Gas Turbine Exhaust Research Articles

Chemical characterization of combustion engine exhaust and assessment of helicopter deck operator occupational exposures on an offshore frigate class ship

Diesel engine exhaust (DE) consists of a complex mixture of gases and aerosols, originating from sources such as engines, turbines, and power generators. It is composed of a wide range of toxic compounds ranging from constituents that are irritating to those that are carcinogenic. The purposes of this work were to characterize DE originating from different engine types on a ship operating offshore and to quantify the potential exposure of workers on the ship’s helicopter deck to select DE compounds. Sampling was conducted on a Norwegian Nansen-class frigate that included helicopter operations. Frigate engines and generators were fueled by marine diesel oil, while the helicopter engine was fueled by high flash point kerosene-type aviation fuel. Exhaust samples were collected directly from the stack of the diesel engine and one of the diesel generator exhaust stacks, inside a gas turbine exhaust stack, and at the exhaust outlet of the helicopter. To characterize the different exhaust sources, non-targeted screening of volatile and semi-volatile organic compounds was performed for multiple chemical classes. Some of the compounds detected at the sources are known irritants, such as phthalic anhydride, 2,5-dyphenyl-p-benzoquinone, styrene, cinnoline, and phenyl maleic anhydride. The exhaust from the diesel engine and diesel generator was found to contain the highest amounts of particulate matter and gaseous compounds, while the gas turbine had the lowest emissions. Personal exposure samples were collected outdoors in the breathing zone of a helicopter deck operator over nine working shifts, simultaneously with stationary measurements on the helicopter deck. Elemental carbon, nitrogen dioxide, and several volatile organic compounds are known to be present in DE, such as formaldehyde, acrolein, and phenol were specifically targeted. Measured DE exposures of the crew on the helicopter deck were variable, but less than the current European occupational exposure limits for all compounds, except elemental carbon, in which concentration varied between 0.5 and 37 µg/m3 over nine work shifts. These findings are among the first published for this type of working environment.

Ceramic Matrix Composites for Aero Engine Applications—A Review

Ceramic matrix materials have attracted great attention from researchers and industry due to their material properties. When used in engineering systems, and especially in aero-engine applications, they can result in reduced weight, higher temperature capability, and/or reduced cooling needs, each of which increases efficiency. This is where high-temperature ceramics have made considerable progress, and ceramic matrix composites (CMCs) are in the foreground. CMCs are classified into non-oxide and oxide-based ones. Both families have material types that have a high potential for use in high-temperature propulsion applications. The oxide materials discussed will focus on alumina and aluminosilicate/mullite base material families, whereas for non-oxides, carbon, silicon carbide, titanium carbide, and tungsten carbide CMC material families will be discussed and analyzed. Typical oxide-based ones are composed of an oxide fiber and oxide matrix (Ox-Ox). Some of the most common oxide subcategories are alumina, beryllia, ceria, and zirconia ceramics. On the other hand, the largest number of non-oxides are technical ceramics that are classified as inorganic, non-metallic materials. The most well-known non-oxide subcategories are carbides, borides, nitrides, and silicides. These matrix composites are used, for example, in combustion liners of gas turbine engines and exhaust nozzles. Until now, a thorough study on the available oxide and non-oxide-based CMCs for such applications has not been presented. This paper will focus on assessing a literature survey of the available oxide and non-oxide ceramic matrix composite materials in terms of mechanical and thermal properties, as well as the classification and fabrication methods of those CMCs. The available manufacturing and fabrication processes are reviewed and compared. Finally, the paper presents a research and development roadmap for increasing the maturity of these materials allowing for the wider adoption of aero-engine applications.

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 2: Numerical Simulation Results

The efficiency of hybrid electric vehicles may be substantially increased if the energy of exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered using a properly designed turbo-generator and employed for vehicle propulsion. Previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% employing a 20 kW turbine on a 100 HP-rated power thermal unit. The innovative thermal unit proposed here is composed of a supercharged engine endowed with a properly designed turbo-generator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In this two-part work, the realistic efficiency of the innovative thermal unit for hybrid vehicles is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors presented a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, thanks to some assumptions and approximations, allows fast determination of the right turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine here considered is quite different from the ones commonly employed for turbocharging applications; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In this paper, Part 2, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantages that could be achieved by the implementation of the turbo-generator on a hybrid propulsion system are evaluated through the performance prediction model under different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbo-compound system could gain vehicle efficiency improvement between 3.1% and 17.9%, according to the output power delivered, with an average efficiency increment of 10.9% evaluated on the whole operating range.

