Materials science has made progress in maximizing or minimizing the thermal conductivity of materials; however, the thermal effusivity—related to the product of conductivity and capacity—has received limited attention, despite its importance in the coupling of thermal energy to the environment. Herein, we design materials that maximize the thermal effusivity by impregnating copper and nickel foams with conformal, chemical-vapor-deposited graphene and octadecane as a phase change material. These materials are ideal for ambient energy harvesting in the form of what we call thermal resonators to generate persistent electrical power from thermal fluctuations over large ranges of frequencies. Theory and experiment demonstrate that the harvestable power for these devices is proportional to the thermal effusivity of the dominant thermal mass. To illustrate, we measure persistent energy harvesting from diurnal frequencies, extracting as high as 350 mV and 1.3 mW from approximately 10 °C diurnal temperature differences.
|Original language||English (US)|
|State||Published - Feb 14 2018|
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): OSR-2015-Sensors-2700
Acknowledgements: The authors acknowledge the Office of Naval Research (ONR), under award N00014-16-1-2144, and King Abdullah University of Science and Technology (KAUST), under award OSR-2015-Sensors-2700, for their financial support regarding this project. We would like to thank Lain-Jong (Lance) Li and Atif Shamim at KAUST for useful discussions regarding the research. V.B.K. is supported by The Swiss National Science Foundation (project no. P2ELP3 162149). We would also like to thank Sensirion for supplying us with high-accuracy digital temperature sensors with BluetoothTM capabilities.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.