•Closed-cycle gas turbine applicable to a wide range of heat sources.•Working fluids include air, nitrogen, supercritical CO2 and helium.•Review of important R&D programmes and operated plants.•Heat ...exchangers are significant driver in the capital cost and technical viability.•Demonstration plant essential before commercial deployment.
In the last few years, there has been considerable interest in closed-cycle gas turbine power plants due to the important contribution it can make to meeting worldwide energy demands. Closed-cycle gas turbine has the potential to serve as power conversion system for a wide range of energy sources such as fossil fuel, concentrated solar power, nuclear, biomass and waste heat. However, there is a need to provide an update on the development of closed-cycle gas turbine with a view to identifying the challenges and the opportunities for future commercialisation. This paper is a review of the research activities and studies carried out worldwide so far on closed-cycle gas turbine. The historical development in chronological order was presented first, followed by a review of some fundamental features such as heat sources, working fluids, heat exchangers and cycle layouts/configurations. Important research programmes and experimental/pilot plants as well as previous commercially operated plants were also reviewed. Moreover, various studies based on modelling and simulation of closed-cycle gas turbine were reviewed, in addition to the operation and control strategies. Based on the review studies, the challenges ahead and potential future breakthroughs were highlighted in different aspects such as heat source technologies, power conversion system and demonstration plant.
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•Dynamic model development in Matlab/Simulink proposed.•Analysis of control strategy for the WHR system.•Dynamic performance evaluation under varying heat source ...condition.•Supercritical CO2 power cycle is promising for WHR application.
Large amount of waste heat is available for recovery in industrial processes worldwide. However, significant proportion (up to 50%) of this thermal energy is released directly to the environment. Application of waste heat to power (WHP) technologies can increase the energy efficiency and cut CO2 emissions from these facilities. Steam Rankine cycle (SRC) and organic Rankine cycle (ORC) are commonly deployed for this purpose. The main drawback of SRC and ORC is the high irreversibility in the heat exchangers. In addition, ORC has limited temperature range and low efficiency while SRC has a large footprint. Supercritical CO2 (sCO2) power cycle is considered an attractive option, which provides better matching of waste heat temperature in the main heater (i.e. low irreversibility). It offers compact design, improved performance and it is applicable to a wide range of waste heat source temperature. The conditions of industrial waste heat sources are highly variable due to continuous fluctuations in the operation of the process. This is likely to significantly affect the dynamic performance and operation of the sCO2 power cycle. In this work, dynamic model in Matlab/Simulink was developed to assess the dynamic performance and control of the sCO2 power cycle for waste heat recovery from cement industry. The case of waste heat at 380 °C utilized to deliver 5 MWe of power was considered. Steady state simulation was performed to determine the design point values. Open loop simulation was performed to show the inherent dynamic response to step change in the temperature of the waste heat. The dynamic performance and control of the system under varying exhaust gas flow rate between 100% and 50% of the design value were studied. Similar study was done for varying exhaust gas temperature between 380 °C and 300 °C. The results showed that the thermal efficiency of proposed single recuperator recompression sCO2 is about 33%. Stable operation of the system can achieved by using cooling water control and throttle valve to maintain constant precooler outlet condition. Dynamic simulation result showed that it is best to allow the turbine inlet temperature to vary according to the fluctuation in the waste heat source. These findings indicated that dynamic modelling and simulation of WHP system could contribute to understanding of the behaviour and control system development under fluctuating waste heat source conditions.
Power generation from coal-fired power plants represents a major source of CO2 emission into the atmosphere. Efficiency improvement and integration of carbon capture and storage (CCS) facilities have ...been recommended for reducing the amount of CO2 emissions. The focus of this work was to evaluate the thermodynamic performance of s-CO2 Brayton cycles coupled to coal-fired furnace and integrated with 90% post-combustion CO2 capture. The modification of the s-CO2 power plant for effective utilisation of the sensible heat in the flue gas was examined. Three bottoming s-CO2 cycle layouts were investigated, which included a newly proposed single recuperator recompression cycle. The performances of the coal-fired s-CO2 power plant with and without carbon capture were compared. Results for a 290 bar and 593 °C power cycle without CO2 capture showed that the configuration with single recuperator recompression cycle as bottoming cycle has the highest plant net efficiency of 42.96% (Higher Heating Value). Without CO2 capture, the efficiencies of the coal-fired s-CO2 cycle plants were about 3.34–3.86% higher than the steam plant and about 0.68–1.31% higher with CO2 capture. The findings so far underscored the promising potential of cascaded s-CO2 power cycles for coal-fired power plant application.
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•Supercritical CO2 cycle was investigated for coal-fired power plant application.•Three s-CO2 cycles were investigated as possible bottoming cycle options.•Integration of coal-fired plant with post-combustion CO2 capture was studied.•Thermodynamic analysis and performance comparison were performed.
Compressed air energy storage (CAES) could play an important role in balancing electricity supply and demand when linked with fluctuating wind power. This study aims to investigate design and ...operation of a CAES system for wind power at design and off-design conditions through process simulation. Improved steady-state models for compressors, turbines and the CAES system for wind power were developed in Aspen Plus® and validated. A pseudo-dynamic model for cavern was developed in Excel. Compressor and turbine characteristic curves were used in model development for process analysis. In the off-design analysis, it was found that the CAES system for wind power at variable shaft speed mode utilise more excess wind energy (49.25 MWh), store more compressed air (51.55 × 103 kg), generate more electricity (76.00 MWh) and provide longer discharging time than that at constant shaft speed mode. Economic evaluation based on levelized cost of electricity (LCOE) was performed using Aspen Process Economic Analyser®, it was found that LCOE for the CAES system for wind power at variable shaft speed mode is lower than that at constant shaft speed mode. Research presented in this paper hopes to shed light on design and operation of the CAES system for wind power and cost reduction.
