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BITS PilaniPilani | Dubai | Goa | Hyderabad

CONCENTRATING SOLAR PHOTO-VOLTAIC

M. PadminiDr. Manoj S. Soni (Assistant Professor)Department of Mechanical EngineeringBITS – Pilani, Rajasthan

IV th International Conference on Advances in Energy Research10-12 December, 2013, IIT Bombay.

BITS Pilani, Deemed to be University under Section 3 of UGC Act, 1956

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Solar Photo-voltaic

• Photo-voltaic uses solar cells made up of semiconductors to generate

dc current from sunlight.

• Currently, polycrystalline and mono crystalline solar panels

generally available have efficiencies range from 12% to 18%.

• As solar panels are costly, such small efficiencies limit its use to only

specific applications.

• So to make this technique economical, there is a need to increase the

efficiency and to bring down the cost.

• One technique is to use concentrating photo-voltaic to increase the

intensity of light falling on solar cell

IV th International Conference on Advances in Energy Research


Concentrating photovoltaic

• Research into CPV started in the 1970s

• A large area of sunlight is focused onto the solar cell using optical

devices.

• Requires less photovoltaic material.

• As photovoltaic cell area required is less, high-efficient but

expensive multi-junction cells can be used economically.

• Optics is less expensive than cells



CPV Techniques

• Parabolic Concentrator

• Hyperboloid Concentrator

• Fresnel Lens Concentrator

• Compound Parabolic Concentrator (CPC)

• Dielectric Totally Internally Reflecting Concentrator (DTIRC)

• Quantum Dot Concentrator (QDC)



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Parabolic concentrator



Parabolic Concentrator

• Transforms an incoming plane wave traveling along the axis into a spherical

wave converging toward the focus.

• All incoming parallel light is reflected by the collector through a focal point

onto a second mirror.

• This second mirror is also a parabolic mirror with the same focal point.

• It reflects the light beams to the middle of the first parabolic mirror where it

hits the solar cell.

• The advantage of this configuration is that it does not require any optical

lenses.

• But losses will occur in both mirrors.



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Hyperboloid concentrator



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Hyperboloid concentrator

• Consists of two hyperbolic sections, AB and A’B’.

• The diameters of the entrance and exit aperture are labeled as d1 and d2

respectively.

• If the inside wall of the hyperbolic profile is considered as a mirror, the sun

rays entering the concentrator from AA’ will be reflected and focused to the

exit aperture BB’.

• The advantage of this concentrator is that it is very compact, since only

truncated version of the concentrator needs to be used.



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Fresnel Lens



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Fresnel Lens

• Comprises several sections with different angles, thus reducing weight and

thickness in comparison to a standard lens.

• Mostly made of poly(methyl methacrylate) (PMMA)

• Possible to achieve short focal length and large aperture while keeping the

lens light.

• They can be constructed

– In a shape of a circle to provide a point focus with concentration ratios of

around 500

– In cylindrical shape to provide line focus with lower concentration ratios.



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Compound Parabolic Concentrator



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Compound Parabolic Concentrator

• When the rim of a parabola is tilted toward the sun, the rays are no

longer concentrated to a point, but are all reflected somewhere below

the focus.

• The rays on the right-hand side reflect below the focus and the rays

on the left-hand side reflect above the focus.

• So the half parabola tilted away from the sun is discarded, and

replaced with a similarly shaped parabola with its rim pointed toward

the sun

• A receiver is now placed in the region below the focus



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Dielectric Totally Internally Reflecting Concentrator



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Dielectric Totally Internally Reflecting Concentrator

• DTIRC take advantage of the optical properties of a dielectric, namely its

refractive index, which leads to total internal reflection.

• Consists of three parts: a curved front surface, a totally internally reflecting

side profile and an exit aperture.

• The front aperture can be a hemisphere, but different designs such as

parabola and eclipse have been developed recently.

• The advantage of DTIRC over CPC is that it offers higher geometrical

concentration gain and smaller sizes.

• The disadvantage of a DTIRC is that it cannot efficiently transfer all of the

solar energy that it collects into a lower index media.



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Quantum Dot Concentrator



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Quantum Dot Concentrator

• QDC is a planar device consisting of three parts;

– a transparent sheet of glass or plastic made doped with quantum dots

(QDs),

– reflective mirrors mounted on the three edges

– An exit where a PV cell is attached

• When the sun radiation hits the surface of a QDC, a part of the radiation

will be refracted by the fluorescent material and absorbed by the QDs.

• Photons are then reemitted in all direction and are guided to the PV cell via

total internal reflection.

• Works with diffuse light so does not need tracking.



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• Rod Lens


Recent Break-through


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Rod Lens

• Solar cell might be damaged if a small portion of the cell, on which unevenly

distributed light concentrates, gets hot.

• In a system with a Rod lens, it is possible to cause light to be shed on the entire

area of the solar cell.

• Can be used in both transmission type and reflection type concentrators

• In both types, light passes through rod lens before striking the solar cell to

enable uniform distribution of the rays.



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Solar Sphere



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• Solar Sphere

– Barcelona-based German-born architect André Broessel has con-

structed an enormous glass ball lens filled with water capable of

harnessing power from the sun and even the moon and converting

it into usable energy.

– He proposes that the spheres could be embedded in buildings al-

lowing for natural light to stream through while capturing valuable

energy

– The orb has been designed to be easily integrated into a building’s

design, replacing giant glass windows with a large sphere.



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APPLICATIONS TO INDIAN MARKET

• Moser Baer Clean Energy Limited (MBCEL) commissioned Asia's largest

solar farm in Banaskantha district of Gujarat.

• The 30 MW solar farm has been set up using 2,36,000 Thin Film modules

with an approximate investment of Rs 465 crore ( $95 million).

• Each module has surface area of 2600 x 2200 mm2 that is 5.72 m2.

• Total area of photovoltaic used was 17.3 Km2.

• We shall compare a new 30 MW plant with and without concentration

according to the current tariff rates.

• If we use 150W thin film polycrystalline cells, we can assert the cost to be

around Rs10000 per piece of area 1335 x 650 mm2.

• Fresnel lens costs around Rs100 per piece of area 350 x 350 mm2.



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Analysis Results

Without concentration With concentration

Expected output 30MW 30MW

PV sheet used150W Thin film Polycrystalline

cells150W Thin film Polycrystalline

cells

Area of photo-voltaic used 1,73,55,000 m2 3,54,183.67 m2

Total cost of PV cells used Rs 200 crore Rs14.16 crore

Area of Fresnel lens used - 1,73,55,000 m2

Cost of Fresnel lens - Rs 4.081 crore

Total cost of installation Rs 200 crore Rs 18.24 crore



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• The area of PV used will be reduced from 17.35Km2 to just 0.35Km2 which

would now cost Rs 14.16 crore.

• Adding to it the cost of Fresnel lens which would be Rs 4.081 crore, the

total material cost adds up to be around Rs 18.24 crore.

• CPV installation requires tracking and cooling mechanisms which would

account for an increase in cost of installation.

• But the amount would still be less than the initial cost and would also result

in a higher efficiency.

• So by installing Fresnel lens, we reduce the installation cost from an

exorbitant amount of Rs 200 crores to just above Rs 18 crores.

Conclusion


BITS PilaniPilani | Dubai | Goa | Hyderabad

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