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  • My dad's installing solar PV cells on his house

    So my dad is retired and tends to shop CD rates to put a little money in. When looking for investments he found that with tax incentives and rebates solar photo voltaic is an attractive investment.

    Don't know the exact numbers but seems the install will cost him about $12,000

    Apparently the state of CO passed a law that says the power companies have to have X% of renewable energy in place by a certain date and one way the power companies are doing it is to subsidize house installs of PV cells.

    My dads house is pretty big 3,000ft^2 ranch with 1/2 finished basement. Gas heat, and Air conditioned. The system is sized to provide about 100% of their electrical needs. Up to the power your house uses you get rebated at residential rates, above that you only get what the electric company buys electricity at so it doesn't pay to make more than your yearly home use.

    The system will be about 900sq feet. My dad figured it will pay off in 10 years and the cells are guaranteed for 25. They are designed to withstand 1" hail and insurance will cover hail damage.

    I think it's very cool. I'd much rather pay for this system than send my money to the middle east and have kids dying for oil. (not that this is a total solution I understand but its a step)

    I have a question:

    I've read (here?) that PV cells never generate the energy it took to make them. I find that hard to believe, how can a mere 900ft^2 of anything take 25 years of an AC'd house worth of energy to make?

  • #2
    To get that calculation to work is the usual "global" costing....

    The total energy cost of the factory that built the cells, the energy cost of the extra equipment to make the materials of which the factory is composed, minimg sufficient ore to make the steel, everything down to the gas to take the bank guy to lunch getting the loan for the factory....... energy cost to take out the trash at the factory, and gas for the workers to get there...it is all included.

    Then the lifetime of the cells is arbitrarily put at about 1/3 of the actual.

    Taken that way, it may very well be that the energy is never recouped.

    The problem with that type calculation is that it is wrong on several levels.

    For one obvious point, it assumes that everything is "used up" and has no scrap value..... i.e. the steel in all the buildings and equipment is counted as "destroyed", the buildings are counted as non-re-usable, even water used in the processes is counted as "destroyed" after use (must be a lot of gamma rays comoing out around there).

    The fallacy in that sort of calculation is that material and refining it is not "lost energy" when the materials are no longer of use in their original form, there is scrap value and melting scrap uses less energy than making new steel from ore. buildings can be re-used, whether they actually are or not, water is typically cleaned at the sewage plant and returned to the environment.

    So many of the energy costs are not really totally allocatable to that use as a PV cell factory.

    Plus, what type of PV is being discussed?

    Old-time single crystal cells? Polycrystalline cells? Thin film amorphous? Space qualified or commercial?

    Energy costs are dramatically different for the different types, yield rates are dramatically different for the different types, and a calculation for the most energy-intensive types is bogus when applied to a different type.
    Last edited by J Tiers; 07-25-2008, 12:49 AM.
    1601

    Keep eye on ball.
    Hashim Khan

    Comment


    • #3
      Twelve grand is about half as much as I have researched for a system for my house. I also have a 3000 sqft house. Mine is in So Cal but I dont need A/C being by the coast, I dont have it now. And heat is also nil.

      But just going off of what I consume, and its been constant for the last five years, although the bill hasent LOL.

      I crunched the numbers for myself and I could not recoup the outlay. It would take me twenty years to recoup the cost, just to break even and start enjoying the benefits from solar. And that was assuming all the equipment was service free, meaning it would not have any failures.

      Just didnt add up for me. Specially if I considered the $24,000 if I placed it in a low bearing account and just removed the normal electric bill monthly from it. I would loose money by sinking it into a whole house system. I ran the numbers many times, not cost effective for me. JR
      My old yahoo group. Bridgeport Mill Group

      https://groups.yahoo.com/neo/groups/...port_mill/info

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      • #4
        You might check again assuming an electric bill 3x what yours is now.......

