Horizontal - Closed Loop
◦ Definitivel Loop design - horizontal borehole closed loop heat exchangers consist of a design that is directionally drilled at an angle to about a 15 feet depth then levels off into a horizontal plain. The angle portion of this horizontal bore will be closer to the earth's surface requiring extra pipe to offset the seasonal extremes in soil temperature and soil drying near the surface.
◦ Horizontal boreholes are usually separated about 20 feet apart horizontally and can have multiple layers that are usually 15 feet deeper than the layer of horizontal borehole above.
◦ Horizontal borehole are not normally as energy efficient as Vertical bore systems because of the extra pipe because the insertion point into the ground is at at the ground surface where the ambient temperature swings during the year have the greatest effect of the ground loop. Horizontal borehole usually require a greater land area than vertical boreholes and have limited use on large buildings because of the land area requirement.
◦ Ground loop design using horizontal trench loops closed loop heat exchangers can have a single straight pipe or multiple pipes installed in a trench. Multiple pipes in a trench can reduce the trench length when in a compact area.
◦ Horizontal trenches can also have the coiled (slinky) arrangement as a substitute for the multiple pipe arrangement.
◦ Horizontal trenches are shallow with the pipe installation laying in a trench that is closer to the earth's surface require extra pipe to offset the seasonal extremes in soil temperature and soil drying near the surface. Horizontal trench systems are not normally as energy efficient as Vertical bore systems because of the extra pipe required and have limited use on large buildings because of the large land area requirement.