Shortest Day of the Year

December 22, 2004 by
Filed under: Solar Energy 

Well, yesterday was the shortest day of the year here in the Northern Hemisphere.

I haven’t seen the numbers from yesterday’s production, but we’ve been getting 9-12 kWh out of the solar panels on a sunny day in December.  Compare that to the record of 42 kWh on a sunny day in June, and you can see what a difference the lower angle of sunshine and shorter days has on the system.

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So now we turn back to longer days.  Our “net producer” months are predicted to be April, May and a bit of June.

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Comments

6 Comments on Shortest Day of the Year

  1. AMac on Wed, 22nd Dec 2004 12:39 pm

    2. Dropped in from WoC.
    A question at a glance; sorry if this is naive. Or, more likely, if you covered your thinking in an earlier post that I haven’t read yet. If net power input from your panels is in the range of 10 to 40 kWh per day, that would appear to translate to a per diem dollar value of ~$2 to $8 of electricity. An investment of ~$10K or ~$50K would be unrecoverable at these yields.
    I anticipate that you didn’t embark on this adventure for economic reasons, and that my concerns are somewhat besides the point.
    I ask because we just moved to a 1950s-built single-family house with an accessible roof that gets lots of sunlight (central Maryland). Lots of things to do regarding efficiency, mainly cutting back on heat loss (winter) and cooling load (summer). My most adventurous daydream so far is to install roof panels as part of a system to pre-heat domestic hot water (it’s electric). I’d sure like to be cost-effective, or nearly so, in what we do.

  2. j.pickens on Sat, 25th Dec 2004 12:53 am

    3. You polluter, you!
    Your solar array, positioned as it is in a too-north latitude, will NEVER EVER produce more energy than it took to produce.
    You are WASTING ENERGY!
    The thermodynamics are just not there.
    Sorry, you might as well get an SUV, you’re wasting your time.

  3. Mark on Sun, 26th Dec 2004 1:17 pm

    4. Dear Mr. Pickens,
    I challenge this.
    I know how much energy is being produced. What energy was required to produce my equipment? The entire equipment list is included in my site.
    Remember, I’ve got at least 25 years warranty, and probably longer life.
    Oh, and I *do* drive an SUV – though I’m looking to replace it with a hybrid SUV next year.
    Mark
    p.s. And if that’s the case, why are all of the greens in Germany (a higher latitude last time I checked) going solar?

  4. j.pickens on Sun, 26th Dec 2004 5:37 pm

    5. Mark,
    You said your installation cost around $52,000.
    For Crystalline or Polycrytalline PV arrays, the energy of production is roughly equal to 50% of the commodity cost.
    Since the bulk of the energy used is in furnaces to melt and purify the silicon, and these furnaces are fired with electricy resistive elements, then the vast majority of the energy utilized was electric.
    So, we are talking about approximately $26,000 worth of electricity.
    If we use the price of electricity for 2002, data available shows an average price of $0.08 per kWh (kilowatt hour).
    Your array utilized $26,000 / $0.08 = 325,000 kWh of electricity.
    If we assume that your array has a 28 year lifespan (25 year plus 3 year grace) we get an annual breakeven production requirement of:
    325,000kWh / 28 = 11,600 kWh /year.
    11,600 kWh /year / 365 days per year = 32 kWh per DAY AVERAGE!
    Based upon what I’m seeing on your site (40kWh/very sunny June day), I don’t think you are even going to come CLOSE!
    Read it and weep, you energy-waster you….
    Now, do you want to hear the truth about hybrid cars before you waste your time there as well?????

  5. j.pickens on Sun, 26th Dec 2004 5:45 pm

    6. By the way, this analysis of energy cost is skewed towards your benefit.
    In actuality, the PV materials used in this country are typically made in parts of the US which utilize very cheap hydroelectric power. Since the producers are using electricity which they negotiate very effectively for, their average electricty costs are more like 2 to 6 cents per kWh.
    Now, you may say, great! We used hydropower to make this array! Non-polluting! YAY!
    Not so fast, to take hydropower, and use it to make PV arrays which are used in areas of the country (Southern CA, AZ, NM, TX, Parts of CO) where energy breakeven is likely, you are doing an environmentally good thing.
    To waste this energy in New Jersey, where you will be lucky to get HALF your energy back, is a great big WASTE!!!!

  6. j.pickens on Sun, 26th Dec 2004 5:47 pm

    7. quote: “p.s. And if that’s the case, why are all of the greens in Germany (a higher latitude last time I checked) going solar?”
    Because they are just as ignorant of thermodynamics as you are.
    They probably also get distorted “feel good” government subsidies just like you got.

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