Onamia School District Saves Energy and Money with a Geothermal System

The Onamia Elementary School in Mille Lacs County, completed in the mid-1990s, was the first large geothermal school project in Minnesota. With the completion of the Rolf Olsen Community Learning Center and the Lions Club Center in 2004, the elementary school is now one of three education buildings with geothermal systems operated by the Onamia School District. Superintendent John Varner couldn’t be more pleased with them.

“These buildings cost very little to operate,” said Varner. “But the biggest benefit is the absence of mold and mildew. We have no mold because the air in our buildings is conditioned. Mold cannot grow because there is never a time when the interiors of our buildings have high humidity.” Varner said that his buildings have been able to keep some areas carpeted and have not experienced any problems with staff or student allergies due to the superior air handling systems and the heating and air conditioning provided by the GeoExchange system.

When the first geothermal system was being designed for the elementary school in the early 1990s, the school received no state funding support. Legislators at that time were not interested in energy efficiency. In 2004, Varner appeared before the Minnesota Senate Education Finance Committee and the Energy Committee to ask for funding support for the construction of the Rolf Olsen Community Learning Center, again to no avail. But Varner was able to negotiate with the local electric utility for help. When it was designed and built in the early and middle 1990s, the Onamia Elementary School benefited from a special 10-year flat rate of $0.049 per kWh granted to all schools using GeoExchange systems by United Power Association (now known as Great River Energy), the electrical utility headquartered in Elk River, Minnesota.

The cost of Onamia Elementary School’s GeoExchange system was about $50,000 more than the estimated cost of a conventional heating system. “We paid a little more for the heat pump system, but we got air conditioning,” said Dick Seemers, district building manager during the time of the project. Energy costs have been much less during the school’s nearly 10 years of operation, in comparison with the costs associated with a conventional heating system.

To create the geothermal system, more than 50 heat pumps were connected to a field of 560 shallow boreholes with more than 10 miles of plastic pipe. Each borehole is about 5 inches wide and 50 feet deep. The pipes are plastic U-tubes inserted all the way to the bottom of the boreholes, like a giant horseshoe. The U-tubes carry a solution of water and antifreeze, which draws heat from the surrounding ground and carries it into the school, where the heat pumps extract the warmth.

In addition to the heat pumps, the school has a ground-source water-to-water chiller, which cools the air that ventilates the gymnasium. During the heating season, ventilation air for the gym and the rest of the school is heated by hot water supplied by the neighboring high school’s natural gas boiler. That boiler also provides service hot water for the elementary school.

The Rolf Olsen Community Center and Lion’s Club Center buildings, completed in December 2004, have 164 wells that provide the basis for the shared geothermal system that they use. Falk Brothers Well Drilling of Hankinson, North Dakota, was the geothermal well contractor. TSP Architects of Minnetonka designed the buildings.

“Once again, we had a higher cost initially to install the heating and cooling system, but long term, our tax savings through energy credits and our energy cost savings will be large,” said Superintendent Varner. “We estimate a seven and a half year payback for the new geothermal system, and then very low energy costs for the next 40 years.”

In addition to the geothermal system, the two new buildings have other energy efficient design elements. All the glass is triple -glazed, the bathrooms have occupancy sensors that control lighting, and the hot water runs off the geothermal system, so no additional hot water heaters are required. The buildings are super insulated above the state building code. Multiple thermostats control multiple zones. An energy management system shuts down areas that are not in use, and cools the buildings at night. The latest in T-8 fluorescent lighting was installed. Special pumping system controls allow the geothermal pumps to ease into operation so they do not draw a surge of electricity on start-up. The control system for the buildings was custom-designed.

“Our next step is the renovation of the 80,000 square foot high school,” said Varner.“ It has a 1973-era boiler running on natural gas. There was a time when we used sawdust to feed the boilers, but the supply of sawdust just wasn’t steady, so the district took out that system.”

The Onamia School District takes pride in their energy efficient buildings and will gladly host visitors from other school districts, legislators, and others interested in seeing how the buildings’ systems operate.

Superintendent Varner gets a half dozen or more calls each year from school districts in Washington state, Ontario, Manitoba, and other places who want to learn more about geothermal systems.

For further information, contact the superintendent John Varner at 320-532-4176, jvarner@onamia.k12.mn.us .

Other Contacts:
Arnie Hedberg, Architect, TKDA (St Paul); 651-292-4519

Dick Seemers, District Building Manager; 320-532-4174

Gary Connett, Great River Energy, Elk River, 320-241-2466

Mark Thiede, Architect TSP1 (Minnetonka) 952-474-3291