Newsgroup: it.discussioni.energie-alternative
Titolo: solare:chi si occupa di concentratori in italia?

qualcuno è a conoscenza di ditte, enti di ricerca, etc... che stanno
lavorando (o commercializzano) prodotti volti alla concentrazione
della luce del sole assolciata all'uso di celle solari?
cioè l'utilizzo di uno o più specchi che concentrino la luce del sole
in un punto in cui si va a piazzare una cella al silicio per aumentare
l'efficienza del dispositivo in termini di spazio occupato/potenza
sviluppata - sono interessato solo a questo, dei molteplici aspetti
dell'uso del concentratore
io conosco solo l'università di ferrara e il progetto di rubbi
a (anche se non ho ben capito se è rivolto al fotoelettrico o
altro...). 
grazie dell'aiuto! 
********************
Visita il mio sito
www.alchemystudio.it
 
************

 
L'Enea ha due progetti sulla concentrazione:
Uno è sul solare termodinamico(niente celle solari):qui trovi tutto il
materiale  
http://www.enea.it/com/solar/index.html
L'altro e sul fotovoltaico a concentrazione,trovi qualcosa qui
http://www.enea.it/com/ene/progetti/fotoconc.html
 e qui
http://www.portici.enea.it/Attivita/SIAM/Index.htm
Purtroppo non conosco aziende italiane che facciano sperimentazione in
questo settore,solo ditte straniere
ciao

questo settore,solo ditte straniere
se sei a conoscenza di qualche link di ditte straniere mi puň
interessare! 
grazie di nuovo
matteo


 matteo
http://www.energyinnovations.com/concentrator.html

 
Ti scrivo un pň di link:
http://www.energoclub.it/a%20solarebis.htm#FVconcentrator
 
Questo č un sito italiano sulle energie rinnovabili,ci sono molte
informazioni e link
http://homepage.mac.com/nekins/syracuse/
Sito su un progetto (giapponese) di fv a concentrazione,il modulo
dovrebbe avere un rendimento del 27%
http://solar.anu.edu.au/pages/chaps.html
Un interessante progetto australiano su un sistema di cogenerazione,fv
a concentrazione con uno scambitore di calore per avere anche acqua
calda
http://www.solar-trackers.com/
Un concentratore molto semplice
http://www.solar20.com/SE/EN/1000-EN_about.php
Questo sistema č molto diverso da tutti gli altri,debole
concentrazione,20 volte
http://www.sunpowercorp.com/html/Products/SPG/conc.html
č un'azienda che vende celle fotovoltaiche (anche con scambiatore di
calore) per sistemi a concentrazione,sia per quelli che usano lenti di
fresnel che per quelli che usano sistemi a parabola
Forse me ne sono dimenticato qualcuno,spero di no
Buona lettura
Ciao

