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Research Papers

# Solar Thermophotovoltaic Converters Based on Tungsten Emitters

[+] Author and Article Information
V. M. Andreev

A.F. Ioffe Physical-Technical Institute RAS, 26 Polytechnicheskaya, 194021 St. Petersburg, Russiavmandreev@mail.ioffe.ru

A. S. Vlasov, V. P. Khvostikov, O. A. Khvostikova, P. Y. Gazaryan, S. V. Sorokina, N. A. Sadchikov

A.F. Ioffe Physical-Technical Institute RAS, 26 Polytechnicheskaya, 194021 St. Petersburg, Russia

J. Sol. Energy Eng 129(3), 298-303 (May 10, 2006) (6 pages) doi:10.1115/1.2734576 History: Received December 05, 2005; Revised May 10, 2006

## Abstract

Results of a solar thermophotovoltaic (STPV) system study are reported. Modeling of the STPV module performance and the analysis of various parameters influencing the system are presented. The ways for the STPV system efficiency to increase and their magnitude are considered such as: improvement of the emitter radiation selectivity and application of selective filters for better matching the emitter radiation spectrum and cell photoresponse; application of the cells with a back side reflector for recycling the sub-band gap photons; and development of low-band gap tandem TPV cells for better utilization of the radiation spectrum. Sunlight concentrator and STPV modules were designed, fabricated, and tested under indoor and outdoor conditions. A cost-effective sunlight concentrator with Fresnel lens was developed as a primary concentrator and a secondary quartz meniscus lens ensured the high concentration ratio of $∼4000×$, which is necessary for achieving the high efficiency of the concentrator–emitter system owing to trap escaping radiation. Several types of STPV modules have been developed and tested under concentrated sunlight. Photocurrent density of $4.5A∕cm2$ was registered in a photoreceiver based on $1×1cm2$$GaSb$ cells under a solar powered tungsten emitter.

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Copyright © 2007 by American Society of Mechanical Engineers
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## Figures

Figure 1

Schematic drawing of a STPV system. Major parts shown: (1) solar concentrator: (2) high-temperature emitter; and (3) PV cells; (4) and backside mirror.

Figure 2

Dependence of calculated spectral tungsten emitter aperture absorptansces with diameter of 12mm and variable emitter length of 15–45mm. Emitter temperature is T=1600K.

Figure 3

Dependence of calculated emitter efficiency for two concentration ratios (CR)=2000x and 8000x (left) and PV conversion efficiency for three band gaps of 0.4eV, 0.7eV, and 1.1eV (right) from tungsten emitter temperature

Figure 4

Dependence of calculated efficiency of STPV module versus single-junction PV cell band gap for different values of tungsten emitter efficiency the ηEm and two system configurations: (a) current technology (AA=0.7, RE=0.5); and (b) advanced technology (AA=0.9; RE=0.9)

Figure 5

Calculated efficiency of STPV module (advanced technology) with the use of monolithic tandem PV cells for various tungsten emitter efficiencies ηEm. The graphs are plotted for various top and bottom band gaps as a set of isoefficiency lines.

Figure 6

Calculated efficiency of STPV module (current technology) with tandem PV cells for different direct sun radiation levels and emitter efficiency of 0.8. The graph is plotted versus bottom cell band gap with the optimal top cell band gap.

Figure 7

Two-stage concentrator based on a Fresnel lens 1 and a quartz meniscus lens (2)

Figure 8

Schematic drawings of the developed cylindrical (a) and conical (b), (c) STPV modules

Figure 9

STPV module with a flat PV receiver (a), a tungsten emitter surrounded by a conical reflector (b), and a complete module (c)

Figure 10

(a) Tantalum emitter (12mm in diameter and 45mm length), installed in the STPV modulle of “cylindrical” type and heated by Fresnel lens; and (b)SiC flat emitter installed in the conical system and heated with the solar simulator system (∼200W at the input of the aperture) (28)

Figure 11

(Circles) measured tungsten emitter temperature as a function of emitter length (emitter diameter is 12mm and direct sun irradiation density is normalized to 800W∕m2); and (dotted line) calculated emitter temperature

Figure 12

Open circuit voltage (VOC, curve 2), fill factor (FF), (curve 3), and efficiency (curves 1,4) of GaSb TPV cell as a function of tungsten emitter temperature. Efficiency was estimated under the following radiation conditions: under the full radiation spectra (curve 1) and under spectra cutoff at λ>1820nm (curve 4)

Figure 13

Average measured thermal irradiation density (GaSb cell short circuit current) (curve 1), left scale, and the estimated STPV module power output (curve 2), right scale plotted for different emitter lengths

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