BECCS opportunities in Brazil: Comparison of pre and post-combustion capture in a typical sugarcane mill

In order to make feasible the efforts that would limit the rise of Earth's temperature to no more than 2 °C, profound changes are required in the energy systems. In this sense, BECCS are considered instrumental to attain possible negative emissions. This draws attention to the sugarcane industry in Brazil, where it is possible to produce fuel ethanol at a relative low cost and a large amount of relatively cheap biomass is available. This paper is part of a research that aims to study the combined production of liquid fuels and electricity, using sustainable sources of biomass and maximizing carbon capture. Two cases related to an innovative technology were evaluated and in both the capture is based on amine technology: pre-combustion capture of CO2 from the fuel gas derived from biomass gasification, and post-combustion capture from gas turbine exhaust gases. Information from the scientific literature was used in modelling the systems, as well as estimating energy penalties and costs associated with capturing, transporting and storing CO2. The results indicate technical feasibility of both capture options, but difficulties in setting the full integration of the power unit (BIG-CC) with the sugarcane mill and the CCS system, due to the high demand for thermal energy as low-pressure steam. The estimated CO2 abatement cost is in the range 60–71 €/tCO2 for pre-combustion capture, and 52–63 €/tCO2 in the case of post-combustion. Feasibility results are impacted by the scale of CO2 capture (0.82–1.44 MtCO2/year), particularly in the pre-combustion case, and the relatively high cost of electricity generation.

Investigations on the Splitter Structure to Improve the Aerodynamic Performance of Gas Turbine Exhaust Diffuser at Different Swirl Angles

Abstract To weaken the flow separation in the exhaust diffuser under real operating conditions and increase the static pressure recovery coefficient of the exhaust diffuser, an exhaust diffuser structure with splitters was proposed. Based on verifying the reliability of the numerical method, the paper numerically explores the influence of the height and width of the splitter on the aerodynamic performance of the exhaust diffuser under three different inlet swirl angles by solving three-dimensional Reynolds-Averaged Navier–Stokes (RANS). The results show that the introduction of the splitter structure into the exhaust diffuser can effectively suppress the separation vortex near the strut, improve the flow state at the exhaust diffuser outlet, and further increase the static pressure recovery coefficient of the exhaust diffuser. The optimal splitter structure can be obtained by comparing the effects of the splitter height and width on the static pressure recovery performance of the exhaust diffuser under different inlet swirl angles. When the inlet swirl angles are 16 degs, 28 degs, and 38 degs, compared with the original exhaust diffuser without splitters, the optimal splitter structure can increase the static pressure recovery coefficient of the exhaust diffuser by 0.036, 0.096, and 0.146, respectively, with a relative increase of 7.3%, 34.2%, and 76.2%. The introduction of the splitter structure helps to improve the aerodynamic performance of the exhaust diffuser.

Hybrid Propulsion Efficiency Increment through Exhaust Energy Recovery—Part 1: Radial Turbine Modelling and Design

