An Earthlinked Earth Loop Installation Demonstration

1. An Earthlinked Earth Loop Installation Demonstration Using inexpensive boring machines in lieu of 100% excavation to install an H5 Pit Earth Loop Configuration

2. The Challenge Texas geothermal well drilling is governed by the Texas Department of Licensing and Regulations (TDLR) and currently, there are only 800 licensed geothermal well drillers in the state of Texas. Of that number, less than 400 have any interest in drilling geothermal wells. Concurrently, Texas has over 14,000 licensed HVAC contractors. This creates a huge imbalance of available resources for installing geothermal and, accordingly, makes it very difficult to reach the critical mass stage for any geothermal installation business in Texas. Add to this dilemma the lack of appropriate drilling equipment and a much larger barrier must be overcome for direct exchange geothermal to achieve any volume.

3. A Work Around • TDLR defines a geothermal well as follows: • Closed Loop Geothermal Well--A vertical closed system well used to circulate water, and other fluids or gases through the earth as a heat source or heat sink. • Because the definition includes the term vertical, a horizontal system is clearly not regulated by the water well driller rules in Texas. As far as that goes, a diagonal well may not meet the criteria of vertical either. However, there is only so much of the elephant that can be consumed in one sitting so we’ll save that battle for another day. • Earthlinked installed a horizontal pit at their headquarters in Lakeland, FL, with earth temperatures about 5° warmer than North Texas so, it stood to reason that a horizontal system would work in Texas. It just needs to be demonstrated.

4. A Work Around • In discussions with Earthlinked about this approach, a couple of things about horizontal pits stood out: • That’s a lot of dirt to excavate and pile up, particularly if it’s a small lot • That’s a lot of disturbed soil to compact back and the reality is it will never reach the level of compaction it had before excavation which impacts the soils ability to transfer heat. • Our idea was to bypass as much of the excavation as we could, bypass as many TDLR rules as we could and have a superior transfer of heat with the ground.

5. The SolutionWe are installing a 1.5 ton system for a small cabin in Parker County, Texas. In lieu of excavating all 185 or so cubic yards of dirt, we excavated 90 cubic yards from three separate pits, one on each end and one at the Ell (denoted by the red lines below). We bored 8 holes 2’ apart from the pit at the Ell in both directions. Since we were doubling the spacing between the earth loops from 1’ to 2’, we expanded the width of the pit from 10’ to 16’ and and shortened the length of the loops from 54’ to 49’ to allow for the additional space between the loops.

6. We leveled the bottom of the pits with a laser, then marked the elevation of the bore holes and spaced them 2’ apart with marker paint. It is critical that the bottom of the pit be level in all directions.

7. Once the boring machine was level, we lined up the bore stem of the machine with a survey stick and carpenter’s level to ensure the survey stick was plumb. Using this approach, we had very good luck hitting our target in the other pit. Getting the hole at the right elevation in the other pit required the pit under the boring machine to be perfectly level. In these soil conditions, we learned to set the boring machine so the boring bit hit the center of our mark on this side of the pit and then we lowered the back end of the machine about 3” from level to compensate for the weight of the boring stem as the holes tended to drift downward as it bored through the sand and clay. The length of this bore was about 25’.

8. Bore holes are 2” in diameter and we pulled rope through the bore holes and tied off with pvc pipe stops. We believe boring all the holes , then pulling the copper and grouting the holes is a more efficient use of time rather than boring a hole, pull the copper, grouting and then repeating the steps. We also believe we could speed up the boring by laying down steel rails for the width of the pit to slide the boring machine across to bore each hole. This would make it easier to move the machine from hole to hole and ensure consistency of the pitch of the bores across the pit. It was tedious trying to get the boring machine at the same level as the previous bores each time we lined up the machine. We would have to shovel dirt out, check it with a level, shovel some more dirt out, check it again and on and on. Setting rails for the whole pit at one time would be much more efficient we think.

9. This is the swivel attached to the end of the bore stem for pulling back the line through the bore hole.

10. This is the pit on one end of Ell. As you can see, we were fairly close to our 2’ spacing. We were certainly well within the 1’ minimum spacing of the loops required in the manual. And the elevation for all the holes were consistent.

11. Cost wise, we are not clear yet if this approach is any cheaper than drilling. However, in the state of Texas, at least, it doesn’t require a driller’s license which we think will be helpful in recruiting dealers because the driller’s risk and regulatory risk has been removed from the equation in one fell swoop. By using this approach, we’ve reduced the amount of excavation by about 50% and reduced the amount of undisturbed soil for the loops. Also, this approach allows for additional spacing between the copper loops which should help with the heat transfer.We think we can reduce the amount of excavation at the ell an additional 15% for an overall reduction of 65%. For this job, we dug a 16’ x 16’ pit at the ell and after looking at the hole, realized we could have excavated at the ell as indicated in the diagram below and reduced the size of the ell pit by ½.