Maximum Exergy Destruction Research Articles

A comprehensive techno-eco-environmental investigation of an efficient biodiesel generation procedure through hydrodynamic cavitation

The growth of cleaner biodiesel generation associated with hydrodynamic cavitation from canola oil via transesterification is acquiring prominence owing to considerably descending energy needs and time. In this work, the conversion of canola oil into biodiesel and glycerol was achieved through the process of transesterification with methanol, employing sodium hydroxide as a catalyst. The newly offered process was investigated from technical, economic, and environmental points of view, and the precision of the results was verified and accepted compared to previously published works. The technical results revealed that the maximum exergy destruction rates as well as exergy efficiency belonged to the transesterification process. The economic study showed that the capital cost of the process was 638.7 MUSD/year. Also, the return period was computed less than 4 years. Moreover, comparison analysis proved that Canola oil proved to be a more advantageous primary material for the production of biodiesel and was more appropriate from the exergoeconomic point of view in comparison to Jatropha oil and other materials. Finally, by increasing the conversion percentage of the reactor, the value of the exergo-environmental index and the factor of exergy stability increased significantly, which was considered as an advantage from an environmental standpoint.

Thermodynamic and economic comparisons of supercritical water oxidation and gasification of oily sludge under hydrothermal flames

Dual-shell reactors using hydrothermal flames as internal heat source were proposed for supercritical water gasification (SCWG) and oxidation (SCWO) of oily sludge to achieve fast preheating and avoid corrosion, salt plugging, and overheating. The SCWG and SCWO systems with hydrogen-rich syngas and electricity outputs, respectively, were established and simulated using Aspen Plus 11. Simulation models were validated by comparing with experimental products and temperature profiles. The maximum exergy destruction coefficients of 28.01% and 24.31% appear in the combustion reactor for both the SCWG and SCWO systems, respectively, indicating the indirect preheating method with hydrothermal flame is critical to the energy efficiency. The increase of reaction temperature promotes hydrogen but inhibits methane formation in the SCWG, and more steam but less syngas is output at higher reaction temperatures. Although more steam and electricity outputs are present at higher reaction temperatures for the SCWO, more fuel input is required. Lower exergy efficiencies are obtained at higher reaction temperatures in both the SCWG and SCWO systems for more energy is output as low grade steam. Less fuel input is required for both the SCWG and SCWO systems at higher feed concentrations, and higher exergy efficiencies can be obtained. The net treatment cost for the SCWG and SCWO systems are 119.19 and 215.47 USD/t, respectively, indicating the SCWG is more economically competitive compared with the SCWO.

Performance analysis of a modified solar assisted ejection-compression heat pump cycle for drying application

In this paper, a modified solar assisted ejection-compression heat pump cycle (SEHPC) is proposed for drying application. Based on the basic ejection-compression heat pump cycle (BEHPC), an auxiliary flash tank and an internal heat exchanger are introduced to improve its heating performances. The introduction of flash tank can improve the heat absorption in evaporator and increase the volumetric heating capacity in condenser, which eventually reduce the throttling losses and enhance the performance of the SEHPC. The performances of the modified cycle with refrigerant R1234yf are analyzed and compared to those of basic cycle by developing the thermodynamic models based on the energy, exergy and economic analysis. Moreover, the main parameters, including evaporation temperature, condensation temperature, generation temperature, ejector back pressure, and the solar radiation intensity, are selected as variables for research. The theoretical results indicate that compared to BEHPC, the mechanical coefficient of heating performance COPw, the thermal coefficient of heating performance COPt, the volumetric heating capacity qhv and the exergy efficiency ηex of SEHPC are increased by 5.2%, 8.4%, 17.1%, and 8.0%, respectively, under a specified working condition. Furthermore, the SEHPC outperforms BEHPC under all given working conditions, especially at high condensation temperature and high generation temperature. The economic analysis results show that the cost per unit of exergy production by SEHPC is 6% lower than that of BEHPC. Additionally, the maximum exergy destruction occurred in the solar collector, which means great optimization potential in solar collector. This study demonstrates that SEHPC has practical performance improvement potential for heat pump drying application.

