CO_(2) can be used as an alternative injectant to exploit geothermal energy from depleted high-temperature gas reservoirs due to its high mobility and unique thermal properties.However,there has been a lack of systema...CO_(2) can be used as an alternative injectant to exploit geothermal energy from depleted high-temperature gas reservoirs due to its high mobility and unique thermal properties.However,there has been a lack of systematic analysis on the heat mining mechanism and performance of CO_(2),as well as the problems that may occur during geothermal energy exploitation at specific gas reservoir conditions.In this paper,a base numerical simulation model of a typical depleted high-temperature gas reservoir was established to simulate the geothermal energy exploitation processes via recycling CO_(2) and water,with a view to investigate whether and/or at which conditions CO_(2) is more suitable than water for geothermal energy exploitation.The problems that may occur during the CO_(2)-based geothermal energy exploitation were also analyzed along with proposed feasible solutions.The results indicate that,for a depleted low-permeability gas reservoir with dimensions of 1000 m×500 m×50 m and temperature of 150℃ using a single injection-production well group for 40 years of operation,the heat mining rate of CO_(2) can be up to 3.8 MW at a circulation flow rate of 18 kg s^(-1)due to its high mobility along with the flow path in the gas reservoir,while the heat mining rate of water is only about 2 MW due to limitations on the injectivity and mobility.The reservoir physical property and injection-production scheme have some effects on the heat mining rate,but CO_(2)always has better performance than water at most reservoir and operation conditions,even under a high water saturation.The main problems for CO_(2) circulation are wellbore corrosion and salt precipitation that can occur when the reservoir has high water saturation and high salinity,in which serious salt precipitation can reduce formation permeability and result in a decline of CO_(2) heat mining rate (e.g.up to 24%reduction).It is proposed to apply a low-salinity water slug before CO_(2)injection to reduce the damage caused by salt precipitation.For high-permeability gas reservoirs with high water saturation and high salinity,the superiority of CO_(2) as a heat transmission fluid becomes obscure and water injection is recommended.展开更多
Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introdu...Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.展开更多
Subsurface geothermal energy storage has greater potential than other energy storage strategies in terms of capacity scale and time duration.Carbon dioxide(CO_(2))is regarded as a potential medium for energy storage d...Subsurface geothermal energy storage has greater potential than other energy storage strategies in terms of capacity scale and time duration.Carbon dioxide(CO_(2))is regarded as a potential medium for energy storage due to its superior thermal properties.Moreover,the use of CO_(2)plumes for geothermal energy storage mitigates the greenhouse effect by storing CO_(2)in geological bodies.In this work,an integrated framework is proposed for synergistic geothermal energy storage and CO_(2)sequestration and utilization.Within this framework,CO_(2)is first injected into geothermal layers for energy accumulation.The resultant high-energy CO_(2)is then introduced into a target oil reservoir for CO_(2)utilization and geothermal energy storage.As a result,CO_(2)is sequestrated in the geological oil reservoir body.The results show that,as high-energy CO_(2)is injected,the average temperature of the whole target reservoir is greatly increased.With the assistance of geothermal energy,the geological utilization efficiency of CO_(2)is higher,resulting in a 10.1%increase in oil displacement efficiency.According to a storage-potential assessment of the simulated CO_(2)site,110 years after the CO_(2)injection,the utilization efficiency of the geological body will be as high as 91.2%,and the final injection quantity of the CO_(2)in the site will be as high as 9.529×10^(8)t.After 1000 years sequestration,the supercritical phase dominates in CO_(2)sequestration,followed by the liquid phase and then the mineralized phase.In addition,CO_(2)sequestration accounting for dissolution trapping increases significantly due to the presence of residual oil.More importantly,CO_(2)exhibits excellent performance in storing geothermal energy on a large scale;for example,the total energy stored in the studied geological body can provide the yearly energy supply for over 3.5×10^(7) normal households.Application of this integrated approach holds great significance for large-scale geothermal energy storage and the achievement of carbon neutrality.展开更多
