Mathematics

Discussion in 'Windtura Generators' started by Bryan, Apr 4, 2012.

  1. I've recently beccame more interested in wind power and have done a lot of research. I've found all the hype about modified automotive alternators modified for wind generations and the fallacies of them.

    I found this company to produce the most reasonable PMA with accurate wattage to wind ratings. I have also found very useful info in these forums, including the link to windspeed page.

    This leads me to the math.

    There are 8766 hours in a year (24*365.25). I consumed 7250 kwh in 2011. My average annual windspeed is slightly above 11mph. The Windtura 750 chart shows a production of about 75w @ 24v @ 11mph.

    The average annual production I can expect from the 750 is 657.45kwh. This equates to 9% of my consumption, representing a cost savings of $52.60 annually (@ .08/kwh - my cost).

    If we assume that to put a GTI system only (no batteries) using the 750 would cost about 2x the cost of the 750 alone by the time the GTI and all other items required are included, then we are talking approximately $2,000.

    That would make the system pay itself off in just over 38 years.

    If I trebled my investment, I would reduce the time by third to 12.7 years.

    Unless somebody can find an error in my math, it isn't really worth the invest for me, is it?
     
  2. windyguru

    windyguru WindyNation Expert

    I would say if you are paying 8 cents per kwh, you are getting a great deal! Your math seems correct (I did not check it line by line).

    Two things to keep in mind that I can think of. First, Uncle Sam does have tax incentives in place on alternative energy systems, including small wind turbines:

    http://www.energytaxrebate.com/

    Secondly, you have to take into account that the average wind speed comes from a distribution of wind speeds so the only way to know the true potential of a wind site is to log the wind speed for a year or longer.

    I would agree with you. If you have access to electricity at $.08/kwh and the wind in your area averages 11 mph, the pay back is going to take a long time. And if your only concern is pay back (saving money), then a wind turbine does not make sense for you.
     
  3. Minnesota

    Minnesota WindyNation Engineer

    Do boats pay for themselves? Do fishing rods pay for themselves? Does anything? Oh perhaps CFL lighting and insulation might have a chance of justifying their initial costs.
     
  4. I calculated the average windspeed from winfinder.com. They had a observation point approxiamtely 10 miles from me. I averaged their avearge monthly windspeeds to calculate the average annual windspeed. Of course to be more accurate. I would need to know how many hours each month the wind blew. As it is I can only make a generous assumption that it blew 24 hours a day.

    I just checked, my cost/kwh is $.08729, so my memory wasn't far off and that difference won't change the math much. There are minor "stepped" transmission charges that wouuld factor in but those vary from season to season and are difficult to calculate. as best as I can figure that would make the "total" cost per kwh around $.11, again not a significant difference. My savings would be $72.32 annually. The payoff would be 27.66 years.

    I did forget about the tax incentives. I will have to check that out.

    Minnesota, your videos on youtube often state your reliance on the math, that is what I'm doing, the math. If a boat is needed for transportaion or work then, yes, they pay themselves off. If it solely a recreational item, it is not expected to pay itself off. MY fishing poles have more than paid themselves off. The amount of fish that I've eaten for the cost of them and my tackle more than offesets the cost of the fish if I were to have purchased the same amount in a store.
     
  5. Even considering the tax incentive, it would still take approximately 20 years to pay itself off.

    Since backup electricity is not a concern of mine, I've only seen the electricity off for a period of 24 hours or longer once my 51 years, it just doesn't seem to be worthy investment for me.

    I think the idea is great and I will keep watching. Maybe my rate will increase or the cost of the equipment will drop to point where it will become feasible for me.
     

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