Thermodynamic performances of a power-to-X system based on solar concentrating photovoltaic/thermal hydrogen production

100% renewable power-to-X (fuel, power, and heat products) systems have great application potential for the achievement goal of carbon neutrality. However, the extensive chain of the power-to-X system could result in low energy utilization efficiency. A novel composite-parabolic-concentrating photovoltaic/thermal-collector-based power-to-X system utilizing 100% solar energy is proposed, which integrates proton exchange membrane electrolysis cells and proton exchange membrane fuel cells to provide heat, electricity, and hydrogen. Thermodynamic models for each subsystem are established, and energy and exergy efficiencies are assessed in the thermodynamic laws. Three operation modes are analyzed to adapt to the variations of solar radiation and a residential building is used as an application scenario to evaluate its thermodynamic and economic performances in dynamic variations of solar radiations and energy demands. The effects of key operating parameters, such as solar radiation intensity, photovoltaic coverage ratio, current density, and operating temperature, on the performances are investigated. The maximum exergy destruction of the concentrator photovoltaic/thermal collector is 93.20% at the rated operating conditions, and the system exergy and energy efficiencies are 9.11% and 48.97%, respectively. The economic results demonstrate that the levelized costs of solar power, hydrogen, and fuel cell power are 0.2936 $/kWh, 21.70 $/kg, and 2.1520 $/kWh, respectively.

Exergy and exergoeconomic analysis of a hybrid airborne wind and solar energy system for power, liquid nitrogen and carbon dioxide production

Airborne wind energy (AWE) systems have emerged as cost-effective and sustainable solutions that have not yet been coupled with solar technologies and integrated power plants to produce energy and on-demand substances. This study proposes an integrated system driven by an innovative AWE and photovoltaic (PV) hybrid system. This combination can harness stronger and more stable wind energy while decreasing system costs and power intermittency. The proposed system combines seven subsystems, including AWE, PV, air separation unit, oxyfuel power plant, absorption refrigeration, a nitrogen liquefaction process, and Organic Rankine Cycle (ORC) to simultaneously generate power, liquid nitrogen, and liquid carbon dioxide. The hybrid AWE-PV system can generate 10.8 MW power to initiate the system to produce 55 MW power, 127.2 m3/h liquid nitrogen, and 98.4 m3/h liquid carbon dioxide. The exergy analysis has been conducted, showing maximum exergy destruction in heat exchangers, and the total exergy efficiency of the integrated structure reaches 90.21 %. The exergoeconomic analysis illustrates that the maximum capital cost occurs in compressors and turbines with a percentage of 51 % (∼4600 $/h) and 26 % (∼2400 $/h), respectively. This first demonstration of implementing hybrid AWE-PV renewable energy sources in an integrated structure can open new perspectives and avenues toward using AWE and its combination with other renewable energy sources in the future.

Machine learning-based optimization and 4E analysis of renewable-based polygeneration system by integration of GT-SRC-ORC-SOFC-PEME-MED-RO using multi-objective grey wolf optimization algorithm and neural networks

This study introduces a new solar-methane-driven setup that recovers waste heat from flue gases to produce electricity, hydrogen, oxygen, fresh water (FW), and domestic hot water (DHW) while reducing the environmental impact of gas turbines. This integration includes the Brayton cycle and solid oxide fuel cell as motive cycles, the steam and organic Rankine cycle, a parabolic trough solar collector (PTC), a proton exchange membrane electrolyzer, multi-effect distillation, and reverse osmosis. Using Engineering Equation Solver software, analyses in energy, exergy, exergoeconomic, and exergoenvironment (4E) are conducted to identify critical system evaluation parameters in thermodynamics, economics, and the environment. Additionally, the proposed system is optimized using an artificial neural network and the multi-objective grey wolf optimizer algorithm, utilizing decision variables identified through sensitivity analysis to enhance system performance. The results of six-objective optimization show energy and exergy efficiencies at 49.48 % and 47.21 %, with a net power production of 133 MW and a total cost rate of $7903/h. Among all the components, the combustion chamber and PTC have the maximum exergy destruction, with values of 58.87 MW and 17.29 MW, respectively. Also, hydrogen, FW, and DHW production rates are 201.6 kg/h, 43.88 kg/s, and 40.98 kg/s, respectively. Moreover, the costs of hydrogen, FW, and DHW are $953.64/h, $57.35/h, and $82.48/h, respectively. Finally, Bloemfontein, Las Vegas, and Tunis are the most favorable regions economically, with a low levelized cost of electricity of $0.05931, $0.06006, and $0.05932 per kWh, along with payback periods of 0.6144, 0.5524, and 1.069 years, respectively.

