Mechanical‐to‐Electrical Energy Conversion with Variable Electric Double Layers

Abstract

The electromagnetic generator requires sophisticated power take‐off systems to effectively capture low‐frequency mechanical motion such as ocean waves and human gait. Conversely, electrostatic generators are variable capacitors, which harness charge separation processes that can directly capture low‐frequency mechanical energy. The fundamentals of mechanical‐to‐electrical energy conversion with an electrostatic generator that exploits the high energy density of electric double layer (EDL) capacitors and varies capacitance by physical manipulation of the electrode–electrolyte interfacial area are elucidated. A model system is designed where all experimental parameters are easy to access in order to gain a detailed understanding of the energy flow in this conversion process. The system, termed a variable EDL generator, is based on titanium electrodes in NaCl aqueous electrolyte and operated as a charge pump. The net positive electrical energy generation of the system in the voltage–charge work‐conjugate plane is analyzed, and it shows that the variable EDL generator can be scaled‐up to spin an electric motor and increase the output power of the generator through the use of waste heat. The detailed analysis of this energy conversion principle suggests multiple avenues to enhance the performance of the variable EDL generator.

Macroscale Electrostatic Rotating Machines and Drives: A Review and Multiplicative Gain Performance Strategy

“…Finally, the Fontana Research Group has published a report on a novel fluid transducer in [84], in which the silicone oil Xiameter PMX-200 50CS was utilized, and later described a HASEL actuator utilizing MIDEL 7131, a synthetic ester-based transformer oil (ε g /ε 0 = 3.2), in [85]. VC energy harvesters [86], [87] and brushless rotary power transfer approaches [88] have demonstrated the use of ionic conducting electrolytes to exploit the double-layer capacitor effect, but this is an entirely different electrostatic liquid mechanism than previously described since charge carriers are in the gap (Category I).…”

Electrochemical metamaterials

“…One class of such materials which is particularly smart are polymer electrolyte electroactuators for robotics [7], reverse actuators such as harvesters of electricity from walking or any other mechanical motion (see e.g. references on piezo [8,9], capacitive [10][11][12] and nanotribological [13,14] devices, and the literature cited there). To avoid ambiguity, I prefer to call all those materials-mechanical metamaterials.…”

Ionotronics for reverse actuation

“…Reverse-actuator devices (REDs) are distinguished by their working principle. These include piezo-, 7,8 nanotribological-, 9,10 and capacitivebased [11][12][13] devices.…”