Conventional steam Rankine cycles and open cycle gas turbines play a dominate role in large-scale power production. However there is a large variety of heat sources for which these option do not offer a technically and/or economically viable solution. In these cases the proper selection of the working fluid and of the cycle configuration allow to increase system efficiency, system flexibility and also to reduce the levelised cost of generated energy. Among these solutions the most studied within the GECOS group are the Organic Rankine Cycles (ORC) and the supercritical carbon dioxide cycles (sCO2).
ORC power systems
Organic Rankine Cycles adopt an organic compound (hydrocarbons, halogenated fluids, siloxanes) as working fluid. The possibility to select the main fluid properties allows to obtain large advantages in the design of the components and to always reach high conversion efficiency.
The challenge
The optimisation of an ORC system for a specific application is always a non-trivial task, because of the need to consider simultaneously:
the choice of the best working fluid
the selection and optimization of the best plant layout and components
the effects of fluid properties on expander efficiency
the influence of all these factors on the cost of the plant
Supercritical CO2 power systems
sCO2 cycles can compete with steam Rankine cycles in high temperature applications thanks to the possibility to increase system efficiency and to increase flexibility. The concept is widely studied in literature but this technology is not commercial.
The challenge
The optimisation of these power plant is non-trivial task because of:
The large number (more than 40) of available cycle configurations differing in optimization criteria and strongly affecting the matching with the heat source
The presence of real gas effects at low temperature and high pressure that allow to reduce the compressor consumption but also requires reliable equation of state and a non conventional turbomachinery design
A challenging design of turbine stages and turbine shaft because of the very compact expander dimension and the high specific power
For further information, contact Dr. Marco Astolfi at marco.astolfi@polimi.it or Dr. Marco Binotti at marco.binotti@polimi.it
Related Projects
Recent publications
2015 |
Chiesa, P; Astolfi, M; Giuffrida, A Blue Energy: Salinity Gradient for Energy Conversion Incollection Gallucci, Fausto; Van Sint Annaland, Martin (Ed.): Process Intensification for Sustainable Energy Conversion, pp. 267–298, Wiley, 2015. @incollection{Chiesa2015267, title = {Blue Energy: Salinity Gradient for Energy Conversion}, author = {P Chiesa and M Astolfi and A Giuffrida}, editor = {Fausto Gallucci and Martin {Van Sint Annaland}}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84946426440&doi=10.1002%2F9781118449394.ch9&partnerID=40&md5=23a1c956e1fd12b03d3252e4e0a2a658}, doi = {10.1002/9781118449394.ch9}, year = {2015}, date = {2015-01-01}, booktitle = {Process Intensification for Sustainable Energy Conversion}, pages = {267--298}, publisher = {Wiley}, chapter = {9}, abstract = {Similar to a difference in elevation, potential energy is also associated with a difference in salt concentration so that electric power can eventually be produced by exploiting the salinity gradient between freshwater of rivers and seawater. Unfortunately, exploiting the salinity gradient for power production is not so easy as waterfalls. The potential energy implied in this salinity difference is of the same order of a hundred meter high water drop. The present technology advancement is still far from any commercial application. This chapter presents the different technologies, such as, The Pressure Retarded Osmosis (PRO) technology and The Reverse Electrodialysis (RED) Technology, for power generation from salinity gradient, which have been so far proposed in the technical literature pointing out the theoretical operating principles, the possible plant configurations and identifying the development gap to bridge so as to achieve technical and economical maturity.}, keywords = {}, pubstate = {published}, tppubtype = {incollection} } Similar to a difference in elevation, potential energy is also associated with a difference in salt concentration so that electric power can eventually be produced by exploiting the salinity gradient between freshwater of rivers and seawater. Unfortunately, exploiting the salinity gradient for power production is not so easy as waterfalls. The potential energy implied in this salinity difference is of the same order of a hundred meter high water drop. The present technology advancement is still far from any commercial application. This chapter presents the different technologies, such as, The Pressure Retarded Osmosis (PRO) technology and The Reverse Electrodialysis (RED) Technology, for power generation from salinity gradient, which have been so far proposed in the technical literature pointing out the theoretical operating principles, the possible plant configurations and identifying the development gap to bridge so as to achieve technical and economical maturity. |
