Exergetic Sustainability Research Articles

Waste to hydrogen: Investigation of different loads of diesel engine exhaust gas

In this study, green hydrogen production by utilizing diesel engine exhaust gas waste heat in steam and organic Rankine with internal heat exchanger with two thermoelectric generators and proton exchange membrane electrolyzer combined system under different load conditions is investigated. Thermo-economic, enviro-economic and exergo-environmental analyses of the maximum hydrogen production point determined for different waste heat conditions are carried out. Total and specific investment cost and levelized cost of hydrogen determined under different loads are compared. Simple and dynamic payback period, profit ratio of investment and net present value of the combined system at different selling prices of hydrogen are determined and their feasibility is analyzed. Carbon reduction and carbon credit gain amount due to green hydrogen produced in line with zero emission targets are compared under different waste heat conditions. Exergetic sustainability index of the system were determined within the scope of exergo-environmental analysis. In terms of economic and environmental performance, a hydrogen cost of 2.04 $/kg was obtained under 100% load and a carbon saving of 7211 $ was achieved depending on the hydrogen produced. Dynamic payback period and net present value were found to be 4.467 years and 404,696 $, respectively, if the hydrogen selling price was 5 $/kg under 100% load. It is found that a 50% load reduction leads to an increase in dynamic payback period and levelized cost of hydrogen by 18.6% and 13.72%, respectively, and a decrease in net present value and profit ratio of investment by 54.39% and 12.39%, respectively. On the other hand, since the exergy destruction decreases with the decrease in the load, exergo-environmental index is found to decrease by 2.03%.

Investigating renewable and sustainable biofuel and biofuel/diesel blends utilizations in a turboshaft engine used on helicopters

In this study, biofuel, various biofuel/diesel blends and jet fuel are used in the turboshaft engine (TSE) of a helicopter. The analyses of thermodynamics, sustainability, environmental and cost formation are applied to the system, and the impacts of biofuel (B100) & its blends with diesel (B10D90, B20D80, B50D50) are compared with JP-8 jet fuel (JF100) and each other. TSE's energy efficiency is computed to be 25.18 %, while the exergy efficiency depending on the fuel type (from maximum to minimum) are found as JF100 (JP-8) (23.462 %) > B10D90 (23.367 %) > B20D80 (23.365 %) > B50D50 (23.359 %) > B100 (23.351 %). The exergy efficiency of the biofuel and its blends are slightly lower than the conventional jet fuel. However, the difference is lower than 1 %. So, the biofuel and its blends can be effectively used in the TSE of the helicopter. Sustainable efficiency factor rates of TSE are also very close for jet fuel (1.307) and biofuel & its blends (1.305). So, exergetic sustainability of the studied fuels are close to each other and they can be used in the helicopter engine in a sustainable way. Biofuel and its blends utilization can also reduce the environmental cost, specific environmental cost, social impact cost, specific social impact cost of CO2 for TSE.

Sensitivity and sustainability analysis of combined cycle plant with integrated LNG pressure energy recovery

Although combined cycle power plants (CCPPs) and liquefied natural gas (LNG) have arisen as solutions to the intermittent nature of renewable energy sources, they still need creative methods for performance enhancement and sustainability of the energy systems. Moreover, the energy efficiency of CCPPs is negatively impacted by environmental conditions, higher specific fuel consumption and a large quantity of waste heat released into the ambient. On the other hand, using seawater as a heating medium in LNG regasification circuits has a detrimental effect on the marine ecosystem. In this context, the LNG pressure energy recovery system through a direct expansion cycle (DEC) integrated with CCPP is proposed to improve sustainability, enhance exergetic performance and to reduce the heat recovery steam generator (HRSG) exhaust loss. To improve the cycle performance, low grade heat harnessed from CCPP is used as the heat source in the DEC rather than seawater. The system performance is analyzed by the energy and exergy method through a mathematical model. Moreover, the sensitivity analysis of the combined system is accomplished to examine the influence of LNG flow rate and ambient temperature on various performance indicators of the total system. It is observed that the integration of DEC boosts the HRSG performance by reducing the stack exergy loss and the efficiency is sensitive to LNG flow rate. The total integrated system energy efficiency ηtot, enhanced to 1.55% compared to the base case. Whereas, for ambient temperature in range of 15 – 45 °C, the system minimum and maximum exergetic efficiency ηex,tot is found to be 54.52 % and 55.94 %. Furthermore, the comparison of exergetic sustainability indicators is calculated and presented for three different simulation cases. The results demonstrate that increase in ηex,tot, affects the environment impact factor, ref and the sustainability index, θsi and improved 2.09 % compared to base case combined cycle.

