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Journal Club
Tuğrul Çağrı CİNKARA
13 July 2011
MIT, mechanical engineering
Solar energy
 Photovoltaic (PV) cell
o electron-hole pair
Solar
Energy
 Solar Thermal Process
o electricity generation by mechanical heat
engines
o solar hot-water system
Challenge
 Significant temperature difference
Solution
 Optically concentrate the solar radiation
by lens.
Depending on the length of the thermoelectric
element, optical concentration must be 40-200 .
 Increase concentrate by using absorber.
Efficiency
 Thermoelectric Device Efficiency
ηte
1- operating temperature
2- materials properties (dimensionless figure of merit ) (ZT)
S 2
ZT 
T
k
Where,
S (seebeck coefficient)
σ (electrical conductivity)
k (thermal conductivity)
T (temperature)
Th  Tc 1  ( ZT ) M  1
te 
Tc
Th
1  ( ZT ) M 
Th
MAX = %8.6 @
T  200 oC
ideal material (ZT=1)
Efficiency
 Opto-thermal
efficiency ηot
 Th has a trade-off between ηte and ηot . Depending on the thermoelectric material and
solar absorber ; 160 C < Th < 250 C
 Bi2Te3 is the best one.
4
  sb (Th4  Tamb
)
ot  optth   1 

 Copt qi


Efficiency
  teot
Device
Performance
Performance
Performance
 Improving ZT of the thermoelectric
materials
 improving of the selected surface
performance
 combination of thermal and optical
concentration