Thermo-economic assessment of a salt hydrate thermochemical energy storage-based Rankine Carnot battery system

Carnot batteries are critical technologies for increasing the penetration of renewable energy sources because they enable suitable energy storage for long-term periods. The achievement of high efficiencies is an important point that determines the sustainability of the Carnot batteries. In this direction, a novel Rankine Carnot battery with heat upgrading capability based on salt hydrate thermochemical energy storage is proposed herein. The steady thermodynamic and economic models for the basic Carnot battery and recuperators introduced Carnot battery, both with a storage capacity of 10 MW/5h, have been established. The thermo-economic performance of the Carnot battery systems and the effects of several key parameters are quantitatively assessed. Results manifest that the Carnot battery with recuperators behaves better in comprehensive performance thanks to the heat recovery by recuperators. The power-to-power efficiency, exergy efficiency, and levelized cost of storage for the basic Carnot battery and recuperators introduced Carnot battery systems are 48.48 %, 38.48 %, 0.2502 $/kWh and 64.1 %, 48.94 %, 0.1922 $/kWh, respectively. The maximum exergy destruction occurs in the heat exchanger for the Carnot battery systems and the throttle's exergy destruction is diminished by 70 % in the recuperators introduced Carnot battery. The compressor and turbine account for the largest cost ratios, i.e., 26.5 % and 24.8 % in the basic Carnot battery and 28.2 % and 27.2 % in the recuperators introduced Carnot battery; while the cost proportion of throttle in both systems is nearly ignorable (0.3 %). Elevating heat source temperature and the reactant's hydration temperature and descending ambient temperature contribute to the improvement of power-to-power efficiency and levelized cost of storage. The isentropic efficiencies of compressor and turbine, especially the latter, have a great impact on the thermo-economic performances. As the daily charging time expands to 7 h, the levelized cost of storage of the recuperators introduced Carnot battery reduces to 0.1434 $/kWh. Replacing the reactive salt of potassium carbonate sesquihydrate (K2CO3·1.5H2O) with magnesium sulfate tetrahydrate (MgSO4·4H2O) brings a lower levelized cost of storage of 0.18 $/kWh. The findings of this study demonstrate great potential for the exploitation of this thermochemical energy storage-based Carnot battery for large-scale electricity storage.

Exergy analysis of ejector‐enhanced dual‐evaporator cycle using effective temperature method

AbstractThis study compares the exergy of an ejector‐based two evaporator cycle (EB‐TEC) with a conventional two evaporator cycle (C‐TEC). The analysis utilizes a modified Gouy–Stodola equation, which provides a more accurate insight of the system irreversibility compared to the standard Gouy–Stodola formulation. Furthermore, the comparison includes three working fluids, that is, R134a, R1234ze, and R600 in both the cycles. The study examines the effects of varying evaporators and condenser temperatures and the dryness fraction at the exit of Evaporator 1. The data is analyzed using an Engineering Equation Solver. The findings indicate that increasing the temperature of the low‐temperature evaporator leads to a drop in exergy losses and enhancement in exergy efficiency in both the cycles. When the temperature of Evaporator 1 is increased, the total exergy of the EB‐TEC is decreased but for the C‐TEC, it is increased. Furthermore, increasing the condenser temperature results in higher exergy destruction in both EB‐TEC and C‐TEC. Notably, the maximum exergy destruction is 49.44 kW for R600, whereas the minimum exergy destruction is 14.42 kW for R1234ze in the EB‐TEC.

