6. Josef Stefan (1835–1893) Ludwig Boltzmann (1844-1906)
where E is the total blackbody
emission rate (W), σ is the Stefan–
Boltzmann constant = 5.67 × 10−8
W/m2-K4, T is the absolute
temperature of the blackbody (K),
and A is the surface area of the
blackbody (m2).
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7. Wilhelm Wien (1864-1928)
where the wavelength is in microns (μm) and the
temperature is in kelvins.
The wavelength at which the spectrum
reaches its maximum point:
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43. • Currently makes up 86% of PV market
• Very stable with module efficiencies 10-16%
Mono crystalline PV Cells
-Made using saw-cut from single
cylindrical crystal of Si
-Operating efficiency up to 15%
Multi Crystalline PV Cells
-Caste from ingot of melted
and recrystallised silicon
-Cell efficiency ~12%
-Accounts for 90% of
crystalline Si market
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44. Silicon deposited in a continuous on a base material such as glass,
metal or polymers
Thin-film crystalline solar cell consists of layers about 10μm thick
compared with 200-300μm layers for crystalline silicon cells
PROs
• Low cost substrate and
fabrication process
CONs
• Not very stable
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45. The most advanced of thin film technologies
Operating efficiency ~6%
Makes up about 13% of PV market
PROs
• Mature manufacturing
technologies available
CONs
• Initial 20-40% loss in efficiency
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46. Copper Indium Diselinide
CIS with band gap 1eV, high
absorption coefficient 105cm-1
High efficiency levels
PROs
• 18% laboratory efficiency
• >11% module efficiency
CONs
• Immature manufacturing process
• Slow vacuum process
Non – Silicon Based Technology
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47. Non – Silicon Based Technology
Cadmium Telluride ( CdTe)
Unlike most other II/IV material
CdTe exhibits direct band gap of
1.4eV and high absorption
coefficient
PROs
• 16% laboratory efficiency
• 6-9% module efficiency
CONs
• Immature manufacturing process
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107. a) Tubular absorbers with diffusive back reflector; b) Tubular
absorbers with specular cusp reflector; c) Plane receiver with plane
reflector; d) Parabolic concentrator; e) Fresnel reflector f) Array of
heliostats with central receiver
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108. where σ is the Stefan–Boltzmann
constant, and e is the thermal emissivity
of the object at absolute temperature T.
Josef Stefan (1835–1893) Ludwig Boltzmann (1844-1906)
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109. The energy balance for thermal equilibrium must include energy output as well
as energy loss, thus
The energy conversion efficiency ηshc of the solar heat collector is then given by
The efficiency ηshc depends on the increase in temperature relative to ambient
temperature, the intensity of solar radiation, and the quality of thermal insulation.
An example of an expression for the efficiency ηshc for a solar heat collector with
commercial insulation is
Is is incident solar intensity at a given time, and Ismax is the maximum solar
intensity observed at the location of the solar heat collector.
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112. Collectors are oriented to track the sun so
that the beam radiation will be directed
onto the absorbing surface .
Parts of a collector are:
Collector: Receiver and the concentrator
Receiver: Radiation is absorbed and
converted to some other energy form (e.g.
heat).
Concentrator: Collector that directs
radiation onto the receiver. The aperture
of the concentrator is the opening through
which the solar radiation enters the
concentrator
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