2014 |
Valenti, G; Murgia, S; Contaldi, G; Valenti, A Experimental evidence of the thermal effect of lubricating oil sprayed in sliding-vane air compressors Journal Article Case Studies in Thermal Engineering, 4 , pp. 113–117, 2014. @article{Valenti2014113, title = {Experimental evidence of the thermal effect of lubricating oil sprayed in sliding-vane air compressors}, author = {G Valenti and S Murgia and G Contaldi and A Valenti}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84916606926&doi=10.1016%2Fj.csite.2014.08.001&partnerID=40&md5=522ceaff0cb3b26b6c4091f54f521194}, doi = {10.1016/j.csite.2014.08.001}, year = {2014}, date = {2014-01-01}, journal = {Case Studies in Thermal Engineering}, volume = {4}, pages = {113--117}, abstract = {A way to increase the efficiency of positive-displacement air compressor is spraying the lube oil to exploit it not only as lubricating and sealing agent but also as thermal ballast. This work seeks the experimental evidence in sliding-vane compressors by measuring the air standard volume flow rate and the electrical power input of three diverse configurations. The first configuration, taken as the reference, employs a conventional injection system comprising calibrated straight orifices. The other two, referred to as advanced, adopt smaller orifices and pressure-swirl full-cone nozzles designed for the purpose; the third configuration utilizes a pump to boost the oil pressure. The laser imagining technique shows that the nozzles generate sprays that break-up within a short distance into spherical droplets, ligaments, ramifications and undefined structures. Tests on the packaged compressors reveal that the advanced configurations provide almost the same air flow rate while utilizing half of the oil because the sprays generate a good sealing. Moreover, the sprayed oil is acting as a thermal ballast because the electrical input is reduced by 3.5% and 3.0%, respectively, if the pump is present or not, while the specific energy requirement, accounting for the slightly reduced air flow, by 2.4% and 2.9%, respectively. textcopyright 2014 The Authors. Published by Elsevier Ltd.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A way to increase the efficiency of positive-displacement air compressor is spraying the lube oil to exploit it not only as lubricating and sealing agent but also as thermal ballast. This work seeks the experimental evidence in sliding-vane compressors by measuring the air standard volume flow rate and the electrical power input of three diverse configurations. The first configuration, taken as the reference, employs a conventional injection system comprising calibrated straight orifices. The other two, referred to as advanced, adopt smaller orifices and pressure-swirl full-cone nozzles designed for the purpose; the third configuration utilizes a pump to boost the oil pressure. The laser imagining technique shows that the nozzles generate sprays that break-up within a short distance into spherical droplets, ligaments, ramifications and undefined structures. Tests on the packaged compressors reveal that the advanced configurations provide almost the same air flow rate while utilizing half of the oil because the sprays generate a good sealing. Moreover, the sprayed oil is acting as a thermal ballast because the electrical input is reduced by 3.5% and 3.0%, respectively, if the pump is present or not, while the specific energy requirement, accounting for the slightly reduced air flow, by 2.4% and 2.9%, respectively. textcopyright 2014 The Authors. Published by Elsevier Ltd. |
