1

Industrial energy costs are $1 per million BTU (MMBTU) or 300kWh, or $3*10^-6 per watt hour (Wh).

http://www.eia.gov/consumption/manufacturing/

Solar has 1 kg of 9n silicon per 100W, at $20/kg. Since raw material prices are mainly energy costs, this is:

($20/kg)/($3e-6/Wh) = 6MWh/kg

Kg per watt solar is:

1kg/100W = 0.01kg/W

That means energy use to build a watt of capacity is:

0.01kg/W * 6MWh/kg = 0.06 mwh = 60kWh

Let's say a 1 watt cell operates for 20 years:

8760*1W*20=180 kWh

At 20% capacity this is:

0.2 * 180kWh = 36kWh

Is this correct?

This is a specific new question and not a dupe of the above.

D J Sims
  • 1
  • 1
  • 13
  • 1
    "Raw material costs are mainly energy costs" is probably an excessive assumption - do you have a citation for that (specifically for silicon)? Where do your other assumptions come from (e.g. 20% capacity, industrial energy costs)? – Chris H May 25 '16 at 09:45
  • The other assumptions are based on what I've seen on this site. Feel free to refute them. Raw material costs reflecting energy costs is a widely used assumption eg http://www.wsj.com/articles/copper-prices-slide-on-oil-dip-1461581413 – D J Sims May 25 '16 at 10:12
  • I would welcome other sources if they disprove my assumptions – D J Sims May 25 '16 at 10:14
  • 3
    Your figure of 8760 seems to be made up of 24hrs times 365 days. The sun doesn't shine 24hrs/day so I think you want something like 10 times 365. The effective number of hours will vary depending on the location, the weather, and whether the panel tracks the sun. Or was the 20% capacity supposed to cover that difference? – Highly Irregular May 25 '16 at 10:48
  • @HighlyIrregular, that part of the calculation is correct - a capacity factor of 0.20 is reasonable in many parts of the world, and does account for day vs night as well as cloudy vs sunny. – LShaver May 25 '16 at 22:04
  • I see two issues with your numbers. First, 20 is way too low - current estimates are 33 years (source). Second, what are your sources for $20/kg of Si and 100W/kg? – LShaver May 25 '16 at 22:29
  • The 33 years is the total lifespan without considering degradation and is thus not a valid comparison – D J Sims May 25 '16 at 22:59
  • @NeilTyson, says who? Any solar PV system begins to degrade from day one. 33 is the "lifespan," the length of time the system lasts until 20% degradation: NREL, again. – LShaver May 26 '16 at 00:15
  • And, if you're just looking at the energy balance, why does degradation matter? Once it's installed there are no more ongoing costs, so even at 99% degradation the energy out still counts against what you put in. – LShaver May 26 '16 at 00:21
  • I cant find where your source supports that claim. If you can't answer the question please do not respond – D J Sims May 26 '16 at 01:06
  • Your second comment doesn't make any sense – D J Sims May 26 '16 at 02:35
  • 4
    better duplicate (closed as dupe of same target, but has PV specific answer http://sustainability.stackexchange.com/questions/2968/is-the-energy-used-to-manufacture-and-install-solar-panels-in-proper-balance-wit – Kate Gregory May 26 '16 at 15:22
  • Energy break-even point for new panels occurred about 2 years ago AFAIR. - using assumptions of whatever august professional body it was that did the calculations. BUT energy costs at source (mainly China) are lower than at point of use (mostly not China) so on a cost basis we are well past break even point. This is effectively exporting Chinese low cost energy. This is as valid as buying cheap Chinese goods with low labour costs is effectively exporting Chinese low cost labour.. – Russell McMahon May 29 '16 at 08:15
  • Can you show your work and how you arrived at that conclusion? – D J Sims Jun 23 '16 at 16:07
  • As it stands you're just asserting baseless claims. – D J Sims Jun 23 '16 at 16:11

1 Answers1

4

Yes, PV is viable.

That's why somewhere around a billion solar panels have been connected to the grid - about 200 GW of capacity, with another 50 GW or so coming online in 2016.

I'm afraid that the costs you have are quite wrong.

Remember, PV generates electricity - that's a higher-quality (high exergy) energy than heat from gas. To get electricity from gas, you get about half the energy out that you put in, and you'll need to buy and manage a power plant.

And most of gas's costs are hidden - there's the externality of pollution.

Total electricity costs from fossil fuels are around us$100-300 / MWh, depending on where you put the marginal social cost of carbon - (somewhere between $100-200 / tCO2e)

Whereas total electricity costs from PV are around us$30-120 / MWh and trending downwards.

410 gone
  • 14,714
  • 6
  • 41
  • 95
  • 2
    While I'm personally pro solar, the argument that it's viable because lots of it has been installed doesn't really hold water, since government subsidies are in many cases the largest motivator for installing solar. – LShaver May 25 '16 at 22:01
  • I am asking about energy costs not monetary costs. Monetary costs are only used in the absence of data for silicon manufacturing energy use – D J Sims May 25 '16 at 23:01
  • @NeilTyson Ah, ok, in that case it's a straight duplicate of an existing question. Thanks for clarifying. – 410 gone May 26 '16 at 05:26
  • No it is not. Please do not respond if you are unable to answer. – D J Sims May 26 '16 at 06:14
  • 2
    @NeilTyson yes, it really does - the answer there completely answers your question here. Your question is whether there's more energy out than in. The other question completely answers that. Your calculations are based on incorrect assumptions, and comments have already pointed that out. If you want to have an open discussion about the numbers, please do so in [chat], not in comments. – 410 gone May 26 '16 at 08:07
  • The answers they give have vague methodology and have no primary source – D J Sims May 26 '16 at 08:08
  • 1
    @NeilTyson if you'd like to see better answers there, then please do consider putting a bounty on that question. – 410 gone May 26 '16 at 12:52
  • @NeilTyson, for one of your data you cite EIA which is not a primary source. You cite no sources for any of your other data. – LShaver May 26 '16 at 18:11
  • As I said I welcome any sources that refute my claims – D J Sims May 26 '16 at 20:38
  • 2
    @LShaver The argument wasn't that solar is viable because there are lots of panels installed. Rather that lots of panels are installed because it's viable. (Implications are reversed.) – Earthliŋ May 28 '16 at 05:51