Talk:Solar cell/Archive 1

message: I just got my solar array installed, and one of the readouts BP Solar is hyping is how many pounds of greenhouse gases are saved. I'd love to know if that's really true, and to see this factiod reflected in the redesigned page. Also, just wondering, does anyone know how much energy and/or greenhouse gases goes into the manufacture of present-day solar panels?
:A lot. The present day semiconductor/solar silicon manufacture uses carbon to reduce silcon from quartz: SiO2+2C -> Si + 2CO. Each mole of silicon generates 2 moles of carbon oxide. But it doesn't stop here. Then the silicon is reacted with chlorine/HCl to produce silicon tetrachloride SiCl4 or trichlorosilane, SiHCl3, which is be purified by distillation. Distillation consumes humongous amount of heat, obtained by, you guessed it, most likely by fossil fuel combustion these days, though technically nuclear or hydropower energy could be used. Once purified by distillation, then the trichlorosilane, or silicon tetrachloride/hydrogen mix, are passed into a hot zone reaction chamber, to decompose to pure silicon, which is then doped, processed (including melted, lots of energy required here too.) A silicon solar panel will have about 40 years of useful lifetime, or even more, the very first built solar panels are still cranking out electricity, though their efficiency has fallen to something like 80% of what it was 40 years ago, but remember, these were the very first solar panels built, current ones might last even better. During these 40 years, depending on your location (whether you are in low solar dose UK, Canada, or high solar dose California/Mexico/Sahara Desert) you get 6 to 30 times the energy invested in creating your solar panels. So overall, over a few decades you do save energy that would otherwise would have had to be obtained from fossil fuels.  Consider it an investment - lots of fossils could have been burnt, but instead, they were invested into your solar panels, and, usually after less than 5 years, you're out of the red zone, and you and  our environment profiting by not releasing more greenhouse gases. See the Net_energy_gain article. Just make sure no baseballs/hurricanes/accidents break your panels, and they do last those 40 years. :) I'm not being totally sarcastic here, but it's more a serious advice, because what you're doing is a very nice thing. 
:Ultimately, we'll have to get off the fossil fuel/carbon metallurgy bandwagon, and silicon and all other metals will be produced purely by electricity/noncarbon heat sources, such as solar furnaces, nuclear furnaces, and hydrothermal/solar electricity. But these days we're not there yet, and chances are that your panels did generate quite a bit of atmospheric greenhouse gases, simply because nobody has the money not to listen to economics and just take some ethical high road. When natural gas is cheap, because its only cost is that of extraction+delivery+profit, without accounting the screwing ourselves in the long run with these greenhouse gases, who the heck are you, as an individual, to deviate from the norm, and not use the currently cheapest method of carbon based silicon production and energy generation? Sillybilly 04:06, 17 October 2005 (UTC)
thread_title:  Greenhouse gases? 

message: Does anyone have information on specialized solar cells for use in satellites?
I imagine there would be very different types for use in places close to the sun 
with high insolation (like  SOHO at earth L1)
or for deep space missions where low temperature would allow higher efficiency using materials 
sensitive to a broader spectrum reaching further down to the infrared. (see [Image:Solar irradiance spectrum 1992.gif]) 84.160.209.236 09:17, 2 October 2005 (UTC)
thread_title:  Question 

