In mid-2009 we started working on the Sangre de Cristo PK-12 School, in support of klipp architecture.  One of the most exciting things about that project was the opportunity to pursue true geothermal heating, because the proposed site is located over a geological hot spot.  The San Luis Valley is well known for existing geothermally fed operations, such as a local community swimming pool and the Colorado Gators Reptile Park. We were aware at the time that Adams State College in nearby Alamosa was also pursuing the possibility of using geothermal heating for a significant portion of its existing campus buildings.

This was exciting because most so-called “geothermal” systems are actually geo-exchange.  That is, they use the constant temperature of the earth as a heat sink, gathering and concentrating heat from the earth in winter and injecting waste heat back into the earth in summer.  In geothermal, naturally hot water is withdrawn from the earth and used to heat the building, in place of boilers, furnaces, or electric heating.  Although geo-exchange systems are very efficient, geothermal has the potential for nearly free heating and even lower utility bills.

Working closely with our mechanical engineers at M. E. Group, we researched other buildings using geothermal heating in the U.S. as well as the local geological conditions.  Unlike the pool at the Glenwood Hot Springs, where 4,000,000 gallons of hot water bubble to the surface every day, the hot spot under our site was 3,000 feet deep.  That’s a pretty deep, and costly, well.

Our next step was to confer with the Colorado Department of Natural Resources.  Recently adopted regulations require any water withdrawn from the aquifer to be replaced in the same “working portion” of the same aquifer.  In other words, water withdrawn from 3,000 feet deep must be re-injected into that aquifer at 3,000 feet deep.  So, instead of one well we would need two, at double the cost.  And the energy required to re-inject water so deep into the earth, where pressures are enormous, is substantial.  

Further complicating the problem was water chemistry.  Water withdrawn from the aquifer to be used for heating the school could not be substantially altered chemically before it is re-injected.  Depending on mineral content and other chemical aspects of the withdrawn water, it might have been necessary to treat it before running it through the heating system.  

After a few months of analysis, and several conversations with Colorado Department of Natural Resources, we concluded that geothermal heating would be prohibitively expensive and technically challenging for the Sangre de Cristo PK-12 School.  We learned that the old style “pump and dump” geothermal operations (in which withdrawn water is not re-injected) in Colorado and elsewhere, no longer comply with current regulations.  In fact, it appears that a geothermal system would only be appropriate for a very large project where the initial high cost can be justified by long term energy savings.  Fortunately, we were able to design the school with a horizontal loop field geo-exchange system that will be reliable, easy to maintain, and deliver exceptional energy performance.

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