Hydraulic balance effect of heating systems considering exergetic sustainability

Hydraulic balance effect of heating systems considering exergetic sustainability

Thermodynamic and environmental performance of a Kalina-based multigeneration cycle with biomass ancillary firing for power, water and hydrogen production

The performance of a Kalina-based multigeneration cycle for power, water, and hydrogen production is investigated from thermo-environmental, sustainability, and thermo-economic perspectives. The plant comprises a gas turbine (GT), Kalina cycle (KC), and vapor absorption system (VAS) as the bottoming cycle and an integrated domestic water heater and proton-electron membrane (PEM) electrolyzer for hydrogen production. The system's models were simulated with Engineering Equation Solver (EES) codes. The results indicate a net energy efficiency of 53.48% and exergy efficiencies of 50.05 %, with an additional 30,178 kW of products from the bottoming cycles. The GT contributed approximately 85.81 % of the overall exergy destruction. The system's exergo-thermal index (ETI) stood at 1.713, with the GT only having an ETI of 2.106. Similarly, the exergetic sustainability index (ESI) of the multigeneration plant was not greater than 2.04. The exergoeconomic analysis shows a low average energy cost from the GT, estimated at 0.836 $/GJ, compared to the Kalina subsystem, which stood at 6.53 $/GJ. The thermodynamic and cost evaluation of the system demonstrates substantial benefits from the plant, which kept the hydrogen production rate at 0.1524 kg/hr.

Exergy analysis and Exergetic sustainability index of package boiler

Energy is one of the basic human needs. Economic growth and population growth in a country which continues to increase is directly proportional to the growth in energy needs required by society. Indonesia is the largest energy user in Southeast Asia, namely more than 36% of Southeast Asia's primary energy use. Utilization of the energy used will reduce the increase in production costs for an industry. The use of energy is better known as energy conservation. Energy and exergy analysis based on the first and second laws of thermodynamics is used to analyze the thermal system of industrial units. This can be applied to equipment units in the fertilizer industry to identify sources of inefficiency, determine their location and the amount of exergy destruction that occur. To reduce exergy destruction, this can be done by modifying the operating conditions of the package boiler. The results show that 94.3% of the total exergy destruction from the boiler package is obtained from the evaporator component with a value of 2.7 x 108 kJ/hr Modification of the operating conditions of the evaporator is carried out by reducing Boiler Feed Water (BFW) inlet temperature with T 100C (196 – 116 oC). The decrease BFW temperature will increase the amount of required latent heat and reduce the convection heat that will be carried by the flue gas to generate superheated steam. Optimization of the BFW temperature is performed be calculating the flue gas temperature and exergoeconomic analysis. Exergoeconomic analysis is performed by calculating the cost rate of exergy destruction (ĊD,k) and exergoeconomic factor (fk). The results obtained were that the temperature was optimum of BFW is at 161°C which resulted the reduction of exergy destruction of 6,2x106 kJ/hr and resulting difference cost losses based on actual data (196 oC) of Rp 1,370,354,743/hr. Exergetic Sustainability Index (ESI) used to demonstrate how reducing a system's environmental impact can be achieved by reducing its exergy consumption (destruction and losses) or increasing its exergetic efficiency. In this research, ESI Value was achieved at 0.918.

