2021 Webinar Series - 21 Designing Utility Scale Ground Loops

Designing Utility Scale Ground Loops: Special Considerations

Geothermal designers are being asked to extend their experience with large campus systems, with commonly owned buildings, to a broad, modular thermal utility capable of supporting an entire city. This session will outline examples of a series of connected ambient loops, similar to a domestic water distribution system. The loops exchange thermal energy with water-source heat pumps installed in area buildings. Hybrid elements can be added to cover peaks or to operate micro-districts until enough load diversity is added to level the system’s loop temperature, reducing or eliminating the need for hybrid inputs.


  • Cary Smith / GreyEdge Group
  • Garen Ewbank / GreyEdge Group







        1. Please, today or tomorrow, write Anna Taylor,  anna_taylor@schumer.senate.gov, Majority Leader Schumer’s Tax and Trade Counsel. Please request that the Senate move the geothermal tax credit back to 25D, and in your own words tell her what the loss of the credits for new construction and the 10K cap would mean for you and your business.
          1. [Garen Ewbank]  it is a concern in both residential and commercial; we need a level tax program and ground source-geothermal-ambient temperature loops included.
        2. Where in Connecticut is this residential Loop?  How old is it?  Is it in full operation?
          1. [Garen Ewbank]  It is not in operation; the first item is training for the work force and that is being set up. Next is the complex systems architecture and then the designing and then the installation. Using the MESA program.
        3. One concern that I see when it comes to the idea of drilling individually under homes or buildings in order to install geothermal systems, apart from the fact that there wouldn’t be enough rigs to go around, is the potential negative impact this type of mass construction may have on ground stability. Imagine the high variation in landforms and geology scattered across the country, these mass underground construction may induce high rates of seismic activity in less-stable regions, which may pose threats to the safety of humans and infrastructure. Hence, microgrid configurations sound like a good approach to me
          1. [Answered Live] ;..Concerns about ground stability and protection of groundwater resources are on the radar of the ground source heat pump industry.  Stability is not as big an issue as you might think as the vibrations from the type of drilling and the size rigs are hardly noticeable to things like an adjacent house. It surprises most people who think it will make the neighbors dishes shake - it doesn’t in our experience. 
            The comment about seismic activity comes up from time to time, since there are some documented cases of deep extraction wells for oil, gas and hot rocks geothermal applications causing instability.  The vast majority of the closed loop, ground source heat pump drilling had effectively no extraction of materials from the earth - it’s just a way to access thermal energy in relatively shallow bores.  The wells are also grouted from bottom to top with a non-permeable grout to prevent contamination between different layers of the aquifer.  So not nearly as deep, no extraction and filling with grout all lessen any negative impact in the communities that adopt this clean energy technology.
        4. Please explain what exactly you mean by "plug and play"
          1. [Garen Ewbank] components on the ambient temperature loop to use as heat sinks and sources such as existing boilers and cooling towers, waste water heat exchange, solar PVT—etc.--.
        5. Great presentation - shows this can be done.  How long do you think it will take for these concepts to take hold on a mass scale?
          1. [Garen Ewbank]  This is the only scalable program and can start tomorrow.
        6. Reminder: that the recent project in NYC near that overpass, the drilling turned out to be a non-issue.
        7. Is there a certification process being considered so that competent people design these systems?
          1. [Garen Ewbank]  Absolutely, the Accredited Installer  (AI), Certified Geothermal Designer (CGD), and the Certified Geothermal Inspector (CGI).