Chattanooga: Geothermal system relies on ground temperature to heat, cool

Chattanooga: Geothermal system relies on ground temperature to heat, cool
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by Amy Williams

Before this week, the layers of red clay and limestone stretching hundreds of feet down beneath the ground near the corner of Main Street and Rossville Avenue might have gone unnoticed.

This week, well diggers began drilling six 280-foot holes into the ground on Chattanooga’s Southside, and the result could mean significant savings in energy costs for Greenspaces, a three-year, $2 million green building initiative backed by the Lyndhurst and Benwood foundations and RiverCity Co.

The holes, or wells, will be used to power a geothermal heat pump that will heat and cool the group’s new digs in a renovated 2,400-square-foot building at 63 Main St.

Greenspaces’ goal is to encourage local builders and designers to develop more energy-efficient and environmentally friendly buildings in Chattanooga. So when the group began looking at ways to heat and cool its building, officials wanted it to reflect the initiative’s mission, said Jeff Cannon, director of Greenspaces.

“When we started the project, we were looking at getting the most energy efficient (heat pump) models we could,” Mr. Cannon said. “(A geothermal heat pump) fits our mission by not putting any undue strain on the environment and it consumes less electricity.”

The new space on Main Street, which occupies a renovated building, will house the group’s offices and resource center, providing economical, green-building solutions, he said.

After getting price quotes from companies that did geothermal and heating, ventilation and air-conditioning work, Mr. Cannon said, the group quickly realized geothermal energy might not be too expensive.

That’s when Richard Parsons of Ringgold, Ga.-based Engineered Services Co-Operative stepped up and offered to do the work — which normally would cost $60,000 — for $48,000, the most that Greenspaces could afford to pay.

The geothermal heat pump could mean a reduction from 25 percent to 50 percent in heating and cooling costs when compared with air-source heat pumps, according to the Tennessee Valley Authority’s Web site.

The savings could mean the geothermal heat pump would pay for itself in 10 years, Mr. Cannon said.

The case for GEOTHERMAL energy

* Up to 40 percent reduction in heating and cooling costs

* Standard, simple controls

* No need for a highly specialized chiller technician or boiler operator

* Highly durable piping (30 and 50 years life expectancy)

* No high-maintenance, freezing-prone cooling tower

* No boiler to clean or maintain

* No air conditioning equipment on roof to cause leaks

* No harmful chemicals

* No danger of fire, asphyxiation or explosion from coal, gas or oil

* Nothing outside to vandalize or steal

* No central system to fail or shut down the entire building.

Source: www.tva.gov

Unlike traditional HVAC systems, geothermal heat pumps use the ground for its heat transfer medium as opposed to air, Mr. Parsons said, and they can be used in commercial and residential projects.

The wells at Greenspaces will be buried on a public utility easement owned by the city. At its highest point, the system will sit 4 feet under surface of the ground — just below the frost line. At its deepest, it will go down 280 feet.

Altogether, six wells are planned to account for the size of the building.

Once the 6-inch-wide holes are cleared, 560 feet of 1-inch wide polyethylene pipe will be pushed into each hole and looped back up.

The system relies on the fixed temperature of the ground, which is between 52 and 58 degrees, according to experts.

A synthetic solution will circulate through the piping, exchanging cold air for heat in the winter and warm air for cooler in the summer.

To drill on the strip of land owned by the city, the Chattanooga City Council voted in May to allow Greenspaces to use the property for the wells, something Mr. Cannon said set a precedent for city government.

“They were 100 percent behind it,” he said.

District 2 City Councilwoman Sally Robinson said she is interested in innovative conservation projects that work to reduce the carbon footprint of the community. She hopes the project will serve as a model to businesses that could consider adopting them as best practices.

“It’s just a very smart way to do things,” she said.


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