Exergy analysis and exergetic sustainability index of package boiler

Exergy analysis and exergetic sustainability index of package boiler

Exergy analysis and exergetic sustainability index of package boiler

Exergy analysis and exergetic sustainability index of package boiler

Thermodynamic Analysis of the Integrated System that Produces Energy by Gradual Expansion from the Waste Heat of the Solid Waste Facility

The rapid increase in consumer societies leads to a rise in waste facilities. Especially when considering the amount of power used in waste plants and the corresponding waste heat generated, an approach to recover waste heat from these facilities has been proposed. Initially, the waste heat from the solid waste facility was assessed using the Rankine cycle. Subsequently, an Organic Rankine Cycle (ORC) system was integrated into the lower cycle of the steam Rankine cycle. The integrated system was completed by harnessing waste heat from the Rankine steam cycle in the carbon dioxide cycle. These power generation systems are designed with two turbines, each with gradual expansion. Using sub-cycles, 1 kg/s of air at 873.2 K was obtained by evaluating the waste heat. In terms of energy efficiency, it can be observed that the R744 gradual expansion cycle exhibits the highest energy and exergy efficiency. Cooling with water in heat exchangers reduces exhaust efficiency. The highest mass flow requirement is found in the ORC system when the R123 fluid is used. The energy efficiency for the entire system was calculated as 22,4%, and the exergy efficiency for the entire system was calculated as 60.7%. When Exergo Environment Analysis was made, exergy stability factor was found to be %60.7, exergetic sustainability index was found to be 2.66. There is also 370K waste heat available, which is recommended for use in drying units. These calculations were performed using the Engineering Equation Solver (EES) program.

5E (energy, exergy, energy level, exergoeconomic, and exergetic sustainability) analysis on a carbon dioxide binary mixture based compressed gas energy storage system: A comprehensive research and feasibility validation

Recently, the application of carbon dioxide binary working fluids in compressed carbon dioxide energy storage systems has been proposed to improve the system characteristics, especially for the condensation problem of carbon dioxide. Based on the previous research, a more comprehensive 5E (energy, exergy, energy level, exergoeconomic, and exergetic sustainability) analysis on a typical transcritical compressed carbon dioxide energy storage system using carbon dioxide binary working fluid is carried out. Propane, propylene, R32, R161, R1234ze, and R1234yf are chosen to compose the binary working fluid with carbon dioxide, respectively. The effect of changing parameters, including pump pressure ratio, compressor isentropic efficiency, and heat exahcnger1 outlet temperature on system performance, is also analyzed. In addition, the feasibility of applying carbon dioxide binary working fluid at high ambient temperature is investigated. According to the results, the performance of heat exchanger1, heat exchanger2, and pump decreases while the performance of the turbine is improved with a higher refrigerant mass fraction from the point of energy level. The compressor, pump, and turbine show potential for optimization according to their higher process energy level difference. The pump power and system operating pressure is reduced at the cost of reducing round trip efficiency when using carbon dioxide binary working fluid. A 1% improvement in compressor isentropic efficiency leads to an increase of nearly 0.4% in round trip efficiency, albeit with reduced turbine power. Increasing the heat exchanger1 outlet temperature from 305 K to 315 K results in a 1% increase in round trip efficiency but with a decrease in the performance of heat exchanger1. Both increasing compressor isentropic efficiency and heat exchanger1 outlet temperature benefit the system economy and exergetic sustainability. A noticeable decrease in system performance is observed when the ambient temperature shifts from 293 K to 303 K. However, this deterioration can be mitigated by raising the pressure of saturated working fluid gas at the compressor inlet. Propylene, R32, and R1234yf are suitable candidates to address the condensation issue, considering the system performance at high ambient temperatures. This paper extends research on the compressed carbon dioxide energy storage system based on carbon dioxide mixtures and provides a reference for the working fluid selection and system optimization for related research.

Experimental study of the thermal performance of heat storage-integrated solar receiver for parabolic dish collectors.

Parabolic dish collectors (PDC) efficiently produce hot fluids for medium-temperature applications. Thermal energy storage employs phase change material (PCM) due to its high energy storage density. This experimental research proposes a solar receiver for the PDC with a circular flow path surrounded by PCM-filled metallic tubes. The selected PCM is a eutectic mixture of KNO3 and NaNO3 (60%:40% by wt). At a peak solar radiation of about 950 W/m2, the receiver surface reached a maximum of 300°C. The modified receiver is tested outdoors with water as a heat transfer fluid (HTF). The energy efficiency of the proposed receiver is about 63.6%, 66.8%, and 75.4% for the HTF at 0.111kg/s, 0.125kg/s, and 0.138kg/s, respectively. The receiver's exergy efficiency is recorded at about 8.11% at 0.138kg/s. The receiver with a maximum reduction of CO2 emission is about 1.16 tons recorded at 0.138kg/s. The exergetic sustainability is analyzed using key indicators, like the waste exergy ratio, improvement potential, and sustainability index. The proposed receiver design with PCM effectively produces maximum thermal performance with a PDC.

