Laying the groundwork for agricultural use of groundsource energy
Just a few feet below the surface of the Earth — seasonally baked dry in summer’s heat and frozen solid in icy winter months — the soil remains a stable 55 to 65 degrees Fahrenheit, depending on the location. This constant temperature represents an incredible source of environmentally friendly, sustainable energy to heat and cool the buildings where we live and work. Ground source energy is an endlessly renewable resource that is not dependent upon the wind blowing, the sun shining nor the burning of fossil fuels. The U.S. Environmental Protection Agency has rated it one of the most efficient of heating and cooling technologies.
For more than a decade, Shawn Xu, an associate professor with the University of Missouri College of Engineering’s Water Resource Center — under the umbrella of civil engineering — has been installing large-scale ground source heat pump systems. His most recent project, partially funded by the U.S. Department of Energy under the American Recovery and Reinvestment Act, is a demonstration project on a large turkey operation in Missouri’s Cooper County. Xu is partnering with the farm’s owner, Chris Holliday, to equip brooder houses, which have notoriously high heating costs, with ground source heating. Work being shared by the pair could fundamentally change the way the poultry industry operates.
“There are 38 [ground source heat pump] projects nationwide,” said Xu. “But I am the only one to propose an agricultural application. I just looked at it from the perspective of who spent the most for propane.”
Ground source heating and cooling systems function by circulating water through a continuous loop of pipes buried underground. In winter, the water in the pipes transfers the earth’s heat into the building and in summer, the circulating water brings cool air into the building, transferring heat back into the ground.
Traditionally, system installation has been achieved by drilling deep vertical holes into the earth. This intensive excavation increases installation costs, whereas Xu’s ground source system design places the pipes horizontally, eliminating the need to drill deep holes, cutting installation costs by up to 30 percent. High initial costs have been the biggest barrier to widespread conversion to ground source systems.
“Horizontal systems are less expensive,” said Xu. “These underground loops will provide almost free cooling for the barn and return heat to change the soil temperature for use next winter.”
When completed, there will be wetlands covering the ground above the construction, which will help with runoff from the large buildings, and will also serve as insulation to keep heat in the ground during the winter.
Holiday said energy costs to raise turkeys are outrageous explaining that, as poults, turkeys require the brooder house to be at a temperature of 90 degrees. “And adult turkeys like a constant temperature of 70 degrees,” Holliday said. “They feel good at that temperature and will eat better.”
Holliday said he raises four broods each year, spending an average of $50,000 annually on propane. “I can burn 3,000 gallons in one week,” he added.
Because he contracts with Cargill to raise turkeys — which splits the cost of propane with him — the company is keeping a close eye on the project, weighing its potential for the entire industry. Xu predicts energy costs will be reduced by 50 to 70 percent.
Holliday, who owns and operates a construction company, was able to do the installation of the system. “I didn’t have to bear the burden of the entire construction myself, and that really made it worthwhile,” he said.
Both Xu and Holliday are hopeful that the project will serve as a model that will provide future geothermal construction projects for them and others.
As this story is published, heat pumps for the first brooder house are installed and are undergoing testing. Work soon will begin on Holliday’s second brooder house, which will use solar-assisted heat pumps. Plans are to install cooling systems for the farm’s two additional barns where adolescent turkeys are raised to adulthood.
“I’d really like this to work,” Holliday said. “No farmer is going to step out like I did, but after they see this work, they’ll all want to do it.”