Combined Cycle Power Research Articles

Semi-Closed Oxy-Combustion Combined Cycles for Combined Heat and Power Applications

Abstract This study focuses on the design and comparison of three utility-scale combined heat and power (CHP) cycles with carbon capture and storage (CCS): (i) a CHP semi-closed oxy-combustion combined cycle (SCOC-CC), (ii) a CHP natural gas combined cycle (NGCC) with postcombustion CCS, and (iii) a CHP NGCC with postcombustion CCS and supplementary firing. Performance evaluations are conducted at the design point and partial load (gas turbine at 30%) for different exports of high-temperature pressurized steam. The comparison is extended against two reference separate production systems with CCS, one based on postcombustion technologies, and another based on oxy-combustion. Simulations of the H-class gas turbines are performed using gas steam (GS), a specific in-house validated software, while the heat recovery steam cycle is modeled using Thermoflex. The CO2 capture processes employ validated models in Aspen Plus. The results highlight the suitability of the SCOC-CC for CHP applications, demonstrating superior performance and flexibility compared to CHP postcombustion technologies at both nominal and minimum loads. The SCOC cycle achieves a maximum first-law efficiency of 65.95%, outperforming CCS technologies that generate electricity and heat separately and enabling fuel savings up to 9.2%.

A theoretical thermodynamic investigation on solar-operated combined electric power, heating, and ejector cooling cycle driven by an ORC turbine waste heat, tri-generation cycle system

The current study investigated a solar thermal power plant to simultaneously produce multiple energy outputs, including electric power, process heating, and cooling. This integrated approach aligns with the concept of a tri-generation system, where three different forms of energy are produced from a single source. The study involves a parametric analysis, where the impact of each influencing parameter including, turbine inlet temperature, and turbine inlet pressure is systematically varied with DNI ranging from 600 W/m2 to 1000 W/m2 to understand its effects on both first-law and second-law efficiencies. Further, the exergy analysis shows the irreversibility's occur within the system. Notably, the central receiver and heliostat are identified as major sources of exergy loss. The comparison to a combined power and heating (CPH) cycle without an ORC-ejector indicates that the additional technologies significantly contribute to improving the system's performance, approximately 3.97 % and 2.3 % for both efficiencies, respectively.

Model-based evaluation of ammonia energy storage concepts at high technological readiness level

Ammonia is a promising carbon-free energy carrier since it can be stored as a liquid at mild conditions and its production process from hydrogen and nitrogen is established and efficient. Several Ammonia-to-Power concepts have been proposed in the literature, many of which employ not-yet-mature electrochemical technologies. We model the charging and discharging phases of three ammonia energy storage concepts in Aspen Plus seeking a compromise between efficient concepts and mature technologies. In the charging phase, ammonia is produced via the Haber–Bosch process using hydrogen from low-temperature water electrolysis for all the considered concepts. For the discharging phase, three ammonia conversion processes are modeled: (i) ammonia is thermally decomposed into nitrogen and hydrogen by using thermal energy from storage, and hydrogen is converted into electricity in a fuel cell; (ii) ammonia is thermally decomposed by using heat generated through the combustion of a fraction of the ammonia stream, and the produced hydrogen is supplied to a fuel cell; (iii) ammonia is used as a fuel in a combined power cycle. We compare these concepts with respect to roundtrip efficiency and levelized cost of electricity. The roundtrip efficiency and the levelized cost of electricity of the modeled concepts are ca. 30–34 % and 0.28–0.31 €kWh−1 (for an electricity purchase price of 0.03 €kWh−1). Concept (i) has both the highest roundtrip efficiency and the lowest levelized cost of electricity. We identify the process bottlenecks via an exergy analysis.

