Antifreeze opinions -- methanol vs. ethanol?

Discussion in 'General Discussions' started by Looby, Jan 12, 2009.

  1. Looby

    Looby Member Forum Leader

    Any opinions on choice of antifreeze -- specifically, ethanol versus ethanol
    (a.k.a. Environol)?

    My geo contractor routinely uses methanol in preference to propylene glycol,
    but I get the feeling that he's never given ethanol serious consideration.

    WaterFurnace's first choice is ethanol (their Environol™ product is ethanol
    plus some blue dye and corrosion inhibitors). Methanol and ethanol appear
    to be very similar with respect to pumping pressure drops and Reynolds
    numbers, but I find WF's argument's in favor of ethanol rather appealing:

    - non-toxic -- essentially, pumping 50 proof vodka around the loop

    - slightly higher specific heat than methanol (very slightly)

    - less corrosive than methanol -- although neither is likely to be a problem

  2. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I guess price would be a factor.. any idea what WF charges for Evironol?
  3. rw1995

    rw1995 Member

    WF gets a lot for their Environol. I can't remember the quote I got at the time, but it was an easy decision. I purchased Methanol from a local fuel/oil supplier for under $5/gal, it comes in 5 gal buckets. In Iowa, they restrict anything other than ethylene glycol if put under 20' in the ground. Methanol was fine for my horizontal loops.
  4. Looby

    Looby Member Forum Leader

    Not a clue. Ethanol should cost no more than gasoline -- especially since there's
    currently a glut of corn ethanol on the market -- but WF can charge whatever
    the traffic will bear.

    I infer from rw1995's response that it's priced at over $5/gal. My system's
    total volume is only 70-80 gal, so it shouldn't need more than about 20 gal
    of pure ethanol (Environol 2000). So, no matter what they charge, it's a tiny
    fraction of the total price tag (to retrofit a 50 year old 2200 sq ft ranch from
    oil-fired HW/baseboard to geo/hot air).

    Mine's a 450 ft vertical loop in highly-fissured, water-saturated shale. The
    static water level is only 8' below the surface, and the driller estimated
    that it was blowing out 20-25 gpm. All the talk here about "short loops"
    has me a little worried, but I'm hoping that the subsurface water flow will
    be a big plus.

  5. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    I believe methanol has a lower viscosity and equivalent freeze protection at lower concentrations. The best heat transfer fluid is water itself, so you generally want to minimize the amount of antifreeze added.

    Combined with the ease of being able to source methanol locally made the decision for me.

    Keep in mind, methanol is highly flammable. You should never see it in concentrations in a ground loop that this would be an issue though (25%), but when you add it, try not to have a smoke in your mouth;)

    JRBGEO Member Forum Leader


    I just had the glycol in my system flushed this past friday and replaced with Environol. It was diluted at 30%. It seems to work better as our 4 ton Envision has not had any "water flow" issues in 4 days and we are keeping the house at 68 degrees. I was "short looped" by my installer to begin with and this was their answer to fix our heating problems. We'll see how well this solutuion holds as colder temps are expected in CT later on this week. I don't know the reason as to why is so expensive, this is just ethanol.
  7. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    We can buy methanol for around $4 gal
  8. rw1995

    rw1995 Member

    My system was around 100-110 gal. Methanol at 20% by mass will get you to a freeze protection to around 0 deg F. 10% by mass will protect down to 20 deg F. I dumped 20 gal into the system getting me into the 15-20 deg protection. My loop EWT is around 50 at this time.

    Keep in mind Methanol and Ethanol are very flammable, the flash point on Methanol is 54 deg F. This means at temps above 54, its giving off enough vapor to ignite with an source. I would dilute it down before adding to the flush cart just to be on the safe side. I went 50/50 with water to get the flash point up in the 75-80 deg F range before pumping.
  9. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader


    where do you live and how are you getting EWT of 50°? Just curious
  10. Looby

    Looby Member Forum Leader

    True, but the difference is very minor -- pumping resistance for ethanol is
    about 2% higher when mixed for 15 F freeze protection (that's 20% V/V for
    methanol or 25% V/V for ethanol).

    Reynolds number for methanol is about 10% higher, but that's not a problem
    in my system -- either one will have an Re above 6000.

    Flash points are similar (methanol 54F / ethanol 62F) and ethanol actually
    has a specific heat slightly higher than water.

    The big differences are toxicity and availability. Undenatured ethanol is
    tightly regulated by US ATF, and you can't use generic "denatured alcohol"
    because there's no telling what's used as a denaturing agent.

  11. DickRussell

    DickRussell New Member

    No, the specific heat of ethanol (pure) ranges from 0.51 at 0 F to 0.55 at 50 F. Units are BTU/lb-F (or cal/gram-C). That's slightly more than half of water's heat capacity.
  12. Looby

    Looby Member Forum Leader

    Sorry, I shoulda been more precise. The heat capacity of
    25% v/v ethanol in water is slightly higher than pure water.
    According to WF's Environol specs, it's about 1.05 BTU/lb-F.

    That's probably related to the fact that an ethanol/water
    mixture is "more compact" than either liquid in its pure
    form, i.e., 1.0 gal water + 1.0 gal ethanol = 1.9 gal total.

    ... 2 + 2 = 5 (for large values of 2)

  13. DickRussell

    DickRussell New Member

    You are quite right. I didn't know that about ethanol/water mixtures. What I found was that mixtures containing 1 to 35 mol% ethanol do have a heat capacity higher than that of just water alone. In Perry's Chemical Engineer's Handbook, 8th edition, there is this table, giving specific heat vs. concentration and temperature.

    Specific heat
    Mole% 3 C 23 C 41 C
    4.16 1.05 1.02 1.02
    11.5 1.02 1.03 1.03
    37.0 0.805 0.86 0.875
    61.0 0.67 0.727 0.748
    100.0 0.54 0.577 0.621
  14. Looby

    Looby Member Forum Leader


    Water Furnace's installation manual uses the same brine
    factor to calculate the heat extraction capacity of either
    ethanol or methanol -- and both have 3% less capacity
    than pure water:

    "Use 500 for pure water, 485 for methanol or Environol™."

    I had overlooked the fact that heat extraction capacity
    depends on mass flow rates rather than volumetric flow
    rates (i.e., pounds/hour rather than gallons/hour), and
    that pure water is heavier than either antifreeze mixture.

    So, for a given circ pump, the heat extraction performance
    of all three should be within 5% -- with the pecking order:

    water > methanol > ethanol



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