Geothermal and Solar Thermal Hybrids

Discussion in 'Geothermal Heat Pump Applications' started by zach, Dec 17, 2011.

  1. zach

    zach Member Forum Leader

    Any installers doing geo/solar thermal hybrid installs? In other words, are you using solar thermal via heat exchanger to heat loop fluid to increase COP in heating? Solar thermal would handle DHW and once satisfied, give heat to the ground loop.

    If so, are you logging data and can you share it?

    I plan to do this at my own home in upstate NY, including logging data, but would be curious as to other results in other areas of North America (don't want to forget my friends in Canada).

    Last edited: Dec 18, 2011
  2. urthbuoy

    urthbuoy Active Member Forum Leader

    Comes up

    This comes up fairly often.

    I'm not a firm believer of adding solar to the loop vs. just using the hot water directly in a buffer tank or such. I do have solar guys wanting to shed their heat in to my loop fields in the summer. Doesn't make sense of course, but to them it does.

    So, honestly, I have seen duplicate systems, but I wouldn't really think of them as hybrids unless we can truly find a way to shorten ground loops that are heating dependent by using solar hot water. Nature doesn't cooperate though with its coldest temperatures in the middle of the night in winter.

    Where the science needs to fill in the gaps is how much short-term thermal storage the soils would have. Until then, we just end up with a full-sized geothermal system with solar hot water support.
  3. docjenser

    docjenser Well-Known Member Forum Leader

    There are a couple of systems up in Alaska where this worked pretty well. There is a school in Fairbanks up here where they did a pilot project with online data streaming. It worked pretty well so far.

    I think running it through a solar thermal panel before it enters the heatpump makes the most sense. But you want to be able to use controls for highest efficiency. Antifreeze concentrations needed for solar thermal panels might be much higher than the one's needed in the ground loop. Might require a heat exchanger.

    Let us know what the final design is. And yes, please measure performance.
  4. Palace GeoThermal

    Palace GeoThermal Active Member Forum Leader

    If I were going to do this, I would have the loop fluid pass through a heat exchanger from the solar panels.

    I tried heating my entire loop with a makeshift solar panel and it didn't work very well.

    It would take a large solar panel to heat up the ground where a small one would heat the loop fluid prior to entering the heat pump.
  5. Mark Custis

    Mark Custis Active Member Forum Leader


    You might want to look at the December 2011 issue of Plumbing and Mechanical. John Seigenthaler has an interesting read on solar thermal.

  6. Chuck6421

    Chuck6421 Guest

    Funny you should ask...

    Not an installer, just a user who's geo was switched on today for the first time, and who's panels are going up tomorrow.

    We'll be using the solar primarily for DHW and what's left over goes to an exchanger to preheat returning water to the loop. If I can offer anything I will.

    BTW, I'm also in Upstate NY and I'd like to hear about options for me to monitor and log all this too. While I'm very satisfied with how my installers have conducted themselves so far, I'm frankly surprised at the lack of monitoring/logging options available. I'm getting thermometers on the in and outs of the two loops (solar and geo) and that's about it. With the complexity of this system I'd really like to have a better idea of it's behavior and how I can optimize it's use. I would've thought the installers would also.

  7. docjenser

    docjenser Well-Known Member Forum Leader

    Best monitoring/Logging solution for the money is the WEL server, hands down.
    Web Energy Logger (WEL), do a search.
  8. Mark Custis

    Mark Custis Active Member Forum Leader

    I goofed

    The article is in Plumbing and Mechanical Engineer, this month.


  9. ACES-Energy

    ACES-Energy Member Forum Leader

    We installed a system this summer at a BOCES facility that is a 6-ton water-to-water radiant with 180 evacuated tubes.

    There is no real domestic water usage currently and the entire solar thermal array is mixing with the loop field.

    Data is being monitored currently online and should have some results to release in a few months of results.
  10. Palace GeoThermal

    Palace GeoThermal Active Member Forum Leader

  11. Palace GeoThermal

    Palace GeoThermal Active Member Forum Leader

    Last edited: Jan 15, 2012

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