A computational study on square and helical magnetohydrodynamic generators including applications to a combined power cycle

A computational study on square and helical magnetohydrodynamic generators including applications to a combined power cycle

Simulation and Energy Analysis of Integrated Solar Combined Cycle Systems (ISCCS) Using Aspen Plus

The aim of this research is to simulate and analyze a combined power cycle (Steam turbine and gas turbine cycles) by studying the effect of changing the natural gas flow rate on the developed power. Therefore, reducing the amount of used natural gas in the combustion chamber of the gas turbine cycle from 9.2 to 4 kg/s showed a significant drop in the power produced by the gas turbine, i.e., from 123.7 to 57.7 MW. Additionally, this change in the combusted natural gas amount affected the heat recovered in both heat recovery steam generators (HRSGs), i.e., from 219.79 to 100.35 MW, respectively. Consequently, the amount of generated steam in the high pressure HRSGs and the power developed in the steam turbine changed from 60.88 to 27.79 kg/s and from 56.39 to 27.13 MW, respectively. A heat exchanger (HFHX) utilizing a heating fluid was used as an external source of energy to compensate the reduction in the generated heat and to increase the amount of generated steam up to 157.32 kg/s, which keeps the power plant capacity at 180 MW. Existing combined local plant data were used in this study and were simulated in Aspen Plus software V11. A sensitivity analysis was made to optimize the cycle operating conditions that use less natural gas and produce the same amount of power.

Predictive modeling of combined cycle power plant performance using a digital twin-based neural ODE approach

This study presents a novel digital twin-based predictive modeling approach to enhance the operation, maintenance, and management of combined cycle power plants. The research aimed to accurately forecast the combined cycle power (CCP) output, a critical performance indicator, to support intelligent decision-making for plant operators and engineers. The proposed framework leverages a neural ordinary differential equation (NODE) model integrated within a digital twin architecture to capture the complex, nonlinear dynamics of combined cycle gas turbine unit (CCGU) system. The predictive model was trained and validated using multivariate time-series data collected from a CCGU, achieving high accuracy with an R2_score of 0.993, a mean absolute percentage error of 0.325 %, and a root mean squared error of 1.518. Importantly, the NODE model demonstrated superior forecasting capabilities compared to traditional machine learning techniques. The digital twin (DT) concept enables seamless real-time data integration, physics-based models, and advanced data analytics to facilitate comprehensive CCGU lifecycle management. This novel approach provides operators with reliable, real-time insights to optimize plant performance, reduce maintenance costs, and improve overall sustainability. The generalization of the NODE model to an independent CCGU unit validated its applicability across diverse power plant configurations, highlighting the originality and practical value of the research. The key contribution of this work is the development of a digital twin-based predictive modeling framework centered on the innovative use of neural ordinary differential equations to enhance the operation and maintenance of critical energy infrastructure. This research advances the state-of-the-art in intelligent asset management for the built environment.

Enhancing thermodynamic performance with an advanced combined power and refrigeration cycle with dual LNG cold energy utilization

Utilizing waste heat to drive thermodynamic systems is imperative for improving energy efficiency, thereby improving sustainability. A combined cooling and power systems (CCP) utilizes heat from a temperature source to deliver both power and cooling. However, CCP systems utilizing LNG cold energy suffers from low second law efficiency due to significant temperature differences. To address this, an “Advanced Power and Cooling with LNG Utilization (ACPLU)” system is proposed, integrating a cascaded transcritical carbon dioxide (TCO2)-LNG cycle with an Organic Rankine cycle (ORC) for improved power generation and an absorption refrigeration system (ARS) for simultaneous cooling. This study evaluates the second law efficiency, net work output, and exergy destruction performance through a sensitivity analysis, optimizing variables such as heat source temperature, superheater temperature difference, ORC and CO2 turbine inlet and condenser pressures, evaporator temperature, and pinch point temperatures of heat exchangers and generator. Compared to previous studies on CCP systems, the ACPLU shows a superior performance, with a second law efficiency of 27.3 % and a net work output of 11.76 MW. Cyclopentane as an ORC working fluid resulted in the highest second law efficiency of 29.06 % and net work output of 12.27 MW. Parametric analysis suggested that heat source temperature significantly impacts net power output. The exergy analysis concluded that a high-pressure ratio and good thermal match between the heat exchangers enhance overall performance. Utilizing artificial neural network (ANN) to produce a multiple-input-multiple-output (MIMO) objective function and performing multi-objective optimization (MOO) using genetic algorithm (GA), an improved second law efficiency and net power output by 28.11 % and 14.16 MW respectively, with pentane as the working fluid, is demonstrated. An average cost rate of 9.121 $/GJ was observed through a thermo-economic analysis. The ACPLU system is promising for medium temperature waste heat recovery, such as, pharmaceutical manufacturing plants.

