Correction: A 6-ton heat pump system will produce 72,000 BTUs per hour. A measurement in the original story was incorrect. The system will pay for itself in about seven years.


FAIRBANKS — Large rolls of black tubing sat like super-sized balls of yarn next to the playground outside Weller Elementary School Wednesday. The sun shined brightly on the south-facing hillside, where a bulldozer carved out a 12-foot hole.

The balls, which are actually polyethylene ground loops, were then rolled out and buried in the ditch, where they will harvest heat from underground to use in the school during the winter. In the summer, six solar thermal panels soon to be mounted on the school will replenish heat to the earth through the same tubes. The system will not only reap savings on heat for the school district but also will test a technology that is young in Fairbanks.

“I would like to see a system that would work well in the Interior and that the public can utilize and save dollars,” said Larry Morris, projects manager for the Fairbanks North Star Borough School District.

The project is an experiment to see how well the systems work in tandem and to collect data on ground source heat pumps, which are common in the Lower 48 but rare in Fairbanks.

“What we’re trying to do here is pair that system with a solar system that will recharge the heat you take out of the ground. In warmer climates, the sun can recharge how much you take out,” said Aaron Sirois, an engineer for PDC Engineering. “We were trying to come up with a solution that’s kind of adapted to Fairbanks.”

A joint effort

The project is a partnership between the Fairbanks school district, PDC Engineering, the Cold Climate Housing Research Center and contractor MCM Roe. Morris contacted the engineering firm several years ago to explore a potential ground source heat pump for the school district. Engineers came up with the concept to marry a heat pump with a solar hot water system. They enlisted the local contractor to install the system and the research center to monitor its performance. Because each group donated time, expertise or equipment to the project (and helped secure discounts from suppliers), the project cost the school district less than $16,000.

The six-ton system will produce 72,000 BTUs per hour, enough to heat a 2,000-square-foot home year-round. Heat-transfer liquid inside the loops absorbs warmth from the ground; the heat is pulled upward by a heat pump located in the school’s penthouse and fed into a heat exchanger system. Air is warmed as it blows past the heat exchanger and distributed throughout the building.

“Every BTU that we put into our heating system, we don’t need out of the boiler,” Morris said.

While the heat pump runs on electricity, it still produces more energy than it consumes, said Andy Roe of MCM Roe.

“For every unit you consume you get three units back,” he said. “That equates to a savings of about 30 percent over heating oil, with today’s heating oil rates.”

Morris estimated the system would pay for itself in slightly less than seven years.

Heat pumps make sense in Fairbanks because even though the ground is colder than in other places, it’s still much warmer than the air, Sirois said. It keeps a moderate temperature by virtue of its thermal mass.

“When you use the ground, you work with a much more stable temperature. The ground might be 35 degrees while the temperature of the air outside is negative 50, so it becomes much easier to harvest that energy,” he said.

The research

But how much does the ground temperature fluctuate, and how will that affect the efficiency of the system?

Researchers will tackle these questions, said Robbin Garber-Slaght, a product testing engineer at the research center.

She will embed 36 sensors in the ground, strung on wires, that send temperature readings to a data logger inside the school.

“Another question is, ‘Are we going to make permafrost by pulling heat out of the ground?’” she said.

The solar thermal panels will operate in the summer to transfer heat back into the ground. It is designed to recharge the heat source and avoid creating permafrost.

“We essentially are able to put the heat right where we want it, when we want it, without waiting for it to trickle down naturally,” Sirois said.

This could overcome the shortcomings of many renewable technologies.

“The problem you run into with renewable energies is when you want the energy, it’s not always available,” he said.

You need batteries to store power from photovoltaic cells and hot water tanks to store solar thermal energy. But this system uses the earth as both an energy source in the winter and a battery in the summer, Sirois said.

By December, the system should be turned on and generating results.

“Now we’re going to have real-time data for the Interior and you’ll be able to show people exactly what you’re getting out of it,” Sirois said.

“I am a big proponent for this technology. I’d really love to see it come up here.”

Contact staff writer Molly Rettig at 459-7590.