The energy industry faces a significant challenge in extracting natural gas from offshore natural gas hydrate(NGH)reservoirs,primarily due to the low productivity of wells and the high operational costs involved.The p...The energy industry faces a significant challenge in extracting natural gas from offshore natural gas hydrate(NGH)reservoirs,primarily due to the low productivity of wells and the high operational costs involved.The present study offers an assessment of the feasibility of utilizing geothermal energy to augment the production of natural gas from offshore gas hydrate reservoirs through the implementation of the methane-CO_(2)swapping technique.The present study expands the research scope of the authors beyond their previous publication,which exclusively examined the generation of methane from marine gas hydrates.Specifically,the current investigation explores the feasibility of utilizing the void spaces created by the extracted methane in the hydrate reservoir for carbon dioxide storage.Analytical models were employed to forecast the heat transfer from a geothermal zone to an NGH reservoir.A study was conducted utilizing data obtained from a reservoir situated in the Shenhu region of the Northern South China Sea.The findings of the model indicate that the implementation of geothermal heating can lead to a substantial enhancement in the productivity of wells located in heated reservoirs during CO_(2)swapping procedures.The non-linear relationship between the temperature of the heated reservoir and the rate of fold increase has been observed.It is anticipated that the fold of increase will surpass 5 when the gas hydrate reservoir undergoes a temperature rise from 6℃ to 16℃.The mathematical models utilized in this study did not incorporate the impact of heat convection resulting from CO_(2)flow into the gas reservoir.This factor has the potential to enhance well productivity.The mathematical models’deviation assumptions may cause over-prediction of well productivity in geothermal-stimulated reservoirs.Additional research is required to examine the impacts of temperature drawdown,heat convection resulting from depressurization,heat-induced gas pressure increment,and the presence of free gas in the formation containing hydrates.The process of CH4-CO_(2)swapping,which has been investigated,involves the utilization of geothermal stimulation.This method is highly encouraging as it enables the efficient injection of CO_(2)into gas hydrate reservoirs,resulting in the permanent sequestration of CO_(2)in a solid state.Additional research is warranted to examine the rate of mass transfer of CO_(2)within reservoirs of gas hydrates.展开更多
Geothermal energy from deep underground (or geological) formations,with or without its combination with carbon capture and storage (CCS),can be a key technology to mitigate anthropogenic greenhouse gas emissions and m...Geothermal energy from deep underground (or geological) formations,with or without its combination with carbon capture and storage (CCS),can be a key technology to mitigate anthropogenic greenhouse gas emissions and meet the 2050 net‐zero carbon emission target.Geothermal resources in low‐permeability and medium‐and high‐temperature reservoirs in sedimentary sequence require hydraulic stimulation for enhanced geothermal systems (EGS).However,fluid migration for geothermal energy in EGS or with potential CO_(2) storage in a CO_(2)‐EGS are both dependent on the in situ flow pathway network created by induced fluid injection.These thermo‐mechanical interactions can be complex and induce varying alterations in the mechanical response when the working fluid is water (in EGS) or supercritical CO_(2)(in CO_(2)‐EGS),which could impact the geothermal energy recovery from geological formations.Therefore,there is a need for a deeper understanding of the heat extraction process in EGS and CO_(2)‐EGS.This study presents a systematic review of the effects of changes in mechanical properties and behavior of deep underground rocks on the induced flow pathway and heat recovery in EGS reservoirs with or without CO_(2) storage in CO_(2) ‐EGS.Further,we proposed waterless‐stimulated EGS as an alternative approach to improve heat energy extraction in EGS.Lastly,based on the results of our literature review and proposed ideas,we recommend promising areas of investigation that may provide more insights into understanding geothermo‐mechanics to further stimulate new research studies and accelerate the development of geothermal energy as a viable clean energy technology.展开更多
A comprehensive thermo-economic model combining a geothermal heat mining system and a direct supercritical CO_(2) turbine expansion electric power generation system was proposed in this paper.Assisted by this integrat...A comprehensive thermo-economic model combining a geothermal heat mining system and a direct supercritical CO_(2) turbine expansion electric power generation system was proposed in this paper.Assisted by this integrated model,thermo-economic and optimization analyses for the key design parameters of the whole system including the geothermal well pattern and operational conditions were performed to obtain a minimal levelized cost of electricity(LCOE).Specifically,in geothermal heat extraction simulation,an integrated wellbore-reservoir system model(T2Well/ECO_(2)N)was used to generate a database for creating a fast,predictive,and compatible geothermal heat mining model by employing a response surface methodology.A parametric study was conducted to demonstrate the impact of turbine discharge pressure,injection and production well distance,CO_(2) injection flowrate,CO_(2) injection temperature,and monitored production well bottom pressure on LCOE,system thermal efficiency,and capital cost.It was found that for a 100 MWe power plant,a minimal LCOE of$0.177/kWh was achieved for a 20-year steady operation without considering CO_(2) sequestration credit.In addition,when CO_(2) sequestration credit is$1.00/t,an LCOE breakeven point compared to a conventional geothermal power plant is achieved and a breakpoint for generating electric power generation at no cost was achieved for a sequestration credit of $2.05/t.展开更多
CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration economy.Petrothermal geothermal energy has a tre...CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration economy.Petrothermal geothermal energy has a tremendous worldwide potential for decarbonising both the power and heating sectors.This paper investigates three potential CPG configurations for combined heating and power generation(CHP).The present work examines scenarios with reservoir depths of 4 km and 5 km,as well as required district heating system(DHS)supply temperatures of 70℃ and 90℃.The results reveal that a two-staged serial CHP concept eventuates in the highest achievable net power output.For a thermosiphon system,the relative net power reduction by the CHP option compared with a sole power generation system is significantly lower than for a pumped system.The net power reduction for pumped systems lies between 62.6%and 22.9%.For a thermosiphon system with a depth of 5 km and a required DHS supply temperature of 70℃,the achievable net power by the most beneficial CHP option is even 9.2%higher than for sole power generation systems.The second law efficiency for the sole power generation concepts are in a range between 33.0%and 43.0%.The second law efficiency can increase up to 63.0%in the case of a CHP application.Thus,the combined heat and power generation can significantly increase the overall second law efficiency of a CPG system.The evaluation of the achievable revenues demonstrates that a CHP application might improve the economic performance of both thermosiphon and pumped CPG systems.However,the minimum heat revenue required for compensating the power reduction increases with higher electricity revenues.In summary,the results of this work provide valuable insights for the potential development of CPG systems for CHP applications and their economic feasibility.展开更多
Geothermal power plants(GPP)with high non condensable gases(NCG)content geothermal fluid have shown to be environmental impacting relating to their energy production,which could be critical if no corrective actions ar...Geothermal power plants(GPP)with high non condensable gases(NCG)content geothermal fluid have shown to be environmental impacting relating to their energy production,which could be critical if no corrective actions are achieved.The GPP of Kizildere 3 U1,located in Türkiye(Denizli),in where the geothermal fluid contains high percentage of CO_(2),99%of the NCG fraction,which represents the 3%of the geothermal fluid mass,is taken as a relevant case study to implement a new innovation consisting of NCG reinjection to reduce the amount of NCGs released to the atmosphere.In order to calculate the present environmental impacts which the plant is causing(baseline);and the potential reduction of environmental impacts which can be achieved with the innovation(reinjection),a life cycle assessment(LCA)calculation were developed.Primary data were collected for all the relevant stages of the energy conversion cycle and complemented where necessary with secondary data from other geothermal power plants studies.The main results of the baseline environmental assessment show that the construction phase is the most impacting phase due to the materials used in the power plant building construction,electrical generation equipment and distributed machinery and infrastructures;the effects in the operation phase are dominated by the geothermal fluid composition.In this sense,the application of CO_(2) reinjection at the Turkish site into the reservoir will prevent the emission of 1,700 tons⋅year1 in the pilot site and 10%of the total emissions released along the life span of the GPP.展开更多
基金This research was financially supported by the National Natural Science Foundation of China(Grant No.51674282)the National Key R&D Programs of China(Grant No.2019YFB1504201,2019YFB1504203,and 2019YFB1504204)+2 种基金the Fundamental Research Funds for the Central Universities,China University of Geosciences(Wuhan)(Grant No.CUGGC09 and CUG200637)the Open Project Program of Key Laboratory of Groundwater Resources and Environment(Jilin University),Ministry of Education(Grant No.202005001KF)Opening Fund of Key Laboratory of Unconventional Oil&Gas Development(China University of Petroleum(East China)),Ministry of Education(Grant No.19CX05005A-201)。
文摘CO_(2) can be used as an alternative injectant to exploit geothermal energy from depleted high-temperature gas reservoirs due to its high mobility and unique thermal properties.However,there has been a lack of systematic analysis on the heat mining mechanism and performance of CO_(2),as well as the problems that may occur during geothermal energy exploitation at specific gas reservoir conditions.In this paper,a base numerical simulation model of a typical depleted high-temperature gas reservoir was established to simulate the geothermal energy exploitation processes via recycling CO_(2) and water,with a view to investigate whether and/or at which conditions CO_(2) is more suitable than water for geothermal energy exploitation.The problems that may occur during the CO_(2)-based geothermal energy exploitation were also analyzed along with proposed feasible solutions.The results