Electrocalorimetric Measurement of the TrueEnergy Stored in Supercapacitors

A simple experimental system based on the energy balance between (i) the input electrical energy supplied to a supercapacitor and (ii) its splitting into stored energy and reversible/irreversible heat is presented to allow the correct measurement of the true energy storage capability of these devices. Unlike conventional approaches that rely solely on electrical measurements, this electrocalorimetric system quantifies the total heat generated during charging and discharging, enabling the decomposition of heat into irreversible losses (Joule heating) and reversible heat (entropic contribution). The net recoverable energy is then determined by subtracting the irreversible heat losses from the total electrical energy supplied to the device. A typical setup consists of an electrical unit with bidirectional capability, high-precision sensing, and a calorimetric enclosure for thermal loss quantification. It has been used to test experimentally one commercial supercapacitor under different electrical conditions. The results show that the usual electrical-only characterization overstimates the true stored energy in these devices by about 5-10\%. The proposed method provides thermodynamically-consistent and more realistic values, which is necessary for their accurate characterization and proper integration in real-world energy applications.