The efficiency of Hybrid Electric Vehicles (HEVs) may be substantially increased if the energy of the exhaust gases, which do not complete the expansion inside the cylinder of the internal combustion engine, is efficiently recovered by means of a properly designed turbogenerator and employed for vehicle propulsion; previous studies, carried out by the same authors of this work, showed a potential hybrid vehicle fuel efficiency increment up to 15% by employing a 20 kW turbine on a 100 HP rated power thermal unit. The innovative thermal unit here proposed is composed of a supercharged engine endowed with a properly designed turbogenerator, which comprises two fundamental elements: an exhaust gas turbine expressly designed and optimized for the application, and a suitable electric generator necessary to convert the recovered energy into electric energy, which can be stored in the on-board energy storage system of the vehicle. In these two parts, the realistic efficiency of the innovative thermal unit for hybrid vehicle is evaluated and compared to a traditional turbocharged engine. In Part 1, the authors present a model for the prediction of the efficiency of a dedicated radial turbine, based on a simple but effective mean-line approach; the same paper also reports a design algorithm, which, owing to some assumptions and approximations, allows a fast determination of the proper turbine geometry for a given design operating condition. It is worth pointing out that, being optimized for quasi-steady power production, the exhaust gas turbine considered is quite different from the ones commonly employed for turbocharging application; for this reason, and in consideration of the required power size, such a turbine is not available on the market, nor has its development been previously carried out in the scientific literature. In the Part 2 paper, a radial turbine geometry is defined for the thermal unit previously calculated, employing the design algorithm described in Part 1; the realistic energetic advantage that could be achieved by the implementation of the turbogenerator on a hybrid propulsion system is evaluated through the performance prediction model under the different operating conditions of the thermal unit. As an overall result, it was estimated that, compared to a reference traditional turbocharged engine, the turbocompound system could gain vehicle efficiency improvement between 3.1% and 17.9%, depending on the output power level, while an average efficiency increment of 10.9% was determined for the whole operating range.

Optimization Design of Gas Turbine Exhaust Ejector Based on ANSYS

Optimization Design of Gas Turbine Exhaust Ejector Based on ANSYS

Techno-Economic Comparison of Several Technologies for Waste Heat Recovery of Gas Turbine Exhausts

Abstract The waste heat recovery from the gas turbine (GT) exhaust is typical for increasing performance and reducing CO2 emissions in industrial facilities. Nowadays, numerous already operating gas turbine plants could be retrofitted and upgraded with a bottoming cycle powered by the exhaust gasses. In this case, the standard solution would be to use a water steam Rankine cycle. However, even if this technology usually yields the best efficiency, other alternatives are often preferred on the lower size scale. Organic Rankine cycles (ORCs) are the commercial alternatives to steam Rankine cycles, but many other alternative cycles exist or can be developed, with potential benefits from safety, technical or economic points of view. This study compares several alternative technologies suited to recover gas turbine waste heat, and a detailed cost analysis for each is presented. On this basis, a guideline is proposed for the technology choice considering a wide range of application sizes and temperature levels typical for waste heat recovery from gas turbines. The compared technologies are ORCs, Rankine cycles (RCs) with water and ammonia mixtures at constant composition, supercritical CO2 cycles (sCO2), sCO2 cycles with mixtures of CO2 and other gasses. As it resulted, ORCs can achieve the lowest levelized cost of energy (32 $/MWh–46 $/MWh) if flammable fluids can be employed. Otherwise, Rankine cycles with a constant composition mixture of water and ammonia are a promising alternative, reaching a levelized cost of energy (LCOE) of 36–58 $/MWh.

Assessment and optimization of a novel waste heat stepped utilization system integrating partial heating sCO2 cycle and ejector refrigeration cycle using zeotropic mixtures for gas turbine

A waste heat stepped utilization system integrating a partial heating sCO2 power cycle and a thermally-driven ejector refrigeration cycle is proposed for gas turbine performance enhancement. The gas turbine exhaust heat is stepped utilized by two gas heaters in the sCO2 power cycle and a waste heater. Then, the exhaust CO2 heat is cascade utilized by the ejector refrigeration cycle using zeotropic mixtures (R245fa/R1234ze) as its working fluid. Detailed energy, exergy, and economic models are built to conduct the system performance investigation. The results show that the proposed system can improve the thermal and exergy efficiency by 28.23% and 2.65% compared with the single sCO2 cycle. The parametric study discloses that there are optimal turbine inlet temperature and compressor inlet pressure for power output and optimal refrigerant mixture ratio, around 0.30, for cooling capacity. Further, multi-objective optimization is implemented, and the overall system efficiency, bottoming system exergy efficiency, and levelized cost of exergy can reach 62.15%, 45.22%, and 0.076 $/kWh, respectively. Finally, to prove the superiority of the integrated system for different application scenarios, the system performance is optimized in the gas turbine part-load. The results reveal that the proposed system can effectively improve the gas turbine performance, especially in the part-load. Under all the gas turbine loads, the proposed system's levelized cost of exergy is no more than 0.076 $/kWh, which provides theoretical references for the development of the gas turbine combined system in practical engineering.