Exergetic sustainability of a traditional four-pan jaggery unit for winter and summer seasons in northern India

The present research aims to examine the energy, exergy and sustainability analysis of a traditional four-pan jaggery unit based on the consumption and resource transformations involved in the sugarcane-based jaggery production process. The exergy analysis has been conducted based on an experimental study with the help of thermodynamic relations including the component-wise specific exergy for jaggery production. The energy and exergy of the jaggery unit are compared during the winter and the summer. The obtained average thermal energy efficiency of the jaggery unit shows an increment of 8.1% as compared to the winter season. In addition, when accounting for the combustion performance of bagasse, the exergy efficiency of jaggery plant in the summer is higher than the winter. Furthermore, negative environmental impacts are indicated by a poor exergy sustainability score during both seasons. In summer, the jaggery facility operates more sustainably than in the winter, as shown by the higher value of environmental benign index. Energy analysis alone conceals the fact that the primary factor in resource use is exergy destruction due to irreversibilities in combustion and heat transfer. By assessing the process fluxes in terms of exergy, this study enhances the transparency of resource consumption and losses in the production of jaggery.

Sustainability evaluation of a heavy-duty diesel engine used in railways

Heavy-duty diesel engines are essential power units for the Rail and Maritime transportation of people and goods. They are inevitable and consume large amounts of petroleum base fuel, producing substantial emissions. Since they are very bulky and costly to run and maintain, their performance, efficiency, and sustainability data are scarce, also. They are stationary constant-speed engines. Their efficiency values are relatively higher than conventional diesel engines. However, with newer pre and post-injections and fumigation techniques, those engines have significant room for improvement. This study thermodynamically examined a 16-cylinder, 4-stroke, and 90lt heavy-duty diesel engine with 1700 kW rated power output at 1500 rpm. Analyzes were performed on four different same-type engines archive data, obtained by permission, including different speeds and load conditions. Mean energetic and exergetic efficiency values were 12.84% and 11.92% at idling speeds of 650 rpm, 32.00%, and 29.70% at 1000 rpm, 31.35% and 29.10% at 1200 rpm, and 31.35% and 29.09% at the maximum speed of 1500 rpm. The waste-exergy ratio was 71%, the exergy destruction factor 45.5, the environmental effect factor was to be 2.44, and the exergetic sustainability index 0.41.

Exergoeconomic and Exergetic Sustainability Analysis of a Combined Dual-Pressure Organic Rankine Cycle and Vapor Compression Refrigeration Cycle

In this paper, an exergoeconomic and exergetic sustainability analysis of a dual-pressure organic Rankine cycle (ORC) and vapor compression refrigeration cycle (VCRC) driven by waste heat is performed for power generation and cooling production. In addition, the most suitable fluid couple among the thirty-five different fluid pairs was investigated for the proposed combined system. The results indicate that the highest energy utilization factor, exergy efficiency, the system coefficient of performance, and net power are calculated for the R123-R141b fluid pair. In terms of exergetic sustainability indicators, the best performance results are obtained for the R123-R141b fluid combination. The minimum unit electricity generation cost and the shortest payback period are calculated as 0.0664 $/kWh and 2.5 years, respectively, for the R123-R290 fluid pair. The system component with the highest exergy destruction is the boiler, with 21.67%. The result of the parametric analysis showed that the thermodynamic performance parameters increase with the increment of the ORC’s boiling temperature. In addition, with the increasing boiling temperature, the environmental effect factor of the system decreases, while the exergetic sustainability index increases. Additionally, as the boiling temperature increases, the total system cost increases, while the unit electricity production cost and payback period decrease. It is suggested to use a R123-R141b fluid couple among fluid pairs created as a result of thermodynamic, exergoeconomic and sustainability analysis.