        I know folks who did their system for $5000, but they have limited needs...... used to have only a generator or kero lamps.
        1601

        Keep eye on ball.
        Hashim Khan

        Comment


        • #5
          The 12k price was after some pretty attractive rebates. I think the actual cost is around 40K.

          Still, give it 5 more years and the actual cost is 12K and electricity has tripled...

          It's kinda cool because my dad is no tree hugger and yet it just made financial sense.

          Don't know the type of cell, I'll ask next time I'm down there.

          Comment


          • #6
            My dad installed Grumman solar water panels on his house back in the 60s. They still operate just fine. He has a big house and usually rents out several rooms to students so there are a lot of showers and hot water use. In the basement is a 200 gallon well insulated hot water tank. As he lives in Berkeley there is plenty of sunshine a lot of the year. I don't recall how much the system cost but over the last 45 years or so it has probably paid for itself many times.

            The hidden cost of PV cells is enormous. To make silicon polycrystalline or especially monocrystalline cells requires the same infrastructure as making silicon chips up to a point. Just the machines to pull the silicon ingots are incredibly expensive. I don't know what a solar cell fabrication foundry costs but a silicon chip fab can start at 1/2 billion to over a billion dollars. The processes used are also extremely energy intensive as the first steps are purifying and melting the silicon, a process similar to making glass except it is done in very small batches compared to glass making. Subsequent steps also involve baking at high temperatures to infuse dopant elements into the silicon. The only cheap part of the process is the raw material, sand.
            Free software for calculating bolt circles and similar: Click Here

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            • #7
              I wonder what the hidden costs of oil, natural gas and coal are...

              Not defending solar pv, I'm looking for data.

              Shipping troops to the middle east cost billions, and oil is still plentiful. Wait till there are actual shortages.

              Gotta do something. I don't see the government laying down plans.

              I fear the next war for oil will be 10x this one.

              Comment


              • #8
                if is sounds to good to be true.....

                look at it this way.

                manufactures are at capacity producing these cells.

                they price them at the ragged edge of ROI.

                if it actually paid back in 5 years it would be the greatest investment.
                I think they price them at the 20 year mark.

                /I could be full of crap, but I just priced a system myself, that's what I found.

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                • #9
                  You have seen the issue that Evan prefers to ignore.

                  The alternatives (basically coal burning) we have at present INCREASE THE RETENTION OF HEAT, AND WILL CONTINUE TO INCREASE IT, SPIRALING UPWARDS IN RETENTION AS LONG AS WE CONTINUE TO USE THEM.
                  And solar cells capture excess heat as long as they are in use. The problem is they CAPTURE HEAT THAT WOULDN'T BE CAPTURED OTHERWISE.

                  The PV alternative is ONE (among others) which offsets not only the direct heating (2x power generated, net) caused by burning coal, BUT ALSO THE LINGERING EFFECTS OF THAT COAL BURNING ON THE RETENTION OF SOLAR GAIN FROM ALL OTHER "CAUSES", BE THEY EVAN'S "BLACK" SOLAR CELLS OR BLACK ROCKS, DIRT, TREES, OR THE OCEANS*.

                  They are not MY solar cells Jerry, they are the latest and "greatest" idea in solar technology. It also doesn't matter which apparent color they are. The apparent color of a solar cell is narrow bandwidth reflection. All the other bands are absorbed. That is on purpose.

                  it is important to remember that the coal alternative increases the retention of heat WORLDWIDE, heating due to land area, oceans, cities, or solar cells. it is not just "local" in effect.

                  Same as with the heat retained with solar cells.

                  Evan and others keep harping on the idea that solar cells (using monocrystalline silicon as the model cell, and only possible cell) "can never pay back their huge energy cost and the horrible chemicals used to diffuse the junction into the silicon"... He ignores the newer technologies which allow cells to be "printed" by the tens of square meters at a time, with less obnoxious chemicals and much less energy input.

