Ahmad Nawaz final.ppt

8/10/2019 Ahmad Nawaz final.ppt

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(http://www.pocket-lint.com/news/126245-transparent-solar-panel-display-charges-your-phone-through-the-screen)

Background & Theory

• European Union wants all the buildings to be near zero energy

up to 2020.

• Readily available energy source is sun.

•Generation of electricity with conventional photovoltaic cells has

several disadvantages

i. Cells remains costly

ii. PV cells respond optimally to direct sunlight

iii. Modules are heavy

iv. Requires space for installation



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Background & Theory

• Another solar harvesting technique was proposed called

luminescent solar concentrator.

•Sunlight penetrates the top surface of inexpensive plastic or

glass wave guide.

•Light is absorbed by luminescent molecules.

•Luminescent molecules can be organic florescent dies,

inorganic phosphors or quantum dots.

• Absorbed light is reemitted at longer wavelengths. And a

fraction of light is concentrated along edge of plate.

•Small PV cells attached to edge of the waveguide collect

the emission light and convert it to electricity.



Background & Theory

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Advantage of LSC over Silicon based PV

• LSC has advantage of over silicon based PV panels.

i. Material for making LSC is inexpensive.

ii. Plastic waveguide is lighter than silicon PV Panels.

iii. Sunlight can better penetrate the surface of the waveguide from all

angles.iv. LSC flexible in design and manufacturing.



Background & Theory

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Short comings & Limitations of LSC:

• Surface loss

• Re-absorbtion of emitted molecules by dye molecules.

• photovoltaic cells.

•Waveguide losses



Background & Theory

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1. Surface Loss:

• Dye emitted photons emitted inside the escape cone will be lostthrough the surface.

• Measurement suggests that 40-55% of all absorbed energy is

lost in the way confirmed by simulation.



Background & Theory

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2. Reaborbtion of emitted molecules by die molecules

• Most organic luminosphores used in LSCs have small stroke

shift, leading to relative large ovelaps between absorption

and emission spectrum.

• As a consequence luminosphores emitted photons can be

reabsorbed by another luminosphores molecules duringtransportation through the waveguide.



Background & Theory2


2. Stroke Shift

• Stokes shift: It is the difference

(in wavelength or frequency units) between positions of the

band maxima of the absorption and emission spectra of the

same electronic transition. It is named after Irish

physicist George G. Stokes.





3. Photovoltaic losses:

• Standard silicon based PV cells has a band gap

corresponding to a photon around 1100nm.

• Photons with energy > threshold may be processed. (as

excess energy)

• Excess energy will be wasted and converted in to heat.

• Spectrum of LSC is limited to infra red wavelength.

• LSC cannot emit spectrum like solar spectrum.





4. Wave guide Losses:

• Around 4% of incoming light is reflected from waveguide surface. (neverenters waveguide)

• so this light is considered as loss.

•This phenomenon is due to reflection of light.

•Therefore, non reflective coatings are pasted on PV cells (due to non

reflective coatings)

•But for LSC’s non reflective coatings are not available so more wave guide

losses.



Theory & Background2


Our Approach (TLSC’s)

• TLSC ( Transport Luminescent Solar Concentrator)

•There is a renowned interest to use this technology for

power producing surfaces by:

a) Improving energy harvesting efficiency

b) Improving Electronic device autonomy

c) Reduction of electric cost

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Ahmad Nawaz final.ppt