indicate that,for a depleted low-permeability gas reservoir with dimensions of 1000 m×500 m×50 m and temperature of 150℃ using a single injection-production well group for 40 years of operation,the heat mining rate of CO_(2) can be up to 3.8 MW at a circulation flow rate of 18 kg s^(-1)due to its high mobility along with the flow path in the gas reservoir,while the heat mining rate of water is only about 2 MW due to limitations on the injectivity and mobility.The reservoir physical property and injection-production scheme have some effects on the heat mining rate,but CO_(2)always has better performance than water at most reservoir and operation conditions,even under a high water saturation.The main problems for CO_(2) circulation are wellbore corrosion and salt precipitation that can occur when the reservoir has high water saturation and high salinity,in which serious salt precipitation can reduce formation permeability and result in a decline of CO_(2) heat mining rate (e.g.up to 24%reduction).It is proposed to apply a low-salinity water slug before CO_(2)injection to reduce the damage caused by salt precipitation.For high-permeability gas reservoirs with high water saturation and high salinity,the superiority of CO_(2) as a heat transmission fluid becomes obscure and water injection is recommended.
基金financially supported by the International Science&Technology Cooperation Program of China(Grant No.2012DFA60760)
文摘Rock is generally complex and heterogeneous,therefore the heterogeneity effects of effective stress and temperature on permeability should be taken into account.In this study,two-part Hooke’s model（TPHM） is introduced to understand the influences of effective stress and temperature on permeability of soft and hard parts（two parts） of rock based on coupling thermo-hydro-mechanical tests.Under a fixed temperature level（25 ℃.35 ℃.50 ℃.65 ℃.80 ℃.90 ℃ and 95 ℃）.the tests were carried out in a conventional triaxial system whereas the confining pressure was remained at 50 MPa.and the pore pressure was increased to the specified levels step by step.i.e.8 MPa,18 MPa.28 MPa.38 MPa.41 MPa,44 MPa.46 MPa and 48 MPa.The temperature-dependent relationships for two parts permeabilities are proposed on the basis of the initial test results.We point out that temperature of 65 ℃-90 ℃ is the threshold for the development of CO2-plume geothermal（CPC） reservoir sandstone cracking under low effective stress（2-9 MPa） based on the relationship between temperature and soft part permeability.Furthermore,we discuss the effect of temperature on the two parts in the rock.The results indicate that as the temperature increases from 25 ℃ to 65 ℃.the flow channel in the hard part has a stronger response to temperature than that in the soft part at a fixed effective stress level,which is opposite to the situation of effective stress.Considering that natural rock is generally heterogeneous with non-uniform pore structure,we suggest a physical interpretation of the phenomenon that before the thermal cracking threshold the two parts have different responses to temperature.
基金supported by the National Key Research and Development Program of China under grant(2022YFE0206700)the financial support by the National Natural Science Foundation of China(52004320)the Science Foundation of China University of Petroleum,Beijing(2462021QNXZ012 and 2462021YJRC012)。
文摘Subsurface geothermal energy storage has greater potential than other energy storage strategies in terms of capacity scale and time duration.Carbon dioxide(CO_(2))is regarded as a potential medium for energy storage due to its superior thermal properties.Moreover,the use of CO_(2)plumes for geothermal energy storage mitigates the greenhouse effect by storing CO_(2)in geological bodies.In this work,an integrated framework is proposed for synergistic geothermal energy storage and CO_(2)sequestration and utilization.Within this framework,CO_(2)is first injected into geothermal layers for energy accumulation.The resultant high-energy CO_(2)is then introduced into a target oil reservoir for CO_(2)utilization and geothermal energy storage.As a result,CO_(2)is sequestrated in the geological oil reservoir body.The results show that,as high-energy CO_(2)is injected,the average temperature of the whole target reservoir is greatly increased.With the assistance of geothermal energy,the geological utilization efficiency of CO_(2)is higher,resulting in a 10.1%increase in oil displacement efficiency.According to a storage-potential assessment of the simulated CO_(2)site,110 years after the CO_(2)injection,the utilization efficiency of the geological body will be as high as 91.2%,and the final injection quantity of the CO_(2)in the site will be as high as 9.529×10^(8)t.After 1000 years sequestration,the supercritical phase dominates in CO_(2)sequestration,followed by the liquid phase and then the mineralized phase.In addition,CO_(2)sequestration accounting for dissolution trapping increases significantly due to the presence of residual oil.More importantly,CO_(2)exhibits excellent performance in storing geothermal energy on a large scale;for example,the total energy stored in the studied geological body can provide the yearly energy supply for over 3.5×10^(7) normal households.Application of this integrated approach holds great significance for large-scale geothermal energy storage and the achievement of carbon neutrality.