Experimental and numerical performance assessment of a hybrid parabolic dish collector with photovoltaic for a distiller

ABSTRACT Environmental pollution has been rising recently, and so clean water needing has also increased. People could have easy access to pure water in all environments and conditions. This study is the solar tracking parabolic dish collector with produced pure water independent of electricity (off-grid). This system is fully renewable and autonomous. This system possesses a receiver, a boiler, a condenser, six 1000 mm diameter parabolic dish collectors, and 1 kW photovoltaic (PV) collectors. Thermal oil uses as the working fluid in the experiments. The experiment measured solar radiation, air temperature, air velocity, oil inlet and outlet temperatures, oil flow rate, receiver side surface temperatures, and instantaneous amount of pure water. Numerical and thermal analysis of the receiver in the experimental setup carry out. ANSYS Fluent 18.1 uses for numerical analysis. Energy and exergy analysis calculates the receiver for pure water production rate. The time interval when the system operates at high performance determines. In this study investigates the behavior of some exergetic indicators on the performance of the experimental setup, the cost of the experimental setup, and the enviro-economic impact of the parabolic dish-type collector. For this purpose, some exergetic factors such as the exergy effect, environmental impact factor, waste exergy rate, improvement potential, and exergetic sustainability index examine. The receiver’s improvement potential is between 1700 and 3000 W. In addition, the sustainability index, waste exergy rate, and environmental impact factor range from 0.32 to 0.36, 0.90 to 0.94, and 2.6 to 3.0, respectively.

Energy efficiency and cost assessment of a residential site with a combined heat and power system optimized with cryptocurrency mining

AbstractCombined heat and power (CHP) systems, an effective way of meeting high energy demand with high efficiency, were adapted to existing large service buildings in most studies. Because of the large daily and seasonal fluctuations in energy and electricity demands of the buildings, optimization problems have come into view and have been studied. This study propounds a holistic design solution for the CHP systems' inadequacy to meet varying consumer energy demands in residential and the excessive electricity demand created by cryptocurrency mining. In addition, the study defines the possible high efficiency and sustainability for residentials producing and consuming heat and electricity by themselves.An energy‐conservative three‐block residential and a CHP system were projected together by a holistic view balancing the residencies' peak thermal demand to the thermal output capacity of the CHP system. The investment return rate of the CHP system was maximized by optimizing the thermodynamic efficiencies and maximizing the electric generation for cryptocurrency mining. The energetic efficiency increased from 40% to an energy utilization factor of 83%, and exergetic efficiency increased from 39% to 42%. The waste‐exergy ratio decreased from 61% to 58%. The engine's environmental effect factor was 1.56 and reduced to 1.38 with the CHP system. The exergetic sustainability index was improved from 0.64 to 0.72. The benefit–cost ratio was estimated as 1.6, with an internal return rate of 79%. Holistic designs considering common values should be considered to improve sustainability.

Energy, exergy, thermoecologic, environmental, enviroeconomic and sustainability analyses and assessments of the aircraft engine fueled with biofuel and jet fuel.

In this study, utilization of a bio-based fuel in a turbojet engine is comprehensively monitored with adapting various useful indicators for the scope of the study based on thermodynamic principles. In this regard, extensive energy and exergy, thermoecologic, environmental, enviroeconomic and sustainability analyses are performed for both the turbojet engines fueled by jet kerosene and fueled by a bio-based fuel. As per the main findings, the mass stream of combustion emissions is measured to be 4.547kgs-1, when the engine is powered by biofuel. The specific fuel consumption and specific thrust are determined as 0.13kgkN-1s-1 and 147.81 kNs kg-1 for jet kerosene-powered case, while they are calculated as 0.15kgkN-1s-1 and 148.23 kNs kg-1 for biofuel-powered case. If biofuel is selected over jet-kerosene fuel, it is observed that the engine has better energy efficiency performance by 18.18%. The engine's environmental effect factor value is found as 4.88 for jet-kerosene usage condition, while it is found to be 4.93 for biofuel utilization case. The overall emitted CO2 emissions is measured as 336,672kg-CO2 year-1 for jet-kerosene usage condition, while it is estimated as 222,012kg-CO2 year-1 for the biofuel utilization case. Also, as far as biofuel is chosen as alternative to jet-kerosene, the environmental damage cost stream, namely the enviroeconomic parameter of the engine, falls from 59,254.27 US$ year-1 to 39,074.11 US$ year-1. It is observed that sustainable efficiency factor and exergetic sustainability index outputs of the components of air compressor are the same for jet-kerosene and biofuel utilization cases, which are 8.31 and 7.31, respectively.