Design and performance estimate of a novel linear fresnel reflector solar-gas combined system for producing electricity and hydrogen

Multi-energy complementary technology is meaningful for promoting the development of solar energy utilization, and the main novelty of this paper is the proposal of a novel linear Fresnel reflector solar-gas combined (LSGC) system which utilizes the organic Rankine cycle driven proton exchange membrane hydrogen production (PEM-HP) subsystem as well as is designed for generating electricity and hydrogen. By using the Ebsilon, the operation performance and exergy analyses of the LSGC system are launched. The results show that the output power and electric efficiency of the LSGC system are 424.8 MW and 45.4%. The solar field contributes a power of 34 MW. The hydrogen production rate of the LSGC system is 182.88 kg/day. The solar field, GTCC and PEM-HP section can reach the coordinated operation effectively during a long term, revealing the technical feasibility of the LSGC system. The exergy analysis results indicate that the solar field has the second maximum exergy destruction and the smallest exergy efficiency, and the combustion chamber has the maximum exergy destruction. The economic analysis shows that the levelized costs of electricity and hydrogen of the LSGC system are 0.045 $/kWh and 5.67 $/kg. The environment effect evaluation shows that compared with the coal power, the LSGC system can reduce the annual emissions of CO2, NOx, SO2 and dust effectively. Those reveal relatively acceptable economic feasibility and environment protection effect of the LSGC system.

Thermodynamic and exergetic evaluation of CO2 liquefaction for ship transport

CO2 liquefaction is significant to ensure CO2 transport safety and improve efficiency. Aiming at the temperature and pressure required for ship transport, this paper examines four liquefaction schemes including the compression refrigeration system, the Linde Hampson system, the precooled Linde Hampson system and the Claude system. The thermodynamic and exergetic ananlysis models are established primarily and total power consumption, liquefaction efficiency as well as exergy efficiency of the four systems are calculated and compared. The precooled Linde Hampson system shows the best performance with the three indicators of 391.74 kJ/kg, 97.97 % and 55.86 %, respectively. Additionally, exergy destruction among the system components are analyzed for Linde Hampson system and precooled Linde Hampson system. The maximum exergy destruction stem is from compressors. Another thing to note is that the proportion of the total exergy destruction with Joule-Thomson (J-T) valves are 19.38 % and 2.63 %, respectively. Furthermore, the replacement of the J-T valve by a liquid expander allowed for 9.35 % and 0.94 % electric power saving for the two systems, respectively. The pressure drop before and after the J-T valve directly determines the effect of this change. The research results could provide some vital reference for choosing proper CO2 liquefaction methods and reducing energy consumption during the process.

Pinch, energy, and exergy analysis for a power-hydrogen cogeneration system fueled by biogas

This paper presents a combined heating, power, and hydrogen system production by utilizing biogas energy. A novel methodology is proposed to identify thermodynamic cycle conditions and reform processes by using biogas as the energy source. Biogas steam and dry reforming methods are considered based on equilibrium data employing the EES program. It is found that biogas has two principal roles for combustion and reforming processes simultaneously. The thermal energy from the combustion of biogas causes its reforming and improves the efficiency of the system by 74%. The exergy efficiency, the overall exergy destruction, and hydrogen efficiency are calculated for various electric powers ranging from 5 to 40 MW. It is found that the combustion chamber has the maximum exergy destruction of about 51%. The parametric study of the system is performed to assess the optimum conditions for producing hydrogen. The optimal condition corresponds to CO2/CH4 = 0.50–0.66, H2O/CH4 = 2–3.6, and the reforming temperature range of 965–1036 K. The conversion of methane and carbon dioxide shows the reduction of the greenhouse gases.