基金funding the project“Safe,Sustainable,and Resilient Development of Offshore Reservoirs and Natural Gas Upgrading through Innovative Science and Technology:Gulf of Mexico–Mediterranean,”through Contract No.EC-19 Fossil Energy。
文摘The energy industry faces a significant challenge in extracting natural gas from offshore natural gas hydrate(NGH)reservoirs,primarily due to the low productivity of wells and the high operational costs involved.The present study offers an assessment of the feasibility of utilizing geothermal energy to augment the production of natural gas from offshore gas hydrate reservoirs through the implementation of the methane-CO_(2)swapping technique.The present study expands the research scope of the authors beyond their previous publication,which exclusively examined the generation of methane from marine gas hydrates.Specifically,the current investigation explores the feasibility of utilizing the void spaces created by the extracted methane in the hydrate reservoir for carbon dioxide storage.Analytical models were employed to forecast the heat transfer from a geothermal zone to an NGH reservoir.A study was conducted utilizing data obtained from a reservoir situated in the Shenhu region of the Northern South China Sea.The findings of the model indicate that the implementation of geothermal heating can lead to a substantial enhancement in the productivity of wells located in heated reservoirs during CO_(2)swapping procedures.The non-linear relationship between the temperature of the heated reservoir and the rate of fold increase has been observed.It is anticipated that the fold of increase will surpass 5 when the gas hydrate reservoir undergoes a temperature rise from 6℃ to 16℃.The mathematical models utilized in this study did not incorporate the impact of heat convection resulting from CO_(2)flow into the gas reservoir.This factor has the potential to enhance well productivity.The mathematical models’deviation assumptions may cause over-prediction of well productivity in geothermal-stimulated reservoirs.Additional research is required to examine the impacts of temperature drawdown,heat convection resulting from depressurization,heat-induced gas pressure increment,and the presence of free gas in the formation containing hydrates.The process of CH4-CO_(2)swapping,which has been investigated,involves the utilization of geothermal stimulation.This method is highly encouraging as it enables the efficient injection of CO_(2)into gas hydrate reservoirs,resulting in the permanent sequestration of CO_(2)in a solid state.Additional research is warranted to examine the rate of mass transfer of CO_(2)within reservoirs of gas hydrates.
文摘Geothermal energy from deep underground (or geological) formations,with or without its combination with carbon capture and storage (CCS),can be a key technology to mitigate anthropogenic greenhouse gas emissions and meet the 2050 net‐zero carbon emission target.Geothermal resources in low‐permeability and medium‐and high‐temperature reservoirs in sedimentary sequence require hydraulic stimulation for enhanced geothermal systems (EGS).However,fluid migration for geothermal energy in EGS or with potential CO_(2) storage in a CO_(2)‐EGS are both dependent on the in situ flow pathway network created by induced fluid injection.These thermo‐mechanical interactions can be complex and induce varying alterations in the mechanical response when the working fluid is water (in EGS) or supercritical CO_(2)(in CO_(2)‐EGS),which could impact the geothermal energy recovery from geological formations.Therefore,there is a need for a deeper understanding of the heat extraction process in EGS and CO_(2)‐EGS.This study presents a systematic review of the effects of changes in mechanical properties and behavior of deep underground rocks on the induced flow pathway and heat recovery in EGS reservoirs with or without CO_(2) storage in CO_(2) ‐EGS.Further,we proposed waterless‐stimulated EGS as an alternative approach to improve heat energy extraction in EGS.Lastly,based on the results of our literature review and proposed ideas,we recommend promising areas of investigation that may provide more insights into understanding geothermo‐mechanics to further stimulate new research studies and accelerate the development of geothermal energy as a viable clean energy technology.
