Electric energy generation from falling droplets has seen a hundred-fold rise in efficiency over the past few years. However, even these newest devices can only extract a small portion of the droplet energy. In this paper, we theoretically investigate the contributions of hydrodynamic and electric losses in limiting the efficiency of droplet electricity generators (DEG). We restrict our analysis to cases where the droplet contacts the electrode at maximum spread, which was observed to maximize the DEG efficiency. Herein, the electro-mechanical energy conversion occurs during the recoil that immediately follows droplet impact. We then identify three limits on existing droplet electric generators: (i) the impingement velocity is limited in order to maintain the droplet integrity; (ii) much of droplet mechanical energy is squandered in overcoming viscous shear force with the substrate; (iii) insufficient electrical charge of the substrate. Of all these effects, we found that up to 83% of the total energy available was lost by viscous dissipation during spreading. Minimizing this loss by using cascaded DEG devices to reduce the droplet kinetic energy may increase future devices efficiency beyond 10%.

在过去的几年里，从液滴下落产生的电能效率提高了 100 倍。然而，即使是这些最新的设备也只能提取一小部分液滴能量。在本文中，我们从理论上研究了流体动力和电力损失在限制液滴发电机 (DEG) 效率方面的贡献。我们将我们的分析限制在液滴以最大扩散接触电极的情况下，观察到这可以最大限度地提高 DEG 效率。在此，机电能量转换发生在液滴撞击之后的反冲期间。然后我们确定了现有液滴发电机的三个限制：(i) 撞击速度是有限的，以保持液滴的完整性；(ii) 大部分液滴机械能被浪费在克服基材的粘性剪切力上；(iii) 基材的电荷不足。在所有这些影响中，我们发现高达 83% 的可用总能量在扩散过程中因粘性耗散而损失。通过使用级联 DEG 设备来减少液滴动能，从而最大限度地减少这种损失，可以将未来的设备效率提高 10% 以上。