                  I'm not even talking about monocrystalline solar cells at all. I am specifically talking about those newer printed cells. That is what the picture I posted is about, the Nanosolar product.

                  They also ignore the fact that the existing electric power grid has yet to (and can never), generate enough power to make the materials used in IT.

                  I never mentioned any "horrible chemicals". The diffusion process is extremely energy intensive.

                  "Hand waving" or not, a simple qualitative look suggests that there are three alternatives......aside from nuclear power, which has already been effectively taken off the table.

                  More handwaving about handwaving?

                  1) stop using power, and go back towards pre-industrial life, accepting the massive human die-off that results. This is the alternative that most traditional environmentalists prefer, whether they admit it or not.

                  2) keep burning coal (stored solar power), which will keep INCREASING the heat retention per watt of solar gain, and raise the earth's temperature. This seems to be Evan's "solution", even though he has already accepted and endorsed the fact that it does and will continue to cause heating, at a steadily increasing rate.

                  Don't make assumptions. Coal is a very dirty way to make power. reducing consumption is much better and is also extremely doable. Putting a light colored roof on my house has cooled the interior considerably in the current hot weather. I don't have air conditioning and don't need it even when it is around 100f outside.

                  3) use alternative means of converting solar power (in it's various forms) to usable power, even if SOME of them DO cause a minute increase in the global average heat input. Keep working on increasing the efficiency of these means so that the effect is minimized**. Add some other means such as geothermal etc, if and as they become more widely usable.

                  The estimated area required to supply the USA from solar power alone is 100,000 sq miles of solar cells. If they trap an excess of 2 kilowatts of heat per hour per sq meter over 3000 hrs per year of sunshine the numbers are staggering. 2,589,988 sq meters per sq mile x 3000 hrs per year x 2 kilowatts x 100,000 sq miles=1,553,992,800,000,000,000 excess watts per year trapped.
                  That's 1.5 EXAWATTS. It is also, not coincidentally, the same as TWO TIMES the current total energy consumption of the USA, the largest consumer on the earth. This is not "a minute increase in global output".


                  it seems obvious that alternative "2" is not a "solution" which will solve anything, regardless of Evan's roof. I can't imagine ANYONE who can think supposing it is worth considering, unless they deny the effect altogether.

                  Alternative "1" will work fine, but may not be very acceptable, since once the environmentalists have all shot themselves to save the planet, the rest will keep right on going as they are until they do it to themselves with a big mess.

                  * The oceans, by far the dominant feature of the earth's surface, are about the same blue color from space as the usual silicon solar cell.

                  One might, with Evan's logic, suppose they reflect about the same amount of energy...... so much for the heating. If we covered the earth 100% with that color, we would logically not equal what the oceans now already absorb, as they have more surface area than the land.

                  The oceans are excellent absorbers of heat. You are misleading yourself and others by thinking that the reflection of a single color of light equates to the reflection of a large amount of energy. It doesn't. Ever notice how an antireflection lens coating looks BLUE?

                  If we covered the land with something that absorbed the same as the oceans do we would have to use something like solar cells. Oops.

                  ** One would accurately presume that ideal solar cells , which are what is being worked on, would be efficient. Clearly, the more efficient the cell, the fewer are needed, and the smaller the amount of area covered by them. Doubling the efficiency halves the area used........ Obviously that is of benefit, even if only on an economic basis.

                  But, we don't have ideal solar cells. Real world efficiency one they are enclosed in slightly dirty glass frames is maybe 10% at best.
                  Free software for calculating bolt circles and similar: Click Here

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                  • #10
                    Color me stupid I guess but if the wars we fight are for oil, why the hell are we paying $4+ for gas and $5+ for diesel? I don't get it.

                    I'd like to do solar myself but not to save the planet. I'd just like to do it out of curiosity. I will do solar on my RV and take great fun in watching it all work.
                    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
                    Thank you to our families of soldiers, many of whom have given so much more then the rest of us for the Freedom we enjoy.