Storage-reduction strategy for NOx reduction from gas turbine exhaust with W–Ti-CeOx catalyst in natural gas power plants

Traditional vanadium-based selective catalytic reduction (SCR) deNOx catalyst can hardly adapt to the gas conditions (much high NO2/NOx ratio at lower temperature) of the start-up and low loading periods for a gas turbine. Therefore, a W–Ti-CeOx catalyst with NOx storage and reduction (NSR) function was developed in this work for gas turbine exhaust NOx elimination. The experimental results reveal that W–Ti-CeOx catalyst exhibits high NO2 adsorption capacity at relatively low temperature while that is quite low for V–W/TiO2. The abundant surface Ce3+ species can be mainly responsible for its high adsorption ability owing to the reaction between NO2 and Ce3+ to form nitrate/nitrite species and NO. Meanwhile, the adsorption capacity of W–Ti-CeOx can easily regenerate at medium–high temperature and NH3-SCR reaction. Furthermore, W–Ti-CeOx also shows good NH3-SCR activity, which can fulfill the deNOx process at high temperature. The addition of W and Ti into ceria can enhance the surface acidity and redox ability, thereby increasing the SCR activity. This work proposes a novel storage-reduction strategy for NOx elimination throughout the operation of gas turbines.

Optimal design of a novel hybrid solar tower‐gas turbine combined cycle with proton exchange membrane polygeneration system: Application of machine learning

AbstractAn innovative polygeneration system is proposed to generate power, heat, hydrogen, and oxygen simultaneously. The system integrates a solar central tower system and the heliostat field, a gas turbine cycle, a supercritical carbon dioxide cycle, an Organic Rankine Cycle with a cyclopentane working fluid, and a Rankine steam cycle, and a Proton Exchange Membrane electrolyzer. In this study, to reduce the gas cycle fuel consumption, the solar tower system is integrated with the gas cycle. In the studied system, a Supercritical Carbon Dioxide cycle and an Organic Rankine Cycle have been used to heat recovery of the exhaust gases of the gas turbine. In addition, Energy, Exergy, Exergoeconomic, Exergoenvironmental, Emergoeconomic, and Emergoenvironmental analyses have been performed for this system hour by hour. A computer code was developed in MATLAB for these analyses, and the results are validated by simulation in Thermoflex software and primary references with high accuracy. A systematic approach based on thermodynamic analysis and a combination of Genetic Programming and Artificial Neural Networks is proposed for optimal design. Multi‐Objective Genetic Optimization has been employed to find optimum design parameters. Due to the reduction of computation time of optimization, the integration of Genetic Programming and Artificial Neural networks have been employed to generate correlations for objective functions based on the decision variables. By adding the solar system, the mass flow rate of natural gas consumption in the gas cycle decreases by about 9% and reaches 1.53 kg/s. Utilizing solar energy and the Rankine steam cycle, the production capacity of the considered cycle increases from 43 to 66 MW. Also, the performance analysis of the Proton Exchange Membrane electrolyzer and the primary cycle shows that this equipment can produce 0.01 g/s of hydrogen from 5 g/s of water entering the equipment per second by consuming 2.33 kW of power. The results show that when the decision variables are considered at the optimal performance point, the exergy efficiency, the total cost, the rate of destruction related to environmental impacts, cost based on emergy, and the rate of destruction environmental effects based on energy improve. The highest percentage of improvement among the objective functions compared to the initial state is related to the exergy efficiency with 46%, and then the environmental impact rate based on emergy with an improvement of 36%.

