INDIANOLA, IOWA — What would be a more fitting application for geothermal energy than an educational nature center in need of an HVAC retrofit? Well, that’s what members of the Warren County Conservation Board thought when the 13-year-old Annett Nature Center here was due for a makeover.
The Annett Nature Center (ANC) is a 9,500-sq.ft., three-story building on 160 acres. It rests on a hillside above a six acre lake and an even larger wetland area. Serving as a base camp for Conservation Board activities, ANC also has displays and exhibits on two levels, offices, kitchen, restrooms, exhibit and program preparation areas, and a garage. A large deck looks out across the lawn. The Iowa Department of Natural Resources, Simpson College and Indianola School District use the facility, and special events often take place here.
How it came to be
In 2009, Warren County received a grant through the Energy Efficiency Community Block grant program, part of the American Recovery and Reinvestment Act. The funds were allocated for an energy conservation project that benefits the citizens of Warren County.
Warren County’s board of supervisors saw a geo retrofit at ANC as the best choice for the funds; it would achieve energy savings while also providing educational opportunities about renewable energy. The new system went online in May. They’re also looking at the installation of a 20 kW wind turbine.
“We hope to break ground on the windmill project toward the end of this year,” said Jim Priebe, director for the Warren County Conservation Board. “It’ll be great to educate visitors and spread awareness of renewable energy sources with the new systems in place.”
In 1997, the original plans for ANC included a geothermal system, but when the building budget got cut, so did the interest in ground-source heat pumps. Instead, five LP gas furnaces totaling 520 MBH were installed to provide heat. Air conditioning was limited to office space, with additional ductwork being added a few years later to cool the rest of the building.
Wyckoff Heating and Cooling, based in Carlisle, Iowa, removed the old furnaces and installed the geothermal system.The third-generation company has 52 field employees and is involved in everything from residential retrofit to commercial design-build projects.
“We do 30 to 40 geothermal installations every year,” said Jerry Johnson, sales manager at Wyckoff. “Single family homes, townhouses, you name it. As a matter of fact, farmers are starting to take advantage of Federal and state tax incentives. We’re currently designing a geothermal system for an 86,000-sq.ft. hog facility.
“The heat load for ANC was calculated almost entirely around the heating demand,” continued Johnson. “Care was taken not to oversize the cooling element for the project.” Although the system’s installation took only a month, the design phase required almost six months.
A total of five ClimateMaster Tranquility 27 water-to-air geothermal heat pumps were installed in ANC’s basement to provide a total of 26 tons of year-round comfort control for the building.
All of the geothermal units distribute warm or cold air through existing ductwork that was connected to the old furnaces. Demand for domestic hot water at ANC, though typically limited to hand-washing and facility cleaning, is now met by a desuperheater, which scrubs heat from the geo systems during the winter months.
“We ran into only one challenge,” said Johnson. “Space in the mechanical room was limited.” Today, the roomis snug, chock full of pipes, Bell & Gossett circulator pumps, and Tranquility 27 heat pumps, all close in proximity and locked in step to meet ANC’s comfort and domestic hot water needs.
A large, flat hilltop on the east side of the building is used as ANC’s front lawn. Here, activities and weddings are held throughout the spring, summer and fall. Managers at ANC wanted to avoid disturbing the area if at all possible, and McNair Geothermal had the answer.
Subcontracted by Wyckoff to install the geo-exchange field, McNair brought in one of their large, track driven horizontal-bore rigs. With the machine, a great deal of know-how and a good operator, the pristine lawn and the soil below it were turned into a high-performance heat source in the winter, and a heat sink in the summer — with no heavy rig damage in sight.
“I run one horizontal bore-drilling rig almost non-stop right now,” said Ed McNair, owner of the company. “I sold half my company to my son in July. He runs another rig full time, and we share a third, depending on who has the heaviest work load”
McNair’s son, Landon Toney, began managing the eastern portion of Iowa for his father’s firm around two years ago. Since then, Toney’s knack for the work, and an increased demand for ground-sourced heat pumps has allowed him to branch out on his own, forming Eastern Iowa Geothermal.
“Together, Dad and I average around 2,000 tons of geo-exchange each year using this equipment,” said Toney. “We cover the entire state of Iowa, northern Missouri, western Illinois, and South Dakota.”
To serve the 26-ton geo system at ANC, McNair installed 18 loops, 300 ft. each. All of the loops offer a capacity of roughly a ton-and-a-half. The 1-in. geothermal pipe was pulled through the boreholes while being backfilled with a 40% bentonite grout solution to ensure optimal soil contact and heat transfer.
“Here in Central Iowa, we’re pretty fortunate to have deep, wet yellow clay,” explained McNair. “It not only allows us to bore easily, but provides the ideal environment for a geothermal exchange field.”
Horizontal boring — which moves easily through heavy, sedentary layers of clay not far from the earth’s surface — is preferred over vertical boring in Iowa for this reason. Also, Iowa law considers anything deeper than 20 feet to be a well, requiring a permit. The issue never arose at ANC with an exchange field that only goes to 15 feet below the surface.
Compared to the price of using a vertical well drilling rig, horizontal boring comes out on top. According to McNair, each ton of geothermal capacity installed using his horizontal bore rigs costs about $1,300.
Connecting all the loops along one side of the exchange field called for the only actual excavation involved in the project. The bore rig was used to tunnel under the foundation from the end of the trench closest to the building. The bit was guided flawlessly through a round hole cut into the basement’s concrete floor. The out-flowing coolant lines were brought into a manifold, making a single pipe, as were the in-flowing tubes. These large, single pipes then feed the five ClimateMaster units.
“The installation work came together in textbook fashion,” concluded Johnson. “When they add the wind turbine, my guess is they’ll disappear from the grid altogether.”