required.
  
  
• It is also called an ultracapacitor.  

5.2  History

• 1957: The first supercapacitor was developed and patented by General Electric in the United States.
  
  
• 1966: The Standard Oil Company patented an “electrical energy storage apparatus”.
  
  
• 2000-01: See Green Cars, Section 8.9.8 (Honda).
  
  
• 2006: Electric buses that use supercapacitors, not power lines, as their source of electricity started operating in China.
  
  
• Further information on vehicles using supercapacitors required. 

5.3  Advantages & Limitations

• Batteries can take from one to several hours to charge. A supercapacitor can be charged in a few seconds.
  
  
• Secondary batteries can only be recharged up to about 1,000 times. Supercapacitors have an operating life possibly in excess of 30,000 hours. Check this figure. How many times can it be charged/discharged?
  
  
• Compared to secondary batteries, supercapacitors can absorb and release energy at a much higher rate.
  
  
• Compared to secondary batteries, supercapacitors have a very low internal resistance.
  
  
• Honda has produced an ultracapacitor capable of providing an output density of not less than 1,750W/kg, nearly twice that of a nickel hydride battery used in their hybrid vehicles.
  
  
• For its weight the energy stored in a supercapacitor is low. A battery of the same weight storing 10-25 times more energy.
  
  
• Supercapacitors are an emerging technology. See Green Cars, Section 10 (Green Web Site Links) for up to date and additional information.