The story of Energy Storage Cells and the Hybrid Capacitor used in Shakelights

Modern lifestyles demand a steady, reliable supply of energy: it lies at the heart of our mobility, our prosperity and our daily comfort. But we should not take this energy security for granted. Typically, energy sources can be divided into three broad categories.  

1.       The first derives from chemical or photphysical energy that relies on oxidizing some reduced substance, usually a hydrocarbon, or absorbing sunlight to generate either heat or electricity. The energy involved is that of a chemical bond or fractions of an electron volt (eV).

2.       The second involves nuclear reactions that release energy either by splitting heavy nuclei or by fusing light nuclei. The energy involved in nuclear reactions is in the region of Mega-eV (MeV) per nuclear reaction.

3.       The third is thermomechanical in the form of wind, water, or geological sources of steam or hot water. The energy involved is in the milli-electron-volt (meV) region form, for example, water falling several tens of meters.

Each energy source has some undesirable characteristics. Any process using fossil fuels produces carbon dioxide, and perhaps also other contaminants, such as nitrogen oxides, sulphur oxides and ash. Nuclear plants produce radioactive fission products. Solar energy and wind energy require large areas and are limited geographically. Geothermal sources are limited to very few locations. At present most of the world's energy supply comes from fossil and nuclear sources. And although mankind is increasingly having to face the issues of resource limitation and environmental pollution, these sources will continue to be important in providing energy worldwide for the next few generations. But to meet increasing global demands for energy and to allow for the depletion of fossil fuel supplies in the coming years, alternative "clean" energy sources, which do not depend on fossil fuels and which have a tolerable environmental impact, must be developed.  

The rapid evolution of mobile and compact systems continues to fuel demands for reduced power consumption and lower voltage operation. Fully understanding the impact on environment when batteries and capacitors are discarded, "environmental friendliness" is an essential consideration during our designing and manufacturing products.  

Various energy storage devices are commercially available to date, which can be categorized into six major groups according to their respective functions:  

·          Conductive polymer capacitors and ceramic capacitors (for smoothing and noise absorption)

·          Aluminum electrolyte capacitors and chip Tantalum capacitors (for de-coupling)

·          Hyper Capacitors (for backup) or electrochemical capacitor

·          Hybrid Capacitors (for quick charge; as presented in EDI Shakelights)

·          Proton polymer battery (for auxiliary power supply)

·          Rechargeable/non-rechargeable lithium or alkaline batteries (for energy sources)

·          Fuel-cell and hydrogen storage cell (the next generations of energy devices)

Our energy storage cells are based on the operating principle of the twin-electric-layer that is formed at the interface between activated charcoal and an electrolyte. The activated charcoal is used as an electrode. The activated charcoal is used in its solid form, and the electrolytic fluid is liquid. When these materials come in contact with each other, the positive and negative poles are distributed relative to each other over an extremely short distance. Such a phenomenon is known as a twin-electric-layer. When an external electric field is applied, the twin-electric-layer that is formed in the vicinity of the activated charcoal's surface within the electrolytic fluid is used as the fundamental cell structure.

The above twin-electric-layer design does not have the solid dielectric that is used in the previous designs, nor does it have the chemical reactions such as are found in batteries and capacitors during charging and discharging. Rather the design has the following advantages: allowing for heavy-duty energy storage in a small device, no need for special charging circuits or for control during discharge, no negative effect on the lifespan due to over-charging or over-discharging, clean energy in terms of its environmental friendliness or eco-friendliness, and no problem with unstable contacts because of the soldering electronic parts.

The theory behind the twin-electric-layer has been known for more than 100 years, but it was not until 1954 that Becker (GE) developed an energy storage device using this concept.  In the early 1960s, Sohio developed an energy storage device, but the first successful product on the market was a twin-electric-layer  capacitor from ELNA Inc., for memory backup applications in the 1970s.  More recently, this industry has recognised Russian manufacturers as leaders in this technology for their large capacitors. Their primary motivation for developing the large capacitors rooted from cold weather starting of various engines and generators. NEC and Pinnacle were two of the first companies in this market.