Campanari, S; Gazzani, M High efficiency SOFC power cycles with indirect natural gas reforming and CO2 capture Inproceedings Proceedings of the ASME Turbo Expo, 2014. @inproceedings{Campanari2014c, title = {High efficiency SOFC power cycles with indirect natural gas reforming and CO2 capture}, author = {S Campanari and M Gazzani}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84922201705&doi=10.1115%2FGT2014-26851&partnerID=40&md5=37050dc8862deef4c7979bc5a6870bb2}, doi = {10.1115/GT2014-26851}, year = {2014}, date = {2014-01-01}, booktitle = {Proceedings of the ASME Turbo Expo}, volume = {3A}, abstract = {Driven by the search for the highest theoretical efficiency, several studies have investigated in the last years the adoption of fuel cells in the field of power production from natural gas with CO2 capture. Most of the proposed power cycles rely on high temperature fuel cells, namely Solid Oxide Fuel Cells (SOFC) and Molten Carbonate Fuel Cells (MCFC), based on the concept of hybrid fuel cell plus gas turbine cycles. Accordingly, high temperature fuel cells are integrated with a simple or modified Brayton cycle. As far as SOFC are concerned, two main plant solutions can be identified depending on the integration with the natural gas reforming/shift section: (i) systems where natural gas is-partially or totally-internally reformed in the fuel cell and (ii) systems where natural gas is reformed before the fuel cell and the cell is fed with a high hydrogen syngas. In both cases, CO2 can be separated downstream the fuel cell via a range of available technologies, e.g. chemical or physical separation processes, oxy-combustion and cryogenic methods. Following a literature review on very promising plant configurations, this work investigates the advantages and limits of adopting an external natural gas conversion section with respect to the plant efficiency. As a reference plant we considered a power cycle proposed by Adams and Barton [8], whose performance is the highest found in literature for SOFC-based power cycles, with 82% LHV electrical efficiency. It is based on a pre-reforming concept where fuel is reformed ahead the SOFC which thus works with a high hydrogen content fuel. This plant was firstly reproduced considering all the ideal assumptions proposed by the original authors. As second step, the simulations were focused on revising the power cycle, implementing a complete set of assumptions about component losses and more conservative operating conditions about fuel cell voltage, heat exchangers minimum temperature differences, maximum steam temperature, turbomachinery efficiency, component pressure losses and other adjustments. Considering the consequent modifications with respect to the original layout, the net electric efficiency changes to around 66% LHV with nearly complete (95%+) CO2 capture, a still remarkable but less attractive value, while requiring a very complex and demanding heat exchangers network. Detailed results are presented in terms of energy and material balances of the proposed cycles. All the simulations have been carried out with the proprietary code GS, developed by the GECOS group at Politecnico di Milano.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Driven by the search for the highest theoretical efficiency, several studies have investigated in the last years the adoption of fuel cells in the field of power production from natural gas with CO2 capture. Most of the proposed power cycles rely on high temperature fuel cells, namely Solid Oxide Fuel Cells (SOFC) and Molten Carbonate Fuel Cells (MCFC), based on the concept of hybrid fuel cell plus gas turbine cycles. Accordingly, high temperature fuel cells are integrated with a simple or modified Brayton cycle. As far as SOFC are concerned, two main plant solutions can be identified depending on the integration with the natural gas reforming/shift section: (i) systems where natural gas is-partially or totally-internally reformed in the fuel cell and (ii) systems where natural gas is reformed before the fuel cell and the cell is fed with a high hydrogen syngas. In both cases, CO2 can be separated downstream the fuel cell via a range of available technologies, e.g. chemical or physical separation processes, oxy-combustion and cryogenic methods. Following a literature review on very promising plant configurations, this work investigates the advantages and limits of adopting an external natural gas conversion section with respect to the plant efficiency. As a reference plant we considered a power cycle proposed by Adams and Barton [8], whose performance is the highest found in literature for SOFC-based power cycles, with 82% LHV electrical efficiency. It is based on a pre-reforming concept where fuel is reformed ahead the SOFC which thus works with a high hydrogen content fuel. This plant was firstly reproduced considering all the ideal assumptions proposed by the original authors. As second step, the simulations were focused on revising the power cycle, implementing a complete set of assumptions about component losses and more conservative operating conditions about fuel cell voltage, heat exchangers minimum temperature differences, maximum steam temperature, turbomachinery efficiency, component pressure losses and other adjustments. Considering the consequent modifications with respect to the original layout, the net electric efficiency changes to around 66% LHV with nearly complete (95%+) CO2 capture, a still remarkable but less attractive value, while requiring a very complex and demanding heat exchangers network. Detailed results are presented in terms of energy and material balances of the proposed cycles. All the simulations have been carried out with the proprietary code GS, developed by the GECOS group at Politecnico di Milano. |