4-E analysis and multiple objective optimizations of a novel solar-powered cogeneration energy system for the simultaneous production of electrical power and heating

Owing to its natural and rich advantages, exploration of solar energy technology has become increasingly popular in recent years to counter the growing crude oil prices. However, its universal adoption is still limited, not only due to environmental restrictions but also due to lower overall efficiency. Rankine cycle is optimised to conduct 4-E (Exergy, Energy, Economic and Ecological) analysis. Furthermore, three sets (R-113, R-11, and R-1233zd) of refrigerants are prioritised and ranked on the basis of 4-E analysis as outcomes. The contemporary study addressed all critical factors and explains the impact of solar irradiance, mass flow rate of molten salt and steam, turbine inlet pressure, and turbine inlet temperature which are eventually weighed and prioritised using combined multi-criteria decision making (MCDM) techniques. The energy efficiency, exergetic efficiency, power/ cost of electricity, and ecological emissions are taken as the indicators of the combined cycle, respectively. The energy efficiency of the hybrid system is improved to 75.07% after including cogeneration cycle, with an increment of 54.58%. In comparison to conventional thermal powerplant setups, the power/cost of electricity and ecological efficiency have been reduced by 68% and upgraded by 16%, correspondingly. Direct normal radiation is the most critical factor followed by turbine inlet temperature. Further, the result indicates that maximum exergy destruction that occurs in the central receiver declines to 39.92%, followed by heliostat and steam turbine which was 27% and 9.32% respectively. In conclusion, the hybrid cycle can furnish cheaper electricity, with lower carbon imprint in sustainable manner with better efficiency.

Maisotsenko Cycle for Heat Recovery in Gas Turbines: A Fundamental Thermodynamic Assessment.

This paper reports the Maisotsenko's cycle-based waste heat recovery system with enhanced humidification to exploit the maximum waste heat recovery potential of the gas turbine. This research uses an integrated methodology coupling thermodynamic balances with heat transfer model of air saturator. The performance of the system is deduced which are assisted with sensitivity analysis indicating the optimal mass flow rate ratio (0.7-0.8) and pressure ratio (4.5-5.0) between the topping and bottoming cycles, and the air saturator split (extraction) ratio (0.5). The net-work output, energy, and exergy efficiencies of the system are found to be ≈58.39MW, ≈55.85%, and ≈52.79%, respectively. The maximum exergy destruction ratios are found as 68.2% for the combustion chamber, 16.0% for the topping turbine, 5.7% for topping compressor, 4.9% air saturator. The integration of Maisotsenko's cycle-based waste heat recovery system with a comprehensive thermodynamic model, as demonstrated in this research, offers valuable insights into enhancing the efficiency, cost-effectiveness, and environmental impact of gas turbines. By presenting fundamental equations related to thermodynamic balances, this work serves as an invaluable educational resource, equipping future researchers and students with the knowledge and skills needed to advance the study of thermodynamics and sustainable energy solutions.

Thermodynamic analysis and comprehensive system optimization of the near zero emission hybrid power based on SOFC-ICE integrated system fueled with ammonia

The highly efficient heat and mass integrations fueled with ammonia of solid oxide fuel cell and reciprocating piston internal combustion engine are conducted from the viewpoints of characters of restrained / unrestrained chemical reaction and principle of energy cascade utilization. According to previous studies, we classified such integrations into serial and parallel topologies. Based on the detailed and verified models, the power matching limits of serial and parallel integrations are proposed first, showing a narrow scale of power matching of fuel cell and engines, due to the finite engine displacement. Furthermore, based on the design concepts of serial and parallel integrations, the improvement and optimization of combined systems were conducted, which showed that the possibly highest efficiency of serial and parallel systems can reach 70.53% and 68.40%, respectively. Additionally, the exergy analysis of systems could prove that such heat and mass integrations can effectively use remaining heats and fuels, leading to less exergy destructions and optimal designs and operation points achievement, while the maximum exergy destruction occurs at engine. Finally, the environmental analysis results showed that the corrected NO, NO2, N2O and NH3 emissions can reach 0.01 mg/kWh, 5.00 μg/kWh, 29.50 mg/kWh and <5 ppm, achieving near zero emissions.

