Francestown opts to continue geothermal system in library

Monadnock Ledger-Transcript
Published: 1/16/2020 2:52:10 PM
Modified: 1/16/2020 2:51:18 PM

Francestown's Select Board is opting to stick with the geothermal heat pump that controls the climate of the George Holmes Bixby Memorial Library after looking into alternatives following a pump failure last winter.

The existing system was originally installed when the library underwent major renovations in 2009. It uses the thermal energy of the groundwater in a 1,000 foot-deep well to regulate the building’s temperatures, heating in the summer and cooling in the winter. The system has worked well, Selectman Henry Kunhardt said, but last winter a valve failed on the heat pump, forcing the library to heat the building with electric space heaters for a week. The repairman who fixed the valve suggested the town replace the aging pump, which operates with refrigerant technology that’s now discontinued, which makes repairs more expensive, Kunhardt said.

Kunhardt acknowledged that last year’s repair, in conjunction with the fact that the system’s initial installation went over budget, might have made some residents worry that the town had installed a lemon of a system. This year, he said the Select Board looked at the costs and benefits of replacing the heat pump and continuing with the geothermal system versus switching to a fossil fuel heat source or an air to air cooling system, like conventional air conditioning. The geothermal system came out on top in operating costs and capital, he said.

“Theoretically, that's the most efficient way to go,” he said. “I’m not sure some of the decisions that were made 10 years ago hold up in the light of day, but we have it working well now.”

In the summertime, the heat pump discharges the heat in the building to the groundwater, which stays a constant 50 degrees year-round, Kunhardt said. An air source heat pump, like a conventional air conditioner, would be working to discharge the heat to outside air that could be just as hot, or hotter than the air it’s working to cool. “So it’s thermodynamically more efficient to send the heat to the lower temperature region – the ground,” he said.

In the winter, the system’s ground-source heat pump utilizes the consistent temperature of the groundwater to heat the building much more efficiently than an air source heat pump, which requires a backup heating system for temperatures between 10 and 30 F, he said. In addition, the library is well-insulated following its renovation, with the books themselves providing additional insulation, he said.

At last year’s town meeting, the town passed a warrant article allocating $50,000 towards the library’s heating and cooling system, which can be utilized at any point through 2024. Now that they’ve decided to continue with the ground-based geothermal system, Kunhardt said the Select Board is attempting to proactively choose a contractor in the eventuality the existing heat pump needs to be replaced. 

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