Evaporation Cold Energy Storage and Thermoelectric Harvesting via Hydrogel-Phase Change Material-Thermoelectric Generator Tandem Structure

Jing CAO; Xiang LIANG; Surasak RUAMRUK; Soe Ko Ko AUNG; Sai Kishore RAVI; Thang Bach PHAN; Tosawat SEETAWAN; Yujie KE; Gang ZHANG; Ady SUWARDI

doi:10.1002/sstr.202500635

Evaporation Cold Energy Storage and Thermoelectric Harvesting via Hydrogel-Phase Change Material-Thermoelectric Generator Tandem Structure

Jing CAO^*
, Xiang LIANG
, Surasak RUAMRUK
, Soe Ko Ko AUNG
, Sai Kishore RAVI
, Thang Bach PHAN
, Tosawat SEETAWAN
, Yujie KE
, Gang ZHANG
, Ady SUWARDI^*

^*Corresponding author for this work

School of Graduate Studies

Research output: Journal Publications › Journal Article (refereed) › peer-review

Abstract

This article presents a tandem hydrogel-phase change material (PCM)-thermoelectric generator (TEG) structure for evaporation-driven cold energy storage and electricity harvesting. The hydrogel layer facilitates water evaporation under ambient conditions, generating a cooling effect that produces “cold energy”. This energy is stored in a PCM layer as latent energy, maintaining a stable temperature gradient without volume changes or leakage. The integrated TEG converts this gradient into electricity during both charging (evaporation-induced cooling and PCM solidification) and discharging (PCM melting and heat release) phases, enabling dual-phase power generation. Experimental results demonstrate a maximum power output of 1.6 mW and a power density of 100 μW/cm² at ambient condition without energy input. In addition, we demonstrate an average power output of 0.3 mW and a power density of 19 μW/cm² for a fully charged PCM under ambient conditions, with a cooling efficiency that reduces surface temperatures of TEG by up to 5°C. This article represents the first demonstration of simultaneous storage and utilization of evaporation thermal energy for electricity generation. This innovative design combines evaporative cooling, latent energy storage, and thermoelectric conversion, advancing sustainable energy solutions for low-grade heat environments and efficiently powering portable electronics.

Original language	English
Article number	e202500635
Number of pages	8
Journal	Small Structures
Volume	7
Issue number	1
Early online date	12 Jan 2026
DOIs	https://doi.org/10.1002/sstr.202500635
Publication status	Published - Jan 2026

Bibliographical note

Publisher Copyright:
© 2025 The Author(s). Small Structures published by Wiley-VCH GmbH.

Funding

This work was supported by the Shun Hing Institute of Advanced Engineering (#RNE‐p3‐24), Chinese University of Hong Kong (4055224), National Research Foundation Singapore (U2411D4011), Agency for Science, Technology and Research (R22I1IR053), and National Research Council of Thailand (B48G660114). Z. Gong is acknowledged for his help with PVA hydrogel preparation. This research is supported in part by project #RNE‐p3−24 of the Shun Hing Institute of Advanced Engineering, The Chinese University of Hong Kong. A.S. also acknowledges funding from CUHK Direct Grant 4055224, and startup funding from The Chinese University of Hong Kong. J.C. acknowledges funding from e‐Asia Joint Research Program award no. R22I1IR053, and LCER Phase 2 ETGC award no. U2411D4011. T. S. and S. R. acknowledge the NSRF via the Program Management Unit for Human Resources & Institutional Development, Research and Innovation (grant no. B48G660114). This research is also funded by the Vietnam National University, Ho Chi Minh City (Grant No. NCM2024‐50‐01).

Keywords

energy harvesting
energy storage
evapolectrics
hydrogels
phase change materials
thermoelectrics
water evaporation

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10.1002/sstr.202500635Licence: CC BY