Simulation of the operation of a gas turbine installation of a thermal power plant with a hydrogen fuel production system

The growth in demand for the production of heat and electricity requires an increase in fuel consumption by power equipment. At the moment, the most demanded thermal equipment for construction and modernization is gas turbine units. Gas turbines can burn a variety of fuels (natural gas, synthesis gas, methane), but the main fuel is natural gas of various compositions. The use of alternative fuels makes it possible to reduce CO2 and NOx emissions during the operation of a gas turbine. Under conditions of operation of thermal power plants at the wholesale power market, it becomes probable that combined cycle power units, designed to carry base load, will start to operate in variable modes. Variable operation modes lead to a decrease in the efficiency of power equipment. One way to minimize or eliminate equipment unloading is to install an electrolysis unit to produce hydrogen.In this article the technology of “Power to gas” production with the necessary pressure at the outlet of 30 kgf/cm2 (this pressure is necessary for stable operation of the fuel preparation system of the gas turbine) is considered. High cost of hydrogen fuel during production affects the final cost of heat and electric energy, therefore it is necessary to burn hydrogen in mixture with natural gas. Burning a mixture of 5% hydrogen fuel and 95% natural gas requires minimal changes in the design of the gas turbine, it is necessary to supplement the fuel preparation system (install a cleaning system, compression for hydrogen fuel). In addition, the produced hydrogen can be stored, transported to the consumer. For the possibility of combustion of a mixture of natural gas and hydrogen fuel in a gas turbine the methodology of calculation of thermodynamic properties of working bodies developed by a team of authors under the guidance of Academician RAS (the Russian Academy of Sciences) V.E. Alemasov has been adapted, resulting in a program that allows to obtain an adequate mathematical model of the gas turbine. The permissible range of the working body temperature is limited to 3000 K. This paper presents the developed all-mode mathematical model of a gas turbine.On the basis of mathematical modeling of a gas turbine, a change in the main energy and environmental characteristics is shown depending on the composition of the fuel gas. Adding 5% hydrogen to natural gas has little effect on the gas turbine air treatment system, the flow rate remains virtually unchanged. CO2 emissions decrease, but there is an increase in the amount of H2O in the turbine exhaust gases.

Investigations on the Aerodynamic Performance of a Gas Turbine Exhaust Diffuser With the Modified Shell Profile

Abstract In this paper, a shell profile design method based on diffuser flow area curve is proposed to improve the static pressure recovery coefficient of the exhaust diffuser over a range of inlet swirl angles. Based on verifying the reliability of the numerical method, the paper first explored the aerodynamic performance of the exhaust diffuser with the original structure and the modified structure by solving three-dimensional Reynolds-Averaged Navier–Stokes. Numerical results well capture the pressure distribution and flow characteristics in the exhaust diffuser. The numerical results show that the shell profile modification method effectively improves the aerodynamic performance of the exhaust diffuser. Compared with the original exhaust diffuser, the secondary vortex near the outer shell of the modified exhaust diffuser is weakened and the axial reverse pressure gradient near the strut is reduced. The static pressure recovery coefficient of the modified exhaust diffuser is significantly increased under different inlet swirl angles. Especially, under the normal working condition with a medium swirl angle (22 deg), the static pressure recovery coefficient increases by 0.034 with a relative increase of 7.6%. Under the extreme working conditions of a large swirl angle (35 deg), the static pressure recovery coefficient increases by 0.074 with a relative increase of 39%. A test rig for measuring the aerodynamic performance of the exhaust diffuser was built, and the validity of the shell profile design method is further verified through experimental measurements.

The study on high temperature exhaust orifice infrared suppression

A type of gas turbine generator unit has lots of advantages, such as small size, light weight, advanced technical performance, strong environment adaptability, rapid start. However, the high temperature exhaust gas generated during the operation of the machine leads to the high temperature and obvious infrared radiation characteristics near the exhaust port. The objective of this paper is to investigate the infrared suppression of the exhaust orifice of the gas turbine generator unit. Meanwhile, some schemes about infrared suppression are proposed, that is, redesigning the exhaust cover or adding grid regenerator of high temperature phase change materials(HTPCMs). The method of computer simulation experiment, relying on Gambit and Fluent for modeling, is used to demonstrate the feasibility of the scheme. Results indicate that the first enrichment of gas turbine exhaust heat can be completed and the exhaust temperature can be reduced by about 200°C when the grid is set as a three-layer pattern crisscrossed up and down.

