Thermoeconomic Considerations Research Articles

Comparison analysis of three CO2-based binary mixtures performing in the supercritical Brayton cycle for molten salt energy storage

It is generally acknowledged that using CO2-based binary mixtures as working fluids in supercritical recompression Brayton cycle for waste heat recovery is a promising technique. This study examines the performance of CO2-Kr (0.76/0.24) and CO2-Xe (0.56/0.44) mixtures, comparing them with pure CO2. Both thermodynamic and thermo-economic considerations are taken into account to establish optimal parameter settings. The findings suggest that the minimum system temperature should be around but not below the critical temperature of the working fluid. The system performs badly at lower pressures and shows nearly the same at higher pressures, with 25 MPa being the recommended value for the main compressor. When the system split ratio and the low temperature recuperator temperature difference are well matched, the heat exchangers exhibit an optimal temperature distribution. The exergy loss distributions of the exchangers in the CO2-Kr and CO2-Xe systems are likewise rather uniform when the input pressure of the main compressor is above the critical pressure of the fluid, typically between 0.2 MPa and 0.4 MPa, enhancing system efficiency. The corresponding temperature difference of the LTR should be within 5 °C above or below the critical temperature of the fluid. This advantageous feature is not immediately apparent in the pure SCO2 cycle.

A novel geothermal system combined with fuel cell and hydrogen generation to store clean sustainable energy storage

This paper presents a thermo-economic assessment of a novel geothermal integrated system enhanced by a fuel cell. The proposed system leverages the advantages of geothermal energy resources, featuring a sustainable and environmentally friendly solution for power generation and district heating applications. Integrating a fuel cell and thermoelectric within the geothermal system aims to improve overall system performance and energy efficiency by converting waste heat into electricity. A detailed mathematical model of the integrated system is developed, incorporating various performance parameters, component efficiencies, and thermo-economic considerations. The model is applied to simulate the system's performance under different operating conditions and parameters. Additionally, sensitivity analyses are conducted to evaluate the effects of key design variables on the system's performance, cost, and environmental impacts. The results indicate that the newly developed system generates 95594 kW of electricity with a total exergy destruction rate of 4616 kW. The electricity cost rate also obtained 0.309 $/kWh. The energy efficiency of the introduced system is 24.08 % and the exergy efficiency is 26.7 %. Comparison with the basic system represents that energy efficiency shows a 15.71 % improvement.

Analysis of a novel concentrated solar power and magnetohydrodynamic liquid metal units integrated system with hydrogen production

The engineers are very interested in concentrated solar power (CSP) due to its renewable energy source nature. However, for this technology to grow, it is crucial to integrate efficient, cost-effective subsystems. On the other hand, since liquid metal magnetohydrodynamic (LMMHD) power generation systems can operate at high temperatures of 600 °C–3000 °C, they are ideal for use as a subsystem of a CSP-based plant to improve efficiency. The use of waste heat recovery units is another method of increasing efficiency and preventing exergy losses. Taking these points into consideration, the proposed trigeneration system includes an LMMHD, a CSP, and humidification-dehumidification and proton exchange membrane units to produce power, freshwater, as well as hydrogen, respectively. Performance evaluation of the presented system includes thermodynamic and thermoeconomic considerations. The results show that the presented system produces 11.87 kW of power, 6.1 m3/h of hydrogen, and 860.2 L/h of freshwater with an energy utilization factor of 45.81%, a total exergy efficiency of 4.63%, and a unit cost of 19.57 $/kWh. The receiver is the most destructive component of the system, with 256.9 kW of exergy destruction. Further, the parametric study indicates that it is possible to maximize the energy efficiency of the system by changing the concentration ratio of the receiver.

The education index in the context of sustainability: Thermo-economic considerations

Sustainable development requires new technical solutions to be realized, due to the new approach to production, consumption, and management of resources. These technologies also require technical skills from workers and citizens. These technical abilities are mostly based on the knowledge of mathematics and sciences, acquired during schooling years. In this study, we develop a thermo-economic analysis of sustainable development in relation to the needs of mathematical and technical skills of future workers. To do so, the Education Index is considered to improve it toward a measure of the technical abilities of young people, maintaining its present social meaning of preventing child exploitation. The result is an improvement of the Thermodynamic Human Development Index, by introducing the OECD-PISA assessment, to allow the decision makers to analyze their policies, based on a more comprehensive vision of the present, to better design the future. Finally, we point out the need to focus public policies on the continuous stimulus of intellectual reasoning and on problem-solving-based education to develop the processing capacity and foster the creative capabilities of the younger population that builds the backbone of the future workforce.

Improved thermo-economic performance of solar desalination via copper chips, nanofluid, and nano-based phase change material

In this work, the performance of a modified double slope still (MDSSS) was evaluated compared to conventional single slope one (CSS). The modifications depended on different additives, namely: copper chips, copper oxide (CuO) nanoparticles/fluid, and paraffin wax as phase change material (PCM). First, the proposed materials were characterized to determine the thermophysical properties and the best ratios. As resulted, the copper chips, and nano-enhanced materials (water and PCM) had higher thermal conductivity than bulk water, and pure materials, respectively. Beyond the characterization, three cases of MDSSS were investigated compared to CSS: copper chips immersed in CuO/water nanofluid (1.5 wt%) (case I), integrating pure PCM container below the basin containing the previous materials (case II), and using nano-based PCM (15 wt%) instead of the pure PCM (case III). Moreover, the thermo-economic performance was evaluated by determining the efficiencies of the first and second laws of thermodynamics and the freshwater cost. As found, all cases showed good performance improvements, and case III was the best from both production and thermo-economic considerations. For this case, the productivity, energy efficiency, and exergy efficiency were enhanced by 113, 112.5, and 190%, respectively, relative to CSS. In addition, the freshwater production cost was saved by 35.3%.