2013 |
Valenti, G; Colombo, L; Murgia, S; Lucchini, A; Sampietro, A; Capoferri, A; Araneo, L Thermal effect of lubricating oil in positive-displacement air compressors Journal Article Applied Thermal Engineering, 51 (1-2), pp. 1055–1066, 2013. @article{Valenti20131055, title = {Thermal effect of lubricating oil in positive-displacement air compressors}, author = {G Valenti and L Colombo and S Murgia and A Lucchini and A Sampietro and A Capoferri and L Araneo}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84870209567&doi=10.1016%2Fj.applthermaleng.2012.10.040&partnerID=40&md5=c1f3f501b3f189500bdbf3f56cada802}, doi = {10.1016/j.applthermaleng.2012.10.040}, year = {2013}, date = {2013-01-01}, journal = {Applied Thermal Engineering}, volume = {51}, number = {1-2}, pages = {1055--1066}, abstract = {The isentropic efficiency of positive-displacement compressors may be improved in order to follow an increasing demand for energy savings. This work analyzes the thermal effect of the lubricating oil presence in the air during compression with the scope of exploiting it as a thermal ballast to mitigate both the gas temperature rise and its compression work. The bibliographic review shows that other authors suggested that oil can have positive effects if properly injected. Here an energy balance analysis is executed with the scope of deriving relations for the gas-liquid compression in analogy with those typical for the gas-only compression and of confirming that ideally the liquid presence may have beneficial effects, making the gas-liquid compression even better than 1- and 2-time intercooled gas compressions. Given these positive results, a heat transfer analysis is conducted to model the thermal interaction between gas and oil droplets within a mid-size rotary vane air compressor. A droplet diameter of the order of 100 $mu$m leads to large reductions of both temperature increase and compression work: air can exit the discharge port at a temperature as low as 60 °C and compression work can be lowered by 23-28% with respect to conventional compressors. Finally, a test rig is constructed and operated to investigate a large-flow and large-angle oil nozzle taken from the market showing that, at the operating conditions of a compressor, oil breaks up into small droplets and undefined structures with large exchange surfaces. textcopyright 2012 Elsevier Ltd. All rights reserved.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The isentropic efficiency of positive-displacement compressors may be improved in order to follow an increasing demand for energy savings. This work analyzes the thermal effect of the lubricating oil presence in the air during compression with the scope of exploiting it as a thermal ballast to mitigate both the gas temperature rise and its compression work. The bibliographic review shows that other authors suggested that oil can have positive effects if properly injected. Here an energy balance analysis is executed with the scope of deriving relations for the gas-liquid compression in analogy with those typical for the gas-only compression and of confirming that ideally the liquid presence may have beneficial effects, making the gas-liquid compression even better than 1- and 2-time intercooled gas compressions. Given these positive results, a heat transfer analysis is conducted to model the thermal interaction between gas and oil droplets within a mid-size rotary vane air compressor. A droplet diameter of the order of 100 $mu$m leads to large reductions of both temperature increase and compression work: air can exit the discharge port at a temperature as low as 60 °C and compression work can be lowered by 23-28% with respect to conventional compressors. Finally, a test rig is constructed and operated to investigate a large-flow and large-angle oil nozzle taken from the market showing that, at the operating conditions of a compressor, oil breaks up into small droplets and undefined structures with large exchange surfaces. textcopyright 2012 Elsevier Ltd. All rights reserved. |
