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Tapping into Alaska’s volcanoes Alaska’s geothermal lease offerings reflect interest in harnessing underground heat, want applications next to Augustine, Mt. Spurr Alan Bailey Petroleum News
Living next to a volcano might not fit into everyone’s comfort zone. But, as most Icelanders would probably testify, it’s a situation that can keep down the energy bills. In the right situation, geothermal energy — heat from inside the Earth’s crust — can provide seemingly endless quantities of hot water or electrical power.
Alaska is well endowed with hot springs and volcanoes that might provide energy to replace at least some use of fossil fuels. For example, in 2006 Chena Hot Springs resort, 60 miles northeast of Fairbanks, spearheaded the use of geothermal energy by replacing expensive diesel generators with a 200-kilowatt power plant driven by hot spring water.
And people have long eyed the chain of volcanoes along the Aleutian Islands, the Alaska Peninsula and up towards the Alaska Range as a source of energy. Part of the Pacific “ring of fire,” these volcanoes provide dramatic evidence of an upwelling of heat from deep inside the Earth. Unalaska in the Aleutians has been investigating the potential for a geothermal power plant tied into the Makushin Volcano near the town of Dutch Harbor. And the village of Naknek, on the Alaska Peninsula, plans to test drill for a geothermal energy source near the village.
Call for applications The Alaska Department of Natural Resources is now calling for applications for geothermal leases next to the Augustine Volcano in the lower Cook Inlet and Mount Spurr, an active volcano on the west side of the Inlet (see “Alaska offers geothermal acreage” in the April 15 edition of Petroleum News). The state is responding to continuing interest in geothermal energy, recognizing the fact that the department has not offered geothermal leases in the Cook Inlet area for about 20 years, DNR told Petroleum News May 7.
Interest in geothermal energy waxes and wanes in response to the price of oil, Chris Nye, a geologist with Alaska Division of Geological and Geophysical Surveys, told Petroleum News on May 2 — the higher the price of oil the more viable alternative energy sources such as geothermal energy become.
Research more than two decades ago resulted in a 1986 University of Alaska Geophysical Institute report on the geothermal potential of Mount Spurr. But with the oil price crash in the mid-1980s interest in geothermal energy in Alaska evaporated. Now, with buoyant oil prices, interest in geothermal energy is likely making a resurgence.
Nye explained that a viable use of geothermal energy requires some form of underground heat flow anomaly, such as a volcano or hot spring.
“Anywhere you go the Earth gets hotter as you go deeper but you need something anomalous to be going on in order to make that heat at depth to be economically achievable,” Nye said.
Needs a market And economic viability also depends on access to a market for the sale of the geothermal energy. Mount Spurr, for example, sits relatively near a good-sized market for electricity in Southcentral Alaska. On the other hand, some well-known hot springs in the remoter Aleutian Islands seem very promising as geothermal energy sources but have no obvious energy market.
Nye explained that there is a series of different types of geothermal application, depending on the type of underground heat source that is available. At the top of the totem pole sit dry steam systems, in which the rocks are hot enough to dispel any underground water. In that situation, power can be generated by pumping water into the rocks and then using the resulting steam generation to power a turbine electrical generator.
More likely in a situation such as Mount Spurr or Augustine is a source of underground water hot enough to boil when it reaches the surface.
“The best we can hope to have is a good, robust geothermal system,” Nye said.
Again, the boiling water would drive a steam turbine.
Boil refrigerant At lower temperatures, the warm underground water might be used to boil some other low boiling point fluid such as a refrigerant. The boiling of that secondary fluid would drive a turbine in a process known as an organic Rankine cycle. The technology of this type of application has improved over the years, to the point where remarkably low temperature sources can viably generate electricity. The Chena power plant, for example, uses spring water at just 165 degrees Fahrenheit in an organic Rankine cycle system.
“Chena is producing hundreds of kilowatts from the lowest temperature fluid in use anywhere in the world,” Nye said.
However, lower temperature geothermal water can also be used to simply heat buildings, rather than generate electricity. The space heating of buildings might seem an improbable application in remote locations such as Mounts Spurr or Augustine but, according to a report by Alaska’s Division of Geological and Geophysical Surveys, in 1993 DNR had leased two tracts near Mount Spurr to a company interested in developing a geothermal hydroponic garden facility.
Mount Spurr potential So, what are the prospects of finding a geothermal energy source at Mount Spurr?
“There is a small zone of tepid hot springs that occurs on the south flank of Crater Peak. It’s not really a robust geothermal spring system,” Nye said (Crater Peak is an active volcanic cone on the south flank of the mountain). Because the springs include water from snow melt or rain, the chemical content of the water does not help in determining the possible existence of a geothermal source at depth.
But a geophysical survey in the 1980s provided tantalizing indications of a possible layer of warm or hot brine 2,000 feet below the plateau at the entrance to the pass on the south side of the mountain. Some soil geochemistry anomalies also pointed to the existence of geothermal water in the area.
“What that (research) program did was identify various geophysical anomalies of which geothermal brine is a reasonable explanation,” Nye said. There are other possible explanations for the anomalies, he said.
If the geophysical anomalies do represent geothermal brine, the brine is perched as a layer within the rocks. It’s likely that the geothermal fluids would have flowed up from a deeper level through a crack in the rocks, and then spread out to form a layer rather like a thunderhead, Nye said. In that case, the source of the fluid would be the logical target for an exploration program, either through further geophysical work or through drilling.
“What you really want to find is the feeder zone,” Nye said. “… If all you have is the wing of the thing, you know that you’re not looking at the hottest part of whatever it is and you’ve got the danger of having a reduced volume of reservoir.”
Augustine unknown Although there is some indication of geothermal potential at Mount Spurr, nothing is known about the potential of Augustine, other than the fact that it is a volcano. And unfortunately there are no hot springs on the flanks of the volcano to provide evidence of water transferring heat towards the surface.
“Mount Augustine is a volcano and it recently erupted,” Nye said. “Therefore, material at many hundred degrees centigrade has moved from somewhere at depth to the surface and has undoubtedly lost some heat. Some of it may be parked somewhere and is still actively losing heat. Whether or not that’s enough extra heat in the shallow crust to make a geothermal resource or not, we don’t know.”
So, does anyone want to find out more about the geothermal potential at Mount Spurr or to go prospecting for a geothermal resource on Augustine Island? We’ll presumably find out after May 14, DNR’s closing date for geothermal lease applications.
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