# Allam power cycle

The Allam Cycle or Allam-Fetvedt Cycle is a process for converting carbonaceous fuels into thermal energy, while capturing the generated carbon dioxide and water.
The inventors are English engineer Rodney John Allam, American engineer Jeremy Eron Fetvedt, American scientist Dr. Miles R Palmer, and American businessperson and innovator G. William Brown, Jr. The Allam-Fetvedt Cycle was recognized by MIT Technology Review on the 2018 list of 10 Breakthrough Technologies.
This cycle was validated at a 50 MWth natural gas fed test facility in La Porte, Texas in May 2018.

## Description

The Allam-Fetvedt Cycle is a recuperated, high-pressure, Brayton cycle employing a transcritical CO$_2$ working fluid with an oxy-fuel combustion regime. This cycle begins by burning a gaseous fuel with oxygen and a hot, high-pressure, recycled supercritical CO$_2$ working fluid in a combustor. The recycled CO$_2$ stream serves the dual purpose of lowering the combustion flame temperature to a manageable level and diluting the combustion products such that the cycle working fluid is predominantly CO$_2$. The pressure in the combustor can be as high as approximately 30 MPa. The combustion feedstock consists of approximately 95% recycled CO$_2$ by mass.
The combustor provides high-pressure exhaust that can be supplied to a turbine expander operating at a pressure ratio between 6 and 12. The expander discharge leaves as a subcritical CO$_2$ mixture predominantly commingled with combustion derived water. This fluid enters an economizer heat exchanger, which cools the expander discharge to below 65 °C against the stream of CO$_2$ that is recycled to the combustor. Upon exiting the economizer heat exchanger, the expander exhaust is further cooled to near ambient temperature by a central cooling system, enabling liquid water to be removed from the working fluid and recycled for beneficial use.
The remaining working fluid of nearly pure CO$_2$ then enters a compression and pumping stage. The compression system consists of a conventional inter-cooled centrifugal compressor with an inlet pressure below the CO$_2$ critical pressure. The CO$_2$ working fluid is compressed and then cooled to near ambient temperature in the compressor after-cooler. At this point, the combination of compressing and cooling the working fluid permits it to achieve a density in excess of 500 kg/m3. In this condition, the CO$_2$ stream can be pumped to the high combustion pressure required using a multi-stage centrifugal pump. Finally, the high-pressure working fluid is sent back through the economizer heat exchanger to be reheated and returned to the combustor.
The net CO$_2$ product derived from the addition of fuel and oxygen in the combustor is removed from the high-pressure stream; at this point, the CO$_2$ product is high-pressure and high purity, ready for sequestration or utilization without requiring further compression.
Mass flow of the Allam cycle components for natural gas fuel (% of total mass entering the combustion stage) :
| Stage of the cycle | Oxygen | Natural gas | Water (H$_2$O) | Carbon dioxide (CO$_2$) | Carbon dioxide (CO$_2$) |
| Combustion Inlet | 4.75% | 1.25% | – | 94% (hot, high pressure) | 94% (hot, high pressure) |
| Turbine Inlet | – | – | 2.75% (very hot steam) | 97.25% (very hot) | 97.25% (very hot) |
| Heat Exchanger Inlet (Exhaust) | – | – | 2.75% (hot steam) | 97.25% (hot, low pressure) | 97.25% (hot, low pressure) |
| Heat Exchanger Outlet (Exhaust) | – | – | 2.75% (steam condensed) | 97.25% (to compressor-pump) | 97.25% (to compressor-pump) |
| Compressor-Pump Outlet | – | – | 2.75% (steam condensed) | 94% (to heat exchanger) | 3.25% (CCS/CCUS) |
| Heat Exchanger Inlet (Recycle) | – | – | 2.75% (steam condensed) | 94% (compressed) | 3.25% (CCS/CCUS) |
| Heat Exchanger Outlet (Recycle) | – | – | 2.75% (steam condensed) | 94% (hot, compressed, to be recycled) | 3.25% (CCS/CCUS) |
In order for the system to achieve high thermal efficiency, a close temperature approach is needed on the high-temperature side of the primary heat exchanger. Due to the cooling process employed at the compression and pumping stage, a large energy imbalance would typically exist in the cycle between the cooling expander exhaust flow and the reheating CO$_2$ recycle flow.
The Allam-Fetvedt Cycle corrects this imbalance through the incorporation of low-grade heat at the low-temperature end of the recuperative heat exchanger. Due to the low temperatures at the cool end of the cycle, this low-grade heat only needs to be in the range of 100 °C to 400 °C. A convenient source of this heat is the Air Separation Unit (ASU) required for the oxy-fuel combustion regime.
When burning natural gas as a fuel, this basic configuration has been modeled to achieve an efficiency up to 60% (LHV) as a power cycle net of all parasitic loads, including the energy-intensive ASU. Despite its novelty, the components required by this cycle are commercially available, with the exception of the combustion turbine package. The turbine relies on proven technologies and approaches used by existing gas and steam turbine design tools.

