Harvesting thermal energy from spring water using a flexible thermoelectric generator

• Published in: Energy conversion and management 2024-08, Vol.313, p.118605, Article 118605
• Main Authors: Amagai, Yasutaka, Ichinose, Aya, Ikawa, Reo, Sakamoto, Moeno, Ogiya, Takumi, Konishi, Momoe, Okawa, Kenjiro, Sakamoto, Norihiko, Kaneko, Nobu-Hisa
• Format: Article
• Language: English
• Subjects: Energy harvesting; Spring-water temperature; Thermoelectric conversion; Thermoelectric generator; Water quality monitoring; Wireless sensor network
• ISSN: 0196-8904
• DOI: 10.1016/j.enconman.2024.118605

Spring-water temperatures are relatively stable, noticeably lower than the ambient-air temperatures in summer and higher in winter. Theoretically, a thermodynamic heat engine can be created using the temperature differences between ambient-air and spring-water temperatures. Herein, we explored the feasibility and performance of a spring-air thermoelectric generator (TEG) designed to generate a 10 mW-scale quantity of electrical power from a small temperature difference less than 20 K using a flexible TEG (f-TEG). The device was fabricated using a folded flexible heat exchange on the air side, an f-TEG, and a cylindrical heat exchanger made of copper on the spring-water side. The use of an f-TEG facilitates direct thermal contact with a heat exchanger at the spring-water side without the aid of an additional heat transfer device, which causes a temperature drop. Outdoor measurements were periodically conducted to assess seasonal variations in the performance of the spring-air f-TEGs. The f-TEG generated a peak power of 11.4 mW, 13.8mW, 2.6mW, and 19.6 mW and averaged power of 3.1 mW, 4.2 mW, 1.1 mW, and 14.7mW for May, August, November, and January, respectively. This high-power spring-air f-TEG successfully powered the commercial temperature datalogger capable of wirelessly transmitting data from the sensor to a smartphone via Bluetooth. Despite its exploratory nature, this proof-of-concept study offers important insights into power generation from thermal energy of spring water and provides a useful guide to designing optimal TEG systems in future applications of water monitoring.