Abstract
This paper introduces the novel concept of dielectric fluid transducer (DFT), which is an electrostatic variable capacitance transducer made by compliant electrodes, solid dielectrics and a dielectric fluid with variable volume and/or shape. The DFT can be employed in actuator mode and generator mode. In this work, DFTs are studied as electromechanical generators able to convert oscillating mechanical energy into direct current electricity. Beside illustrating the working principle of dielectric fluid generators (DFGs), we introduce different architectural implementations and provide considerations on limitations and best practices for their design. Additionally, the proposed concept is demonstrated in a preliminary experimental test campaign conducted on a first DFG prototype. During experimental tests a maximum energy per cycle of and maximum power of has been converted, with a conversion efficiency up to 30%. These figures correspond to converted energy densities of with respect to the displaced dielectric fluid and with respect to the mass of the solid dielectric. This promising performance can be largely improved through the optimization of device topology and dimensions, as well as by the adoption of more performing conductive and dielectric materials.
Highlights
The static coupling between electrical and mechanical energy has been extensively studied for the implementation of sensors, actuators and generators, often referred to as electrostatic transducers
Than electromagnetic systems, operation of electrostatic transducers as actuators and generators is cyclical in nature and often requires that a priming energy is applied to the mechanically variable capacitor (MVC) prior to the beginning of the cycle
This paper presents and investigates a MVC transducer that relies on the variation in volume of a dielectric fluid
Summary
The static coupling between electrical and mechanical energy has been extensively studied for the implementation of sensors, actuators and generators, often referred to as electrostatic transducers. Electromechanical coupling between fluids and electrical fields is known since the end of nineteenth century [14,15,16,17], previous studies only have considered devices where the change in capacitance is implemented through the movement of a fluid between fixed stiff electrodes, such as the dielectrophoretic pumps [18, 19] In this contribution instead, the capacitance modulation is obtained by means of a pressurized dielectric fluid that stretches apart and separate the compliant electrodes of a variable volume capacitor. As compared to DETs, DFTs: (1) can potentially feature a larger ratio between converted and stored elastic energy, which makes it possible to decrease the mechanical energy input required to operate the device, as explained in section 2.1; (2) are potentially less affected by the dielectric strength of the employed material since the electrical breakdown in liquids is often reversible while in solids it is not.
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