A Case Study for Mount St. Augustine
“Anywhere” Geothermal Energy
Grid-scale geothermal energy production is theoretically possible anywhere on earth. Drill deep enough and the thermal gradient will reach temperatures hot enough to power entire cities (400C). However, “significant engineering innovations will be required to realize the full potential of superhot rock, such as rapid ultra-deep drilling methods, heat- resistant well materials and tools, and deep heat reservoir development in hot dry rock.”
Geothermal Energy Storage
Traditional geothermal electrical power generation occurs on-site with transmission lines extending to the the power grid. These transmission lines can add hundreds of millions of dollars to the cost of a project and make it prohibitively expensive to connect geothermal energy sources to consumers.
What if instead of generating power on-site, the extracted geothermal heat could be stored and transported? American GeoPower has patented a method that uses molten salts to tap heat from hot rocks (250-600C) that can do just that. It uses the same proven salts as Concentrated Solar Power (CSP) in a closed loop system that is more power dense and doesn’t require high pressures to operate.
Geothermal Energy Transport
Molten Salts can be fine-tuned to allow for greater temperature ranges (150-500C). The fact that they do not have to travel under pressure makes them potentially cheaper to transport than LNG. They would need heat insulated containers with temperature sensors and the ability to be heated back up to 130C in the event of freezing. Salts in a frozen state could still be transported back to the geothermal source and reactivated in this manner.
“Molten salts high-temperature properties such as the volumetric storage density, viscosity and transparency are similar to water at room temperature.
The major advantages of molten salts are low costs, non-toxicity, non-flammability, high thermal stabilities and low vapor pressures. The low vapor pressure results in storage designs without pressurized tanks.
Molten salts are suitable both as heat storage medium and heat transfer fluid (HTF). In general, there is experience with molten salts in a number of industrial applications related to heat treatment, electrochemical treatment and heat transfer for decades.”
Mount Saint Augustine
Mt Augustine is located less than 200 miles from Anchorage, AK, and is easily accessible by sea. Power producing Infrastructure onsite could be at risk from natural hazards making molten salt transport an appealing alternative.
“Development of a resource on Augustine ... would help Alaska meet its renewable energy targets. However, the viability of the resource on the island is totally unknown at this point. The two most often cited concerns are the distance from the island to the grid, and the presence of geologic hazards. Geologic hazards listed by the DNR include; volcanic ash clouds, ash fallout and volcanic bombs, pyroclastic flows, debris avalanches (as occurred on Augustine in 1883), tsunamis, earthquakes, directed blasts, lahars and floods, volcanic gases, and lava flow. The closest connection to the existing Railbelt grid is probably Nanwalek or Homer, about 50 miles away. However, if the Pebble prospect were developed this project would be only 15 miles away from Pebble's potential energy grid (at the port site for the mine).”
Commercial Potential
If a commercially viable resource is identified and a project designed, development of the project would likely include construction of wells and pipelines, a power plant with turbine and cooling system facilities, roads, personnel housing, transportation and maintenance facilities, and subsea power transmission lines most likely to Anchor Point or Homer (Kagel et al. 2007; Soltani et al. 2021). (italics added)
Alaska’s Energy Infrastructure
“The Railbelt electrical grid stretches from Fairbanks through Anchorage to the Kenai Peninsula and provides roughly 79 percent of the state’s electrical energy. Nearly 73 percent of the Railbelt’s electricity comes from natural gas, mostly supplied by one monopoly producer.
Major power generation facilities along the Railbelt include Chugach Electric Association’s (CEA) 332-MW natural gas-fired plant west of Anchorage at Beluga, Anchorage Municipal Light and Power’s (ML&P) 120 MW natural gas-fired Combined Heat and Power plant in Anchorage, CEA and ML&P’s 204 MW natural gas-fired power plant in Anchorage and Golden Valley Electric Association’s (GVEA) 181 MW facility near Fairbanks fueled by naphtha from the Trans-Alaska pipeline system. Homer Electric Association (HEA) has three natural gas fired power plants at Nikiski, Soldotna and Bernice Lake that total 204 MW and Matanuska Electric Association’s (MEA) 171-MW dual-fuel (gas or diesel) generation station near Eklutna was added in 2015.”
Thermal Heat and the Power Grid
Could the thermal energy from St Augustine replace what is produced by Anchorage Municipal Light and Power’s (ML&P) 120 MW natural gas-fired Combined Heat and Power plant in Anchorage? If temperatures of 450C are accessible, then the potential energy from three boreholes could theoretically replace the output from this power plant. This is borne out from studies in Iceland that found that one “supercritical” hot rock well could produce 36 MWe of energy:
“This means that a few superhot rock wells can bring substantial commercial energy to the surface. This high energy potential has been demonstrated in Iceland, where the Iceland Deep Drilling Project’s “Krafla” borehole produced natural superhot water at 452°C and an estimated 36 megawatts of energy (MWe) production potential. In comparison, a typical commercial hydrothermal geothermal project produces about 3-5 MW per well. For comparison, the Reykjanes geothermal field in Iceland, one of the hottest producing field in the world at 290-320°C, has 12 wells producing a total of 100 MWe from 2 turbines.15 Superhot rock energy has the potential to produce the same amount of heat in 2-3 wells.”
Shipping Heat
Offload temperatures: 500C assuming normal range for this type of volcanic source.
Temperature on arrival: Molten Salts lose approximately 1C degree of heat per day. This means that ten days transit at 500C would still have working heat of 490C.
Vessel type: Create towable low draft tank barges with holds and pumps capable of storing high temperatures.
Shipping containers: In future design containers that can be reheated at source to allow for freezing of salts and fungible use with CSP. Standardize for shipping on existing tankers, trains and trucks.
Description of Reception Terminal: Should be as near as possible to power plant for quick dispatch and turnaround adapted to 1C loss per day.
Energy output: A ship with 440,000 tons of molten salt at 500C that is kept at 150C after off loading will have an energy delta of 350C which amounts to 40 gigawatts per ship load.
Conclusion
Mt. Saint Augustine provides ideal geographical and geological conditions to introduce Geo-Salt storage and transport. It is easily accessed by ship and only a day’s travel up Cook Inlet to Anchorage and its power grid.
Alaska is fortunate to have a plentiful mix of energy which includes both fossil fuels and renewables. Geothermal is an ideal fit within these sources given the abundance of volcanic activity to be found within the state of Alaska and along the Aleutian Island chain.
This mode of energy transport can not only incentivize geothermal in remote locations but also creates a potential for energy exports to the continental USA and other energy hungry destinations.