                    It is true, there is nothing free about freedom, don't be so quick to give it away.

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                    • #11
                      Originally posted by Evan
                      The hidden cost of PV cells is enormous. To make silicon polycrystalline or especially monocrystalline cells requires the same infrastructure as making silicon chips up to a point. Just the machines to pull the silicon ingots are incredibly expensive. I don't know what a solar cell fabrication foundry costs but a silicon chip fab can start at 1/2 billion to over a billion dollars. The processes used are also extremely energy intensive as the first steps are purifying and melting the silicon, a process similar to making glass except it is done in very small batches compared to glass making. Subsequent steps also involve baking at high temperatures to infuse dopant elements into the silicon. The only cheap part of the process is the raw material, sand.
                      going back to what J Tiers posted, there are a lot of assumptions in the "hidden costs". for one thing, growing Si for solar cells isn't the same thing as growing it for 12" Si wafers used to manufacture 45nm technology ICs. second, i worked for a company that owned the entire integrated circuit process (Si refining through ingot growing through wafer fab through device packaging and final test and shipment), and when they sold everything, it went CHEAP (to the Chinese). i'm sure that "recycled" equipment would have no problem turning out PV-cell-grade Si ingots. the equipment was no longer suitable for any IC technology below 0.25um without considerable investment.

                      i have no idea how much energy is used to make a PV cell though, so i don't know how long it takes to recoup that expense.

                      andy b.
                      The danger is not that computers will come to think like men - but that men will come to think like computers. - some guy on another forum not dedicated to machining

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                      • #12
                        for one thing, growing Si for solar cells isn't the same thing as growing it for 12" Si wafers used to manufacture 45nm technology ICs
                        It is if you are making monocrystalline cells. The requirements for purity etc are exactly the same to grow a large single crystal of silicon. It's what you do with it after you make it where the processes differ.
                        Free software for calculating bolt circles and similar: Click Here

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                        • #13
                          Hi Evan,

                          I agree with most of your post, but single crystal Cz - pulled Si for solar is quite different than what your need for microelectronics. The purity requirements are not nearly as stringent for solar as they are for microelectronics. Cz Si for solar pv is pulled quicker and typically has a higher amount of impurities than microelectronics grade material. I know this is an aside from the original topic.

                          For what its worth, "energy" payback time for an installed grid tied solar pv system goes from 10 months to over 3 years depending on location and type of cell. The "monetary" payback time without subsidies is approximately never.

                          Jesse

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                          • #14
                            Originally posted by Evan
                            It is if you are making monocrystalline cells. The requirements for purity etc are exactly the same to grow a large single crystal of silicon. It's what you do with it after you make it where the processes differ.
                            Which is to a large extent last century technology anyway.......

                            Mono crystalline cells are a tad more efficient, but quite a bit more expensive than any other type.

                            The action is in amorphous and various thin film cells. Trying to stack the deck by quoting last century costs and impacts is just fraudulent.

                            You decide how you want the argument to come out, then add costs and make assumptions until it comes out how you decided you wanted it.... THAT is "new science" at work.

                            Makes the Salem witch trials seem remarkably intelligent and open-minded......
                            1601

                            Keep eye on ball.
                            Hashim Khan

                            Comment


                            • #15
                              I looked into building a small backup system just to run a few lights and maybe a fridge in the event of another 2 -3 week long hurricane outage.

                              I wasn't practical,even as a backup.

                              If all the system cost me was $12,000 it still wouldn't be practical.Last years and the preceding 10 years my total bill was less than $1200 for the whole year.I did zero maintenance on anything and only had a couple nuisance outages besides the storm.

                              But as mentioned the real total cost of the system was more than $12,000,closer to $40,000.No way would I invest $40k in a system since 33 years would be the break even,maybe more or less.

                              My question is where does the subsidy for solar come from?Taxpayers?Industry?MUCH higher rates down the road?
                              I just need one more tool,just one!

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