Waste-to-Energy Processes as a Municipality-Level Waste Management Strategy: A Case Study of Kočevje, Slovenia

The escalating challenge of waste management demands innovative strategies to mitigate environmental impacts and harness valuable resources. This study investigates waste-to-energy (WtE) technologies for municipal waste management in Kočevje, Slovenia. An analysis of available waste streams reveals substantial energy potential from mixed municipal waste, biodegradable waste, and livestock manure. Various WtE technologies, including incineration, pyrolysis, gasification, and anaerobic digestion, are compared. The results show that processing mixed municipal waste using thermochemical processes could annually yield up to 0.98 GWh of electricity, and, separately, 3.22 GWh of useable waste heat for district heating or industrial applications. Furthermore, by treating 90% of the biodegradable waste, up to 1.31 GWh of electricity and 1.76 GWh of usable waste heat could be generated annually from biodegradable municipal waste and livestock manure using anaerobic digestion and biogas combustion in a combined heat and power facility. Gasification coupled with a gas-turbine-based combined heat and power cycle is suggested as optimal. Integration of WtE technologies could yield 2.29 GWh of electricity and 3.55 GWh of useable waste heat annually, representing an annual exergy yield of 2.98 GWh. Within the Kočevje municipality, this amount of energy could cover 23.6% of the annual household electricity needs and cover the annual space and water heating requirements of 10.0% of households with district heating. Additionally, CO2-eq. emissions could be reduced by up to 20%, while further offsetting emissions associated with electricity and district heat generation by 1907 tons annually. These findings highlight the potential of WtE technologies to enhance municipal self-sustainability and reduce landfill waste.

Introducing and performance evaluation of a novel Multi-Generation process for producing Power, fresh Water, oxygen and nitrogen integrated with liquefied natural gas regasification and carbon dioxide removal process

The objective of this paper is to develop and evaluate a new integrated multigenerational system comprised of cryogenic air separation, hydrate-based desalination, combined cycle and oxyfuel power plants, carbon dioxide amine absorption, and transcritical carbon dioxide power cycle, employing liquefied natural gas cold energy. This integrated multi-generation system, applicable for liquefied natural gas importer terminals with access to seawater, produces approximately 2,533 MW net output power and 1,985 kg/h fresh water. In addition, this integrated multi-generation process produces 16,735,861 kg/h high-purity liquid oxygen (100 mol%), 4,773,633 kg/h liquid nitrogen with 99.71 mol% purity, more than 31,724,465 kg/h high-purity gaseous nitrogen (99.9 mol%), and 90,903,230 kg/h low-purity gaseous nitrogen (83.38 mol%). About 5907.3 MW of produced power is generated by liquefied natural gas expander. The performance of this system is evaluated by energetic methods. The results of energy analysis show the specific energy consumptions of the air separation products are 0.551 kW/kg and 1.93 kW/kg for liquid oxygen and nitrogen, respectively. Moreover, in the hydrate-based desalination subsystem, the specific energy consumption is 0.5 kW/m3 for produced pure water. The combined cycle power plant includes two gas turbines, three steam turbines, and a three-pressure level heat recovery steam generation. The thermal efficiencies of gas turbine cycles (Bryton), steam turbine cycles (Rankine) and combined power cycles are 26.3 %, 29.6 %, and 36.2 %, respectively. The flue gases from power plants enter the carbon dioxide amine absorption subsystem. The separated carbon dioxide is used as a working fluid to produce 372.1 MW power in transcritical carbon dioxide cycle. The results of energy analysis for carbon dioxide amine absorption subsystem show that the specific energy consumption, the ratio of captured carbon dioxide per unit mass of liquefied natural gas and the carbon dioxide removal efficiency are 6.60 kW/kg, 33.91 kg/tone, and 90.06 %, respectively. Approximately 2,905,000 kg/h of liquid carbon dioxide is obtained as the byproduct of this multi-generation process. Additionally, sensitivity analysis is conducted to determine key parameters influencing the main energetic indexes. Finally, the amount of attainable regasified natural gas reaches 257,523 tone/h by applying this multi-generation system with total 86 % energy efficiency.