Cipollone, R; Valenti, G; Bianchi, G; Murgia, S; Contaldi, G; Calvi, T Energy saving in sliding vane rotary compressors Inproceedings Institution of Mechanical Engineers - 8th International Conference on Compressors and Their Systems, pp. 173–181, 2013. @inproceedings{Cipollone2013173, title = {Energy saving in sliding vane rotary compressors}, author = {R Cipollone and G Valenti and G Bianchi and S Murgia and G Contaldi and T Calvi}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84888623970&partnerID=40&md5=5644780f2bc24012e51c2a58450a8ee3}, year = {2013}, date = {2013-01-01}, booktitle = {Institution of Mechanical Engineers - 8th International Conference on Compressors and Their Systems}, pages = {173--181}, abstract = {Electrical energy for producing compressed air in industrial contexts represents an important share of the overall electricity consumption: this figure accounts for 4-5%. Compressed air is produced by means of rotary volumetric machines which are proven to be more suitable than other types (dynamic, reciprocating, etc...) in terms of pressure and flow rate delivered. Sliding Vane Rotary Compressors (SVRC) compared to screw type compressors are not as widespread. However, thanks to the technological development made in the last two decades, they are characterized by premium specific energy consumption and demonstrate unforeseen potential in terms of energy saving due to some intrinsic features specifically related to this machine. The paper focuses the attention on a new technology under development related to the oil injection inside the machine able to cool the air during compression. A comparison between the results of a mathematical model of the new injection oil technology and experimental p-V measured by means of piezoelectric transducers is shown. The compression work reduction measured on the shaft and observed integrating the p-V cycle gives a strong consistency to the modelling toward a comprehensive physically consistent software platform and to the injection technology. textcopyright The author(s) and/or their employer(s), 2013.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Electrical energy for producing compressed air in industrial contexts represents an important share of the overall electricity consumption: this figure accounts for 4-5%. Compressed air is produced by means of rotary volumetric machines which are proven to be more suitable than other types (dynamic, reciprocating, etc...) in terms of pressure and flow rate delivered. Sliding Vane Rotary Compressors (SVRC) compared to screw type compressors are not as widespread. However, thanks to the technological development made in the last two decades, they are characterized by premium specific energy consumption and demonstrate unforeseen potential in terms of energy saving due to some intrinsic features specifically related to this machine. The paper focuses the attention on a new technology under development related to the oil injection inside the machine able to cool the air during compression. A comparison between the results of a mathematical model of the new injection oil technology and experimental p-V measured by means of piezoelectric transducers is shown. The compression work reduction measured on the shaft and observed integrating the p-V cycle gives a strong consistency to the modelling toward a comprehensive physically consistent software platform and to the injection technology. textcopyright The author(s) and/or their employer(s), 2013. |
2012 |
Chiesa, P Novel cycles: humid air cycle systems Incollection Rao, Ashok D (Ed.): Combined Cycle Systems for Near-Zero Emission Power Generation, pp. 162–185, Woodhead Publishing, 2012. @incollection{Chiesa2012162, title = {Novel cycles: humid air cycle systems}, author = {P Chiesa}, editor = {Ashok D Rao}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84904027000&doi=10.1016%2FB978-0-85709-013-3.50005-5&partnerID=40&md5=753ee64e248192e8ff24a1264af78bd0}, doi = {10.1533/9780857096180.162}, year = {2012}, date = {2012-01-01}, booktitle = {Combined Cycle Systems for Near-Zero Emission Power Generation}, pages = {162--185}, publisher = {Woodhead Publishing}, chapter = {5}, abstract = {This chapter is devoted to gas turbine cycles where water vapor is mixed with air to increase specific power output and efficiency. Basic configurations like steam injected, recuperative water injected and humid air turbine cycles are considered. Mass and thermal balances are reported for each plant, thermodynamic merits and technological drawbacks are illustrated and their performance compared on the basis of homogeneous assumptions. Problems related to operating commercial gas turbine engines in humidified air cycles are also discussed.}, keywords = {}, pubstate = {published}, tppubtype = {incollection} } This chapter is devoted to gas turbine cycles where water vapor is mixed with air to increase specific power output and efficiency. Basic configurations like steam injected, recuperative water injected and humid air turbine cycles are considered. Mass and thermal balances are reported for each plant, thermodynamic merits and technological drawbacks are illustrated and their performance compared on the basis of homogeneous assumptions. Problems related to operating commercial gas turbine engines in humidified air cycles are also discussed. |
