Sometimes, the solutions to the world’s most vexing problems are right under our noses. Or in the case of energy, right under our feet. Geothermal energy, from the boiling bowels of our planet, holds warm promise for a renewable energy-powered future. There’s scads of it, and unlike wind or solar energy, it’s available all hours of the day. According to one oft-cited report (PDF) that MIT submitted to the Department of Energy, 2% of the heat up to 6 miles below the U.S. could provide 2,500 times as much energy as the country uses. The catch, of course, is--how do we get to it? Well, sometimes nature kindly brings it right to us.
One of the zanier sounding experiments (PDF) involving what’s known as Enhanced Geothermal Systems tech involves the Newberry Volcano in Bend, Oregon, artificial wells, and several million gallons of water. AltaRock Energy and Davenport Newberry Holding, backed by Google, the DOE, and others, have been exploring ways to tap into thermal energy at the Pacific Northwest volcano. This summer, the companies are planning to test the site to see if it will be commercially viable to create a geothermal power plant in the area.
The Newberry site is a great place to fish for geothermal energy because the hot rocks are closer to the soil than they are in most other places. This means the wells don’t need to be too deep to expose water to the earth’s heat.
At the Newberry project site, the companies will pump several million gallons of water at a high pressure into wells a little over 10,000 feet deep. The water will circulate underground, creating channels and crevices for itself known as microfractures, maximizing the surface area so that more water is in contact with hot rocks. The water will slosh around, heat up, and return to the surface through a second well as scalding hot water. If the tests are successful, someone will be able to build a power plant above the area and harvest the water’s heat for power.
"Think of an upside-down tree of fractures," Ernie Majer, an EGS researcher at Lawrence Berkeley labs explained to Co.Exist. "It starts out in the trunk, and it goes into the branches, and the tiny little leaves." Ideally, Majer says, you’d like a very leafy tree of fractures to give the water plenty of contact with the rocks.
The effects of pumping the water into the well under high pressure--"microseismic events"--will be measured with a series of sensors located underground. By looking at the microseismicity, scientists can tell if the water is creating the required microfractures--which will mean the water is getting maximum exposure to the hot rocks--a healthy indication that a commercial plant may be viable. It will also give researchers an idea of whether the water pumping is triggering any larger seismic events. Given that they’re on an active volcano, triggering earthquakes would be a bad idea.
This EGS loop may, to some, sound ominously similar to hydrofracking, a technique that energy companies use to flush out natural gas underground. Fracking has been found to pollute groundwater with the chemicals used in the fracking water, and is suspected of causing geological damage, like recent earthquakes in Ohio. But hydroshearing--the technique used at the Newberry site, is an entirely different kind of rock breaking, Majer says.
At a fracking site, the tiny fractures already exist underground--they’re the pockets in the rock that are filled with gas. The goal there is to create a single channel--a well--to let that gas out. "There’s no tree trunk there," Majer says. "In one case you’re sucking [the microfractures] dry, and in the other case … you’re making them wet."
Majer and his team have been signed on by the DOE to monitor earthquake activity around EGS sites like Newberry. This summer, AltaRock engineers will be scoping out the area to test if the site has what it takes to support a commercial plant. Natural seismicity in the area is low, and there isn’t a fault line in sight (just a mountain with the potential to spew molten lava), so all signs point to a safe run when the tests on the site begin.