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GEOTHERMAL SOLAR COMBO

Discussion in 'General Discussions' started by CURLY, Jan 31, 2009.

  1. CURLY

    CURLY New Member

    Has anybody seen or thought of running solar heated water back through the ground loop? This would allow the ground loop to "recharge" during parts of winter.

    Earl
  2. engineer

    engineer Active Member Forum Leader

    This is periodically discussed here and / or at GBT

    I've yet to read of any system able to preserve the heat (or 'cold') put in the ground during one season for the months needed to endure through spring or fall, the shoulder seasons. The heat is conducted, convected, radiated, or advected away during the off season.

    There is an example from a century ago: Before home refrigerators became widely available in the 1920s and 1930s, people sawed ice blocks from frozen lakes during winter, stored them buried in feet of sawdust all spring, and then sold them all summer for use to refrigerate food.

    Unfortunately the tons of ice equivalent heating and cooling needed to be stored for a single home's seasonal heating and cooling needs runs into the thousands.

    It might take a multi-million gallon underground tank insulated to R100 to provide useful seasonal storage
  3. waterpirate

    waterpirate Active Member Forum Leader

    solar boost

    We did the math for a green house project that was never launched last year. Since cooling would never be done with the system we were going to circulate the fluid from the loop field through a collector system to raise loop field temps during summer.
    We got a PE involved and found out that the heat of rejection/ absorbtion was so high that there was no need to "boost" temp in summer. The loop field would corect it self back to 52 with no use and temp would not drop in winter enough to warrant the expense or effort in solar collector.
  4. engineer

    engineer Active Member Forum Leader

    "The loop field would correct it self back to 52"

    That's the nut no one yet seems to have cracked.
  5. gabby

    gabby New Member Forum Leader

    This is not a new concept.......see below for some reading or do a google search on thermal store. Costs is a different topic. Also if you like this concept you might enjoy the enertia home design, which basically stores and designs structures to use these principles on a daily basis versus seasonal basis. Hybrid Solar House > Science > Advantages


    Seasonal thermal store - Wikipedia, the free encyclopedia

    Ground cold storage and utilization - Patent 4240268

    openPR.com - Press release - TEC MANAGEMENT - Heat & Cold Storage beneath Residential and Commercial Buildings

    For your added reading is a pdf attachment.........
  6. waterpirate

    waterpirate Active Member Forum Leader

    Clarification= vertical field in super saturated wet sand. PE came up with if you shut the system down in late march, by may the fluid would be corrected back to 52, ready to start heating again in late october.
  7. Palace GeoThermal

    Palace GeoThermal Active Member Forum Leader

    I have been thinking about doing something like this on my house. We have some bright sunny days in January along with some cold nights.

    My EWT right now is 45°, I have temp sensors buried in the ground ( at levels of 5' and 9', the depth of my loop) away from my loop that are reporting 49° and 52°.

    So my loop and the soil right around the loop are colder than the soil away from the loop.

    My theory is that some heat put into the loop will not migrate away too far since it would soon run into ground that is warmer. My soil is heavy clay with out any ground water present.

    I can see how trying to store the heat long term would be hard, but I am interested in the short term. Storing the heat during the day for use that night.

    Admittedly my loop temp doesn't need any boosting, if the idea worked, future jobs could be done with less loop in the ground.


    Comments appreciated;);)
  8. Mark Custis

    Mark Custis Active Member Forum Leader

    Depending

    on the type of collector they will work with a cloud cover. I think it is a grand idea. Heat pumps are moving heat not making it so it would work short term for sure.
  9. waterpirate

    waterpirate Active Member Forum Leader

    no laughing please

    O.K. here is the idea I had. The poop loop.:eek:

    For houses with on site septic disposal and a closed loop ewt that is low. Could a bypass be rigged to run the fluid through the tank via a coil to pick up btu's, with monitoring so that the temp in the tank would not be lowered to inhibit composting?

    Here the average system is based on 500 to 1,000 gpd being introduced into the tank. The majority of the fluid introduced to the tank would be a minimum of 55 degrees or higher.

    Just a thought. Similar to the "battery concept" only we get a steady recharge daily.
  10. CURLY

    CURLY New Member

    To clarify

    My post dealt with "periods during the winter". On a daily basis if you like. We see huge temperature swings during the winter; 50 or 60 degrees is not uncommon. These swing periods usually last less than 5 days. Wouldn't injected 100 degree solar water into the ground loop during these swings provide better performance and comfort (in terms of warmer air from the HP) if the loop temperature was only increased during this period?

    Earl
  11. Palace GeoThermal

    Palace GeoThermal Active Member Forum Leader

    This idea has been discussed before. I can see some merit there.

    A few years ago, there was a lot of fanfare in our city when a guy got permission to put a heat exchanger on the city sewer line under the road.

    Haven't heard how it has been working.


    The question is: will you ever see any payback? The same question applies to trying to put solar heat into your loop.

    I am going to try the solar heat into the loop and see how it works.
  12. gabby

    gabby New Member Forum Leader

    If one has a heat exchanger, one could try multiple experiments...throwing convention out of the window so to speak. Basically taking the metal exchanger used for lakes in a closed loop system principle, with a slight twist, one could take a hot water tank ( Storage unit/preheater) to heat the output side of a pump feeding the loop. You could build your own tank with a radiator that the loop water traverses through prior to entering the loop. The desuperheater supplies the surrounding water.
    The second possibility is to use backflow preventors on the exit port of a desuperheater feeding a hot water tank that is in series with the exit port of your pump, mixing the hot water with the cold water of the loop....think of it as a expansion tank for the loop. If you use antifreeze in your system you wouldn't want to go this way.
    Copper tubing comes in sizes up to 1 5/8" 100' coils...enough to make your own radiator that you can immerce into a tank of say 100 degree water.
    It would take a couple of days to raise the the LWT and inject more warmth into the loop bed, but it will and can happen, especially if the delta difference is large between loop and bed. The earlier you did this in the heating season, the better the overall results would be. You could use most any metal coils, copper just has the best transfer properties.

    If you want to try this on the cheap, a 55 gallon barrel can have urathane foam sprayed on the outside to insulate it--2" should be about R11-R14.
    The lid has two threaded openings that you could use for entrance and exit ports for the tubing. You could use multiple sealants to seal the lid, water tight. You could drill and weld fittings on the side for the hot water from the desuperheater.

    That's just off the top of my head....multiple solutions/multiple problem areas to think about.

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