2011 |
Margarone, M; Magi, S; Gorla, G; Biffi, S; Siboni, P; Valenti, G; Romano, M C; Giuffrida, A; Negri, E; Macchi, E Revamping, energy efficiency, and exergy analysis of an existing upstream gas treatment facility Journal Article Journal of Energy Resources Technology, Transactions of the ASME, 133 (1), 2011. @article{Margarone2011, title = {Revamping, energy efficiency, and exergy analysis of an existing upstream gas treatment facility}, author = {M Margarone and S Magi and G Gorla and S Biffi and P Siboni and G Valenti and M C Romano and A Giuffrida and E Negri and E Macchi}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-79953057127&doi=10.1115%2F1.4003627&partnerID=40&md5=475439bfc8f30660331cc7f34997cb3e}, doi = {10.1115/1.4003627}, year = {2011}, date = {2011-01-01}, journal = {Journal of Energy Resources Technology, Transactions of the ASME}, volume = {133}, number = {1}, abstract = {Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design. This work analyzes the revamping options of an existing upstream gas facility, chosen because representative of a wide set of plants. It presents a flexible process simulation model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, which includes the performance maps of all turbomachineries and the main characteristics of the investigated modifications. The model may be used to run simulations for various gas input conditions and to predict the performance over 1 year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to the one calculated with state-of-the-art technologies. In addition, exergy and environmental analyses are executed. textcopyright 2011 American Society of Mechanical Engineers.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design. This work analyzes the revamping options of an existing upstream gas facility, chosen because representative of a wide set of plants. It presents a flexible process simulation model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, which includes the performance maps of all turbomachineries and the main characteristics of the investigated modifications. The model may be used to run simulations for various gas input conditions and to predict the performance over 1 year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to the one calculated with state-of-the-art technologies. In addition, exergy and environmental analyses are executed. textcopyright 2011 American Society of Mechanical Engineers. |
2010 |
Margarone, M; Magi, S; Gorla, G; Biffi, S; Siboni, P; Valenti, G; Romano, M C; Giuffrida, A; Negri, E; Macchi, E Revamping, energy efficiency and exergy analysis of an existing upstream gas treatment facility Inproceedings ASME 2010 4th International Conference on Energy Sustainability, ES 2010, pp. 339–348, 2010. @inproceedings{Margarone2010339, title = {Revamping, energy efficiency and exergy analysis of an existing upstream gas treatment facility}, author = {M Margarone and S Magi and G Gorla and S Biffi and P Siboni and G Valenti and M C Romano and A Giuffrida and E Negri and E Macchi}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-84860274198&doi=10.1115%2FES2010-90213&partnerID=40&md5=ec792a745c2fd3d6e082f6216d49af92}, doi = {10.1115/ES2010-90213}, year = {2010}, date = {2010-01-01}, booktitle = {ASME 2010 4th International Conference on Energy Sustainability, ES 2010}, volume = {1}, pages = {339--348}, abstract = {Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design point and inefficiently. This work analyzes the revamping options of an existing upstream gas facility, which is chosen because representative of a wide set of plants. A flexible numerical model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, includes the performance maps of all turbo machineries and the main characteristics of the investigated modifications in order to run simulation for many gas input conditions and to predict the performance over a year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to that calculated with state-of-the-art technologies. In addition, an exergy and an environmental analyses are executed. textcopyright 2010 by ASME.