Antonio Carlos M. de Queiroz

Electrostatic vibrational energy harvesting using a variation of Bennet's doubler

A capacitive electrostatic generator with a structure suitable for a vibrational energy harvester is described. The device is a variation of the classical “doubler of electricity”. The device has only one moving part, only diodes as electronic components, and can generate any voltage, limited only by a nonlinear loading device. A simple version suitable for recharging a battery is discussed, and the results of a practical demonstration implementation are shown.

Doublers of electricity

This article presents a review of the forgotten history of the doubler of electricity, which by the end of the 18th century was the first apparatus used for the generation of electricity without using friction. Several examples are described, including a new one for a rotating doubler developed as an electrostatic generator.

Electrostatic energy harvesting without active control circuits

This work discusses some structures of electrostatic generators that can be used for energy harvesting from mechanical vibrations or rotating movement, that do not require any active control circuit for their operation. The structures use an unstable generator to bias another generator, or just variable capacitors, which form the main generator. Their action is similar to electric generators based on electrets.

Electrostatic energy harvesting using doublers of electricity

This paper describes an investigation about how to use a kind of electrostatic generator known as “doubler of electricity” as a practical micropower generator. The device has a structure that is amenable to miniaturized construction as a MEMS device powered by ambient vibration. A simple battery charger that does not require any control circuit is studied, and the inherent instability of the device is exploited to allow greater power output, with experimental results of a large scale proto-type presented.

Analysis of the doubler of electricity considering a resistive load

This work shows a detailed analysis of an electrostatic generator based on Bennets doubler, that can be used for vibrational energy harvesting, considering the effect of a resistive load on the behavior of the device. Two levels of approximation are used in the analysis, with results compared with precise simulations. The analyses allow a prediction of the voltage multiplication factor per cycle as function of the load, and quick evaluation of the load that the device can tolerate.

Balanced transconductor-C ladder filters with improved linearity

Balanced transconductor-C filters simulating passive LC ladder structures can be built with different arrangements of the balanced transconductors, what reduces the input voltages over the transconductor inputs, reducing the nonlinearity of the filter. The need of common-mode feedback circuits can also be eliminated by structural changes in the transconductors. The paper investigates the synthesis procedure and the stability properties of these modified filters.

Batteryless Electrostatic Energy Harvester and Control System

This work shows how an electrostatic energy harvester based on a “doubler of electricity” can be used as energy source for low-power applications, without the need of a battery, and describes a suitable control system for it. The fact that the generator can be made to start from very small initial charge, which can be provided by electrical noise or external interference, is used to eliminate the need of a battery.

Analysis of the operation of a regenerative electrostatic energy harvester

The operation of an electrostatic energy harvester based on the electrostatic generator known as “Bennets doubler,” is analyzed in detail, with the objective of finding the relations of the capacitance values, frequency of operation, and other parameters, with the resulting waveforms and the harvested power when the device is used in conjunction with a DC/DC converter. The results are compared with simulations, and are verified with a macroscopic physical prototype with parameters similar to a microelectromechanical version.

Energy harvesting with 3D-printed electrostatic generators

An investigation is made about the practicability of building electrostatic generators suitable for energy harvesting applications using 3D-printed electromechanical structures. The generators are based on variable capacitors, using structures similar to Bennets doubler, or more complex charge multipliers. Normal ABS plastic is used for insulating and mechanical structures, and conductive ABS is used for conducting parts as capacitor plates. As these generators work at very high impedance levels, the relatively high resistivity of the material used as conductor has acceptably small effect, and the technique can be used as an inexpensive alternative for experimenting with generator structures.

Energy harvesting using symmetrical electrostatic generators

This paper describes possible regenerative electrostatic generators that can be obtained when two variable capacitors are used, in a symmetrical configuration. The studied structures require also two load capacitors and four switches or diodes, and produce two opposite output voltages. It is shown that some versions can produce a voltage multiplication factor per cycle that can reach 2. 618, greater than the maximum of 2 of the previously studied devices based on Bennets doubler. As those, the proposed structures a re also compatible with microelectromechanical systems, and may be suitable for energy harvesting applications.