From solar cells to ocean buoys: Wide-bandwidth limits to absorption by metaparticle arrays

TL;DR

This paper derives a wide-bandwidth upper bound for absorption in metaparticle arrays, applicable to wave-scattering problems like ocean-buoy energy extraction, and suggests design strategies for performance enhancement.

Contribution

It introduces an analytical upper bound for absorption enhancement based on reciprocity, applicable to general wave-scattering arrays, and proposes design improvements such as membranes.

Findings

The derived bounds closely match simulation results for random and optimized arrays.

Reciprocity conditions underpin the fundamental limits to absorption.

Membranes on water surfaces significantly improve energy absorption.

Abstract

In this paper, we develop an approximate wide-bandwidth upper bound to the absorption enhancement in arrays of metaparticles, applicable to general wave-scattering problems and motivated here by ocean-buoy energy extraction. We show that general limits, including the well-known Yablonovitch result in solar cells, arise from reciprocity conditions. The use of reciprocity in the stochastic regime leads us to a corrected diffusion model from which we derive our main result: an analytical prediction of optimal array absorption that closely matches exact simulations for both random and optimized arrays under angle/frequency averaging. This result also enables us to propose and quantify approaches to increase performance through careful particle design and/or using external reflectors. We show in particular that the use of membranes on the water's surface allows substantial enhancement.