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Surface oil and gas treatment facilities in service for decades are likely to be oversized due to the natural depletion of their reservoirs. Despite these plants might have been designed modularly, meaning they comprise multiple identical units serving the same task, such units operate often in conditions far from the design point and inefficiently. This work analyzes the revamping options of an existing upstream gas facility, which is chosen because representative of a wide set of plants. A flexible numerical model, implemented in the HYSYS environment and dynamically linked to an Excel spreadsheet, includes the performance maps of all turbo machineries and the main characteristics of the investigated modifications in order to run simulation for many gas input conditions and to predict the performance over a year of operation and for different possible future scenarios. The first objective is to assess economically the considered options, which shall be applied only if yielding short return times of the investment since the reservoir is mature. Moreover, all options are appreciated adopting a figure of merit, here defined, that compares the overall energy consumption to that calculated with state-of-the-art technologies. In addition, an exergy and an environmental analyses are executed. textcopyright 2010 by ASME. |
1994 |
Chiesa, Paolo; Lozza, Giovanni; Meechi, E; Consonni, Stefano; Macchi, Ennio; Consonni, Stefano Assessment of the thermodynamic performance of mixed gas-steam cycles: part B: water-injected and hat cycles Inproceedings Proceedings of the ASME Turbo Expo, pp. 1–13, 1994. @inproceedings{Chiesa19941, title = {Assessment of the thermodynamic performance of mixed gas-steam cycles: part B: water-injected and hat cycles}, author = {Paolo Chiesa and Giovanni Lozza and E Meechi and Stefano Consonni and Ennio Macchi and Stefano Consonni}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0027928257&partnerID=40&md5=b2f03c0f9c3ea2dbcdcb9783466a7a36 https://www.scopus.com/inward/record.uri?eid=2-s2.0-84924419789&doi=10.1115%2F94GT424&partnerID=40&md5=d45b98db5a35e7eb658b382dfcc86f04}, doi = {10.1115/94GT424}, year = {1994}, date = {1994-01-01}, booktitle = {Proceedings of the ASME Turbo Expo}, volume = {4}, pages = {1--13}, abstract = {Part B of this paper focuses on intercooled recuperated cycles where water is injected to improve both efficiency and power output. This concept is investigated for two basic cycle configurations: a Recuperated Water Injected (RWI) cycle, where water is simply injected downstream the HP compressor, and a Humid Air Turbine (HAT) cycle, where air/water mixing is accomplished in a counter-current heat/mass transfer column called 'saturator'. For both configurations we discuss the selection and the optimization of the main cycle parameters, and track the variations of efficiency and specific work with overall gas turbine pressure ratio and turbine inlet temperature (TIT). TIT can vary to take advantage of lower gas turbine coolant temperatures, but only within the capabilities of current technology. For HAT cycles we also address the modelization of the saturator and the sensitivity to the most crucial characteristics of novel components (temperature differences and pressure drops in heat/mass transfer equipment). The efficiency penalties associated to each process are evaluated by a second-law analysis which also includes the cycles considered in Part A. For any given TIT in the range considered (1250 to 1500°C), the more reversible air/water mixing mechanism realized in the saturator allows HAT cycles to achieve efficiencies about 2 percentage points higher than those of RWI cycles: at the TIT of 1500°C made possible by intercooling, state-of-the-art aero-engines embodying the above cycle modifications can reach net electrical efficiencies of about 57% and 55%, respectively. This compares to efficiencies slightly below 56% achievable by combined cycles based upon large-scale heavy duty machines with TIT = 1280°C.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Part B of this paper focuses on intercooled recuperated cycles where water is injected to improve both efficiency and power output. This concept is investigated for two basic cycle configurations: a Recuperated Water Injected (RWI) cycle, where water is simply injected downstream the HP compressor, and a Humid Air Turbine (HAT) cycle, where air/water mixing is accomplished in a counter-current heat/mass transfer column called 'saturator'. For both configurations we discuss the selection and the optimization of the main cycle parameters, and track the variations of efficiency and specific work with overall gas turbine pressure ratio and turbine inlet temperature (TIT). TIT can