Annett Nature Center
Geothermal System
Goes Online
In 2009, Warren County received funding through the Energy Efficiency Community Block Grant program, a part of the American Recovery and Reinvestment Act (ARRA). The funds were allocated for an energy conservation project that will benefit the citizens of Warren County. After looking at a number of options, the Warren County Board of Supervisors decided that a geothermal and wind energy project at the Annett Nature Center was the best option to achieve energy savings and provide educational opportunities about renewable energy. While details of the wind energy phase are still being worked out, the geothermal phase went online Tuesday, May 18, 2010.
Geothermal is literally heat from the earth. Ground-source heat pumps use the earth or groundwater (the earth in the case of the ANC) as a heat source in winter and a heat sink in summer. Using resource temperatures of 4°C (40°F) to 38°C (100°F), the heat pump, a device which moves heat from one place to another, transfers heat from the soil to the house in winter and from the house to the soil in summer (from the Geo-Heat Center).
Accurate data is not available on the current number of these systems; however, the rate of installation is thought to be between 10,000 and 40,000 per year. The current production of geothermal energy from all uses places third among renewables, following hydroelectricity and biomass, and ahead of solar and wind. Despite these impressive statistics, the current level of geothermal use pales in comparison to its potential. The key to wider geothermal use is greater public awareness and technical support (Geo-Heat Center). The Annett Nature Center will use this project to provide education on geothermal systems and their potential benefits in many applications.
Wyckoff Industries of Carlisle, Iowa, and their subcontractors, moved on-site in mid-April. The first order of business was to begin installation of the geothermal field. Horizontal loops were bored under the field east of the Nature Center at a depth of about 15 feet. Horizontal boring minimized soil disturbance in a high-use area of the Annett Nature Center grounds. Using the near constant soil temperatures at the depth, the loops use fluid pumped through the tubes to transfer heat either out of or into the building. New heat pumps, some needed electrical upgrades, and a new water heater were installed. The geothermal field was pressure tested, filled with a water/methanol mixture, purged of air, and any leaks between the manifolds and the heat pumps were sealed.
The boring rig pushed, dug, and drilled pipe through the geothermal field.
Pipe was automatically fed through the rack shown here and attached to the previously bored pipe. Depth and position of the line was controlled by a radio in the boring head that relayed a signal to a worker carrying a receiver and walking above the line.
When the line emerged on the other side of the field, it was attached to the geothermal tubing and pulled back through the hole. The hole was injected with a bentonite solution to insure good soil contact with the geothermal tubing. Eighteen one-inch tubes were put in the field in order to make nine loops. Nearer the building, three loops each were tied together into two-inch tubes and fed into the mechanical room in the basement of the nature center. In the basement, the three out-flowing tubes were brought into a manifold, making a single pipe, as were the in-flowing tubes. These large, single pipes then feed the circulaton to the five heat pumps and the water heater.
After the lines were installed, a backhoe was used to dig a trench to allow the loops to be sealed and buried…
all without disturbing the open space above the geothermal field.
Two sets of two-inch tubing (a third would be added soon) circulate the geothermal field through the ANC mechanical room. The previous furnaces (natural gas) can be seen in the background.
Close up of the feeder lines coming into the ANC basement. The boring rig was flawlessly guided by radio to hit this hole.
No heating or cooling of any kind! The old furnaces and water heater have been removed.
The first of five heat pumps (a total of 26-tons capacity) to be fitted to the old duct work.
The feeder lines were tied into two manifolds (inflow and outflow) that feed the new units.
Another view of the manifolds.
The new water heater is also powered by the geothermal field.
The diagram above shows how the fluid in the geothermal field flows to and from the nature center.
