Free Whitepaper: How To Measure Geothermal Heat Pump Performance (COP)

Ever wonder if your geothermal system is running as efficiently as promised? A commonly asked question from homeowners is “How do I measure my GHP system’s heating efficiency?” The purpose of this article is to give detail as to how this can be done. The measurements and calculations are not difficult to perform, but they do take specific equipment and a bit of an understanding of how the measurements need to be taken.

 

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  • http://www.smartguidetogeothermal.com/ Don Lloyd

    Thank you for the COP calculation. The only question I have is the 500 factor in the HE definition. I can see that a factor of 60 is needed to get from a minute to an hour but that leaves a factor of 8.5 that I am too stupid to figure out.

    This calculation is, however a rather cumbersome job and only gives a one time number. What the world needs is a display on the heat pump, (or on the thermostat or on the computer) that provides a continuous display of COP or EER. This can be done if we could measure the temperatures of the refrigerant at the entrance to the evaporator heat exchanger (T cold) and the entrance to the condensing heat exchanger (T hot).

    Then it would be simple formula: T hot divided by (T hot—Tcold) = COP

    The problem is that I do not know how to get these temperature measurements. Maybe the manufacturer can be convinced to add this.

    Your thoughts?

    Don Lloyd

    Author of “The Smart Guide to Geothermal” , PixyJack Press,

    • http://www.smartguidetogeothermal.com/ Don Lloyd

      With regard to my previous comments, I must make it clear that the temperature measurements must be converted into Kelvin to make this work.

      Don Lloyd

    • Lev Zvenyach, PE

      Hi Don,
      Your calcs will only give maximum possible COP of compressor represented by the Carnot Cycle. Actual heat pump refrigeration cycle is vapor compression refrigeration cycle that is by default is less efficient. In addition, it would not take in the account all other losses (or in case of heat pump additional work necessary to overcome refrigeration cycle limitations). Your maximum theoretical COP could be as much as 60% better than actual.

  • Michael Breckon

    This white paper by Ryan Carda comes right from Chapter 2 “Performance of GSHP Equipment” of the IGSHPA (International Ground Source Heat Pump Association) manual. Too bad people’s only interest in this book is to pass the exam before it becomes a paper weight.

    • http://www.heatspring.com Chris Williams

      Michael,

      Yes it is. Ryan authored it and gave us consent to report. I’m confused what you about people passing the exam, if this a bad thing?

      Chris

  • http://smartheating.org Bruce Gray

    I could not get your form to work, the bottom part does not show, it is eclipsed by the size of the form.

    Can you email to: education@smartheating.org

  • Ed_Resor

    Eng. Carda,

    Thank you for sharing an excellent and practical article. It is nice to see that some manufacturers are offering optional sensors and memory to calculate and store this data for up to 13 months. I hope continuous data will show that the actual COP for many heat pumps is significantly higher than the standard full load COP tested at 32 degrees, especially when the heat pump operates most often at part load and when a large enough ground loop does not drop to 32 degrees until near the end of winter.

    When investigating this test for an ice rink, I found that differential pressure gauges are available to simplify and improve the accuracy of the pressure measurements. Also, manufactures often provide a conversion table for pressure drop to gpm that is corrected for the use of antifreeze. As you note, a flow meter is difficult and expensive. A flow meter might be easier to connect to an open system where using both the flow meter and the pressure drop would provide a check for fouling of the heat exchanger.