基金funded by the Mexican National Council of Science and Technology(CONACYT in Spanish),under the Sectorial Fund for Energy Sustainability,CONACYT-Secretaiy of Energy(No.S0019-2012-04).
文摘A comprehensive thermo-economic model combining a geothermal heat mining system and a direct supercritical CO_(2) turbine expansion electric power generation system was proposed in this paper.Assisted by this integrated model,thermo-economic and optimization analyses for the key design parameters of the whole system including the geothermal well pattern and operational conditions were performed to obtain a minimal levelized cost of electricity(LCOE).Specifically,in geothermal heat extraction simulation,an integrated wellbore-reservoir system model(T2Well/ECO_(2)N)was used to generate a database for creating a fast,predictive,and compatible geothermal heat mining model by employing a response surface methodology.A parametric study was conducted to demonstrate the impact of turbine discharge pressure,injection and production well distance,CO_(2) injection flowrate,CO_(2) injection temperature,and monitored production well bottom pressure on LCOE,system thermal efficiency,and capital cost.It was found that for a 100 MWe power plant,a minimal LCOE of$0.177/kWh was achieved for a 20-year steady operation without considering CO_(2) sequestration credit.In addition,when CO_(2) sequestration credit is$1.00/t,an LCOE breakeven point compared to a conventional geothermal power plant is achieved and a breakpoint for generating electric power generation at no cost was achieved for a sequestration credit of $2.05/t.
基金Funding from the Bavarian State Ministry of Education,Science and the Arts in the framework of the Project Geothermal-Alliance Bavaria。
文摘CO_(2) Plume Geothermal(CPG)systems are a promising concept for utilising petrothermal resources in the context of a future carbon capture utilisation and sequestration economy.Petrothermal geothermal energy has a tremendous worldwide potential for decarbonising both the power and heating sectors.This paper investigates three potential CPG configurations for combined heating and power generation(CHP).The present work examines scenarios with reservoir depths of 4 km and 5 km,as well as required district heating system(DHS)supply temperatures of 70℃ and 90℃.The results reveal that a two-staged serial CHP concept eventuates in the highest achievable net power output.For a thermosiphon system,the relative net power reduction by the CHP option compared with a sole power generation system is significantly lower than for a pumped system.The net power reduction for pumped systems lies between 62.6%and 22.9%.For a thermosiphon system with a depth of 5 km and a required DHS supply temperature of 70℃,the achievable net power by the most beneficial CHP option is even 9.2%higher than for sole power generation systems.The second law efficiency for the sole power generation concepts are in a range between 33.0%and 43.0%.The second law efficiency can increase up to 63.0%in the case of a CHP application.Thus,the combined heat and power generation can significantly increase the overall second law efficiency of a CPG system.The evaluation of the achievable revenues demonstrates that a CHP application might improve the economic performance of both thermosiphon and pumped CPG systems.However,the minimum heat revenue required for compensating the power reduction increases with higher electricity revenues.In summary,the results of this work provide valuable insights for the potential development of CPG systems for CHP applications and their economic feasibility.
文摘Geothermal power plants(GPP)with high non condensable gases(NCG)content geothermal fluid have shown to be environmental impacting relating to their energy production,which could be critical if no corrective actions are achieved.The GPP of Kizildere 3 U1,located in Türkiye(Denizli),in where the geothermal fluid contains high percentage of CO_(2),99%of the NCG fraction,which represents the 3%of the geothermal fluid mass,is taken as a relevant case study to implement a new innovation consisting of NCG reinjection to reduce the amount of NCGs released to the atmosphere.In order to calculate the present environmental impacts which the plant is causing(baseline);and the potential reduction of environmental impacts which can be achieved with the innovation(reinjection),a life cycle assessment(LCA)calculation were developed.Primary data were collected for all the relevant stages of the energy conversion cycle and complemented where necessary with secondary data from other geothermal power plants studies.The main results of the baseline environmental assessment show that the construction phase is the most impacting phase due to the materials used in the power plant building construction,electrical generation equipment and distributed machinery and infrastructures;the effects in the operation phase are dominated by the geothermal fluid composition.In this sense,the application of CO_(2) reinjection at the Turkish site into the reservoir will prevent the emission of 1,700 tons⋅year1 in the pilot site and 10%of the total emissions released along the life span of the GPP.