message: Materials and efficiency
...
Efficiency is the ratio of the electric power output to the light power input. Around noon on a clear day, the solar radiation at the equator is about 1000 W/m². So a 10% efficient module of 1 square meter has a power output of about 100 W. Solar cell efficiencies vary from 6% for amorphous silicon-based solar cells to 30% or higher with multiple-junction research lab cells.
The common method to express economic costs of electricity generating systems is to calculate a price per kilowatt-hour (kWh).
- begin section removed -
Part of this calculation which can be counterintuitive is that with no fuel cost and low maintenance cost, the economically relevant efficiency metric is not generally thermodynamic efficiency (e.g. energy in vs. energy out,) but rather capital efficiency — that is, the initial cost per watt of a solar cell is a stronger determinant of economic viability than is its efficiency.  (e.g. a 30% efficient solar cell costing $2 is much less desirable than a 10% efficient cell costing $1 in most applications.)
- end section removed -
I deleted that section because I think the statements that are already there, such as "The common method to express economic costs of electricity generating systems is to calculate a price per kilowatt-hour (kWh)." are succint enough to represent the message from the erased section and the long winded discussion that follows here. 
First of all, the very last statement is nonsense - a 30% efficient solar cell costing $2 is much less desirable than a 10% efficient cell costing $1 in most applications? Rephrased, into a specific example, this means that under identical, say 100 watt solar radiation intensity, the first unit will deliver 30 watts for $2, the second unit 10 watts for $1. The whole purpose of the unit is to generate watts, so the first one will give 15 watts/$, the second 10 watts/$. Which is better? 
Now on to the discussion of financial vs. energy profitability, at least a perspective on it. 
The net energy gain article has a discussion on this topic, though it could be clearer. Basically energy in vs. energy out will translate into dollars in vs. dollars out sometime in the future, though it's true that future is not here yet. This is because energy prices will take on whatever price the market demands, energy is simply a must, no way around it. Prices will simply climb to whatever is necessary if demand is high but supplies are low, until it hits the pricepoint at which new supplies can generate. These days energy is extremely cheap, practically free, therefore the bulk of cost in solar cells is the human sweat and not the energy input. So while we have  coal, natural gas, oil and cheap nuclear, it's financially-cheap energy-wise, but financially-expensive human-sweat-wise to create silicon. This is only sustainable while you have practically free coal, natural gas, etc, whose cost is basically punch a hole in the ground and put the finished product it in a barrel, or on a railcar, but such supplies are finite and are rapidly getting used up. The millions of years used by biomass to accumulate all the fossils underground are treated as an economic externality. When you completely run out of non-renewable energy sources, and you have to rely on energy generated by your solar panel or windmill to make new solar panels and windmills, and then you have to add the worker's labor cost on top of that, the picture becomes much grimmer. So yes, if you, as the microeconomic consumer need to make a decision right now, this moment, all that counts to you is capital cost per delivered watt + expected lifetime, for the solar panel you buy today. It doesn't matter to you if the price of panels goes up or down after you bought your panel and it's installed, it's installed, it's done, you sunk your cost to it, can't change the past, you may be angry that you missed the boat if the price falls, or snicker in glee how lucky you were to buy the panels before their prices rose, but yes, as far as a financial microeconomic decision goes today, all you care today is delivered watts per dollar. That is a short sighted view though, it doesn't solve the big problem, ultimately the real macroeconomic problem has to be solved of having something that's sustainable long term, and then the dollars in vs. dollars out will be closer to energy in vs. energy out, but in the meantime we can use the energy in vs. energy out as a closer approximation to reality trying to decide what works, what's sustainable, until the financial world wakes up to same reality and catches up in pricing. Basically cheap fossil fuels can sustain cheap solar panel prices as long as you have cheap fossil fuels, but when you're out of fossils, what will count is energy in vs. energy out, the energy required to make the panel will have to come from the energy generated by the panel, and not from practically free fossil energy. You can basically buy some time - instead of burning this pile of cheap coal, let's make a cheap solar panel out of it, that will return 10x the energy over 40 years compared to if we just burned it now, so you can have cheap solar panels for a while. You can also have wars in the meantime, to take over more cheap energy supplies, to protect the luxurious way of life, but sooner or later what you took from others will run out too, and what happens then? Will there be an abundant cheap supply of energy where we can live in this current luxury world where energy costs are practically nil? If not, then using the energy in vs. energy out metric is a lot closer to reality than the current financial price of renewable/sustainable supplies that's pegged at the cost of nonrenewable fossils. Of course human labor sweat costs will always matter, and add to the picture, I'm not saying they won't, but 5-10 cent/kWh prices these days may be so far off from the sustainable scenario that we might as well ignore current prices and look at the net energy gain instead, see what inherent price that allows. However, if the answer is yes, and there will be cheap energy, such as if we can successfully develop fusion, then this whole discussion is mute, because we're back to the good life the easy, wasteful ways, and we simply don't give a ..., because we don't have to care. But it's very hard to run reactors that don't evaporate at a couple million degrees that fusion reactions require, even with all that magnetic containment. Cross your fingers for fusion - and cross your toes too extra for ITER not to succumb to intellectual property licensing quabbles and simply go up in smoke, end in a standoff, in a showdown, because it took half a decade to settle on where to do it in the first place, forget about trying to decide who gets what from the chickens that get counted long before they hatch, when the whole point is trying to find a darn way to hatch them at all so that people on this planet can live at all without a massive drop in world population. Without fusion, in the meantime, looking at what we got, what's doable, energy in vs. energy out, rate of energy return is a very important parameter in any kind of long term sustainable financial analysis, unlike the dollars/watt, which only deals with the current transient situation that will massively fluctuate anytime the market goes haywire -  demand surges because everyone wants to buy before prices go even higher so prices go even higher because everyone wants to buy til they reach so ridiculously sky high that the market finally wakes up, and everyone stops buying because they are waiting for prices to fall further before they buy so prices fall even further because nobody buys, to a ridiculously low point, where the whole cycle repeats. To tame all this, the long term sustainable pricepoint determined by the energy in vs. energy out besides the human labor factor is what a lot of sensible people will go by, and ignore the occasional price fluctuations, and if the price is above their sustainable energy in vs. energy out price estimate, they won't buy, so prices will not reach sky high. See the entertaining tulip mania for further details on what current price that's not in sync. with some long term sustainable estimate, how the dollars per watt not in sync with energy in vs. energy out, what all that can lead to.  Sillybilly 19:20, 7 January 2006 (UTC)
thread_title:  Explanation why I removed a section  

message: Hello I think the theory section really needs some good quality sources. Just a request.
Neozero497 04:53, 9 November 2007 (UTC)
thread_title:  Source Request

message: Article says: "3. An array of solar panels converts solar energy into a usable amount of direct current electricity". It's explaining that a solar panel converts solar energy into electricity by saying that step 3 is converting solar energy into electricity! Someone with knowledge on this subject should write a more precise explanation. -- ironcito 16:23, 16 February 2006 (UTC)
thread_title:  Simple explanation