Enhancement of the Power-to-Heat Energy Conversion Process of a Thermal Energy Storage Cycle through the use of a Thermoelectric Heat Pump

The principal strategy for achieving a neutral climate entails enhancing the share of renewable energies in the energy mix, in conjunction with promoting innovation in efficient technologies. Thermal energy storage systems have the potential to efficiently handle the intermittent nature of renewable energy sources. Furthermore, these systems can effectively handle shifts in both heat and electrical demand. Thus, efficient power-to-heat technologies are needed to boost thermal energy storage. This manuscript explores the potential of utilising a thermoelectric heat pump system in conjunction with electric resistances for charging a thermal energy storage. In order to achieve elevated temperatures, the thermoelectric system integrates thermoelectric heat pump blocks in a two-stage configuration. Air has been employed as a heat transfer medium for sensible heat storage. Higher airflow rates improve the performance of thermoelectric heat pump system. Moreover, its impact on the optimal voltage supply of the thermoelectric system is observed when it is combined with an electric resistance to achieve elevated temperatures. In comparison to the basic charging process that solely relies on the electric resistance of a thermal energy storage at 120 °C, a significant 30 % increase in power-to-heat energy conversion has been achieved by including the thermoelectric heat pump system. In fact, it efficiently elevates the temperature from the initial ambient temperature of 25 °C to a remarkable 113.1 °C, achieving a coefficient of performance of 1.35 with an airflow rate of 23 m3/h. Therefore, the use of this technology to enhance a complete process of storing excess renewable energy in the form of heat for subsequent use in both heat and electricity through a combined heat and power cycle is demonstrated.

Waste Heat Recuperation in Advanced Supercritical CO2 Power Cycles with Organic Rankine Cycle Integration & Optimization Using Machine Learning Methods

Supercritical CO2 (sCO2) stands out for concentrating solar power (CSP) due to its superior thermophysical and chemical properties, promising higher cycle efficiency compared to superheated or supercritical steam. Leveraging the waste heat from sCO2 cycles through the organic Rankine cycle (ORC) as a low-grade energy source enhances overall thermal efficiency. This research explores advanced sCO2 power cycles and introduces a novel approach by integrating machine learning and genetic algorithms for optimizing cycle performance. Utilizing a thermodynamic model-derived dataset, various machine learning algorithms, including Random Forest, XGBoost, and Artificial Neural Network are employed for prediction, evaluation and optimization. This innovative integration enables a comprehensive understanding of the complex dynamics of sCO2 power cycles. Subsequently, the study employs multi-objective optimization for the systematic evaluation and optimization of the combined power cycles, incorporating multiple bottoming cycles to maximize efficiency. The findings not only showcase the superiority of the unified sCO2ORC cycle but also emphasize the impact of integrating advanced computational methods in achieving optimal performance. The sCO2 cycle is explored in recompression, partial cooling, and main compression intercooling configurations. Recompression cycles utilize a single cooling system, while partial cooling and main compression intercooling layouts integrate a pair of ORCs at two precoolers. The ORC cycle enhances the recompression cycle through heat recuperation, extracting enhanced power originating from the bottom cycle. Critical parameters are taken into consideration to carry out optimization and performance evaluations. such as cycle temperatures, recuperator effectiveness, bottoming cycle pressure ratio, and condensation temperature. Results indicate that the combined partial cooling sCO2ORC cycle yields the optimal net output power of 7994.541 kW and thermal efficiency of 53.365 %. The findings highlight the capacity to propel and promote the utilization of waste heat recovery in energy technologies through enhanced and optimized power cycle designs, contributing to their advancement and widespread adoption.

