J. Semicond. > 2016, Volume 37 > Issue 2 > 024002, doi: 10.1088/1674-4926/37/2/024002
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SEMICONDUCTOR DEVICES

Thermo-electronic solar power conversion with a parabolic concentrator

Olawole C. Olukunle and Dilip K. De

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 Corresponding author: Dilip K. De, Email: dilip.de@covenantuniversity.edu.ng

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Abstract: We consider the energy dynamics of the power generation from the sun when the solar energy is concentrated on to the emitter of a thermo-electronic converter with the help of a parabolic mirror. We use the modified Richardson-Dushman equation. The emitter cross section is assumed to be exactly equal to the focused area at a height h from the base of the mirror to prevent loss of efficiency. We report the variation of output power with solar insolation, height h, reflectivity of the mirror, and anode temperature, initially assuming that there is no space charge effect. Our methodology allows us to predict the temperature at which the anode must be cooled in order to prevent loss of efficiency of power conversion. Novel ways of tackling the space charge problem have been discussed. The space charge effect is modeled through the introduction of a parameter f (0 < f <1) in the thermos-electron emission equation. We find that the efficiency of the power conversion depends on solar insolation, height h, apart from radii R of the concentrator aperture and emitter, and the collector material properties. We have also considered solar thermos electronic power conversion by using single atom-layer graphene as an emitter.

Key words: thermos electronic power conversion, solar parabolic concentrator, modified thermionic equation, space charge, magnetic field, anode temperature



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Fig. 1.  (a) The work function W of the emitter is higher than that of the collector. The difference is equal to eVout. (b) The presence of a +ve gate parallel to the cathode and collector, with hole of radius R and a magnetic field perpendicular to the gate towards the collector[Œ1,10].

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Fig. 2.  (a) Schematic diagram with relevant parameters of the thermionic power converter with a parabolic concentrator. The emitter is placed at a height h from the centre of the base. (b) Two surfaces 1 and 2 of the thermionic emitter considered in this work. Surface 1 is irradiated by concentrated solar energy. It is surface 2 that is cesiated to lower the work function and not surface 1.

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Fig. 3.  The surface area of the emitter for two different values of H (Figure 1) of a parabolic concentrator of R=1 m.

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Fig. 4.  Emitter temperature T2(K) versus emitter cross section different solar insolations during thermo-electron emission. Parabolic mirror radius R=1 m. Anode temperature T3=373 K.

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Fig. 5.  Power output against emitter cross section for the same conditions as in Figure 4.

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Fig. 6.  (Color online) Effect of reflection coefficient (rm)of the parabolic mirror on output power for Io=1000 W/m2 assuming no space charge effect mirror radius R=1 m.

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Fig. 7.  (Color online) Variation of efficiency η against solar insolation for various emitters crosses assuming no space charge effect and the same condition as in Figure 5.

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Fig. 8.  (Color online) The effect of space charge on solar thermos electronic power conversion efficiency. In this calculation, it is assumed that the space charge effect reduces the effective current collected by the collector by 40%.

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Table 1.   Computations showing the effect of collector temperature T3 (373 to 573 K) on emitter temperature T2 and power output for solar insolation 500 W/m2 with parabolic concentrator of radius R=1 m. We=1.5 eV; Wc=1 eV.

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Table 4.   The effect of output power for output voltage Vout=(We – Wc)/e=1.0 eV for different emitter cross sections s, as solar insolation varies from 500 to 1000 W/m2. Such that, T3=373 K. We=2 eV, and Wc=1 eV.

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Table 2.   The effect of collector temperature T3 (673 to 873 K) on emitter temperature T2 and power output for solar insolation 500 W/m2 with parabolic concentrator of radius R=1 m.

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Table 3.   The effect of output voltage Vout=(We – Wc)/e=0.5 eV on output power for different emitter cross section s, as solar insolation varies from 500 to 1000 W/m2. Such that T3=373 K, We=2 eV, and Wc=1.5 eV.

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    Received: 13 October 2015 Revised: Online: Published: 01 February 2016

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      Article Navigation >  Journal of Semiconductors  > 2016  >  37(2): 024002
      Olawole C. Olukunle, Dilip K. De. Thermo-electronic solar power conversion with a parabolic concentrator[J]. Journal of Semiconductors, 2016, 37(2): 024002. doi: 10.1088/1674-4926/37/2/024002 O. C. Olukunle, D. K. De. Thermo-electronic solar power conversion with a parabolic concentrator[J]. J. Semicond., 2016, 37(2): 024002. doi:  10.1088/1674-4926/37/2/024002.Export: BibTex EndNote
      Citation:
      Olawole C. Olukunle, Dilip K. De. Thermo-electronic solar power conversion with a parabolic concentrator[J]. Journal of Semiconductors, 2016, 37(2): 024002. doi: 10.1088/1674-4926/37/2/024002

      O. C. Olukunle, D. K. De. Thermo-electronic solar power conversion with a parabolic concentrator[J]. J. Semicond., 2016, 37(2): 024002. doi:  10.1088/1674-4926/37/2/024002.
      Export: BibTex EndNote
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      Thermo-electronic solar power conversion with a parabolic concentrator

      doi: 10.1088/1674-4926/37/2/024002
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      • Corresponding author: Email: dilip.de@covenantuniversity.edu.ng
      • Received Date: 2015-10-13
      • Published Date: 2016-01-25

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