A combined cooling and power transcritical CO2 cycle for waste heat recovery from gas turbines

• A combined cooling and power cycle working with CO 2 is proposed for waste heat recovery from a gas turbine. • Efficiencies of the combined system and its COP are evaluated for three configurations (simple, split and cascade) versus different cycle parameters. • Although the split configuration has the highest net power generation at high and moderate heat source temperatures, in the case of low temperature waste heat from the gas turbine (less than 420 °C), net power of the simple cycle surpasses and the split cycle gives the lowest net power. • The split configuration yields the highest thermal efficiency between the three investigated configurations except at low condenser pressures. • The split cycle has a slight supremacy in heat recovery efficiency at intermediate and high gas turbine exhaust temperatures. This supremacy persists over all the investigated cycle parameters. • For low CO 2 mass fractions into the refrigeration part, cascade configuration has the highest COP. • For high CO 2 mass fractions into the refrigeration part, simple configuration has the highest COP. • The split cycle is the most efficient configuration regarding the total system efficiency. Hence, it can be selected as the candidate cycle configuration for further optimization in a future study. A transcritical carbon dioxide (T-CO 2 ) cycle is analyzed for waste heat recovery from a gas turbine. The cycle is proposed to produce combined power and cooling using carbon dioxide as a single pure working fluid. Simple, cascade and split cycle configurations are compared for power generation using a recuperator while a low-temperature loop is added for the cascade and split cycles. In a previous report in the literature the power generation part alone was presented for the three configurations and it was concluded that the split cycle can produce the highest power among the three systems. Here, the same configurations are studied combined with a compression refrigeration cooling effect with the same working fluid, and a parametric study is conducted. The power cycle is a T-CO 2 cycle which absorbs the waste heat from a gas turbine. The effect of different parameters like cooling load, splitters mass fractions, turbine pressure and condenser pressure are investigated and a comparison between the three configurations are demonstrated. It is shown that, for instance, in case of higher temperatures of gas turbine exhaust the split configuration has the highest net power production while using gas turbine exhaust flow of temperatures less than 420 °C the simple configuration produces the maximum output power. From the cooling perspective, for values of turbine inlet pressure higher than 222 bar, abs. the cascade cycle indicates the best cooling performance while the split one takes this position at lower turbine inlet pressures.

Особенности проектирования высокотемпературных пластинчатых теплообменников для малоразмерных газотурбинных двигателей

An increase in the fuel efficiency of small-sized gas turbine engines can be achieved by regenerating the heat of the turbine exhaust gases. A rational layout solution in this case is a turboshaft scheme, where the effective power is generated on the shaft of a free turbine, and the turbine exhaust gases are released into the environment without doing useful work. When creating a turboshaft engine with heat recovery, the concept of developing engine family on the base of unified gas-generator was considered. The concept involves the development of a modular system, where the addition or exclusion of individual large units allows changing the type of engine at minimal cost. The article presents the layout solution of a small-sized turboshaft gas turbine engine with heat recovery, developed on the basis of a unified gas-generator and using a gearbox to transfer effective power to a propeller or a rotor. A plate heat exchanger module with a corrugated heat exchange surface for a small-sized turboshaft gas turbine engine has been designed. The heat exchange matrix was developed using a complex techniques of computer-aided design, calculation and manufacture of plate heat exchangers. Some design features of high-temperature plate heat exchangers are identified, the most important of which is the non-uniformity of temperature fields in the heat exchange matrix. Taking into account the non-uniformity of temperature fields, the heat exchanger module is a collapsible structure allowing the replacement of the heat exchange matrix and providing compensation for thermal expansion of the heat exchanger elements. The designed plate heat exchanger module for a small turboshaft gas turbine engine will be manufactured and tested on the bench

Optimization of Gas Turbine Exhaust Volute Flow Loss

Optimization of Gas Turbine Exhaust Volute Flow Loss

Study of an integrated gas turbine -Molten carbonate fuel cell-organic Rankine cycle system with CO2 recovery

