Any Advances in HDPE Pipe in the works (thermal cond.)?

Discussion in 'General Discussions' started by Guest, Jul 8, 2008.

  1. Guest

    Guest Guest

    GeoThermal Newbie Questions???!

    Hi ALL!
    So...I'm a Newbie to this whole Geotherm Idea! I understand how it works. But I don't think in my case it'll do anything for me!
    I live in Western MAss.
    My house, the main part was built in 1873, classic hand Hewnd Beams Etc. It doesn't look like it from the outside, because of Aluminum siding.

    What I have is an OLD Utica Boiler, at least 45 years old, with a Becket Burner that's about 8 yrs old. I also get my Hot Water from it. No indirect Hot Water Tank. I have radiators. I understand that an exchanger usually works with Hot Air, and a Forced Hot Air system. I don't have this. The other thing I hear is Radiant Heat, well that won't work for me either. Is there something I can do with replacing that Boiler?

    Are there Tax Credits out there? Or are we waiting till after the Elections?

    Many thanks, Ted
     
  2. TechGromit

    TechGromit Member

    You right, a water to water Geothermal system can't heat the water hot enough to be directly used in radiators, it could be use to heat the floor up if tubing was installed all along the flooring or with duct work with a Water to Air system, but there no way to get a Geothermal system hot enough to use existing radiators.
     
  3. Having only been in the industry for a little while, it still strikes me as a bit odd that HDPE pipe is the industry standard when it has such poor thermal conductivity properties. I know it's tough and will last long beyond my lifetime, but are any manufacturers showing any interest in improving the thermal properties of the pipe, or is it a case of a material repurposed from another industry (natural gas) and the market isn't big enough to warrant any additional innovation? I would love to see a unicoil that comes close to the conductivity values of the surrounding soil, and maybe doing less drilling in the process.
     
  4. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Thermal conductivity of HDPE exceeds almost all soils. The soil thermal conductivity/diffusivity is almost always the rate limiting step in the heat transfer process.
     
  5. gabby

    gabby Member Industry Professional Forum Leader

    The 3806 and 4000 series are being replaced by the PE100 material; a tougher coating with overall improved characteristics, simplifying the different variety of product lines that basically do the same job. I don't remember if the thermal properties have increased, but a simple google search on PE100 HDPE pipe should give you a chart or detailed explanation. This has been in process for over a year now.

    There are new ( I call experimental) heat exchanger columns (24' deep) that work like a combination standing water column and closed loop system....1 per ton. It is basically a cylinder container 24" in diameter some 24' long that is buried vertically to simulate a closed loop system. You should find a more detailed explanation doing a google search for geo heat exchangers.
     
  6. I'd guess we work in very different geologic areas-we are on solid bedrock below about 10' around nashville, and limestone ranges from about 1.4-2.5 K if I recall correctly (we use 1.5-1.8 as an average for calculations), so if the HDPE has a K value of 0.40, it seems like we could reduce drilling a bit if a better conducting pipe were available. Our grout has a thermal cond of around 1.0.

    Also, I'd love to learn more about the closed standing columns that you mentioned Gabby. Is there a name for them so I can do some research? Standing columns are a rare thing around here b/c of poor water quality, but a closed version would be worth looking into. Sounds promising.
     
  7. gabby

    gabby Member Industry Professional Forum Leader

    How close are you to Symrna, or Murfreesboro?

    This is an excerpt from a previous post concerning SWC…standing water column….very deep holes, 6” diameter….more like a open loop recycle system.

    "Standing column well
    A standing column well system is a specialized type of open loop system. Water is drawn from the bottom of a deep rock well, passed through a heat pump, and returned to the top of the well, where traveling downwards it exchanges heat with the surrounding bedrock.[10] The choice of a standing column well system is often dictated where there is near-surface bedrock and limited surface area is available. A standing column is typically not suitable in locations where the geology is mostly clay, silt, or sand. If bedrock is deeper than 200 feet (61 m) from the surface, the cost of casing to seal off the overburden may become prohibitive.
    A multiple standing column well system can support a large structure in an urban or rural application. The standing column well method is also popular in residential and small commercial applications. There are many successful applications of varying sizes and well quantities in the many boroughs of New York City, and is also the most common application in the New England states. This type of ground source system has some heat storage benefits, where heat is rejected from the building and the temperature of the well is raised, within reason, during the Summer cooling months which can then be harvested for heating in the Winter months, thereby increasing the efficiency of the heat pump system. As with closed loop systems, sizing of the standing column system is critical in reference to the heat loss and gain of the existing building. As the heat exchange is actually with the bedrock, using water as the transfer medium, a large amount of production capacity (water flow from the well) is not required for a standing column system to work. However, if there is adequate water production, then the thermal capacity of the well system can be enhanced by discharging a small percentage of system flow during the peak Summer and Winter months.
    Since this is essentially a water pumping system, standing column well design requires critical considerations to obtain peak operating efficiency. Should a standing column well design be misapplied, leaving out critical shut-off valves for example, the result could be an extreme loss in efficiency and thereby cause operational cost to be higher than anticipated."




