Pairing Integrated Gasification and Enhanced Geothermal Systems (EGS) in Semiarid Environments

Abstract

We explore the feasibility of combining the circulation of supercritical CO 2 in EGS reservoirs with integrated gasification combined cycle (IGCC) power generation. The symbiotic benefits of this pairing increase net power output over the use of either system in isolation, reduces water use per MWe, and substantially reduces fugitive emissions over conventional thermal power plants. A prototypical plant set in the arid southwestern U.S. (environs of Albuquerque, NM) could sustain anticipated circulation rates of 800−1600 kg/s of CO 2 in a 200°C reservoir, resulting in a thermal output of ∼150−300 MWthermal to augment the 550 MW from IGCC. This design would reduce annual emissions by 8,200 tons of NOx, 20,000 tons of SO 2 , and 4.35 million tons of CO 2 over conventional thermal plants in an optimal pairing.

Changes in Pore Structure of Dry-hot Rock with Supercritical CO2 Treatment

“…As a clean and renewable energy source, geothermal energy may be used for both power generation and heating. − At present, artificial stimulation (heat, force, chemistry) is mainly used to extract geothermal energy, that is, Enhanced Geothermal System (EGS). − In EGS, water is usually used as the fracturing medium in the hydraulic stimulation and the heat exchange medium in heat mining technology. − The thermal recovery efficiency of medium- and low-temperature geothermal resources is limited by fluid properties, wellbore depth, and heat transfer efficiency. , In addition to the high energy consumption of the thermal cycle, there are disadvantages such as scaling in the wellbore caused by water–rock interactions, when water is used as the heat-exchange medium. , Also, with changes in in situ stress and reservoir pressure, water has a risk of activating faults and inducing earthquakes. At this moment, earthquake events induced by hydraulic fracturing in dry-hot rock have occurred in Basel, Switzerland, and Soultz, France, among other places. − The physical properties of CO 2 suggest that it can be used as a heat-exchange medium.…”