THERMOPHOTOVOLTAICS

What is thermophotovoltaics Working Efficiency Active components and material selection Advantages over photovoltaic cells Applications

CONTENTS

Static energy converters that convert thermal

radiation into electricity by means of photo voltaic diode

MAIN COMPONENTS ARE: Thermal emitter Photovoltaic diode Spectral control component(filter)

What are thermo photovoltaic cells?

Work on the same principle of solar cell 1.Emitter converts heat into radiation 2.This is selectively filtered by optical filter.

Part of it is transmitted to PV diode and the rest is reflected back to emitter

3.The PV diode converts the transmitted photons with energies in excess of the diode energy band gap into charge carriers

Working of TPV

The photons below the band gap are partially absorbed and converted into waste heat and partially recycled back to emitter by the back side contact

The absolute upper limit for efficiency in TPVs is the Carnot efficiency that of an ideal heat engine

The efficiency is given by:

Tcell is the temperature of the converter

Temit is the temperature of the emitter

Efficiency

For a practical TPV maximum efficiency is 83% for

Tcell = 300 K and Temit =1800 K

CAUSES OF INEFFICIENCIES: Emitters : deviations from perfect absorbing and

perfect black body behavior Filters :  practical filters often reflect a small

percentage of light in desired wavelength ranges or transmit light of non-ideal wavelengths

Converters :  inefficiencies associated with non- radioactive recombination and ohmic losses exist

 

EMITTERS : Factors to consider while choosing emitters1.Efficiency 2.Temperature resistance 3.Cost

Existing emitters: Polycrystalline silicon carbide (SiC): 1.thermally stable up to 1700 c 2.radiates in the longer wave lengths 3.cheaper and used in commercial applications

Tungsten: 1.temperature same as that of SiC 2.radiates in the visible and near IR range 3.used in burner TPVs

Active components and material selection

Other selective materials used for emitters are Rare earth oxides (Yb2 O3 & Er2 O3) and photonic crystals

PHOTOVOLTAIC DIODES: Factors to consider are 1. availability 2. low cost 3. ease of manufacture 4. low energy band gapExisting PV diodes are: Gallium antimonide (band gap of 0.72 ) Indium gallium arsenide antimonide (band gap of 0.55

eV) Indium gallium arsenide(band gap of 0.75 eV)

Requires less maintenance Any fuel may be used to heat the radiant

surface High photo voltaic conversion efficiency of

radiation to electricity owing to recycling of unabsorbed photons

Can generate current densities 300 times that of conventional photo voltaic cells

Advantages of TPV over photo voltaic cell

Military applications In space Commercial applications Off - grid generators Recreational vehicles

Applications

Burner TPVs

http://www.mit.edu/~ivanc/Publications/2004_1D%20and%202D%20Photonic%20Crystals%20for%20TPV%20Applications.pdf

http://en.wikipedia.org/wiki/Thermophotovoltaic

Refernces

Thank you