What is the energy cost of making silicon?

[LordChallen]

I'm trying to determine how much energy it takes to melt down sand into silicon, and convert it to solar panels.

any info would be great.

Thanks.

 

[Bystander]

https://en.wikipedia.org/wiki/Silicon

 

[CWatters]

Are you interested in the energy payback time...

http://info.cat.org.uk/questions/pv/what-energy-and-carbon-payback-time-pv-panels-uk/

A more recent study by researchers from the Netherlands and the USA (Fthenakis, Kim and Alsema, 2008), which analyses PV module production processes based on data from 2004-2006. They find that it takes 250kWh of electricity to produce 1m2 of crystalline silicon PV panel.

 

[rootone]

Bulk crystalline Silicon is sold for industrial purposes at about 1 or 2 dollars/euro for a Kg, though prices fluctuate of course.
That's the stuff you need to make solar panels, not melted sand.
Sand is (mostly) Silicon Dioxide, to make the pure Silicon the oxygen needs to be taken away.
Usually this is done using Carbon which robs the Oxygen from the Silicon, and releases it as Carbon Oxides.
I guess the major cost involved in the process would be supplying the heavy duty heating that is needed for the reaction to occur.

 

[LordChallen]

Thank you for the reply. Yes I am trying to find the cost of creating solar panels in terms of carbon and energy. So far it looks like you get about 3 times your investment back out of the solar panels. Of course this depends upon the location of the solar panels. Some countries have better solar exposure. In the early days of solar I heard that there wasn't much benefit besides the off-grid feature of solar panels. I was trying to find out if that was still true.

 

[LordChallen]

Does anyone know the standard rate of repair that the Earth can return carbon dioxide to oxygen?

 

[CWatters]

Thank you for the reply. Yes I am trying to find the cost of creating solar panels in terms of carbon and energy. So far it looks like you get about 3 times your investment back out of the solar panels.

The reference I posted says the energy payback time is around 2.5 to 3.5 years. However the panels might generate for 20 to 25 years. That suggests they produce around 8 times the energy it takes to make them.

 

[rootone]

I think it might be difficult to make solar panels from scratch in a small scale workshop, even if you start with already purified Silicon.
You'll be competing with very large industries (In China especially), who mass produce solar panels and sell them in millions inexpensively.
You might save some cost by hand assembling banks of photovoltaic cells- the active components of a completed panel into your own panel design.
The result may not perform any better than the 'off the shelf' panels though.

 

[CWatters]

Does anyone know the standard rate of repair that the Earth can return carbon dioxide to oxygen?

It appears to be about half the rate we are producing it and reducing according to...

http://www.smh.com.au/environment/c...de-emissions-says-report-20140909-10ejo1.html

Michael Raupach, formerly of the CSIRO and now at the Australian National University, said land and oceans take up about half of all CO2 emissions and help show the pace of global warming.

Despite some year-to-year variability, particularly on land, a pattern is emerging over decades suggesting the sinks "are not keeping pace with rising CO2 concentrations in the atmosphere", Professor Raupach said.

"This is partly a sign that the efficiencies of the all-important land and ocean CO2 sinks are weakening," he said.

Professor Raupach was lead author of a paper published in Biogeosciences in July which showed that during the 1959-2012 period, about 44 per cent of the total anthropogenic CO2 emissions remained in the atmosphere. During the period, the combined land and ocean CO2 sink rate declined by about one-third.

 

[OmCheeto]

Bulk crystalline Silicon is sold for industrial purposes at about 1 or 2 dollars/euro for a Kg, though prices fluctuate of course.
...

That appears to be about an order of magnitude too low. [ref: $20/kg China] [ref: $11.50-$17.50/kg]
But I like CWatters reference better: 250 kwh/m²
Though, it should be noted, that his reference is 9 years old.
From a website I just found: "the degradation rate is less than 0.5% for panels made before 2000, and less than 0.4% for panels made after 2000. That means that a panel manufactured today should produce 92% of its original power after 20 years" [ref]

From some silly calculations I've just done, a modern solar panel won't degrade to 50% until it's 125 years old, by which time it will have produced 24,270 kwh of energy.
Which to me, looks like it will have produced 100 times as much energy as it took to produce it.

Of course, lots of people want to see a return on their investment, in their lifetime. So this is just "crazy" talk, on my part.