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Why $/kwhr is not the right way to evaluate supercapacitor cost

Supercapacitors: the best solution in high power, long life, wide temperature applications

Among the first questions that is asked by a customer considering supercapacitors for energy storage is – “what does a supercapacitor cost on a $/kwhr basis”. This is the universal metric for evaluating the cost a battery. However, the appropriate question to be asked is – “what the cost of the Amperics supercapacitor as implemented in this given application”.

In high power, high cycle and wide temperature applications Amperics’s supercapacitors are the most efficient options whether on the basis of cost, weight or volume. Amperics’s Supercapacitors have 10X the power density(kw/kg) and charge/discharge at 100C rates, 100X lifetime(100K cycles vs 300-100 cycles) and unlike a battery has an almost flat performance over the rated operating temperature o -40 degrees C to +6 degrees C.

Lets consider a specific application – Engine starting. This is an application that demands currents ranging from a low of 80A to a high of several hundred Amps for a few seconds( 3 second) in temperatures that can routinely range from a low of -20 degrees C in the American midwest in the dead of winter to a high of 45 degreesC in the summer in Arizona. The actual energy used in this application is 0.8 whr to 3whr. However, the power performance of a lead acid battery is so low that in order for a battery to deliver 80A to 300A for a few seconds, it needs to sized between a low 250Ahr (3kwhr at 12V) to a high of 750Ahr (9kwhr at 12V)!! This is an oversizing of the required energy by a factor of 100X! This also required in order ensure performance at low temperatures where the available amps drops off dramatically from the name plate performance at 25 degrees C. Further, these lead acid batteries have to be replaced every 2-3 years in normal use and much sooner in commercial vehicles like trucks at a cost of $120 for a group24 unit to as much as $300 for a group 31 unit.

In contrast, in this application the Amperics 12V modules store about 1whr or the energy that is needed. !! Given the high power capability it will charge off the alternator in seconds. Further, there is no degradation in performance at lower temperatures. Amperics’s 12V modules in this application is priced equivalently while lasting more than 10 years.

This makes Amperics’s supercapacitor solution cheaper over the by factor 2X-5X over the course of 10 years. This does not take into account this increased reliability vis a vis a lead acid battery.

As the above case study elucidates, if the analysis is performed with $/kwhr as the leading metric under consideration it takes one down path that results in an inaccurate conclusion.

In any application that requires a) high currents for short durations with relatively long periods of latency in between b) lifetime cycles of the application is in excess of 3000 c) wide operating temperatures are wider than 0 degrees C on the low end and 40 degrees C on high end, an intelligent and wholistic look at whether supercapacitors either as a standalone alternative or a in a hybrid configuration with either a Lead Acid or Li Ion battery is warranted.