Control of thermal radiation for energy applications. Shanhui Fan Ginzton Laboratory and Department of Electrical Engineering Stanford University

Transcription

1 Control of thermal radiation for energy applications Shanhui Fan Ginzton Laboratory and Department of Electrical Engineering Stanford University

2 Thermal radiation: an ubiquitous aspect of nature Sun (6000K) Human Body (~ 310K) Tungsten light bulb (~3000K) Outer Space (3K)

3 Conventional view of a blackbody 2000K (Well, it is black.) Typically strongly absorbing/emitting in both the solar and the thermal wavelength range Broad-band, broad-angle absorption.

4 Strong angular emission from SiC grating Greffet et al, Nature 416, 61 (2002)

5 Narrow-band thermal radiation from gold antenna w=0.4µm, l = 1.7µm Gold L. Zhu et al, APL 102, (2013) X. Liu et al, PRL 107, (2011)

6 Daytime radiative cooling emissivity Wavelength (micron) A mirror in the solar wavelength range. black in the 8-13 micron window. E. Rephaeli, A. Raman and S. Fan, Nano Letters 13, 1451 (2013).

7 Radiative access to the universe 300K Blackbody Spectrum

8 Stanford daytime radiative cooling experiment Sample: 8 inch wafer A. Raman, M. Anoma, L. Zhu, E. Rephaeli, and S. Fan, Nature 515, 540 (2014).

9 Emissivity of the photonic cooler Strong solar reflection Strong and selective thermal emission

10 Rooftop Setup

11 Daytime Cooling Experiment: Results A. Raman, M. Anoma, L. Zhu, E. Rephaeli, and S. Fan, Nature (2014).

12 Towards Fundamental Limit of Radiative Cooling Z. Chen, L. Zhu, A. Raman, and S. Fan, Nature Communications (2016, in press) (Supported by a GCEP project)

13 Ultra-High Performance Continuous Radiative Cooling Over Day and Night Z. Chen, L. Zhu, A. Raman, and S. Fan, Nature Communications (2016, in press)

14 Indoor cooling In a typical office environment, 40-60% of heat dissipation of human body is through thermal radiation. Controlling thermal radiation is therefore important for indoor cooling.

15 Design textile for indoor cooling application Normal textile (such as cotton) Cooling textile Visible Thermal IR Visible Thermal IR Blocks both IR and visible Blocks visible, but allow IR to go through

16 Nanoporous polyethylene (PE) P. Hsu et al, Science 353, 1019 (2016). collaboration with Prof. Y. Cui s group at Stanford

17 Visible and thermal spectra Visible spectrum Thermal infrared spectrum Transmission Transmission Wavelength (nm) Wavelength (micron) P. Hsu et al, Science 353, 1019 (2016). collaboration with Prof. Y. Cui s group at Stanford

18 Shockley-Queisser Limit P N V Sun Semiconductor PN junction Photons with energy below band gap are not absorbed by the semiconductor Photons above the band gap are absorbed, but each photon only contributes part of its energy % efficiency limit depending on concentration

19 Solar thermophotovolatics Broadband absorber Selective emitter P N Compress the spectral bandwidth of light that is incident on the PV cell R. M. Swanson, Proc. IEEE 67, (1979) S. Fan, Nature Nanotechnology 9, 92 (2014).

20 Solar Thermo-Photovoltaics (STPV) P N Sun (T s = 6000K) Intermediate Absorber and Emitter (T i = 2544K) Solar Cell (T e = 300K) The sun to the intermediate The intermediate to the cell P. Harder and P. Wurfel, Semicond. Sci. Technol. 18, S151 (2003);

21 The record today in solar thermophotovoltaics Solar to electric energy conversion of 6.8% D. M. Bierman, Nature Energy 1, (2016)

22 6000K Our GCEP Project 2544K 300K P N PIs: Shanhui Fan, Mark Brongersma, and James Harris To develop structures and materials for emitters that are stable at high temperature. To achieve high efficiency cell specifically tailored for TPV applications.

23 Enhancing stability of thermal emitter under high temperature Tungsten inverted opal ~3000 o C No thermal treatment 1000 o C 1 micron 1200 o C 1400 o C K. Arpin, S. Fan and P. Braun et al, Nature Communications 4, 2630 (2013).

24 Flat Tungsten Thermal Emitter With Spectral Tailoring SiC W Y. Guo and S. Fan, Optics Express (2016, in press).

25 Thermal Metasurfaces for Full Control of Thermal Radiation Brongersma group

26 Phase-gradient thermal metasurface for the focusing of the thermal radiation Brongersma group

27 Previous work: world-record multi-junction cell J sc,tandem = min{j sc,top, J sc,mid, J sc,bot } J out InGaP GaAs GaInNAsSb bottom middle top Combined V app Harris group Solar Junction record efficiency 44% V oc,tandem =V oc,top +V oc,mid +V oc,bottom

28 High-efficiency low band gap cell for TPV applications n + n p p + InP window In 0.53 Ga 0.47 As emitter In 0.53 Ga 0.47 As base InP BSF n + GaSb window n In 0.2 Ga 0.8 As 0.18 Sb 0.82 emitter p In 0.2 Ga 0.8 As 0.18 Sb 0.82 base p + GaSb BSF Harris group

29 Summary Sun (6000K) Human Body (~ 310K) Tungsten light bulb (3000K) Outer Space (3K) Control of thermal radiation offers tremendous opportunity for energy applications.