A huge amount of energy is consumed by recovering CO2 in the gas turbine (GT) exhaust gas with the traditional method because of the low CO2 concentration. A new system integrated with gas turbine, MCFC and ORC with CO2 capture is proposed in this article. CO2 in the gas turbine exhaust gas is concentrated by the MCFC electrochemical reaction. Compared with traditional CO2 capture methods, it effectively decreases the energy consumption of CO2 capture. The mid-temperature exhaust gas heat is recovered by two stages organic Rankine cycle systems. The influences of the major parameters on the new system performance are deeply studied. Also, the thermal and economic performances of the new system are compared with those of the reference system without CO2 capture and with CO2 capture based on the traditional mono-ethanol ammine (MEA) method. The results show that, when the CO2 capture rate is 0.85, the thermal efficiency of the new system is 62.34%, 3 percentage points higher than that of the gas steam combined cycle system without CO2 capture; and the exergy efficiency is 60.08%, 2.47 percentage points higher than that of the gas steam combined cycle system without CO2 capture. Its economic performance will be improved with the reduction of the MCFC cost in the future.

Technoeconomic assessment of a concentrated solar tower-gas turbine co-generation system

This paper presents a technoeconomic assessment of a solar-driven co-generation system that suits medium/large-scale water production and power generation. The system consists of a concentrated solar tower combined with a gas turbine cycle for power generation and combines reverse osmosis (RO) with multi-effect distillation (MED) for the desalination. Two operational scenarios for the gas turbine exhaust waste heat were assessed for energy efficiency, cost, and environmental impact. The first scenario involves maximizing power generation using organic Rankine cycle operation. The second scenario uses the waste heat from the solar gas turbine cycle to operate the multistage flash (MSF) to produce more water. The co-generation system with the two scenarios were modeled using MATLAB Simulink toolbox. The results reveal that the second scenario yields remarkable results in terms of lower hourly costs (2974 $/h), total water price (0.27 $/m3), and CO2 emissions (401 tCO2). MSF has the highest exergy destruction rate (5.632e6 kW), followed by the solar gas turbine cycle (8.843e6 kW). However, RO had the lowest exergy destruction rate (3294 kW), followed by the organic Rankine cycle (1.023e4 kW).

Thermodynamic performance analysis of a novel PEMEC-SOFC-based poly-generation system integrated mechanical compression and thermal energy storage

The issues arising from the intermittent nature and extreme weather conditions of renewable energy must be addressed urgently. Green hydrogen produced from electrolysis powered by renewable energy has been widely regarded as an ideal energy storage scheme in the energy revolution of the 21st century. A novel proton exchange membrane electrolysis cell (PEMEC)-solid oxide fuel cell (SOFC)-based poly-generation system integrated mechanical compression energy storage (MCES) and thermal energy storage (TES) is proposed. The MCES-assisted PEMEC efficiently produces and stores green hydrogen, while hydrogen-fueled SOFC is employed to generate electricity, achieving higher efficiency and zero greenhouse gas emission. The energy from compression heat and gas turbine exhaust gas is enormously recovered by TES and then utilized by absorption chiller/heater in the cascade way to produce heating, cooling, and domestic hot water. Thermodynamic models and operating strategies are constructed. The energy and exergy analyses are performed to evaluate the system performance and the effects of key parameters of SOFC and PEMEC on performance. The results show that under design conditions, the energy efficiencies of the novel system for summer, transitional season, and winter are 82.61%, 79.36%, and 87.30%, meanwhile, the exergy efficiencies are 43.85%, 44.47%, and 45.58%, respectively. Finally, sensitivity analysis results show that properly increasing the operating pressure or temperature can significantly improve the total exergy output and exergy efficiencies of SOFC and the hybrid system. When the pressure varies from 1 bar to 13 bar, the total exergy outputs are increased by 27.08%, 26.33%, and 20.78% in the summer, transitional season and winter, respectively. The SOFC energy efficiency is improved from 34.19% at 800 ℃ to 53.72% at 1000 ℃. The system exergy efficiency enhances when the PEMEC operating pressure ranges from 1 bar to 20 bar or the temperature varies from 50 ℃ to 90 ℃, furthermore, the optimal operating condition is 5 bar and 67 ℃.