
Is it time to move away from silicon-based solar? - turing
http://arstechnica.com/science/2014/02/is-it-time-to-move-away-from-silicon-based-solar/
======
kken
PV "breakthroughts" are a dime dozen. Usually things quickly break apart due
to these reasons:

1) The solar cell has to stable for 20 years in the field, not the 5 minutes
it requires to collect the data for your publication.

2) You have to make 200 million cells per year with a yield >98%. Can you
really do that?

3) Manufacturing cost on paper and in reality are two completely different
things. Reducing material consumption is good, but it is not the only cost
driver. Again: YIELD.

The first point is something that can be partially answered with a lot of
additional research. Doable by a university, but often much more frustrating
than the research they'd really want to do.

The only answer to the last two points is to try it on a large scale. And
people did that for many technologies, see Nanosolar, Solyndra and many more.
The problem is that so many failed, that currently nobody is willing to invest
in new PV technologies.

Right now there is only silicon, CIGS thing film and CdTe thin film on the
market. I doubt that a new technology is going to become relevant anytime soon
as all of these technologies still have some room to breathe.

The article mentions, that 15 years passed without a new efficiency record in
Si based solar cells. This is completely meaningless until that number is
approached by mass manufactured cells.

~~~
bdcs
64% of residential solar costs are the so-called soft costs of permitting and
installation. PV's tech problems are smaller than its social/political
problems. [http://cleantechnica.com/2013/12/12/nrel-soft-costs-now-
larg...](http://cleantechnica.com/2013/12/12/nrel-soft-costs-now-largest-
piece-solar-installation-costs/)

~~~
kken
Yes, especially in the US. There is also a huge bureaucracy problem.

Even at the current cost of PV and the current electricity prices, residential
PV generation amortises in areas where a lot of air conditioning is required.
This basically applies to the entire south west of the US.

The problems rather seem to be ignorance and an unwilligness to see a house as
a long term investment.

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outworlder
What about lower efficiency, but much cheaper panels? What is it that drives
price up so much? Production capacity? Market forces?

~~~
msandford
That's exactly the direction some folks have gone.

[http://en.wikipedia.org/wiki/Copper_indium_gallium_selenide_...](http://en.wikipedia.org/wiki/Copper_indium_gallium_selenide_solar_cells)

One of the startups, nanosolar, seems to have failed.

[http://en.wikipedia.org/wiki/Nanosolar](http://en.wikipedia.org/wiki/Nanosolar)

You can actually pick up some nanosolar stuff on ebay right now.

[http://www.ebay.com/itm/like/151190922913?lpid=82](http://www.ebay.com/itm/like/151190922913?lpid=82)

I am not sure if there are any other companies still trying to make a go of
this but last I checked -- a couple of years ago -- there were two or three
others.

~~~
canistr
I was always under the assumption that Gallium Arsenide was the future after
silicon.

What's the difference between GaAs and CIGS?

~~~
msandford
A number of people realized that they could lay down really thin films of CIGS
materials and process the cells reel-to-reel. Imagine loading up a 10 ton roll
of thin stainless steel in the morning and having 200 acres (or some crazy
number) of solar cells by evening. If they had been able to sort the process
technology out it would have been INCREDIBLE.

But of course the devil was in the details. This was a hardware based company
so it's not terribly surprising that their R&D time went out past their
funding. Look at how badly hardware Kickstarts do on average, blowing multiple
"deadlines" because often-times hardware is more difficult than software. Not
that it's impossible, but it's definitely unforgiving.

When it absolutely has to be exactly right the first time it's going to take a
lot longer than you think, even once you account for the fact that its' going
to take a lot longer than you think.

------
higherpurpose
> But that manufacturing innovation hasn't been matched on the basic research
> side; it's been over a decade since the last time anyone set a new
> efficiency record for silicon cells.

> The material in question is gallium arsenide, which can be fashioned into
> solar cells with efficiencies twice those of silicon

What about this breakthrough doubling the typical solar panel efficiency to
44.7%? Isn't it based on silicon solar panels, too?

[http://www.ise.fraunhofer.de/en/press-and-media/press-
releas...](http://www.ise.fraunhofer.de/en/press-and-media/press-
releases/presseinformationen-2013/world-record-solar-cell-
with-44.7-efficiency)

~~~
deeviant
No, anything in that range of efficient is a multi-junction cell. Multi-
junction cells use a range of layered materials, each tuned to a narrow
spectrum in which they can convert more efficiently than silicon, for
instance.