## Applications

Construction began in March 2016 in La Porte, Texas on a 50 MWth industrial test facility to showcase the Allam-Fetvedt Cycle, finishing in 2017. In 2018, the Allam-Fetvedt Cycle and supporting technologies were validated, allowing OEMs to certify components for use with future production plants.
On November 15, 2021, at approximately 7:40 pm EST the test facility successfully synchronized to the ERCOT grid proving that the Allam Fetvedt Cycle was capable of generating power at 60 Hz.
This test facility is owned and operated by NET Power, which is owned by Constellation Energy Corporation, Occidental Petroleum (Oxy) Low Carbon Ventures, Baker Hughes and 8 Rivers Capital (the inventor of the technology).
NET Power was awarded the 2018 International Excellence in Energy Breakthrough Technological Project of the Year at the Abu Dhabi International Petroleum Exhibition and Conference (ADIPEC).

## Patent history

Patents :
| Publication Number | Title | Application Date | Publication Date | Current Assignee | Legal Status & Events | Inventor Name |
| US20100300063A1 | Apparatus and Method for Combusting a Fuel at High Pressure and High Temperature, and Associated System and Device | 2010-02-26 | 2010-12-02 | 8 RIVERS CAPITAL, LLC | Granted Pledge Transfer | PALMER, MILES R.; ALLAM, RODNEY JOHN; BROWN, JR., GLENN WILLIAM |
| US9416728B2 | Apparatus and method for combusting a fuel at high pressure and high temperature, and associated system and device | 2010-02-26 | 2016-08-16 | 8 RIVERS CAPITAL, LLC | Granted Pledge Transfer | PALMER, MILES R.; ALLAM, RODNEY JOHN; BROWN, JR., GLENN WILLIAM |
| US20110179799A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2010-08-31 | 2011-07-28 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; PALMER, MILES; BROWN, JR., GLENN WILLIAM |
| US8596075B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2010-08-31 | 2013-12-03 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; PALMER, MILES; BROWN, JR., GLENN WILLIAM |
| US20120067056A1 | System and method for high efficiency power generation using a nitrogen gas working fluid | 2011-09-19 | 2012-03-22 | 8 RIVERS CAPITAL, LLC | Granted Pledge | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON |
| US20120067568A1 | Method of using carbon dioxide in recovery of formation deposits | 2011-09-19 | 2012-03-22 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; FREED, DAVID ARTHUR; BROWN, JR., GLENN WILLIAM |
| US8869889B2 | Method of using carbon dioxide in recovery of formation deposits | 2011-09-19 | 2014-10-28 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; FREED, DAVID ARTHUR; BROWN, JR., GLENN WILLIAM |
| US9410481B2 | System and method for high efficiency power generation using a nitrogen gas working fluid | 2011-09-19 | 2016-08-09 | 8 RIVERS CAPITAL, LLC | Granted Pledge | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON |
| US20130205746A1 | Partial oxidation reaction with closed cycle quench | 2013-02-11 | 2013-08-15 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; PALMER, MILES R. |
| US8776532B2 | Partial oxidation reaction with closed cycle quench | 2013-02-11 | 2014-07-15 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; PALMER, MILES R. |
| US20130199195A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2013-03-14 | 2013-08-08 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM |
| US9062608B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2013-03-14 | 2015-06-23 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM |
| US10018115B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2013-03-15 | 2018-07-10 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM; FETVEDT, JEREMY ERON; FORREST, BROCK ALAN |
| US20130213049A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2013-03-15 | 2013-08-22 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM; FETVEDT, JEREMY ERON; FORREST, BROCK ALAN |