A closed-loop linear engine generator using inert gases: A performance and exergy study

This paper introduces air, argon, and helium used as working fluids in a first-of-its-kind closed-loop Linear Engine Generator (LEG) to reveal its performance map, energy flow, exergy destruction, and exergy efficiency. Properties of the working fluids affect the LEG designs, e.g., compression ratio and applicable temperature range, in turn, impacting system efficiency and power output. A comparison is made between open-loop and closed-loop models using air at a peak temperature below 1095 K, based on a laboratory prototype of an open-loop LEG. The closed-loop models using air, argon, and helium achieve impressive efficiencies of 43.92%, 43.74%, and 51.30%, respectively, at the intake pressure of 0.85 bar and intake temperature of 225 K. The LEG using air shows the highest power output of 2448 W, while the helium version generates 2044 W and the argon version 1850 W. The exhaust energy loss is one of the major energy losses, which is comparable to the mechanical power output, while the friction loss ranges from 7.4% to 9.3%. The compressor and expander have low exergy destructions and high exergy efficiencies of more than 96%. In the closed-loop systems, the maximum exergy destruction rate is seen at the condenser affected by the coolant's low temperature.

Exergetic Performance of Jet Impingement Bifacial Photovoltaic-Thermal Solar Air Collector with Different Packing Factors and Jet Distributions

Jet impingement is a promising cooling mechanism to increase the rate of heat transfer in solar air collector. However, the effects of an impinging air jet on the exergetic performance of a bifacial photovoltaic-thermal with different packing factors are entirely unclear. In this research, a jet impingement bifacial photovoltaic-thermal solar air collector was developed and its exergetic performance was assessed. Jet plate reflectors with different geometric configurations are proposed to enhance the cooling and light absorption at the rear part of the bifacial photovoltaic module. Additionally, the link between exergetic performance and each variable’s design and operational characteristics was examined through indoor experiments. The results showed that the maximum exergy efficiency of the bifacial photovoltaic-thermal with packing factor of 0.66 and 36-hole jet plate reflector has 11.88% under solar irradiance of 900 W/m2, and mass flow rate of 0.025 kg/s. The maximum exergy input, exergy destruction, and improvement potential of the proposed system are 402.81 W, 345.62 W, and 304.78 W, respectively.

Thermodynamic analysis of an efficient pressure-swing CO2 capture system based on ionic liquid with residual pressure energy recovery

In this work, an efficient pressure-swing ionic liquid-based CO2 capture system with residual pressure energy recovery is proposed. In this system, the N2–O2 mixture from flue gas which is not absorbed by the ionic liquid in the absorber flows into the turbine to recover the energy for the purpose of reducing energy consumption. 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) are selected as the capture solvent and a comprehensive thermodynamic analysis is performed. The total energy consumption of the new system is 1.770 GJ/tCO2 under design conditions which is 28.45% lower than the conventional system for [Bmim][BF4] and 1.737GJ/tCO2 which is 28.84% lower than the conventional system for [Bmim][PF6]. The effect of absorption pressure, desorption temperature, heat storage fluid flow rate, distribution ratio of heat storage fluid in the intercooler, flue gas composition and type of heat storage fluid on system thermodynamic performance were analyzed. The result shows that relatively lower capture pressure, the lower desorption temperature, the lower heat storage fluid flow rate, the more heat storage fluid distributed in the first intercooler and the higher CO2 fraction in flue gas can improve the thermodynamic performance of the system. Also, the exergy analysis represents that cold tank and the capture module are the two components with maximum exergy destruction. And the comparison results with the conventional system show that the new system has significantly lower energy consumption and capture cost.

