# Confinement effect on solar thermal heating process of TiN solutions

## TL;DR

This paper presents a theoretical model analyzing how confinement effects influence the solar thermal heating and steam generation efficiency of TiN nanoparticle solutions, highlighting localized heating as a key factor.

## Contribution

The study introduces a quantitative theoretical approach incorporating confinement effects to better understand solar heating in TiN nanoparticle solutions, validated by experimental data.

## Key findings

- Increased nanoparticle concentration reduces solar radiation penetration.
- Photon localization occurs near the solution surface at high concentrations.
- Localized heating enhances steam generation efficiency.

## Abstract

We propose a theoretical approach to describe quantitatively the heating process in aqueous solutions of dispersed TiN nanoparticles under solar illumination. The temperature gradients of solution with different concentrations of TiN nanoparticles are calculated when confinement effects of the container on the solar absorption are taken into account. We find that the average penetration of solar radiation into the solution is significantly reduced with increasing the nanoparticle concentration. At high concentrations, our numerical results show that photons are localized near the surface of the solution. Moreover, the heat energy balance equation at the vapor-liquid interface is used to describe the solar steam generation. The theoretical time dependence of temperature rise and vaporization weight losses is consistent with experiments. Our calculations give strong evidence that the substantially localized heating near the vapor-liquid interface is the main reason for the more efficient steam generation process by floating plasmonic membranes when compared to randomly dispersed nanoparticles. The validated theoretical model suggests that our approach can be applied towards new predictions and other experimental data descriptions.