| US20140053529A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2013-11-04 | 2014-02-27 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; BROWN, JR., GLENN WILLIAM; PALMER, MILES R. |
| US8959887B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2013-11-04 | 2015-02-24 | PALMER LABS, LLC; 8 RIVERS CAPITAL, LLC | Granted Pledge | ALLAM, RODNEY JOHN; BROWN, JR., GLENN WILLIAM; PALMER, MILES R. |
| US20140290263A1 | Partial oxidation reaction with closed cycle quench | 2014-06-12 | 2014-10-02 | 8 RIVERS CAPITAL, LLC; PALMER LABS, LLC | Granted | ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; PALMER, MILES R. |
| US9581082B2 | Partial oxidation reaction with closed cycle quench | 2014-06-12 | 2017-02-28 | 8 RIVERS CAPITAL, LLC; PALMER LABS, LLC | Granted | ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; PALMER, MILES R. |
| US10927679B2 | High efficiency power production methods, assemblies, and systems | 2014-07-25 | 2021-02-23 | 8 RIVERS CAPITAL, LLC | Granted | PALMER, MILES R.; FETVEDT, JEREMY ERON; ALLAM, RODNEY JOHN |
| US20140331687A1 | High Efficiency Power Production Methods, Assemblies, and Systems | 2014-07-25 | 2014-11-13 | 8 RIVERS CAPITAL, LLC | Granted | PALMER, MILES R.; FETVEDT, JEREMY ERON; ALLAM, RODNEY JOHN |
| US10047671B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2015-01-23 | 2018-08-14 | 8 RIVERS CAPITAL, LLC | Granted | ALLAM, RODNEY JOHN; BROWN, JR., GLENN WILLIAM; PALMER, MILES R. |
| US20160215693A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2015-01-23 | 2016-07-28 | 8 RIVERS CAPITAL, LLC | Granted | ALLAM, RODNEY JOHN; BROWN, JR., GLENN WILLIAM; PALMER, MILES R. |
| US20150252724A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2015-05-20 | 2015-09-10 | 8 RIVERS CAPITAL, LLC | Granted | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM |
| US9869245B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2015-05-20 | 2018-01-16 | 8 RIVERS CAPITAL, LLC | Granted | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM |
| US20160319741A1 | System and method for high efficiency power generation using a nitrogen gas working fluid | 2016-07-14 | 2016-11-03 | 8 RIVERS CAPITAL, LLC | Granted | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON |
| US9611785B2 | System and method for high efficiency power generation using a nitrogen gas working fluid | 2016-07-14 | 2017-04-04 | 8 RIVERS CAPITAL, LLC | Granted | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON |
| US10054046B2 | System and method for high efficiency power generation using a nitrogen gas working fluid | 2017-03-10 | 2018-08-21 | 8 RIVERS CAPITAL, LLC | Granted | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON |
| US20180016979A1 | System and method for high efficiency power generation using a nitrogen gas working fluid | 2017-03-10 | 2018-01-18 | 8 RIVERS CAPITAL, LLC | Granted | PALMER, MILES; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON |
| US10989113B2 | System and method for power production using partial oxidation | 2017-09-13 | 2021-04-27 | 8 RIVERS CAPITAL, LLC | Granted | FORREST, BROCK ALAN; LU, XIJIA; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; PALMER, MILES R. |
| US20180073430A1 | System and method for power production using partial oxidation | 2017-09-13 | 2018-03-15 | 8 RIVERS CAPITAL, LLC | Granted | FORREST, BROCK ALAN; LU, XIJIA; ALLAM, RODNEY JOHN; FETVEDT, JEREMY ERON; PALMER, MILES R. |
| US10975766B2 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2018-06-13 | 2021-04-13 | 8 RIVERS CAPITAL, LLC | Granted | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM; FETVEDT, JEREMY ERON; FORREST, BROCK ALAN |
| US20180291805A1 | System and method for high efficiency power generation using a carbon dioxide circulating working fluid | 2018-06-13 | 2018-10-11 | 8 RIVERS CAPITAL, LLC | Granted | ALLAM, RODNEY JOHN; PALMER, MILES R.; BROWN, JR., GLENN WILLIAM; FETVEDT, JEREMY ERON; FORREST, BROCK ALAN |