Cite this

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title = "Evaporation Cold Energy Storage and Thermoelectric Harvesting via Hydrogel-Phase Change Material-Thermoelectric Generator Tandem Structure",

abstract = "This article presents a tandem hydrogel-phase change material (PCM)-thermoelectric generator (TEG) structure for evaporation-driven cold energy storage and electricity harvesting. The hydrogel layer facilitates water evaporation under ambient conditions, generating a cooling effect that produces “cold energy”. This energy is stored in a PCM layer as latent energy, maintaining a stable temperature gradient without volume changes or leakage. The integrated TEG converts this gradient into electricity during both charging (evaporation-induced cooling and PCM solidification) and discharging (PCM melting and heat release) phases, enabling dual-phase power generation. Experimental results demonstrate a maximum power output of 1.6 mW and a power density of 100 μW/cm2 at ambient condition without energy input. In addition, we demonstrate an average power output of 0.3 mW and a power density of 19 μW/cm2 for a fully charged PCM under ambient conditions, with a cooling efficiency that reduces surface temperatures of TEG by up to 5°C. This article represents the first demonstration of simultaneous storage and utilization of evaporation thermal energy for electricity generation. This innovative design combines evaporative cooling, latent energy storage, and thermoelectric conversion, advancing sustainable energy solutions for low-grade heat environments and efficiently powering portable electronics.",

keywords = "energy harvesting, energy storage, evapolectrics, hydrogels, phase change materials, thermoelectrics, water evaporation",

author = "Jing CAO and Xiang LIANG and Surasak RUAMRUK and AUNG, \{Soe Ko Ko\} and RAVI, \{Sai Kishore\} and PHAN, \{Thang Bach\} and Tosawat SEETAWAN and Yujie KE and Gang ZHANG and Ady SUWARDI",

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AU - CAO, Jing

AU - LIANG, Xiang

AU - RUAMRUK, Surasak

AU - AUNG, Soe Ko Ko

AU - RAVI, Sai Kishore

AU - PHAN, Thang Bach

AU - SEETAWAN, Tosawat

AU - KE, Yujie

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AU - SUWARDI, Ady

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N2 - This article presents a tandem hydrogel-phase change material (PCM)-thermoelectric generator (TEG) structure for evaporation-driven cold energy storage and electricity harvesting. The hydrogel layer facilitates water evaporation under ambient conditions, generating a cooling effect that produces “cold energy”. This energy is stored in a PCM layer as latent energy, maintaining a stable temperature gradient without volume changes or leakage. The integrated TEG converts this gradient into electricity during both charging (evaporation-induced cooling and PCM solidification) and discharging (PCM melting and heat release) phases, enabling dual-phase power generation. Experimental results demonstrate a maximum power output of 1.6 mW and a power density of 100 μW/cm2 at ambient condition without energy input. In addition, we demonstrate an average power output of 0.3 mW and a power density of 19 μW/cm2 for a fully charged PCM under ambient conditions, with a cooling efficiency that reduces surface temperatures of TEG by up to 5°C. This article represents the first demonstration of simultaneous storage and utilization of evaporation thermal energy for electricity generation. This innovative design combines evaporative cooling, latent energy storage, and thermoelectric conversion, advancing sustainable energy solutions for low-grade heat environments and efficiently powering portable electronics.

AB - This article presents a tandem hydrogel-phase change material (PCM)-thermoelectric generator (TEG) structure for evaporation-driven cold energy storage and electricity harvesting. The hydrogel layer facilitates water evaporation under ambient conditions, generating a cooling effect that produces “cold energy”. This energy is stored in a PCM layer as latent energy, maintaining a stable temperature gradient without volume changes or leakage. The integrated TEG converts this gradient into electricity during both charging (evaporation-induced cooling and PCM solidification) and discharging (PCM melting and heat release) phases, enabling dual-phase power generation. Experimental results demonstrate a maximum power output of 1.6 mW and a power density of 100 μW/cm2 at ambient condition without energy input. In addition, we demonstrate an average power output of 0.3 mW and a power density of 19 μW/cm2 for a fully charged PCM under ambient conditions, with a cooling efficiency that reduces surface temperatures of TEG by up to 5°C. This article represents the first demonstration of simultaneous storage and utilization of evaporation thermal energy for electricity generation. This innovative design combines evaporative cooling, latent energy storage, and thermoelectric conversion, advancing sustainable energy solutions for low-grade heat environments and efficiently powering portable electronics.

KW - energy harvesting

KW - energy storage

KW - evapolectrics

KW - hydrogels

KW - phase change materials

KW - thermoelectrics

KW - water evaporation

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Evaporation Cold Energy Storage and Thermoelectric Harvesting via Hydrogel-Phase Change Material-Thermoelectric Generator Tandem Structure

Abstract

Bibliographical note

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Keywords

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