L’INNOVAZIONE TECNOLOGICA NELLA PRODUZIONE NAZIONALEDI SISTEMI E COMPONENTI LOW- E HIGH-CPV.

: an innovative CPV solution

in cooperation with

®

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Motivations [1]

Why «Concentrated PV»?

1. Traditional photo-voltaics based on silicon solar cells needs large sensitive areas due to its rather low (~14%) efficiency

2. Moreover silicon solar cells have (– 0,2÷0,4 %/K) large dependence on temperature: a problem in very hot climates

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Motivations [2]

1. The use of high efficiency (~40%) triple junction (3J) solar cells allows for more compact modules

2. 3J solar cells have lower (– 0,04 %/K) temperature dependence: a great advantage in hot climates

3. TwinFocus® original design allows industrialization through reliable and mature technologies already successfully used in automotive industry (largely using recycled and recyclable plastic, aluminum, and glass)

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TwinFocus® uses well known triple junction Solar Cells

A series of three junctions, each one sensitive to a different spectral range

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Funding and manpower of the R&D program

• Padova University 81,000€ 2007-8

• WP3 in the frame of Polo Fotovoltaico (joint program of Regional Government and Padova University with global value 3M€),

253,000€ 2011-2013

• Centro Fermi~80,000€ 2008-2012

• Regional Fellowships plus 4 years of junior grant from Centro Fermi

• Strong and effective industrial cooperation

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TwinFocus® uses non-imaging optics and off-axis reflectors

Secondary optics

solar cell0.25

.50 cm.50 cm

.25

250X

500X

Very uniform irradiation profile on cellextremely critical for thermal budget

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TwinFocus® implementation- Area of mirrors: 22x18x14 cm3

- Area cell 0.3 cm2 (x2)

- Geometrical concentration: ~580 X

Refractive or reflective secondary optics:-Savosil: low temperature molded quartz-polished metal cones

Patent pending (PCT/IB2011/054484)

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TwinFocus® uses passive heat sink

Thermal budget at 600 Suns: 13W

Tcell=85 oC @ Tair =35 oC

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• AtemEnergia srl is a Spin-Off company* of the University of Padua, Italy. It was authorized in July, 2010.

• The experience of the founders was matured in different fields of Experimental Physics in Italy (LNL,LNGS, Centro Fermi) and abroad (CERN, FermiLab) and in very advanced automotive industry (Unitek).

• Mission of AtemEnergia is the development of advanced technologies for renewable energies, solar CPV in particular, and other high tech products.

* University holds 5% stock ownership

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Thanks to mature industrial technologies provided by:

Optical polishing

Thermoplastic molding

Mold design

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has been realized

0 1 2 3 4 5 6 70

2

4

6

8Power 7,96 WFF = 82 %eff. 25,2 %

DNI 880 W/m2

Power (W) Current (A)

Voltage (V)

Pow

er (W

)

0,0

0,4

0,8

1,2

1,6

Curre

nt (A

)

®

Field measurement ina working tracker for test

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TwinFocus® field measurements

Typical efficiency is 24%.

Data collected withSun exposure.

Haze effect id visible in the second part of the day.

Una cella fotovoltaica in cui viene iniettata corrente elettrica( Jinj)emette luce (elettroluminescenza, EL) analogamente ad un LED

Lo spettro di elettroluminescenzadi una cella a tripla giunzione (3J) mostratre picchi relativi alle tre band-gap dellegiunzioni

L’intensità dei picchi di EL delle tre sub-giunzioniin funzione di Jinj cresce esponenzialmente

La conversione di energia radiante in energia elettrica e viceversa è descritta da un’unica relazione, detta di “reciprocità” (RR);la grandezza che quantifica il fenomeno è la Quantum Efficiency

Jinj

CARATTERIZZAZIONE DI CELLE SOLARI MEDIANTE LUCE DI ELETTROLUMINESCENZA

La luce di EL emessa da una cella 3J di efficienza notapuò essere raccolta da un cella da testare ed esserericonvertita in corrente/tensione.

Jinj

Jpv

L’efficienza di riconversione viene determinata dallamisura della tensione di circuito aperto (Voc) della cella pv.

LED

PV

Voc della cella pv in funzione di Jinj

della cella LED presenta un andamento legato al funzionamentocombinato delle tre sub-giunzioni

Questo tipo di studio costituisce unaaffidabile e maneggevole procedura per testarele performances delle tre sub-giunzioni di una cella 3J.

Jinj

LED

PV

Voc

Voc vs Jel

-

0.50

1.00

1.50

2.00

2.50

- 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00

Jinj [mA]V

oc

[V]

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40 TwinFocus® reflectors will be assembled in a rigid frame 1m x 2m x 0,14m. Measured power 320W. Weight: 95kg all included.

Prototype frame during assembly on tracker

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Quasi-industrial production line

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Six pre-industrial prototypes, high precision low profile trackers under construction : ~30m2, 5,2kWp

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A demonstrator of this system is now acquiring data. The project of this first version of TwinFocus® has been completed and a lot of effort is now spent to develop an even cheaper and more efficient CPV system.

Next step will be an XR (reflective and refractive) optics with a concentrating factor near to 1000X, a more homogeneous illumination profile of the solar cell, and a lighter and more efficient heat sink .