------
acd
The material used in silicon solar cells Galium Arsenide isn't an
environmental friendly material. For us to have large quantity of solar power
the materials used in the solar cells can't be dirty in themselves or the
environmental advantage are lost.

Here are some alternative links

Organic solar cell [http://www.heliatek.com/newscenter/latest_news/neuer-
weltrek...](http://www.heliatek.com/newscenter/latest_news/neuer-weltrekord-
fur-organische-solarzellen-heliatek-behauptet-sich-mit-12-zelleffizienz-als-
technologiefuhrer/?lang=en)

A question in my mind is if plants is the ultimate solar cell, cheap to
produce, naturally converting solar energy into biomass, sugar and potentially
diesel. There are also ecoli based solar conversion.

Boing Green diesel breakthrough [http://www.energypost.eu/exclusive-report-
boeing-reveals-big...](http://www.energypost.eu/exclusive-report-boeing-
reveals-biggest-breakthrough-biofuels-ever/)

Ecoli biogasoline [http://cleantechnica.com/2013/09/30/kaist-researchers-
produc...](http://cleantechnica.com/2013/09/30/kaist-researchers-produce-
gasoline-from-escherichia-coli/)

------
Egregore
As an active user of silicon-based solar in self sustained home I would say
that we need a more efficient and cheap battery technology. By cheap I mean
cost/cycles, current lead acid batteries offer less than 1000 cycles
considering 30% usage, improving number of cycles 10 fold and usage to 100%
would be great.

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ars
Is he trying to violate the laws of thermodynamics?

    
    
      The front has to let sunlight in, but then keep photons from
      escaping. ..... This takes photons from a broad area and
      funnels them into the PV chip. The other end of the U acts
      like a reflective cap, making it very hard for a photon to
      escape from the chip without being reflected back into it.
    

So basically a funnel with a wide part and a narrow part? And since it's
narrow it's less likely for a photon to enter?

That actually doesn't work - the intensity at the narrow end is higher, and
the total number of photons going in each direction is exactly the same.

One way mirrors do not, and can not, exist.

(One thing that does work is having slanted walls and lots of reflections
giving many opportunities for the photon to be absorbed. But if it doesn't it
will inevitably escape again.)

~~~
hrjet
Somebody has already explained it in the comments in the article:

"The light coming in the from sun is pretty directional, and a parabolic setup
will focus it down to a handy point. The photons being emitted by the the chip
are more diffuse and so most will be reflected back down to be re-captured."

------
scythe
Alta Devices has been in the thin-film GaAs space for years. They've attracted
nine-figure investments and posted really spectacular efficiency of ~28% in
GaAs thin films. It's all very exciting, but these discoveries are not
untrodden ground.

[http://en.m.wikipedia.org/wiki/File:PVeff(rev131204)a.jpg](http://en.m.wikipedia.org/wiki/File:PVeff\(rev131204\)a.jpg)

[http://www.greentechmedia.com/articles/read/Sources-Alta-
Dev...](http://www.greentechmedia.com/articles/read/Sources-Alta-Devices-GaAs-
Solar-Startup-Purchased-by-Chinas-Hanergy)

------
InclinedPlane
There's nothing wrong with silicon PV arrays, they're easy to manufacture in
high volumes and low cost, they have reasonable efficiency levels and high
durability. The problem facing greater adoption of solar power continues to be
the storage problem. If people want to improve deployment of solar power then
they should work on that problem first and foremost.

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meepmorp
I'd think the greater natural abundance of silicon, coupled with the lower
toxicity vs an arsenic compound, would make such a move unlikely in
deployments that don't require maximum power output for a given area
(satellites, for example).

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the_cat_kittles
there are nascent technologies for refining silicon into solar grade that are
like 30-50% cheaper than what is currently used, they just need to be brought
up to production scale. So, to answer the title- no

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ck2
gallium arsenide costs a fortune, way more than twice of silicon

