New energy tech almost always starts at the expensive end and trickles down. Tesla was selling a sports car long before it sold anything resembling a family sedan, and the fanciest heating systems tend to land in buildings with a doorman. So I find it kind of refreshing that one of the more interesting geothermal projects in the country is headed for affordable apartments in Boise, Idaho.<\/p>\n
Boise’s been pumping hot water out of the ground to heat its downtown since the Reagan administration. The city now runs the biggest municipal geothermal heating system in the US, according to the Department of Energy<\/a>, with over 20 miles of pipe keeping more than 6 million square feet of buildings warm. Next, it wants to bring that water to the Lusk District, a neighborhood on the edge of Boise State University, where a developer plans to put up more than 300 affordable homes.<\/p>\n The latest piece of that puzzle landed on October 27, when the city announced<\/a> that Micron Technology had put $2.5 million of gap funding into the project. City officials describe the whole thing as the first attempt by an American city to heat multifamily affordable housing with geothermal. Jake Wood, who runs affordable housing development at the developer, J. Fisher Companies, went a little further: “No other U.S. city has tried this.”<\/p>\n So is that true?<\/p>\n As far as I can tell, yes, but the wording’s doing some work. That same Energy Department page lists a community geothermal pilot at the Barry Farm redevelopment in Washington, D.C., backed by an affordable housing group and meant to serve apartments too. That one’s a heat pump system, though, and it isn’t being led by a city.<\/p>\n Most building geothermal you’ve heard about is the heat pump kind. The ground stays at a fairly steady temperature, and a heat pump moves warmth out of it, like the boreholes we covered outside a Boston office<\/a>. Boise gets to skip that step because its water comes up at 177 degrees. For comparison, your water heater’s probably set around 120.<\/p>\n The city draws that water from three wells, 400 to 800 feet deep, according to a paper co-written by Jon Gunnerson, who manages the city’s geothermal program. One set of pipes carries it downtown, and each building pulls about 50 degrees out of it on average. A second set collects what’s left, and it gets pumped back underground to warm up again.<\/p>\n It’s the same basic recipe geologists are chasing under a soccer field in Cologne<\/a>, except Boise’s been cooking with it for decades. The system melts snow off some sidewalks too, which sounds pretty great if you’ve ever owned a shovel. And the city says<\/a> the carbon it avoids each year is like pulling more than 2,000 gas cars off the road.<\/p>\n The city’s network isn’t even the oldest one in town. Two 400-foot wells east of downtown were already flowing with hot water all on their own by March 1891. That’s what artesian means: pressure underground pushes the water up, and you don’t need a pump.<\/p>\n A banker named C.W. Moore built a resort around that water, the Natatorium, with a pool held at 98 degrees all year. He piped it into his mansion as well, and his neighbors soon wanted in. Early customers paid $2 a month per home, when coal was running $7 a ton.<\/p>\n That became the Warm Springs system, which dates to 1892 and is still running today. A history in ASHRAE Journal says the first wooden pipes were judged “dangerous and useless” within a few years. My favorite part of that history is the pump.<\/p>\n In 1927, the water company installed a variable-speed pump in a well house right next to the Idaho state penitentiary. Automatic controls weren’t available, so prison trustees (meaning inmates trusted with the job) stayed in the well house around the clock and adjusted the speed by hand. If the pressure downtown drifted, a water company employee called a supervisor, the supervisor called the prison switchboard, and the switchboard called the well house. That setup apparently lasted until the 1970s, which is frankly an astonishing run for a phone tree.<\/p>\n The city’s own network came along in March 1983. By the following year, it had 15 buildings and under 6 miles of pipe. Now it’s at about 100 buildings, by the city’s count, and more than 20 miles.<\/p>\n For a while, the city also did something pretty shortsighted. It dumped its used water in the Boise River, and the Idaho Department of Water Resources says water levels in one monitoring well fell 30 feet in the first four years. The city finished an injection well in 1999 to put the water back, and the levels recovered. If you’re ever in town, the city has a walking route that goes from City Hall to that well, which sits in Julia Davis Park, and I’ll admit I’d take it.<\/p>\n Boise has four separate geothermal heating districts, and they get mixed up a lot. The State Capitol, for one, runs on the state’s system and not the city’s. Gunnerson’s paper says it’s the only US state capitol heated by geothermal.<\/p>\nBoise’s water doesn’t need a heat pump<\/h2>\n
Boise’s oldest system had inmates running the pump<\/h2>\n