Innovations to Reduce the Cost of the Closed Loop Ground Heat Exchanger

Although we advocate installing closed loop systems for the reasons stated in my previous post, this does make it difficult for us to be competitive with the majority of other contractors who cling to “pump and dump” (open loops) in order to install geothermal heat pumps for the least cost. Unfortunately, in recessionary times like these, consumers are less concerned with life cycle and environmental costs than they are with initial installed cost. It makes no matter if their open loop system may have half the life span of a closed loop, if installing an open loop system at two thirds (or even half) the cost will get them the same utility rebates and government incentives. As I am not the greatest salesperson and have yet to find a program that shows me ROI of closed loops vs. open loops, I find myself losing these jobs more often than not. Despite all of the benefits, most potential residential geothermal consumers are unwilling to pay the additional price tag of a properly designed and installed closed loop system. This is why we need to find more significant ways to reduce the cost of the ground loop heat exchanger.

By far the largest cost component of the GHEX (ground heat exchanger) is bore drilling. In our area, typical costs to drill and install the GHEX can be anywhere from $17 to $20 per foot. At a typical bore depth of 180-200 feet per ton of cooling, a cost of $3000 to $4000 per ton for just the ground loop can send most consumers back towards open loops or conventional fossil fuel/electric systems. That is why it is essential to do a proper Manual J load analysis with all of the relevant envelope information to make sure that you are not over-sizing the equipment and pushing folks away. Another factor, at least in the metro New York area, is how relatively few certified ground loop installers and drillers there are. Fortunately, these costs are coming down as more drilling contractors get IGSHPA certified and familiar with installing closed loops as an additional revenue stream as compared to standard domestic water and geothermal wells. However, with the renewable energy tax credit sun setting in 2016, do we have time for this economy of scale to happen without some technology push? Probably not.

Rygan HPGX

Enter the entrepreneur who finds ways to wring more thermal performance and BTUs per foot out of a GHEX through innovation. Take, for example, the Thermonexus HPGX by Rygan and the Kelix Thermacouple, two GHEX innovations developed to reduce required bore depths and increase thermal performance. With a 300′, 6″ round bore, Kelix claims that their Thermacouple “supports heat transfer rates of up to 5 tons (60,000 BTUhr) with deep Earth environments rich in aquifers”. While Rygan makes no specific claim on thermal performance, they do say, “HPGX® advanced materials offer the toughest and highest yielding thermal performance of any closed geoexchange system”. The real question is, how much actual cost will installing these high thermal performance GHEX systems save the contractor and consumer? Also, how can we estimate thermal performance for these systems in different regions.

This link will take you to a data logging site that shows the live performance of three types of ground loop heat exchangers operating now. The top system is a 5 ton Earthlinked DX system (refrigerant) which we have not discussed here. The second system is a WaterFurnace Envision system operating on 2- 500′ standard U loop bores. The third system is apparently a Carrier 5 ton water source heat pump operating on a Kelix 300′ Thermacouple.

As always, to keep up to date with what’s new in HVAC technology, visit our website at airideal.com and follow us on Twitter @airideal and at our Facebook page!

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2 comments on “Innovations to Reduce the Cost of the Closed Loop Ground Heat Exchanger

  1. Dave says:

    Good article – thanks for the info. Are you aware of anyone laying a loop in foundation trenches during new construction, just as a supplement to a traditional air-source heat pump? That seems like a good way to boost performance with minimal cost, but maybe there are things i’m not thinking of. I wrote a blog post on it here: http://creativelogical.blogspot.com/2011/08/air-source-heat-pump-with-ground-assist.html

    • airideal says:

      We are very reticent to install horizontal ground loops around a foundation wall. Firstly, there are plenty of issues with freeze/thaw and expansion and contraction that can cause foundation problems. I have seen pictures where such installations have cracked or buckled a foundation because of ice. Secondly, horizontal loops will require more like 400-600 feet of ground loop per ton and perimeter circumference will most likely not give you the conductivity and heat transfer you are looking for.

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