Electrostatic Wave Energy Conversion: A Review of Devices, Theory, and Hurdles

Wave energy is a continuously available resource with tremendous potential. However, utility-scale wave energy harvesting has experienced limited commercial success to date. Many of these shortcomings can be attributed to the fundamental mismatch between the low-frequency nature of ocean waves and the physical principles of conventional electromagnetic generators used in today's WECs, leading to WECs that are large, expensive, and inefficient. As such, a growing number of researchers are investigating electric machinery based on electrostatics as a viable alternative for WEC generators. Not only are electrostatic WECs generally more efficient than their electromagnetic counterparts at low-speed operation, but they also tend to be constructed from abundant, lightweight, and inexpensive materials, which could make WECs economically competitive with other energy sources. This paper first characterizes electrostatic WECs from a theoretical perspective to gain insight into their physical nature and then reviews existing electrostatic WEC technologies, which include variable-capacitance and triboelectric generators. Performance metrics for existing electrostatic WECs are presented. Finally, the key challenges in electrostatic WEC technology are identified along with several strategies to overcome these hurdles in future research.