In rete c'era anche una bellissima tesi di laurea australiana sui
concentratori statici (che non richiedono l'inseguitore).  Questo
cambierebbe enormemente le cose, per quanto riguarda i costi per watt
installato.
Peccato che non e' piu' in linea... era all'indirizzo
http://www.pv.unsw.edu.au/thesis/bowden/ch04/4_2.htm
 che mi ero
bookmarkato.
C'e' ancora qualcosa nella cache di Google. Posto qui le conclusioni
della tesi, se non altro per salvarne una copia.
Chissa' perche' le tecnologie e i sistemi per produrre pacchi di
energia a basso costo spariscono sempre dalla circolazione..... BOH!
8. Conclusion
This thesis demonstrates innovative static concentrator design
concepts based on three-dimensional light steering techniques. Static
concentrators offer a compromise between high concentration systems
that require tracking, and one-sun flat-plate modules. By combining
the cost advantages of concentration with the simplicity of
non-tracking modules, static concentrators are capable of achieving
significant cost reductions compared to conventional flat-plate module
designs. In order to successfully implement static concentrators they
must be thin enough to be used in place of conventional flat-plate
modules. Moreover, the level of concentration achieved by a static
concentrator design must be sufficiently high to compensate for the
slight increase in material and fabrication cost. The cost benefits of
high efficiency photovoltaic modules have demonstrated the need for
high optical collection in static concentrator designs.
The new concentrator designs developed in this thesis extend the use
of static concentrators to allow their incorporation into building
structures, such as roof tiles. Previous static concentrator designs
have either been too bulky to fit within the confines of a roof tile,
or have used impracticably small solar cells. In addition, a new use
for static concentrators has resulted from this thesis, that of using
static concentration to improve the light collection of circular solar
cells. The concentration of light onto circular solar cells allows the
use of cheaper starting wafers, without the loss in module efficiency
normally associated with the low packing factor of circular cells.
The angular distribution of a light source determines the maximum
concentration that can be obtained. Very high levels of concentration
can be achieved from point sources, while much smaller levels of
concentration can be achieved from broad diffuse sources. To obtain
the highest levels of concentration from sunlight, tracking systems
must be used to follow the path of the sun across the sky. However,
high levels of concentration are only achieved at the expense of
collecting the diffuse light. Static concentrators offer the
advantages of concentration, but are much more similar to flat-plate
one sun modules in their dimensions and ability to capture diffuse
light. By using the Typical Mean Year solar radiation data, the
maximum module efficiency as a function of the module collection
efficiency was calculated for the Sydney region. The data for Sydney
was also used to compare the performance of the proposed static
concentrator designs to that achieved by an ideal flat-plate module.
This showed that even in a coastal location such as Sydney, where
there is a reasonable degree of cloud cover, that it is possible to
achieve concentration ratios of almost 5:1, while still directing
almost all the light entering the module to the solar cells. This is
in contrast to tracking concentrator designs, which, although reaching
higher levels of concentration, have a much poorer response to
locations with a high degree of diffuse light.
Through the use of a computer ray tracing program, especially written
for this thesis, new three-dimensional designs were developed. The new
designs all have a high optical efficiency, to maintain the module
power conversion efficiency but cover a range of irradiance gains. The
tilted groove structure achieved performance figures close to the
ideal, with an irradiance gain of 4.7 while directing 95% of the light
that enters the module to the solar cells. By modifying the tilted
groove structure, a grooved linear trough concentrator was developed
that fitted into the dimensions of a standard roof tile and has a
number of manufacturing options. The grooved trough concentrator
achieved an irradiance gain of 3.5, with a module optical efficiency
of 0.85, when realistic assumptions were taken into account for the
material parameters. The diamond concentrator allows the concentration
of light onto very large solar cells with a minimal module depth and
manufacturing options very similar to current modules. The diamond
concentrator achieved an irradiance gain of 1.85, with a module
optical efficiency of 0.91 and a module thickness of only 2.6 cm with
a 100 cm² solar cell. Static concentrators were also developed for
circular solar cells and achieved an irradiance gain of 1.34 with an
optical efficiency of 0.94. The module was only 1.2 cm thick with
solar cells 10 cm in diameter. Without concentration, the low packing
factor of the round solar cells would normally reduce optical
efficiency to 0.75.
The design and analysis take into account practical considerations,
such as the effect of absorption, non-ideal reflection and temperature
increases. Even with such parasitic losses the concentrator designs
can be used to reduce the apparent cost of photovoltaic cells, while
maintaining a high efficiency module. The effect of changes in the
angular distribution of sunlight with location on the module
performance was noted to be small, as was the effect of misalignment
in the tilt angle, with the maximum variation from the performance in
Sydney being 5% in both cases.
High efficiency, low cost bifacial cells are necessary to utilise the
full benefits of static concentrators. The specifications for a high
efficiency solar cell have been put forward and the front grid
optimised to reflect the increased importance of cell series
resistance under concentration. By re-optimising the front grid
pattern, cell series resistance losses will only be marginally greater
under concentration than at one-sun conditions. The processing
parameters necessary for a solar cell under concentration were
developed and suggest that the cell efficiency under concentration
will be higher than that at one-sun. A new technique for
simultaneously lowering the cell series resistance and shading loss
has been suggested. This uses angular grooves to form the buried
contacts in the solar cell, thus producing potentially zero percent
shading loss.
The temperature increase of the cells in the module is of particular
importance as the concentration ratios approach 4. However, by using
optical materials with a high thermal conductivity, the slight loss in
efficiency caused by increased temperature will be compensated by the
increase in efficiency due to the higher Voc under concentration.
A number of prototypes were fabricated which verified the accuracy of
the ray tracing programs. One of the prototypes was measured to have a
concentration ratio of 2.5 and an optical efficiency of 0.75 despite
using a very crude encapsulation technique.
The practical material considerations were also taken into account and
techniques for module manufacture and preliminary costings were
developed. This shows that the static concentrator roof tile is
capable of producing modules with lower cost and higher efficiency
than standard flat-plate modules.
© 1996 Stuart Bowden