AFRC first: Grissom goes geothermal to heat, cool

Published Nov. 7, 2013
By Tech. Sgt. Douglas Hays
434th ARW Public Affairs

GRISSOM AIR RESERVE BASE, Ind. -- Breaking ground on a building renovation also meant breaking ground on a first for Grissom and the Air Force Reserve Command.

When the renovations began in the spring for Bldg. 671, housing Grissom's maintenance operations and command post, base civil engineers sought a way to move into the green and save energy costs via geothermal heating and cooling.

Geothermal energy is clean, sustainable heat from the Earth.

Sam Pier, 434th Civil Engineer Squadron mechanical engineer, said he had some experience with geothermal exchange and wanted to incorporate the technology into the design.

"When we knew the building was going to be renovated, Wayne Raby, 434th CES project manager, and I sat down and thought about what type of systems we wanted to utilize in the 14,900 square foot facility," added Pier. "I had experience with residential type geothermal units and wanted to see if there was a way to incorporate that technology here."

While the use of geothermal energy to heat and cool facilities isn't an option in all cases, a study was done and the determination was made that it would work. So, Raby and Pier generated the requirement for the designers to incorporate the use into the renovation project.

Getting heat from the ground to come out in a register in an office starts well below ground - 300 feet below to be exact.

Crews drilled 28 wells 300 feet down, the last 240 feet through limestone, to install a closed-loop geo-exchange system.

To make it all work, water is pumped through a pipe, down through a vertical loop, called a circuit, and back in closed supply and return lines and into a vault where each can be isolated. Grissom has four vaults in its geo-exchange field, with each tying into a variable refrigerant flow system that heats or cools the facility based on the season.

Contractors Gus Callahan and Cristian Coffey worked the trenches hooking up the vertical circuits to the vaults in the geo-exchange field behind the facility.

"You're not going to stay clean doing this work," Callahan joked as he and Coffey worked in close-quarter trenches, two feet wide by about 6 feet deep.

While the geothermal loop installation may not be neat and clean, once finished, base officials estimate that it will be very effective.

"It's the combination of two super-efficient systems," Pier said.

AFRC is trying to reduce as much energy as possible, and it's a great way to conserve energy and use the ground as a heat source, Pier said.

"AFRC is excited about it and we are too," he added.

The cost of the installation ran about $100,000; however, he estimates the base should see a payback in energy savings in about 10 years or less.

"It's highly efficient, very low maintenance and redundant," Pier said. "If we develop a problem in a vertical circuit, we just shut down that circuit in the vault and utilize the remaining 27 vertical circuits until the repair is made - while still operating at 100 percent."

As more and more emphasis is being placed on energy conservation and going green when possible, Pier said that other geo-exchange loops may be used at Grissom in the future.

"We will look for those opportunities when we can, but the conditions have to be right," he said. "There are underground utilities and systems that have been placed in the past and the geo-exchange field takes up a sizeable area."

Grissom is home to the 434th Air Refueling Wing, the largest KC-135R Stratotanker unit in AFRC, as well as three Army Reserve units and a Marine Corps Reserve communications detachment.

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Finishing touches

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AFRC first: Grissom goes geothermal to heat, cool

Public Affairs Staff