Harvesting raindrop energy: theory

Abstract

At present, the energy autonomy of a microsystem is limited by the lifespan of the battery. Hence the development of an energy harvesting concept, whereby the energy needed to power the sensor is taken from the operating environment. However, there is no single solution suitable for all types of environment. In this paper, we look at a still unexploited source of energy: rain. Our system recovers the vibration energy from a piezoelectric flexible structure impacted by a water drop. This paper describes in detail the theoretical study undertaken to optimize the mechanical system.

Electromagnetic energy harvesting from vibrations induced by Kármán vortex street

“…The voltage induced in the loop of the coil can be calculated using Eqs. (8) and (10). A velocity history of the magnet needed in Eq.…”

“…By harvesting energy from the environment, miniature sensing/actuating devices can be self-powered in order to avoid the replacement of finite power sources. Sources of energy harvesting can be flowing water [8,9], rain [10], tides [11], wind [12], sunlight [13], and geothermal heat [14].…”

Hybrid Decentralised Energy for Remote Communities: Case Studies and the Analysis of the Potential Integration of Rain Energy

“…Assuming the absence of stochastic variables such the effect of wind, a spherical model can be adopted for a relatively small (≤2 mm in diameter) falling raindrop [29,30]. This assumption derives from the surface tension of water, which holds the raindrop together against air drag.…”

“…The few rare existing literature on harvesting rainfall energy has opted for piezoelectric material as the primary transducer [29,30,34]. Piezoelectric material yields an electrical charge polarisation when mechanical strain is induced, and vice versa.…”

“…This relies on direct impact induced kinetic-to-electric energy transfer via piezoelectric material [29,30]. This mechanism is illustrated in Figure 4.…”