Update | Supercritical CO2


An expanding range of potential applications


Power projects of various kinds are aiming to exploit the advantages of supercritical CO2 as a working


fluid relative to steam, which include high density (twice that of steam), low viscosity and ability to operate at high temperatures, with high volumetric heat capacity, allowing it to carry more energy per volume than steam. The end result is much more compact power plant equipment


California Resources Corporation and its carbon management business, Carbon TerraVault, have recently announced the signing of a memorandum of understanding (MOU) with Net Power Inc. to develop gas fired power plants in California that will employ the Allam–Fetvedt cycle. This uses oxy-combustion of carbon fuels and a high- pressure supercritical CO2


working fluid in


a highly recuperated cycle that “captures all emissions by design”, with the only byproducts being liquid water and a stream of high-purity, pipeline-ready carbon dioxide.


Under the terms of the MOU, the parties plan to conduct feasibility studies on locating Net Power’s facilities close to CTV’s underground storage vaults. The parties say they plan to focus on the initial deployment of up to 1 GW of generating capacity in northern California employing Net Power’s new modular power plants, with CO2


sequestered in CTV’s reservoirs.


Each of Net Power’s 250 MW utility-scale modular plants is expected to require less than 20 acres.


The MOU marks Net Power’s initial entry into California’s power market and positions CTV as an early strategic partner in the deployment of Net Power’s power technology, the partners note. The FEED study being conducted with EPC partner Zachry for Project Permian – intended to be the first utility scale plant to employ the ‘Net Power Cycle’ – is close to completion, with initial power generation projected to occur between the second half of 2027 and first half


of 2028. Orders for some of the long-lead items have been placed (eg, 345 kV circuit breakers and transformers) and Air Liquide was selected as air separation unit supplier (2 x 50%) for the Project Permian FEED.


Work continues at the La Porte demonstration site to prepare it for four phases of equipment validation in partnership with Baker Hughes. The La Porte site work has included enhancements to piping and instrumentation, relocation of carbon dioxide compression equipment and updates to the distributed control system.


The equipment validation test campaigns at La Porte are “intended to de-risk the utility- scale turboexpander,” which will be deployed as part of Project Permian and future projects. The four test phases are: oxy-fuel burner configuration selection (underway); single demonstrator combustor can validation; single utility-scale combustor can validation; and full demonstrator turboexpander validation. The Allam-Fetvedt Cycle technology is owned by 8 Rivers and the natural gas powered version is exclusively licensed to NET Power. Investors in NET Power include Occidental (42%), Baker Hughes (4%), Constellation (17%), SK Group (15%) and Rice family (5%).


STEP Demo


The 10 MWe Supercritical Transformational Electric Power (STEP) Demo pilot plant in San Antonio, Texas, has reported successful completion of phase 1 testing, “demonstrating operability, efficiency, and commercial readiness of the supercritical carbon dioxide power cycle.”


Above: Utility scale turbo expander for sCO2


(source: Baker Hughes) Right: sCO2 turbine rotor, 16 MW gross (source: STEP Demo) 10 | January/February 2025| www.modernpowersystems.com


The STEP Demo project, led by GTI Energy in collaboration with Southwest Research Institute, GE Vernova’s Advanced Research, the US Department of Energy’s National Energy Technology Laboratory, and several industry partners, is the world’s largest and most advanced indirectly fired sCO2


power plant


designed to demonstrate and validate the sCO2


Brayton power cycle (see Modern Power CLEAR


Natural gas and oxygen combine resulting in


Air separation unit separates oxygen from air


NATURAL GAS IN AIR IN Air separation


OXYGEN IN


INDUSTRIAL GASES


NITROGEN ARGON OXYGEN


Compressor/pump PRESSURE


reheated to be used again in the process


Recirculated CO2 is CO2 HIGH CO2 is repressurised,


for sequestration or commercial use


captured CO2


Schematic of natural gas fuelled Allam-Fetvedt cycle, aka Net Power Cycle (source: Net Power)


is exported OUT High pressure to pipeline


PRESSURE CO2


HIGH CO2 PRESSURE LOW CO2 PRESSURE LOW Water separator LOW


PRESSURE CO2


CO2


and water vapour


COMBUSTOR WATER


expands and turns the


The CO2


turboexpander to generate electricity


ELECTRICITY WATER OUT TURBOEXPANDER WATER WATER


goes into the heat exchanger to cool


The CO2 mixture mixture


Water is removed from the CO2


Heat exchanger


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