Exponential solar growth

[swbluto]

I read in a solar energy book that a typical solar cell could recoup the amount of energy required to produce the cell in about 1 to 2 years. This probably just the "noticeable" energy involved and not necessarily the "human labor", but let's say by some future mechanism, we may be able to automate the labor part and so the time required to recoup the initial energy expenditure was lengthened (Possibly 3-5 years). Even so, if all the energy collected from a solar cell could be directed towards the production of future solar cells, would this imply potential exponential growth? The limiting resource then wouldn't be energy, but whatever materials required. However, silicon is simply made from sand and there's tons of that around, right?

Just to give a practical example of this mechanism, let's say the solar cell "reproduces" another solar cell in 5 years. The typical "lifespan" of a solar cell is 25 years, though it could go well beyond that point - it just seems 25 years was the industry standard for the guarantee of solar cells. But just for the sake of the example, let's say it's 25 years.

We start with 1 solar cell. 5 years later, another solar cell is produced from the energy collected from the first. At year 5, we have two solar cells. At year 10, those two solar cells create another two solar cells. We have 4 cells by year 10. By year 15, we have 8 cells and by year 20 we have 16 cells. By year 25, we would have 31 cells, because the first cell's "life" expired. As you can see, the rate of production increases exponentially as time goes on. (the derivative of an exponent is an exponent)

It just seems to be an interesting thought. Of course, there are material limitations that I'm glossing over, some of which may be important as the demand for those materials grow to a critical size (More demand = higher price), but what if the material limitations are fairly scant?

 

[dak664]

That would be fine except for consumer preference for the lowest price. Cells made using the cheapest fuel with the least external costs (i.e. pollution) will be the ones people will buy, and barring political intervention that will only accelerate fossil fuel depletion until the costs of renewable energy vs. nonrenewable energy reverses.

 

[dogman dan]

Cool to realize that could be possible. I do agree that solar cells will continue to be made using fossil fuel energy in the forseeable future. People will go for the cheapest price per watt. But we might be able to make a few solar cells before the fossil fuel completely runs out.

I think it's a damn shame though, that a trophy house on the golf course can be built in the US, and still have poorly insulated walls, glass facing the wrong way, and not one solar cell on the 4000 square foot roof. We're talking guys who are buying houses over a half mil, that are not even well insulated. By the time a guy spends that kind of money, he should be forced to build leed platinum.

 

[swbluto]

Yes, definitely, the energy used to create solar cells in the near future will be derived from whatever cheapest energy source (And, that should remain true for a long time) and if that happens to be oil, then that's great. That'll represent a sort of "initial" energy investment and then it seems plausible that it seems possible that it'll "reproduce" in reinvesting its own energy extraction into its own creation. This is very similar to the way that money used as an investment can be used to generate more money, and then the stockpile of money grows exponentially in a way that's popularly termed as "compounding" with "compound interest". (Actually, given that it would be possible to invest money in an initial solar panel, and then "grow solar cells" by going the energy reinvestment route, and then the resulting offspring was sold for profit, it would be like a possible form of compounding of money. The success of that, though, depends heavily on future solar technology and their may be great leaps and bounds that makes older solar technology vastly inferior and thus very cheap, and the investment would erode. It would also erode in the presence of other investors exploiting the same principle, and then the market supply would be flooded. But it does seem pretty romantic to make an initial investment in your own energy supply, and then the rest of your energy future is set.)

I'm actually beginning to think that the principle behind the grey goo scenario could actually be exploited by solar means. Imagine whatever "life", whether or intelligent or not, that uses the sun as the energy it needs to reproduce - you can imagine that it'd be possible they could become the dominant species being able to take advantage of solar energy conversion in a way that current animals cannot, in a way that doesn't require as much dependency on other lifeforms as current animals do, including humans.

