L’INNOVAZIONE TECNOLOGICA NELLA PRODUZIONE NAZIONALE
DI SISTEMI E COMPONENTI LOW- E HIGH-CPV.
®:
an innovative CPV solution
in cooperation with
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
2
Motivations [2]
1. The use of high efficiency (~40%) triple junction (3J) solar cells
allows for more compact modules
1. 3J solar cells have lower (– 0,04 %/K) temperature
dependence: a great advantage in hot climates
1.
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)
3
TwinFocus® uses well known triple junction Solar Cells
A series of three junctions, each one sensitive to a
different spectral range
4
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
5
TwinFocus® uses non-imaging optics and off-axis reflectors
0
.25
.25
solar cell
.50 cm
Secondary
optics
.50 cm
500X
250X
Very uniform irradiation profile on cell
extremely critical for thermal budget
6
TwinFocus® implementation
Patent pending (PCT/IB2011/054484)
- 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
7
TwinFocus® uses passive heat sink
Tcell=85 oC @ Tair =35 oC
Thermal budget at 600 Suns: 13W
8
• 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
9
Thanks to mature industrial technologies provided by:
Mold design
Optical polishing
Thermoplastic molding
10
has been realized
Field measurement in
a working tracker for test
DNI 880 W/m2
8
1,6
Power 7,96 W
FF = 82 %
6
eff. 25,2 %
1,2
4
0,8
2
0,4
0
0
1
2
3
4
5
Voltage (V)
6
7
Current (A)
Power (W)
®
0,0
Power (W)
Current (A)
11
TwinFocus® field measurements
Typical efficiency is
24%.
Data collected with
Sun exposure.
Haze effect id visible
in the second part of
the day.
12
CARATTERIZZAZIONE DI CELLE SOLARI MEDIANTE
LUCE DI ELETTROLUMINESCENZA
Una cella fotovoltaica in cui viene iniettata corrente elettrica( Jinj)
emette luce (elettroluminescenza, EL) analogamente ad un LED
Jinj
Lo spettro di elettroluminescenza
di una cella a tripla giunzione (3J) mostra
tre picchi relativi alle tre band-gap delle
giunzioni
L’intensità dei picchi di EL delle tre sub-giunzioni
in 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
Jpv
La luce di EL emessa da una cella 3J di efficienza nota
può essere raccolta da un cella da testare ed essere
riconvertita in corrente/tensione.
PV
LED
Jinj
Voc
PV
LED
L’efficienza di riconversione viene determinata dalla
misura della tensione di circuito aperto (Voc) della cella pv.
Jinj
Voc vs Jel
2.50
2.00
Voc [V]
Voc della cella pv in funzione di Jinj
della cella LED presenta un
andamento legato al funzionamento
combinato delle tre sub-giunzioni
1.50
1.00
0.50
-
10.00
20.00
30.00
40.00
50.00
Jinj [mA]
Questo tipo di studio costituisce una
affidabile e maneggevole procedura per testare
le performances delle tre sub-giunzioni di una cella 3J.
60.00
70.00
80.00
90.00
100.00
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
15
Quasi-industrial production line
16
Six pre-industrial prototypes, high precision low profile
trackers under construction : ~30m2, 5,2kWp
17
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 .
18