Research On Thermal Field Manipulation And Thermal Energy Harvesting Using Metamaterials

Under dual pressure of energy and environment,new materials and devices for increasing efficiency of energy,harvesting energy form ambient environment and converting it to DC voltage for mini power or recharging,and solar light to chemical energy conversion(clear fuels)have been challenging hot spots for researchers.Promoting energy efficiency,finally comes down to prevent heat loss and increase thermoelectric conversion efficiency.Inhomogeneous and isotropic natural materials fail to harvest thermal energy,while metamaterials,a group of property-oriented artificial materials,are apt to manipulate multi-physical fields.Thermal metamaterials,which are anisotropic and spatially artificial,can manipulate thermal field,including concentrating,shielding,and inverting heat flux.With special designed structures to increase heat flux density and temperature gradient in concentration core,it is an ideal candidate for thermal energy harvesting.Heat flux concentration in two-dimensional cases has been proved in theory,simulations and experiments but without further study in energy utilization.Furthermore,owning to rigorous requirement of inhomogeneous and extreme material parameters,as well as fabrication and measure difficulties,three-dimensional thermal energy harvester is still in fancy.In this paper,a flower-shaped thermal harvesting metamaterials was originally promoted.Numerical simulations implied that heat flux could be concentrated into the target core and a temperature gradient turned out to be more than two times larger than the applied one without obvious distortion or perturbation to the temperature profile outside the concentrator.We experimentally measured temperature transitions of the actual device to validate the novel structure with consistency of the simulated results with original methods.Two-dimensional extension of the flower-shaped thermal energy harvester was verified in theoretical,simulations and experiments as well,with results corresponded to three-dimensional cases.For further combination of thermal energy harvester and thermoelectric generator,two-dimensional fan-shaped and a hybrid ceramic-metal structure were also developed in this thesis.With ultra-efficiency independent of geometrical size,the flower-shaped thermal harvester facilitated multiple scale energy harvesting with splendid efficient and might help to improve thermoelectric devices efficiency in a totally new perspective.It may also beneficial to future all-in-one electric systems,solar planes and thermal therapy.