Actually, let's say energy flows where-ever it does the most benefit. So, the solar cells may not directly reinvest their own creation but actually go to other projects, like construction or just the energy needed to run any business. Well, considering this is kind of what energy companies do, I wonder how this works out. An energy company invests in solar technology. That energy company sends that energy to many companies, including one that happens to produce solar cells that the energy company buys from. So the energy produced by the energy company creates the profits it uses to buy future solar cells, so this form of exponential solar growth should already go on in principle. The doubling rate might not actually be 5 years (Add in efficiencies of the market and the fact that not all energy is going to reinvestment but mostly consumption), it may be something on the order of 10 to 15 years. As long as the doubling rate is less than the average lifetime of a solar panel, it seems exponential solar growth should occur anyways. Are we seeing that in the industry? I think I've seen that mentioned on a wikipedia page once, but I can't seem to find it.

 

[spinningmagnets]

Although most sand has a high percentage of silicon, the type of silicon used in solar-PV cells must be of an unusual purity. That being said, the future of PV popularity is good. Competition and growth prospects have driven big corporations to invest heavily, and improved processes are coming on-line.

For the record, if somebody invents a new process that allows them to make PV cells for 1/10th the cost of current methods, that doesn't mean when the product comes on-line that it will also cost 1/10th the previous sales price. Typically the first year or so it will be priced about 10% below current prices, just enough to grab a lot of customers. As competition increases by other competitors using similar manufacturing methods, price will slowly come down.

 

[dnmun]

the fundamental posit it not true. it takes at least ten times that many years to recover the energy needed to produce the purified silicon solar cells and mount them and place them in the field.

we can do it for cheap now because we have free energy from oil and coal. but the energy used by wacker here to purify silicon comes from the dams on the river providing cheap power on long term sweetheart deals with the boneville power authority.

prices we cannot get as customers of the utilities.

solar hot water heating panels however will pay for their production costs within 5-10 years. true costs.

i really don't even understand how people can believe that solar panel producing electricity is more effective than just turning off a light. same amount of energy. so much hype.

 

[swbluto]

the fundamental posit it not true. it takes at least ten times that many years to recover the energy needed to produce the purified silicon solar cells and mount them and place them in the field.

Do you have a source for this claim?

Even if you do, do you think the current high amount of energy needed is largely due to something that could be potentially eliminated or vastly minimized? (I.e., human labor. A corresponding robot requires less than a tenth of the amount of energy (and energy is quantifiable in terms of money, so we can make comparisons between machine and human energy costs.) than that of a human to live.)

Also, see:
http://www.orkla.com/eway/ehs/2008/focus-solar-technology.aspx

They're a solar company, though, so I would expect bias. Despite that, they cast their competitors as requiring a disappointing "two years" to recover their costs. If they were biased, I would expect them to cherry-pick the worst value for their competitors which doesn't even come close to the lifespan of a solar cell.

Also, see:

http://www.greenenergyohio.org/page.cfm?pageID=58

They seem to include commercial costs involved (Which includes things like setup, transportation and the such), and project a payment payback between 4 to 8 years (which can be converted into an energy comparison, even though the commercial cost includes profit).

 

[317537]

My last post was ignorant to the op's so I deleted it.

How about using solar panels, and still turning off that switch. The amount of energy one uses is fundamental to the same aspect of consumption. If you turn that light off etc the need for many panels is not so demanding. Using L.E.D’s that live for ages and are more efficient than cfl's by producing confined light spectrums helps every bit.

I look at the power poles and overhead wires between homes, the maintenance and equipment that’s carried around on the power companies service vehicles, coal trucks and the building of the parts from tires to injectors. Coal is not as free as one may suggest.

I think of all those power poles and thousands of miles of high tensile cable between homes and the power station, the gear to hold them up, high voltage transformers, the energy to produce the electricity to begin with, off the grid self sufficient power production is definitely on the cards as a viable solution.

 

[Jay64]

we can do it for cheap now because we have free energy from oil and coal.

Where do we get free energy from oil and coal from?