Performance Analysis of a Solar Cogeneration Power Combined Cycle at Variable Operational and Design Conditions

This paper is to investigate the performance of a solar cogeneration power combined cycle( SCPCC), in which a computer program, called “ SCPCC Design" has been developed using MATLAB for the analysis. In addition the System Advisor Model (SAM) software has been used in the analysis. Here, many operational and design parameters are taken in consideration to determine the overall efficiency of the proposed cycle, such as compressor pressure ratio, combustion temperature in the gas turbine unit, inlet steam pressure, exhaust gases temperature and process heat mass fraction. The solar thermal energy obtained from the solar field is obtained according to the specifications of Libyan Capital, Tripoli City, and through all the year. The results obtained from this study have shown a clear influence for these parameters on the overall efficiency, where it increases with combustion temperature, steam pressure and mass fraction, while it decreases with compressor pressure ratio .

Correction: Thermodynamic and exergoenvironmental assessments of solar-assisted combined power cycle using eco-friendly fluids

Correction: Thermodynamic and exergoenvironmental assessments of solar-assisted combined power cycle using eco-friendly fluids

Comprehensive analysis of combined power cycles driven by sCO2-based concentrated solar power: Energy, exergy, and exergoeconomic perspectives

Integrating Brayton cycles, utilizing supercritical carbon dioxide (sCO2) as a working medium, with a concentrating solar power (CSP) system is an attractive solution to enable high-temperature clean production of electricity. In this study, different power cycle configurations were coupled with the CSP system to examine and compare their energy, exergy, economic, and exergoeconomic performances to express a comprehensive view. A study of the impact of different parameters was also carried out to inspect the performance of each system under different operating conditions. The governing equations characterizing system performance and economics have been rigorously solved using MATLAB® R2021a, ensuring accuracy and reliability in the present analysis. Energy assessment reveals that, in indirect systems, the thermal efficiency of the recompression Brayton cycle (RBC) surpasses direct cycles by 0.9%, while the organic Rankine cycle (ORC) in dual cycles exhibits a 2% thermal efficiency advantage over triple cycles. For CSP, direct systems enhance efficiency by approximately 1.5%, compared to indirect systems, with dual cycles outperforming single and triple cycles. Exergy analysis indicates a 1.3% exergy efficiency increase for RBC in indirect systems, compared to direct systems, while ORC demonstrates an exceptional 35.66% exergy efficiency improvement in dual systems. Direct CSP systems exhibit higher exergy values than indirect counterparts. Overall exergy efficiency rankings place triple systems at the top (27%), followed by dual (25%) and single cycles (20%) for both direct and indirect systems. Exergoeconomic analysis reveals that the indirect triple cycle (ITC) system bears the greatest expense, totaling 56,968 USD per annum. Compared to the ITC systems, the indirect single- and dual-cycle systems reduce the cost by 8.2% and 1.15%, respectively.

Thermodynamic and exergoenvironmental assessments of solar-assisted combined power cycle using eco-friendly fluids

Thermodynamic and exergoenvironmental assessments of solar-assisted combined power cycle using eco-friendly fluids

Exergoeconomic and Thermodynamic Analyses of Solar Power Tower Based Novel Combined Helium Brayton Cycle-Transcritical CO2 Cycle for Carbon Free Power Generation.

In the present study, a novel combined power cycle for solar power tower (SPT) system consisting of helium Brayton cycle (HBC) and transcritical CO2 (TCO2) for waste heat recovery is being studied for carbon-free generation. The performance of the proposed SPT based combined cycle (SPT-HBC-TCO2 cycle) is compared with SPT based basic cycle (SPT-HBC) based on exergoeconomic and thermodynamic analyses. It is concluded that the SPT-based combined cycle (SPT-HBC-TCO2 cycle) produces a thermal efficiency of 32.39% and exergy efficiency of 34.68% with an electricity cost of 1.613 UScent kWh-1. The exergy and thermal efficiency of the SPT-based combined cycle are enhanced by 13.18% and 13.21% respectively, while electricity cost is reduced by around 2% as compared to the SPT-based basic cycle (SPT-HBC) configuration at base conditions. A notable finding is that, despite the additional expenditures related to the bottoming cycle, the cost of electricity is lesser for the proposed combined cycle. Additionally, a comparison with the related prior published research exhibits that the performance of the current novel system is superior to that of the systems based on steam rankine cycle and supercritical CO2 cycles.

