A Multidirectionally Thermoconductive Phase Change Material Enables High and Durable Electricity via Real-Environment Solar–Thermal–Electric Conversion

Abstract

A solar thermoelectric generator (STEG) that generates electricity from sunlight is expected to be a promising technology for harvesting and conversion of clean solar energy. The integration of a phase-change material (PCM) with the STEG even more enables engines to durably generate power in spite of solar radiation flux. However, its photothermal conversion and output electricity is still limited (<15 W/m 2 ) by the PCM's deficient thermal management performance, i.e., restricted thermal conductivity and nonuniform heat-transfer behavior under concentrated sunlight radiation. In this study, a biomimetic phase-change composite, with centrosymmetric and a multidirectionally aligned boron nitride network embedded in polyethylene glycol, is tailored for the STEG via a radial icetemplate assembly and infiltration strategy, which behaves in a highly and multidirectionally thermoconductive way and enables a rapid transfer of heat flux and uniform temperature distribution with respect to even a spot-like heat source. As a consequence, a powerful STEG is tactfully designed via the integration of this high-thermal-management characteristic and maximum collection of solar beams, for durable and real-environment solar−thermal−electric conversion, with its photothermal energy conversion efficiency of up to 85.1% and a high peak power density of 40.28 W/m 2 .

Ultrarobust Photothermal Materials via Dynamic Crosslinking for Solar Harvesting

“…Considering the favorable photothermal performance of the film under simulated solar irradiation, the fluctuation of output performance could be ascribed to the uncertainty of outdoor solar intensity, which is in consistent with previous literature. [ 55 ] To this end, we envision our composite film possesses significant advantages in solar harvesting applications.…”

Ultra‐Stable Phase Change Coatings by Self‐Cross‐Linkable Reactive Poly(ethylene glycol) and MWCNTs

“…The light‐to‐heat transduction efficiency (η) is a critical parameter of PCMs materials. The values of the coatings were calculated according to Equation (2): [ 1 ] where m is the weight of the composite, Δ H is the transition enthalpy of the PCMs obtained from DSC test, P is the power of the light source, and t 1 , t 2 represents the time before and after the phase change, respectively. Under the irradiation of simulated light source (xenon lamp), the calculated efficiency of RPCMs‐10000, RPCMs‐10000/CNT‐1.0 wt%, RPCMs‐10000/CNT‐1.3 wt%, and RPCMs‐10000/CNT‐2.0 wt% were 46.4%, 84.1%, 85.3%, and 86.4%, respectively.…”

“…Phase change materials (PCMs) can absorb and release large amount of latent heat at constant transition temperature, and have been widely used in thermal management. [ 1–3 ] Solid–liquid and solid–solid were two basic phase change states that studied most in literatures. [ 4 ] However, for the PCMs based on solid‐liquid phase transition, to prevent leakage and deformation of the materials is the primary requirement in actual applications, [ 5 ] because the constituent, for example, paraffin, fatty acid, poly(ethylene glycol) (PEG) would melt into liquid above the phase transition temperature.…”

A Structured Phase Change Material with Controllable Thermoconductive Highways Enables Unparalleled Electricity via Solar‐Thermal‐Electric Conversion

“…Very recently, our group reported a conifer-inspired phase change composite by a radial ice-template method, with the typical centrosymmetric and multi-directionally arranged boron nitride thermal pathways embedded in polyethylene glycol, which raises the peak power density of a STEG to 40.28 W m −2 in the real-environment experiment of solarthermal-electric conversion. [19] However, this lab-scale achievement is still incomparable with commercial photovoltaic technologies. Further high electricity output requires a much higher temperature gradient and a more efficient heat-exchange platform for the optimal solid-solid heat exchange.…”

“…In general, the current thermo-conductive phase change composite is constructed by the blending of the inorganic filler (e.g., graphene, boron nitride, carbon nanotubes) with a PCM matrix. Attributed to divergent phonon vibration modes between filler and matrix, judicious engineering strategies have been proposed to relieve the phenomenon of interfacial phonon scattering, such as inducing orientation of anisotropic filler, [15][16][17] assembly into the interconnected filler network, [18][19][20] and taking advantage of synergistic fillers. [21,22]…”