Proposal of a proton exchange membrane fuel cell-based hybrid system: Energy, exergy and economic analyses and tri-objective optimization

This article presents energy, exergy and economic analyses and tri-objective optimization of a hybrid system that comprises a proton exchange membrane fuel cell and a recuperative-regenerative organic Rankine cycle. The novelty of this study is the utilisation of a recuperative-regenerative organic Rankine cycle rather than the basic configuration of the organic Rankine cycle to recover waste heat from the fuel cell. The simulation results showed that the proposed system generates a net power of 1195.6 kW, with an exergy efficiency of 44.37% and a product cost rate of 160.78 $/h at the base condition. The hybrid system is found to be more efficient and cost-effective as compared to a standalone fuel cell with 15.05% and 15.06% improvements in energy and exergy efficiencies, respectively, and a 9.28% decrement in unit product cost. The fuel cell is the component with maximum exergy destruction rate of 636.72 kW, accounting for 90.62% of the total exergy destruction. Further, it is also observed that the fuel cell accounts for 89.2% of the total levelized cost rate of the hybrid system. Then a tri-objective optimization is carried out on the system using Pareto Envelope-based Selection Algorithm-II with net power output, exergy efficiency, and product cost rate as the objective functions. The optimization results showed that the proposed system generates a net power of 1271.52 kW, with an exergy efficiency of 49.48% and a product cost rate of 152.62 $/h. It implies that at the optimal conditions, the hybrid system's net power and exergy efficiency increased by 6.35% and 11.51%, respectively, and the product cost rate was reduced by 4.98%. Finally, this study showed that the inclusion of recuperative-regenerative organic Rankine cycle as compared to other organic Rankine cycle layouts improved the performance of the suggested hybrid system compared to similar other systems reported in the literature.

Thermodynamic assessment of biomass-fueled solid oxide fuel cell integrated gas turbine hybrid configuration

The combined use of a gas turbine and solid oxide fuel cell(SOFC) is investigated. Pine sawdust is utilized as the gasifier's feedstock, and syngas, which is produced as a byproduct, is processed, and used in fuel cells. Steam reformation and the water-gas shift reaction are two examples of electrochemical processes. Unused fuel is expelled from the fuel cell and burned in the combustion chamber. The quantitative and qualitative analyses were carried out to examine the energy and exergy analysis of the proposed hybrid system, using the first and second laws of thermodynamics, respectively. The novelty of this paper is to utilize waste heat from the gas turbine is used to minimize the temperature gradient in SOFC. Additionally, the impact of pressure ratio and turbine inlet temperature (TIT) will be discussed in a novel perspective with the help of an unique performance plot. The irreversibility of the system causes exergy destruction, which raises the losses related to the components. Maximum exergy destruction is found in SOFC followed by water heat exchanger and gasifier. At pressure ratio 4 and TIT 1250 K, the maximum thermal efficiency of the suggested hybrid system is 62.12%.

Comparison and evaluation of energetic and exergetic performance of an evacuated tube solar collector using various nanofluid

There is a growing interest in renewable energy sources cause the worsening impact of fossil fuel development and abuse on the ecological environment. Solar collectors are major facilities that utilize solar energy, many studies and techniques have been employed to increase the efficiency of the collectors. This paper aims to evaluate the thermal performance of an evacuated tube solar collector(ETSC) in the solar thermal system by using Al2O3, CuO, Fe3O4 and Multi-walled carbon nanotube(MWCNT) nanofluid as working fluids. An evaluation approach for the energy, exergy and entropy of ETSC were proposed. Furthermore, the energy gained and stored by nanofluid in the solar collector was also been studied. The ETSC shown highest energy and exergy efficiency when the 0.01 vol%-MWCNT nanofluid was used which was 33.1% higher than that of water, and it was the same situation of exergy efficiency while the highest was 3.17 under the optimum situation. In addition, the energy gained by 0.01 vol%-MWCNT nanofluid showed the highest potential of energy absorption than other nanofluid, the maximum exergy destruction and entropy generation were achieved when water was used as working fluid of solar collector while the lowest were observed when MWCNT nanofluid with 0.01 vol% was used. Compared to normal working fluid in the ETSC, the use of nanofluid with high thermal conductivity can save more fossil fuels and coals which have a positive effect on protecting the environment.