Geothermal: Harnessing the Earth’s Energy

Michelle Peiffer

Michelle Peiffer

What is Geothermal Energy?

Geothermal Energy is heat (thermal) that comes from the earth (geo). The layers of the earth are heated in different gradients, originating from the 4,000-mile deep core, which has a temperature similar to that of the sun of around 9,000 degrees Fahrenheit (F). The heat gradually lessens as it reaches the surface of the earth, where the temperature of the top soil more accurately represents the temperature of the atmosphere. Just ten feet below the surface of the ground, the temperature of the earth maintains a constant temperature of 50-60 degrees F in all seasons. Geothermal heat pumps make use of the earth’s constant temperature as a natural source for heating and cooling.

Geothermal Power Plant

Photo courtesy of the Department of Energy.

Geothermal Energy has been used for thousands of years, dating back as early as 10,000 years ago on this continent when Native Americans used hot springs for relaxation and cooking. Today, we use this natural heat source in a variety of ways ranging from highly technical geothermal energy plants that use hot water and steam to generate electricity to individual home and business use for heating and cooling.

How Does it Work?

In a residential or business setting, a geothermal well field is determined based upon the heating and cooling needs and the size of the building. This field is the area where geothermal tubing is placed into the earth – or in water such as wells or ponds – and where the temperate maintains a constant temperature throughout the year. The tubing can be laid vertically or horizontally, depending on the site. The tubing is most often made of plastic, although other materials such as copper have been used. The tubing is filled with a liquid that runs into the earth, where it is either heated or cooled, and then brought back to the surface to assist in maintaining a more constant building temperature.

For heating: In the winter, the cool water from the building is sent into the earth, heated to a temperature between 50-60 degrees F, and then brought back into the building where it transfers the therms in order to heat the building.

For cooling: In the summer, the warmer atmospheric temperature is transferred into the tubing liquid at the ground level and circulated into the earth where it cools and returns to the surface, bringing down the temperature of the building.

Vertical Geothermal Loop Field

Photo courtesy of

Geothermal heating is especially beneficial in keeping a building’s temperature at a comfortable constant throughout the year. During extreme weather conditions, only small amounts of additional heating or cooling may be necessary.

What are the Benefits of Geothermal Energy?

According to the U.S. Environmental Protection Agency (EPA), geothermal heat pumps are the most energy efficient, environmentally clean and cost-effective systems for temperature control. Geothermal pump systems burn no fossil fuel on site and generate far fewer greenhouse gas emissions than conventional furnaces. Even considering the emissions generated from the electrical power plant used to operate the system, total emissions are far lower than conventional systems.

Geothermal energy owners enjoy lower utility bills (25% to 70% lower as compared to conventional systems), lower maintenance and higher levels of comfort year-round. Since geothermal energy systems use no fuel on site, a potential source of poisonous carbon monoxide within the home or building is also eliminated. The waste heat removed from the home’s interior during the cooling season can be used to provide nearly cost-free hot water, resulting in a total savings of about 30% annually while lowering emissions even further.

According to the U.S. Department of Energy (DOE) Office of Geothermal Technologies, nearly 40% of all U.S. emissions of carbon dioxide (CO2) are the result of using energy to heat, cool and provide hot water for buildings. This is about the same amount of CO2 generated by the transportation industry. If the number of residential geothermal energy systems reaches 100,000, the result would be a reduction of greenhouse gas emissions equivalent to removing almost 59,000 vehicles off the road.

Why is Geothermal a Good Choice for Green & Main?

The ultimate goal for this pilot project is to transform a mixed-use business and residential building into a demonstration building that highlights energy efficient technology as it merges with historical preservation, all the while striving to reach LEED Platinum certification. Since Iowa has such extreme weather fluctuations, geothermal energy is a perfect fit because it will keep the building at a constant comfortable temperature, somewhere between 50-60 degrees F, thus greatly minimizing the project’s need for additional heating and cooling.

When developing the landscape, the parking lot was the perfect place to position a geothermal well field. Engineers selected the position because of the proximity to the building and the ability to create a vertical closed loop design, which means that the tubing is inserted in the earth vertically rather than horizontally.

Geothermal Energy Systems typically have the lowest life-cycle cost of any heating and cooling system. Heating and cooling costs for the 4,700 square foot Green & Main building are estimated to cost around only $2 a day. Geothermal systems and installation have dramatically improved over the past years and costs associated with the system have dropped significantly, with an average payback of around 7 years.

Meet our Partners in the Well Field Installation, Barker Lemar.

Barker Lemar

Barker Lemar headquarters, West Des Moines, Iowa.

The engineering consultants at Barker Lemar were instrumental in the development of the geothermal energy well field at Green & Main. From the very onset, they provided a series of earth borings to test the soil for the system installation. Barker Lemar has long been experts in environmental drilling and, in the late 1990’s, furthered their reach by installing geothermal tubing. They have set the benchmark for performance by investing time and energy into educating the consumer and designer on such topics as conductivity testing, drilling methods and implementing overall keys to a successful project.

Barker Lemar was a natural fit into the best practices component of the Green & Main project. The expertise provided in the well field directly correlated with the case study being developed as part of the Solid Waste Alternatives Program (SWAP) grant. Using recycled content as an insulator for the geothermal tubing and measuring temperature gradients between supply and return lines, the study will allow us to compare different insulators and then measure each one’s effectiveness. Tracy Lemar, vice president of Barker Lemar, explains that the pipes in the building can be very close in spots, so using an insulator is one way to increase efficiency by preventing the pipes from transferring the heat back and forth as it’s exiting and entering the building.

Lemar designed the insulation system and originally considered using tire-derived aggregate (TDA). After careful research, the decision was reached to bypass the TDA because of load requirements from the parking lot that sits above the geothermal well field. Recycled glass was ultimately chosen as the best aggregate product for performance. Crushed glass looks a lot like sand and was poured around all the piping and buried in the trenches where the tubes are close together. The heat conductivity will be measured by thermal couples in the building where data will be collected from the trench. The data will then be used to compare the glass against other typical materials, such as insulation board, to measure the differences in conductivity.

Lemar said that the reason he chose to be a part of the Green & Main project was due to the developer’s vision, Chaden Halfhill. “I was very impressed with his vision on how to transform a building that was probably one of the least energy efficient in town, to one of the most energy efficient. We are very excited to be a part of this project and wanted to be involved in the mission.”


– Michelle Peiffer is director of communications strategy for Indigo Dawn.



    Pete Sherinian KFMG Radio/Green City.
    Very cool, The next show I do with Chaden should include this part of the buildings contruction.

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