Geothermal From GreenFire: The Lowest Cost Energy (+ CCS)

"CO2-G [CO2 Geothermal] is projected to have the lowest cost of any form of energy and is the only source of energy that permanantly sequesters carbon."

Those are the words of Mark Muir, co-founder of GreenFire Energy, a startup with an innovative twist on geothermal energy. 

Conventional geothermal energy entails tapping a heat source at relatively shallow depths and capturing the heat as steam to turn a turbine. Enhanced Geothermal Systems (EGS) create geothermal energy in hot dry rock by sending pressurized water down an injection well. Water travels through fissures, capturing the heat of the rock when it is forced out of a second well as hot water, which is then converted into electricity via a steam turbine or a binary power plant.  The cooled water is sent back into the earth to heat up again.

GreenFire dispenses with the water and instead uses carbon dioxide as the geothermal "feedstock."

"Geothermal ends up with the lowest cost – but conventional geothermal has big cooling towers and pumps. Hopefully we can get away from all that," adds Muir.

He projects that Carbon Dioxide Geothermal (CO2-G) can have a lower LCOE than any other scalable form of energy.

According to the CEC (California Energy Commission), there are 43 operating geothermal power plants with an installed capacity of about 1,750 megawatts in California, almost two-thirds of the United States' 3 gigawatts of geothermal generation. Geothermal energy production in the U.S. is a $1.4 billion industry – far bigger than the U.S. solar market.  And unlike solar, geothermal power is baseload power – available 24 hours a day, 365 days a year. Iceland gets over a quarter of its electricity from geothermal sources.

GreenFire's CO2 can come from natural sources or from the emissions of coal plants.

One of the largest natural deposits of CO2 is located in the the St. Johns Dome, a region extending across Arizona and New Mexico. It is a perfect site for GreenFire because it has the CO2 resource, a thermal reservoir, access to transmission lines and there are two power plants right at the dome and four more within a 200-mile radius. GreenFire is in a joint venture with Enhanced Oil Resources, the company with the leases to the CO2.

So, in addition to producing low-cost geothermal power, CO2-G can actually find a use for the carbon captured from coal plants.

This is important. Coal provides 50 percent of the U.S.'s electricity and according to EPRI, The Electric Power Research Institute – coal is here to stay. EPRI predicts that coal will continue to dominate our electrical production. But in order to meet any carbon legislation, it's going to have to be coal with carbon capture and sequestration (CCS). 

The U.S. DOE will be making $55 million available to develop advanced carbon capture technologies at existing power plants. An economical technology for CCS has not yet emerged. 

Although not involved in reducing the cost of carbon capture, Greenfire believes they can save up to $25 per ton in total CCS costs (which are predicted to be in the range of $40 to $80 per ton once the process becomes commercial). The energy for for carbon capture could be a third of the plant's output. CO2-G essentially provides the power for the Carbon Capture.

We covered available CCS technologies such as membranes, solvents, solid sorbents and condensed-phase capture in an article earlier this year.  

GreenFire has the option of harvesting the kinetic energy from the wellhead. Since CO2 expands much more than water – it creates a highly pressurized situation.  That expansion's kinetic energy can be harnessed by a new type of energy transducer, the "free piston linear alternator," from the likes of Greenwell Renewable Power.

GreenFire is a small company and is looking for funding.  Muir estimates that he'll need about five years and substantial backing to put together a demonstration site. "It's not inconceivable for the money to come from smart VCs" but the likely source would be funding from the coal industry, "because its a matter of life and death in a carbon constrained world," according to Muir. 

Muir estimates that 5 percent of the world's coal plants might be eligible for the GreenFire CCS technique.