vary to take advantage of lower gas turbine coolant temperatures, but only within the capabilities of current technology. For HAT cycles we also address the modelization of the saturator and the sensitivity to the most crucial characteristics of novel components (temperature differences and pressure drops in heat/mass transfer equipment). The efficiency penalties associated to each process are evaluated by a second-law analysis which also includes the cycles considered in Part A. For any given TIT in the range considered (1250 to 1500°C), the more reversible air/water mixing mechanism realized in the saturator allows HAT cycles to achieve efficiencies about 2 percentage points higher than those of RWI cycles: at the TIT of 1500°C made possible by intercooling, state-of-the-art aero-engines embodying the above cycle modifications can reach net electrical efficiencies of about 57% and 55%, respectively. This compares to efficiencies slightly below 56% achievable by combined cycles based upon large-scale heavy duty machines with TIT = 1280°C. |
Macchi, Ennio; Consonni, Stefano; Lozza, Giovanni; Chiesa, Paolo Assessment of the thermodynamic performance of mixed gas-steam cycles: part A: intercooled and steam-injected cycles Inproceedings American Society of Mechanical Engineers (Paper), pp. 1–12, 1994. @inproceedings{Macchi19941b, title = {Assessment of the thermodynamic performance of mixed gas-steam cycles: part A: intercooled and steam-injected cycles}, author = {Ennio Macchi and Stefano Consonni and Giovanni Lozza and Paolo Chiesa}, url = {https://www.scopus.com/inward/record.uri?eid=2-s2.0-0028090833&partnerID=40&md5=c3ee52287066a3ead2dc0415af473b1e}, year = {1994}, date = {1994-01-01}, booktitle = {American Society of Mechanical Engineers (Paper)}, pages = {1--12}, abstract = {This paper discusses the thermodynamics of power cycles where steam or water are mixed with air (or combustion gases) to improve the performance of stationary gas turbine cycles fired on clean fuels. In particular, we consider cycles based on modified versions of modern, high-performance, high-efficiency aero-derivative engines. The paper is divided into two parts. After a brief description of the calculation method, in Part A we review the implications of intercooling and analyze cycles with steam injection (STIG and ISTIG). In Part B we examine cycles with water injection (RWI and HAT). Due to lower coolant temperatures, intercooling enables to reduce turbine cooling flows and/or to increase the turbine inlet temperature. Results show that this can provide significant power and efficiency improvements for both simple cycle and combined cycle systems based on aero-engines; systems based on heavy-duty machines also experience power output augmentation, but almost no efficiency improvement. Mainly due to the irreversibilities of steam/air mixing, intercooled steam injected cycles cannot achieve efficiencies beyond the 52-53% range even at turbine inlet temperatures of 1500°C. On the other hand, by accomplishing more reversible water-air mixing, the cycles analyzed in Part B can reach efficiencies comparable (RWI cycles) or even superior (HAT cycles) to those of conventional 'unmixed' combined cycles.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } This paper discusses the thermodynamics of power cycles where steam or water are mixed with air (or combustion gases) to improve the performance of stationary gas turbine cycles fired on clean fuels. In particular, we consider cycles based on modified versions of modern, high-performance, high-efficiency aero-derivative engines. The paper is divided into two parts. After a brief description of the calculation method, in Part A we review the implications of intercooling and analyze cycles with steam injection (STIG and ISTIG). In Part B we examine cycles with water injection (RWI and HAT). Due to lower coolant temperatures, intercooling enables to reduce turbine cooling flows and/or to increase the turbine inlet temperature. Results show that this can provide significant power and efficiency improvements for both simple cycle and combined cycle systems based on aero-engines; systems based on heavy-duty machines also experience power output augmentation, but almost no efficiency improvement. Mainly due to the irreversibilities of steam/air mixing, intercooled steam injected cycles cannot achieve efficiencies beyond the 52-53% range even at turbine inlet temperatures of 1500°C. On the other hand, by accomplishing more reversible water-air mixing, the cycles analyzed in Part B can reach efficiencies comparable (RWI cycles) or even superior (HAT cycles) to those of conventional 'unmixed' combined cycles. |