Around here we do things a little differently, but Twisted?
The first borehole geo system I ever saw hurt. Reason being I was the drillers helper and it’s hard work especially for a 150 lb scrawny guy.
Looking at the hole with 2 pipes randomly in it surrounded by grout which has a thermal conductivity ranging from near styrofoam all the way up to better than styrofoam, I figured there must be a better approach. There were methods to improve the TC of the grout (thermal conductivity) up from around .4 to .8 or better. A good TC in rock is maybe 2.0 so you get the point of the styrofoam. I started researching and formulating my own grout materials and even tried graphite, so messy.
At a trade show in Germany I saw a double U-tube for the first time. It uses spacers to hold the 4 pipes up against the wall of the borehole where the action is, so the grout material didn’t matter as much. I ordered some spacers and drilled a 600 ft hole. One single hole for a 5000+ sq ft home! The results were amazing and we did more and more of these. The only drawback was that it was a lot of work to arrange and get this much pipe down a hole.
Then I saw a Twister borehole heat exchanger and had to try this out. It seemed like a natural progression from the dU-tubes without the work. An improved quad U-tube with a twist! The manufacturer, agreenability.com claims 30% less drilling but my own results show even better.
