What is the energy cost of making silicon?

1. Jan 3, 2017

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.

2. Jan 3, 2017

3. Jan 8, 2017

CWatters

Last edited: Jan 9, 2017
4. Jan 8, 2017

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.

5. Jan 9, 2017

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.

6. Jan 9, 2017

LordChallen

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

7. Jan 9, 2017

CWatters

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.

8. Jan 9, 2017

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.

9. Jan 10, 2017

CWatters

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

10. Jan 10, 2017

OmCheeto

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 wont 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.