GeoThermal energy along with hydroelectric are the only renewable energy sources that operate on a 24/7 basis.
GeoThermal energy is generally located in ideal locations to utilize the existing formation permeability and natural geofluids for power generation..
Alternative geothermal systems have been reseached since the early 70's especially hot dry rock as a geothermal source, known as Enhanced Geothermal System. The hot dry impermeable brittle rock is conventionally hydraulic fractured with invasive fluids and thus the potential for induced seismicity can be significant in EGS, especially due to the significant volumes of elastic brittle rock being fractured in the attempt to achieve fracture connection between injector and producer wells. The EGS geothermal field experimental trial in hot elastic brittle rocks in Basel, Switzerland was shut down due to induced seismicity during hydrofracturing activities and the plant was never completed.
After 40 years of field research and extensive field trials in the USA, UK, Australia, France, Germany, Japan, Sweden and Switzerland, EGS has not become a viable commercial option due to 1) the difficulity of connecting the injector and producer wells by hydraulic fracturing, 2) the inability to enhance hydraulic fracture connection to achieve commercial viable flow rates and heat flux, and 3) induced seismicity issues during construction and operation.
Conventional geothermal exploration and deployment can be both expensive and carry significant risk, since all three factors need to be present at the site:
- Hot environment
An alternative is a geothermal energy system in hot low perm anelastic ductile formations - an engineered solution to create permeability, store captured carbon dioxide, extract and sell minerals, especially Lithium, from the groundwater brine and sell desalinated extracted groundwater from the system.To utilize carbon dioxide as the subsurface working fluid requires a meaningful carbon tax on emitters; otherwise the carbon dioxide is simply released to the atmosphere and not captured and stored. If such a carbon tax is not in place, then the system uses recirculated groundwater as the subsurface working fluid, operating with a reduced efficiency and with no upfront carbon storage revenue from a cashflow perspective to offset the system's Capex.
August 2017 - Funding for the Geothermal Energy trial cell has been approved, subject to the bench scale performance of the lithium enrichment cell, for the final design, land and lease acquisition for construction in the 4th qtr 2018 in the Salton Sea Geothermal Field, Imperial County, California. The trial cell will extract groundwater geothermal brines, store and cycle supercritical carbon dioxide in the sub-surface for electric power generation, and extract lithium from the geothermal brines. Revenue for the trial cell is from four streams: 1) carbon dioxide storage, 2) electric power generation, 3) minerals extracted from the groundwater brine, primarily Lithium, and 4) sale of desalinated groundwater.
The lithium enrichment cell uses alternating polarity electrodes constructed from calcined petroleum coke proppant as developed by Asbury Carbons in association with GeoSierra, for GeoSierra's ERG - electric resistive heating enhanced bitumen/heavy oil recovery process - see Electric EOR. The calcined coke proppant is coated with different compounds to produce the alternating polarity lithium and chloride ion selective electrodes, that extract the lithium ions from the geothermal brines and concentrates the lithium ions in a battery grade lithium concentrate solution.
Without significant lithium revenue, baseload geothermal electrical power generation in southern California is not an attractive investment, primarily due to the lack of a meaningful tax on carbon emissions, the regulated electrical pricing is tied to the current natural gas price, and the low revenue/MWhr for baseload electricity. Using supercritical carbon dioxide as the subsurface working fluid, a large portion of the baseload generation can be provided as on-demand peak generation capacity, thus significantly increasing the revenue/MWhr. The performance of the lithium enrichment cell and the siting of the field trial in high lithium groundwater are both crucial for a successful field trial of the lithium enrichment process.