    Some answers from a note to Phil:

    I have to thank Phil Rawlings, CGD and the publication, “Earth Insights” that lead me to him for clarification between the open/closed loop system Mark is installing in Massillon, Ohio. My comparison of a SCW to a tank (to him) was like calling a “Chef” a cook….I took my scolding and thanked him for his clarifications.

    I will give excerpts of his comments for those interested in SCW. The caps are not him yelling, it is the way to differentiate my question and his answer in the same body of text.

    THE STANDING COLUMN WELL DESIGN CONCEPT IS NOT A CLOSED LOOP SYSTEM - PART OF THE OVERALL DESIGN APPROACH DEPENDS ON OPEN LOOP TYPE COMMUNICATION WITH THE WATER RESOURCES THAT EXIST IN THE FORMATION AND RECIRCULATION THROUGH THE WATER COLUMN WHICH ALLOWS SOME WATER THAT HAS ABSORBED HEAT TO LEAVE THE WELL BORE THROUGH THE NATURAL FUNCTION OF THE AQUIFER AND SOME COOL, UNEFFECTED WATER TO ENTER THE COLUMN FROM THE AQUIFER THE SAME WAY.
    THE STANDING COLUMN CONCEPT IS A LINEAR FOOTAGE DESIGN COMBINED WITH THE PREVIOUSLY MENTIONED INTERACTION WITH THE AQUIFER ITSELF. A CONTAINED VOLUME OF WATER WILL NOT PROVIDE THE SAME CAPACITY/PERFORMANCE AS THE WELL COLUMN.

    http://docs.google.com/viewer?a=v&q=cac ... _FjlbrJZEw

    http://www.northeastgeo.com/main/ec.cfm

    http://docs.google.com/viewer?a=v&q=cac ... g7i22-JWKg

    There is also the GeoColumn:

    http://www.geoenergyusa.com/technology.htm
     
  8. Gabby-we are about 30 miles from Murfreesboro, 15 miles from Smyrna. I should have clarified-I was more interested in the "experimental" SCW you described-I've read up on standard SCW and they are appealing but we don't have any experience with them yet and it's unlikely that we'd install one unless a customer demands it (unlikely). I'd like to know more about the 24' x 24" system you mentioned. Not sure if our rig could drill a 24" hole, but it'd be worth looking into. Is there a name for these experimental SCW systems?
     
  9. gabby

    gabby Member Industry Professional Forum Leader

    Sounds like LaVergne, Tennessee area...I was stationed at Stewart AFB (now Stewart National Guard base) in Smyrna. The 24" column is called a Geocolumn....last URL in the list.
    If memory serves me, they use a telephone pole auger to drill the hole. The kind for putting up 90' poles instead of towers for high tension lines, which I would assume would be region dependent due to soil conditions and rock formations. They could also use a Forstner/core drill looking thing they use for cutting through mountains or installing air shafts for deep mining operations. The largest I have seen is 3' in diameter. I think there is a picture of the truck they use in that url.....looks small to me.
     
  10. Thanks Gabby-it was late when I was reading last night & missed the last link. Looks a bit impractical for most of the residential applications we run across just b/c we are on solid rock, but I'll bookmark it just in case. I really want to try standing columns, but may have to do it on my house first to see the pros/cons firsthand. We are required to grout from bottom to top on vertical closed loops, which keeps the cost pretty high no matter how fast we drill, and I'd like to find more economical solutions for geo by the time the tax credits expire in 2016 so we can keep expanding the market.
     
  11. gabby

    gabby Member Industry Professional Forum Leader

    The cheapest solution is a spring with appreciable flow rate that you can harness for the geo unit. A 20-40 foot fall will give you the pressure, the gal/min will determine the size of unit you can accommodate. Tennessee has lots of springs so it may prove a viable option. If the water quality is poor you can do what Mark did, a combination open loop to a container and a closed loop for the unit.
    The biggest problem with SWC is the depth you need per ton...nominal 200-300 ft/ton. A commercial application (Condo complex or school) with multiple wells is affordable to them, not the normal resident. It all depends on the geology and recovery rate of the column. There are a few cases where a shorter depth can be used with low recovery rate wells. The well is actually in the aquifer or close enough to act as a heat sink for the well. Not everyone has a spring of 25 gal/min, or even 10 gal/min. It is a case by case determination as to what will or will not work. Physics can work with you or against you, but no one can repeal their laws...maybe twist them a tad to one's benefit by approaching a problem from a different direction.
    A flooded mineshaft is considered a bad thing unless you aren't mining, then it's a godsend for a closed loop system.
    Good luck with lowering costs and opening the possibilities to more people....we would all like to see that happen and tell OPEC to stick it. :lol:
     

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