Assessment of Whole Milk Powder Production by a Cumulative Exergy Consumption Approach

The production of food is a sector that consumes a significant amount of energy and encompasses both agricultural and industrial processes. In this study, the energy consumption of whole milk powder production, which is known to be particularly energy-intensive, was examined. The study used a cumulative exergy consumption approach to evaluate the overall production process of whole milk powder, including the dairy farm (raw milk production) and dairy factory (powder production) stages. The results showed that raw milk production dominated energy and exergy consumption and carbon dioxide emissions. An amount of 68.3% of the total net cumulative exergy consumption in the system was calculated for raw milk production. In the dairy factory process, the highest energy/exergy consumption occurred during spray drying, followed by evaporation and pasteurization. In these three processes, 98.3% of the total energy consumption, 94.6% of the total exergy consumption, and 95.7% of the total carbon dioxide emissions in powder production were realized. To investigate the improvement potentials in the system, replacing fossil fuels with renewable energy sources and using pasture feeding in animal husbandry were evaluated. While using alternative energy sources highly influenced powder production, pasture feeding had a high impact on consumption in raw milk production. By using renewable energy and pasture feeding, the exergy efficiency, cumulative degree of perfection, renewability index, and exergetic sustainability index values for the overall process increased from 40.5%, 0.282, −0.22, and 0.68 to 68.9%, 0.433, 0.65, and 2.21, respectively.

Drying Characteristics, Kinetic Modeling, Energy and Exergy Analyses of Water Yam (Dioscorea alata) in a Hot Air Dryer

In this study, drying characteristics, kinetic modelling, energy and exergy analyses of a convective hot air dryer are presented for water yam. The drying experiments were carried out at temperature levels of 50, 60, and 70°C and slice thicknesses of 3, 6, and 9 mm. The effects of drying variables on the drying rate (DR), moisture diffusivity (Deff), activation energy (Ea), energy utilization (EU), energy utilization ratio (EUR), exergy loss (EXL), exergy efficiency (EXeff), improvement potential (IP), and exergetic sustainability index (ESI) were investigated. The results showed that increasing air temperature increased the DR, Deff, EU, EUR, EXL, EXeff, IP, and ESI, while increasing the slice thickness increased Deff and Ea, but decreased the DR. The highest Deff and Ea values were 4.2 × 10−8 m2/s, and 53 KJ/mol, respectively. EU and EUR varied from 10 to 150 J/s and 0.39 to 0.79, respectively. EXL and EXeff varied between 2 and 12.5 J/s and 58 to 75 %, respectively. Midilli’s model had the best performance in predicting the moisture ratio of water yam with coefficient of determination (R2 = 0.9998), root mean square error (RMSE = 0.0049), and sum of square error (SSE = 0.0023).

Optimization of energy and exergy parameters for a conceptual after burning turbojet engine

In this study, parametric cycle analysis of a conceptual turbojet engine with an afterburner (TJEAB) was conducted at sea level conditions-zero Mach. Based on this analysis, exergetic sustainability parameters of TJEAB were scrutinized for military mode (MM) and afterburner mode (ABM). Constitutively, several design parameters of TJEAB were chosen so as to optimize performance and exergetic parameters which consist of specific fuel consumption (SFC), overall efficiency, exergy efficiency, environmental effect factor (EEF) and exergetic sustainability index (ESI). In this context, compressor pressure ratio (CPR), turbine inlet temperature (TIT) were preferred due to high effect of these variables on engine performance. CPR ranges from 4 to 11 whereas TIT varies from 1150 K to 1550 K. According to optimization of performance parameters, minimum SFC was achieved as 28.59 g/kN.s at MM and 43.95 g/kN.s at ABM. On the other hand, maximum overall efficiency is determined as to be 13.07 % at MM and to be 8.5 % at ABM. As for exergetic parameters, exergy efficiency was calculated as maximum with 30.85 % at MM and 23.2 %at ABM. Finally, maximum exergetic sustainability index of TJEAB was computed as 0.446 at MM and 0.269 at ABM. It is thought that energetic and exergetic parameters analyzed in this analysis could guide in designing turbojet engines in terms of lower fuel consumption thereby environmental-benign.