Ecotech Energy Blog

Are super capacitor ‘batteries’ the future for renewable energy applications?

The ultra high output super capacitor applications seem to be gaining traction in the renewable energy (particularly in solar power systems) industry of late, due to their battery beating performance.

Part 1: What is a super capacitor and how does it work? 

A super capacitor differs from a conventional capacitor in both construction and operation. Conventional capacitors comprise of two conductive plates which are separated by a dielectric material. Once voltage is applied to the plates, charged ‘electrons’ accumulate on one plate, depleted from the other (forming an opposite positive charge). The ‘separation’ of charges creates an electric field within the dielectric medium whereby energy is stored. Once the charge builds up to saturation, the capacitor is fully charged, and if a path is created for the charge to flow, the capacitor discharges, allowing current to flow.

However, super capacitors by design are different. Supercaps also comprise of two electrodes (plates), but usually made of carbon. The carbon plates are separated by an electrolyte and a separator (which allows ions to flow within the electrolyte). Once voltage is applied to the electrodes, positive ions flow (defuse) to the negative plate and visa versa, resulting in an electric charge building up at each plate, forming a ‘double layer’. Each double layer acts as an individual simple capacitor described above, with the system effectively operating as two capacitors in series. Super capacitor capacitances (proportional to energy storage) are exponentially larger than conventional capacitors due to:

  • Capacitance is directly proportional to the electrode surface area, while inversely proportional to the electrode separation difference. Conventional capacitor electrode separation is determined by the size of the dielectric, which range in the tens of micros, while supercap distances are in the nanometer range.
  • The carbon electrodes utilised in supercaps allow for larger surface areas, due to the spongy nature.

*The following blog ‘part 2’ shall cover the direct comparisons between batteries and supercaps.