The maximum photocurrent density Jmax is given by the number of photons with energies above the bandgap energy hvg presented in the radiation spectrum multiplied with the elementary charge e0 Eq. Hence, the combination of different filter types can lead to a better overall performance. A cuboid system using a radioisotope heat source has been examined. American Institute of Physics, pp 293—313 Chapter 6 Cavity Design and Optical Control 6. Doctoral thesis, Albert-Ludwigs-Universität Freiburg im Breisgau References 51 52. The filter consists of a thin metal layer sandwiched between one or more dielectric layer on each side.
Assuming a quartz glass thickness in the range of centimetres, three wavelength intervals for the transmission can be distinguished for quartz glass. These are the material composition and the physical structure. An advantage of metals is that they tend to have high thermal conductivities and this results in uniform radiator temperatures. Another major disadvantage of single crystalline materials is usually their higher costs due to the growth process compared to fused silica. Proceeding of the 6th international conference on thermophotovoltaic generation of electricity, Freiburg, Germany, 14—16 June 2004. American Institute of Physics, pp 425—454 30. The bandgap of InAsSbP cells between 0.
Most practical systems aim for an edge filter rather than a band-pass filter design. All three materials are used as resistive elements in electrical heating in vacuum or protective atmospheres to prevent oxidation. For air, at ambient temperature the mean path Lp with the unit cm is given by a simple approximate formula, where p is the pressure in torr1 Eq. American Institute of Physics, pp 249—258 63. The assessment of partial efficiencies allows the identification of critical efficiencies and the optimisation of the overall efficiency.
The remainder of this section focuses on combined radiative and conductive heat transfer in semitransparent dielectric media without convection. Narayanaswamy A, Cybulski J, Gang Chen 2004 , 1D metallo-dielectric photonic crystals as selective emitters for thermophotovoltaic applications. The second part focuses on systems. Proceedings of the 6th international conference on thermophotovoltaic generation of electricity, Freiburg, Germany, 14—16 June 2004. For a blackbody radiation distribution, it needs to be additionally considered that only 25% of the radiation is above the peak energy e. A similar conclusion is also drawn in Sect. Spektrum Akademischer Verlag, Heidelberg 5.
The emphasis is placed on the understanding of the critical aspects of efficient thermophotovoltaic system design. Series on photoconversion of solar energy, Imperial College Press, London 73. The material was initially developed as a structural material for aircraft engines and gas turbines. Accessed 28 Oct 2010 26. A good thermal shock resistance, usually achieved by low thermal expansion materials, is important for the start-up and cooling-down process of the system.
The reduced short wavelength transmission leads to low electrical power densities and this is usually undesirable. Semicond Sci Technol 18:165—173 28. The discussion about optical control in the next chapter focuses mainly on the radiative heat transfer in the cavity in terms of the spectral, angular and spatial distributions. In order to increase the heat transfer rate a liquid—gas phase change boiling in the heat carrier can be utilised. It can be summarised that radiators based on micro- and nano-structures can be designed with a suitable spectrally selective performance. The Gaussian shape transmission characteristic also has no sharp cut-off wavelength so that some out-of-band transmission occurs.
The current-voltage characteristic can be described by the Shockley diode equation Eq. Roth A 1990 Vacuum technology, 3rd edn. Denver, Colorado, 18—21 May 1997. Semicond Sci Technol 18:221—227 43. This is especially true for the intermediate power range around 10 W to 10 kW.
Hence, it cannot be considered a sole cell issue. In the past, there have been other hindrances in the development of the technology. In comparison, crystalline materials cannot absorb long wavelength radiation due to their usually wide window compare Table 3. Proceeding of the 5th conference on thermophotovoltaic generation of electricity, Rome, Italy, 16—19 Sept 2002. About 60% of the input power is infrared radiation 0.