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•Improved model of CAES for wind power developed in Aspen Plus®.•Models developed based on characteristic curves of compressors and turbines.•Steady-state models for CAES and validated, pseudo-dynamic model for cavern.•Performance analysis of CAES for wind power at off-design conditions with two modes.•Economic evaluation on LCOE performed using Aspen Process Economic Analyser®.
•A new CCHP system including CAES, ORC and a refrigeration system is proposed.•Develop steady-state models and validate of CAES, ORC and refrigeration system.•To carry out thermodynamic analysis to ...evaluate the system performance.•To perform process analysis to study the effect of operating conditions.•The RTE and overall exergy efficiency of the system are 66.35% and 51.21%.
Compressed air energy storage (CAES) is increasingly investigated as a viable technology for balancing electricity supply and demand. The main purpose of CAES is to overcome the intermittent problem when renewable energy is introduced. However, the round-trip efficiency (RTE) of the CAES system commercially developed is still low (around 54 %) and requires further improvement. This study proposed a novel combined cooling, heating and power (CCHP) system, which improves the RTE in two ways: (i) organic Rankine cycle (ORC), which recovers the waste heat and produces extra power; (ii) single effect absorption refrigeration, which delivers cooling capacity with further recovery of waste heat from the flue gas. Steady-state process simulation of the CAES system, ORC and single effect absorption refrigeration system was developed in Aspen Plus® software. The proposed system was evaluated through process, energy, and exergy analysis. The effect of various working parameters on the performance of the CCHP system was also analysed. The results indicated that under design condition, the proposed CCHP system can produce about 206 MW electrical energy, 28 MW heating and 0.2 MW cooling capacity. The RTE of the proposed system (at 66.35%) showed an improvement of 12.35% when compared with the CAES system commercially deployed. The overall exergy efficiency is about 51% and the total exergy destruction of the components of the system is 477 MW. The combustion chamber is responsible for more than half of the exergy destruction.
•Nitrogen closed Brayton cycle for small modular sodium-cooled fast reactor studied.•Thermodynamic modelling and analysis of closed Brayton cycle performed.•Two-shaft configuration proposed and ...performance compared to single shaft.•Preliminary design of heat exchangers and turbomachinery carried out.
Sodium-cooled fast reactor (SFR) is considered the most promising of the Generation IV reactors for their near-term demonstration of power generation. Small modular SFRs (SM-SFRs) have less investment risk, can be deployed more quickly, are easier to operate and are more flexible in comparison to large nuclear reactor. Currently, SFRs use the proven Rankine steam cycle as the power conversion system. However, a key challenge is to prevent dangerous sodium-water reaction that could happen in SFR coupled to steam cycle. Nitrogen gas is inert and does not react with sodium. Hence, intercooled closed Brayton cycle (CBC) using nitrogen as working fluid and with a single shaft configuration has been one common power conversion system option for possible near-term demonstration of SFR. In this work, a new two shaft nitrogen CBC with parallel turbines was proposed to further simplify the design of the turbomachinery and reduce turbomachinery size without compromising the cycle efficiency. Furthermore, thermodynamic performance analysis and preliminary design of components were carried out in comparison with a reference single shaft nitrogen cycle. Mathematical models in Matlab were developed for steady state thermodynamic analysis of the cycles and for preliminary design of the heat exchangers, turbines and compressors. Studies were performed to investigate the impact of the recuperator minimum terminal temperature difference (TTD) on the overall cycle efficiency and recuperator size. The effect of turbomachinery efficiencies on the overall cycle efficiency was examined. The results showed that the cycle efficiency of the proposed configuration was comparable to the 39.44% efficiency of the reference cycle. In addition, the study indicated that the new configuration has the potential to simplify the design of turbomachinery, reduce the size of turbomachinery and provide opportunity for improving the efficiency of the turbomachinery. The findings so far revealed that the proposed two-shaft CBC with nitrogen as working fluid could be a promising power conversion system for SM-SFRs near-term demonstration.
Power generation from coal-fired power plants represents a major source of CO2 emission into the atmosphere. Efficiency improvement and integration of carbon capture and storage (CCS) facilities have ...been recommended for reducing the amount of CO2 emissions. The focus of this work was to evaluate the thermodynamic performance of s-CO2 Brayton cycles coupled to coal-fired furnace and integrated with 90% post-combustion CO2 capture. The modification of the s-CO2 power plant for effective utilisation of the sensible heat in the flue gas was examined. Three bottoming s-CO2 cycle layouts were investigated, which included a newly proposed single recuperator recompression cycle. The performances of the coal-fired s-CO2 power plant with and without carbon capture were compared. Results for a 290 bar and 593 °C power cycle without CO2 capture showed that the configuration with single recuperator recompression cycle as bottoming cycle has the highest plant net efficiency of 42.96% (Higher Heating Value). Without CO2 capture, the efficiencies of the coal-fired s-CO2 cycle plants were about 3.34–3.86% higher than the steam plant and about 0.68–1.31% higher with CO2 capture. The findings so far underscored the promising potential of cascaded s-CO2 power cycles for coal-fired power plant application.
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