Concrete Progress is an ongoing series of columns by Peter Brewitt devoted to exploring America’s infrastructure. It is part of Orion’s two-year Reimagining Infrastructure project. Above, students tour Colorado Mesa University’s geoexchange system. Photo courtesy of CMU Sustainability Council.
I’ve seen some lively weather this winter, and I bet you have too. By now, though, the Polar Vortex of early January has retreated to its northern lair, people from Montana to Maine to Mississippi are eager to thaw out like Han Solo, and Californians have retreated to baseline smugness. But the Vortex isn’t over. In its wake come gigantic heating bills and, of course, equally gigantic clouds of carbon from the oil and coal we all burned to keep body and soul together. This set me to thinking about how we can maintain a reasonable indoor climate without ruining the outdoor climate, or our bank accounts. I found an answer at Colorado Mesa University, in Grand Junction, Colorado: geoexchange climate systems.
In the Rocky Mountains, you can freeze or you can roast. Grand Junction’s average January low is 17 degrees. In July, the high is 93. Changing that kind of climate—adding fifty degrees or removing twenty—sucks up a lot of energy. Dig down below the frost line, though, and you’ll find a steady year-round temperature of about 61 degrees. CMU pipes water between the surface and the underground, using the thermal gradient to regulate their buildings’ temperature. The reward is savings of $300,000 a year and a reduced carbon load of 8,000 metric tons. That is the equivalent of close to a million gallons of gasoline.
How did this happen? In 2007, Colorado governor Bill Ritter set a goal of reducing the state government’s energy use by 20 percent over five years. One of the ways to do this was to require state-funded buildings to be LEED certified. The leadership at CMU (known then as Mesa State College) took this to heart; they had already been looking to grow the institution, and to do it sustainably. The school contracted with a company out of Salt Lake City called Sound Geothermal to design a geoexchange heating/cooling system for a new classroom building. As the project got underway, they figured that they might as well add a dorm, and then other buildings, to create a district energy system, controlling multiple buildings. As CMU expands—and it has more than doubled in size in the past six years—so has its geoexchange network. All new buildings or significant remodels are connected, and by now 13 buildings, taking up 1.2 million square feet, are either on the system or will be soon. They’re even connecting the university pool and its 800,000 gallons of water.
I should note here that systems like this are often confused with geothermal power. While they are similar, the difference is that geothermal power is made from easily accessible mantle heat in volcanic spots like Iceland and New Zealand. Geoexchange just moves thermal energy, and can do it pretty much anywhere.
A field of heat-exchange coils, a common feature of many residential geoexchange systems. The coils are usually buried at a shallow depth near the structure they’ll heat and cool.
CMU’s geoexchange system works much like Toronto’s deep lake cooling, which I wrote about in November: water flows through pipes buried 350-500 feet underground, cooling down or warming up before being pumped through the university’s buildings to deliver or absorb heat. The difference lies in geoexchange’s heating ability, and its ability to shift heat back and forth from one part of campus to another. Imagine a winter dawn in Grand Junction. The rising sun hits the south face of dorms full of sleeping students. Guided by CMU Facilities Services’ control centers, this energy is distributed throughout the building—and if this isn’t enough, heat from libraries and performing arts centers—empty at that time of day—is routed to the dorms as well, getting young Coloradans out of bed and into the world. As the sun rises, the dorms’ heat is sent on to classrooms and dining halls, guided by the movements and needs of the community. If the combined heat in the buildings is insufficient, then heat is pumped out of the ground. At day’s end, the heat returns to the dorms to keep undergraduates cozy while they study Proust, or organic chemistry, or domestic beer.
Could geoexchange be coming to your town? It may have already. Consider how many colleges, research parks, hospitals, prisons, bases, and high schools there are across the country. Thousands of them have put in geoexchange systems, though few are as flexible as CMU’s. There are a few drawbacks: the upfront costs are significant, in some places it’s challenging locating a spot to bury the pipes, and the systems themselves aren’t completely perfect—CMU retains traditional heating and cooling systems for the most extreme times. But take another look at the numbers in the second paragraph. These things are moneymakers. You can just as easily put in geoexchange in your own home. The system pays for itself, sometimes in as little as three years (CMU’s will pay off in about twelve), depending on your geology and how well your state supports green energy, and it’ll add thousands of dollars to your home’s value if you decide to sell.
A lot of the things I write about in this space are closely tied to their geography, and only apply in specific circumstances—but every house is built on the ground. Honestly, I expect that geoexchange will soon be the standard climate control system for most of the United States. If you want to learn more, Sound GT’s website offers a lot of information, and you can also look here.
Peter Brewitt has wondered about infrastructure ever since a flood kept him away from three days of kindergarten. He’s currently at work on a PhD at the University of California, Santa Cruz, where he’s researching the ways people restore and remake their environments.