With Geothermal, it's good to be boring
“The government is committed to taking a look at geothermal on its projects,” stated Bruce Kunkle, special project sales with mechanical contractor R.W. Mead & Sons, Fraser, MI, a member of the Geothermal Heat Pump Consortium (GHPC) and the Michigan Geothermal Energy Association. Due to a memorandum of understanding which the GHPC negotiated with the Postal Service, as well as other government entities, geothermal systems are now automatically considered for all new and retrofit hvac projects.
He then found two subcontractors with quite a bit of experience in the field - loop contractor Michigan Energy Services of Brighton, MI and drilling contractor Earth Energy Loop Systems of Dewitt, MI - and he was able to get his price down to a reasonable level.
Kunkle remarked that if systems were selected just on upfront cost, “geothermal probably would never be put in.” Its benefit comes from long-term energy savings. Considering the long haul, the Postal Service selected the R.W. Mead bid.
The original design called for a vertical loop. As Rob Derksen, co-owner of Michigan Energy Services, noted, vertical loops are commonly used in commercial installations. But there was some concern about potentially explosive methane gas in that area since they would be going down 250 ft. Also, where the vertical loop was to be drilled, “yards and yards of concrete chunks had been buried to build a berm that goes around the perimeter of the property,” said Kunkle.
When the contractors saw the big hunks of concrete and the extensive excavation that it would require, they changed the design to a horizontal loop that would be located under the parking lot.
Kunkle pointed out that “It’s unusual to be going under 12 inches of concrete.” A difficulty with this approach was that the rebar in the concrete threw off the sensing device used for tracking the drilling head. Driller Jerry Shooltz was able to maintain the spacing between bores, but “he was not able to run in a straight line,” said Kunkle. Although the bores curve a bit, it does not affect the performance of the system.
“This loop can be an energy source for a minimum of 60 years,” stated Kunkle, providing long-term value.
FHP Manufacturing Inc. (Flor-ida Heat Pump), Ft. Lauderdale, FL, supplied the heat pumps - two 5-ton models. The application required 480-V units and the company was able to meet this requirement. A desuperheater is installed on one of the heat pumps to provide partial hot water heating.
No backup heat was specified originally. But Kunkle said that backup heat is recommended for this area and he convinced the Postal Service to add less than 5 kW of supplemental heat at 0Â¿F design temperature. “Proper engineering is critical” for a successful geothermal system, he emphasized, as well as “close supervision of installation.”
The installation was started the second week of April and it was completed by the beginning of July. Kunkle related that this is the first geothermal heat pump system installed in this district by the Postal Service.
By working to provide a reasonable price and on-time installation, he and his subcontractors certainly hope there are more to come.