On May 26, 2008, the small, rural town of Parkersburg, Iowa, (population 1,900) was nearly leveled by an enormous EF-5 tornado — the most devastating twister to strike the Hawkeye state in decades. Packing winds estimated by the National Weather Service in excess of 250 mph, the storm unleashed a 43-mile-long path of destruction spanning three counties. But it was Parkersburg that took the biggest hit — eight people killed, 282 homes demolished and another 400 heavily damaged — 23 businesses lost including City Hall, the town’s only grocery store and the Aplington-Parkersburg High School.
Despite the destruction, there was never a question that the resilient folks of the community located in northeast Iowa would rebuild. By sunrise the next day, fleets of equipment had arrived on the scene and cleanup was under way. The same day, school administrators met to begin laying the groundwork for rebuilding the school.
Shortly thereafter, architects were commissioned to submit bids for rebuilding the school. Design specifications were to include two noteworthy features: a geothermal heating/cooling system and a lower-level storm shelter — just as a precaution.
Superintendent Jon Thompson said the decision to go geothermal made sense on several fronts. He and the five other committee members who led the rebuilding planning process researched as many options as possible given the short timeframe.
“We conducted energy audits, plus, we visited with other schools in our area that have had success with geothermal,” Thompson says. “It quickly became evident that geothermal was the way to go. A geothermal system was the most economical and cost-efficient for the majority of the new building.”
Although Thompson admits installing geothermal costs more up front than a conventional system, the monthly savings in reduced energy bills over time will help free up money for things more directly related to education — such as new textbooks, computers and teachers.
“Schools have different pots of money to pay for different types of things,” Thompson explains. “Installing a geothermal field costs more initially, but it’s money that comes from a separate pot, not from school operating funds. We were also able to receive assistance from various sources after the tornado to help fund construction. Reducing our monthly utility costs created more dollars from our operational fund to do thing like buy textbooks and hire more teachers.”
The committee determined the most efficient route was to combine geothermal with a conventional system that will be used to heat and cool the gym only. Thompson explained the rationale.
“One of the things we discovered is that for large, open spaces, geothermal isn’t as efficient as in areas divided by rooms with lower ceilings,” Thompson says. “I’m not an expert, but it has something to do with the amount of air that has to change over. In the case of the gym, an area that isn’t always occupied, a conventional system was the more cost-effective approach.”
A-One Geothermal, based in Earlham, Iowa, was selected to install the geothermal system after participating in an extensive bidding process. Founded in 1975, the family-owned business has a long geothermal installation track record. A-One got its start installing water and sewer lines and then during the 1990s, expanded services to include fiber-optic installations using horizontal directional drilling (HDD).
Over the years, A-One founder and vice president Dale McNair had always been intrigued by the geothermal concept, and took the initiative to learn more about it. When the fiber-optic market went bust in early 2000, McNair had become a geothermal expert and decided to make it his core business.
“We were installing geothermal systems in the 1970s, long before most people had even heard of it,” McNair says. “When the fiber market began nose-diving, we were well-positioned with geothermal. As geothermal became more popular, so did the demand for installers. It now accounts for over 90 percent of our business.”
Stay in the Loop(s)
A typical geothermal system features several loops buried underground either vertically or horizontally. The loops — extending 200 ft or more, depending on the need — are filled with environmentally-safe antifreeze and connected to a geothermal heat pump.
During the heating cycle, the system automatically pulls heat from the ground via the antifreeze in the loops and circulates it through the geothermal heat pump, which concentrates the heat and distributes it throughout the structure via duct work. At the same time, the antifreeze constantly cycles back through the loops, where it reheats, and the process repeats itself.
Often the first step in the installation process is to complete a conductivity test. Since ground composition varies from site to site, conductivity results help to more accurately project the potential energy storage capacity of a specific formation. This is especially important for larger installation projects.
McNair prefers the HDD approach for installing the U-shaped loops, citing a number of advantages. “HDD is a more cost-effective installation method,” McNair says. “It also takes less time and fewer resources than vertical drilling. There is also less ground disturbance and more field installation options. We’ve installed horizontal systems under parking lots, driveways, existing structures and athletic fields.”
McNair’s fleet of HDD equipment includes four Vermeer models of varying size. His crew used a Vermeer D36x50 Navigator model to install the geothermal field at Parkersburg. The field consists of 58 loops and stretches 420 ft from north to south, installed in “piggyback” formation with one line at a depth of approximately 30 ft and a second installed directly above at 15 ft. Bentonite grout, a substance that helps maximize conductivity, is pumped into each of the bores as the loops are pulled back through.
The series of loops connect to several 8-in. supply lines that feed to an underground “vault” where the fluid-filled loops transfer the stored energy to the high school. The entire configuration was installed directly underneath the school’s softball field with minimal disruption. The project took eight weeks to complete.
The number of loops necessary to support a specific system is determined by the size and condition of the structure and the capacity of the ground formation to store energy. The amount of energy generated by each loop will vary by design. McNair explains that in order for a geothermal system to operate at peak efficiency, accurately calculating the size of the system, i.e., the number of loops needed, is critical.
“There is a tendency for most people to think the bigger the system — the more loops — the better,” McNair says. “In reality, nothing could be further from the truth. With geothermal, it’s all about being able to accurately calculate the requirements of the structure and nothing more or less.”
No one disputes that it costs more up front to install a geothermal system. But there’s also no disputing the energy savings and payback. All systems begin paying for themselves immediately in the form of monthly energy savings, and the additional up-front investment is likely recouped within four to six years, depending on the size of the system. McNair says a conservative estimate for monthly utility cost-savings is 50 percent, while many systems can save up to 70 percent over the cost of operating a conventional system.
Not unlike the example shared by Thompson, whose school can now afford to buy more textbooks and computers with funds that previously would have gone to paying monthly heating bills, the same can be said for any homeowner, business or nonprofit organization who chooses the geothermal route. And once installed, maintenance is minimal and repairs nearly nonexistent.
Randy Happel is a features writer for Two Rivers Marketing, based in Pella, Iowa.