Conventional vs. alternative biogas utilizations: An LCA-AHP based comparative study

This study compares the performance and the environmental impacts of three biogas utilization processes: combined heat and power cycle, dimethyl ether production, and methanol production. The processes are evaluated based on key performance indicators and life cycle assessments. Results show that molar methane conversion in the reforming unit is 93% for both dimethyl-ether (DME) and methanol processes. Methanol reactor reports a per-pass hydrogen conversion of 21%. DME production achieves an 89% conversion rate. The chemical pathways exhibit a 33% molar conversion of COx, contributing to the conversion of CO2 into advanced chemicals. The environmental footprint is evaluated through a life cycle assessment. Biogas cogeneration has the lowest global warming potential since DME and methanol production processes are influenced by steam production and electricity intake from the national grid, which relies on fossil fuels. An analytic hierarchy process is employed to assess the overall performance of the processes. DME production performs best with a score of 39%, followed by cogeneration with 31%, and methanol production with 30%. Different case studies are examined by modifying the weight criteria for each impact category. The findings provide that cogeneration and DME technologies perform better in all the iterations.

Cascading the Transcritical CO2 and Organic Rankine Cycles with Supercritical CO2 Cycles for Waste Heat Recovery

Concentrating solar power (CSP) applications can benefit from the superior thermophysical and chemical properties of supercritical CO2 (sCO2), which offers greater cycle efficiency in contrast to supercritical or superheated steam cycles. The transcritical CO2 (TCO2 cycle) excels in low-grade waste heat recovery (WHR), while the organic Rankine cycle (ORC) is also a potential option for WHR from sCO2 cycles. This study focuses on the thermodynamic assessment and optimization of combined power cycles, incorporating multiple bottoming cycles, to enhance overall thermal efficiency. The configurations employed include recompression, partial cooling, and main compression intercooling within the sCO2 cycle. Waste heat recovery is achieved using both TCO2 and ORC. The parametric analysis explores key variables such as turbine inlet temperature, main compressor inlet temperature, recuperator effectiveness, pressure ratios in the bottoming cycles, and condensation temperatures of the bottoming cycles. Furthermore, this research conducts performance analysis of the proposed combined cycle configurations. The results underscore the substantial enhancement of combined cycle performance with regard to thermal and exergy efficiency. A rise in the highest temperature that can occur in the sCO2 cycle leads to improved thermal efficiency. The Main Compressor Inlet Temperature (MCIT) exhibits an efficiency increase of up to 40°C–45°C, attributed to pseudocritical effects, followed by a decline. Among the various configurations, the combined partial cooling cycle generates the highest net output power. The study finds that the combined main compression model consistently outperforms other layouts, yielding a 2-2.5% increase in efficiency. Optimization of the intermediate pressure value for the partial cooling (PC) and main compression (MC) cycles at 10 MPa further contributes to enhanced performance. This study not only presents the optimized operating conditions for each combined cycle but also offers a comparative analysis of these models under different boundary conditions. The findings from this research significantly advance the utilization of waste heat and the development of clean power generation.

Thermodynamic performance analysis of solar-biomass based gas turbine- Rankine–Kalina combined triple power cycle

Thermodynamic performance analysis of solar-biomass based gas turbine- Rankine–Kalina combined triple power cycle

Evaluation of iron-based chemical looping for hydrogen production from biomass using combined power cycle with carbon capturing and storage

The current article presents a thorough thermodynamic analysis of a unique multigeneration system where it is capable of hydrogen production with carbon capturing and storage (CCS). The system produces electrical power by integrating combined Brayton and Rankine cycles to maximize efficiency, while the solar system generates the required thermal energy input. The system aims to produce methane through the biomass pyrolysis of propylene. Additionally, the system uses a series of reactors within its iron-based chemical looping process to produce hydrogen, while simultaneously capturing and storing carbon dioxide, which aims to increase the overall sustainability of the system. The study further includes comprehensive energy and exergy analyses of all system components and an evaluation of the system's overall performance. The metrices used to evaluate the system's performance are primarily the overall energy and exergy efficiencies along with various production and capture rates. The results show that the overall system energy efficiency is 27%, while the corresponding exergy efficiency is 25%. Also, the hydrogen production rate and carbon dioxide capture rate achieved by the system are 10.5 kg/s and 1120 kg/s, respectively.