A performance evaluation of the ejector refrigeration system based on thermo-economic criteria through multi-objective approach

This work investigates an exhaust heat-driven ejector refrigeration system with the thermo-economic considerations. The system is thermally modelled and is optimized considering the performance coefficient and the total annual cost as two objectives using heat transfer search algorithm. Generator temperature, evaporator temperature and condenser temperature are considered as design variables. A 2-D shock circle model is used to simulate the ejector component with R245fa refrigerant. The results of multi-objective optimization are discussed using the Pareto frontier obtained between both conflicting objective functions. The effect of varying the nozzle throat diameter and the ecological function on the thermo-economic objectives is presented and discussed. The sensitivity analysis of the objective functions to the decision variables is investigated. Further, the exergo-economic results at the optimal point are also presented and discussed. The results reveal that the ejector and the generator are the leading contributors to the exergy destruction and hence to the total annual cost. The coefficient of performance and total annual cost at the best optimal point are 0.3 and 25,903 $/year, respectively. The optimized product unit cost of the system is 53.8 $/GJ with 10.5% exergy efficiency.

Waste Heat Recovery and Conversion into Electricity: Current Solutions and Assessment

The main energy consumption sectors are the residential, industry and transport. In all of them, a part of the energy consumption is not used and generally rejected as heat in the environment. This is named the waste heat. Firstly, the main way is to optimize the process to reduce the fuel consumption. Then, if there is a residual waste heat, a valorization way is to convert this heat into electricity. Some technologies are developed. The main technology is the Organic Rankine Cycle engine. Then, a new concept, named Turbosol, is based on the quasi-isothermal expansion of a water and oil mixture in a nozzle. Some piston engines are also developed, based on Stirling, Ericsson and Joule cycles. All these technologies are named externally heated engines. Some other research studies concern the thermo-electric effect and the thermo-magnetic effect. In this article, a non-exhaustive list, with description and comments on these technologies is proposed. The aim is to assess the potential of them and identify the current limits. To compare the different technologies in first law efficiency terms is not sufficient. Some new criterions are proposed. The first consideration is to assess the heat rate consumption referred to the heat rate available. To assess the quality of waste heat to power conversion, it is pertinent to evaluate the power output divided by the available heat rate. Then, because of the second law, it is pertinent to evaluate the exergy recovery ratio. These new waste heat criterions are compared to the classical first law efficiency in different cases. Then, the main current issue is to produce enough electrical power output to ensure the profitability. Some thermo-economic considerations are proposed, including the impact of a waste heat taxation.

Cyanobacteria and Microalgae: Thermoeconomic Considerations in Biofuel Production

In thermodynamics, the useful work in any process can be evaluated by using the exergy quantity. The analyses of irreversibility are fundamental in the engineering design and in the productive processes’ development in order to obtain the economic growth. Recently, the use has been improved also in the thermodynamic analysis of the socio-economic context. Consequently, the exergy lost is linked to the energy cost required to maintain the productive processes themselves. The fundamental role of the fluxes and the interaction between systems and their environment is highlighted. The equivalent wasted primary resource value for the work-hour is proposed as an indicator to support the economic considerations on the biofuel production by using biomass and bacteria. The equivalent wasted primary resource value for the work-hour is proposed as an indicator to support the economic considerations of the biofuel production by using biomass and bacteria. Moreover, the technological considerations can be developed by using the exergy inefficiency. Consequently, bacteria use can be compared with other means of biofuel production, taking into account both the technologies and the economic considerations. Cyanobacteria results as the better organism for biofuel production.

Thermoeconomic considerations in the allocation of heat transfer inventory for irreversible power systems

In this paper, thermoeconomic optimization of irreversible power systems with finite thermal capacitances for design situation is performed. Investigation is made with respect to the case of specified power output where exact expressions are determined without the use of an internal irreversibility parameter. The use of an internal irreversibility multiplier can omit important details even though it provides insight into real system behavior. Compared to the endoreversible case, the optimum hot-to cold-end unit cost ratio does not result in equal division of heat exchanger conductances and shows variation in the cycle thermal efficiency despite a constant fluid temperature ratio. It is also noted that optimization of the non-dimensional cost function does not translate into optimization of the thermal efficiency.

Thermoeconomic considerations in the allocation of heat transfer inventory for irreversible refrigeration and heat pump systems

In this paper, thermoeconomic considerations are given to heat exchanger inventory allocation in irreversible refrigeration cycles and heat pumps with finite thermal capacitances. Investigation is made with respect to specified rate of cooling and heating for the refrigeration cycle and heat pump, respectively. Exact expressions are obtained without the use of an internal irreversibility parameter. The optimum hot-to cold-end unit cost ratio resulted in unequal division of heat exchanger conductances for the heat pump in contrast to the endoreversible case where they were the same. At a constant evaporator to condenser fluid temperature ratio, the COP of both refrigeration and heat pump systems was found to vary in an almost asymptotic manner in contrast to the endoreversible case where it was constant. In conclusion, it is best to measure the effect of internal dissipation by deriving exact mathematical expressions as the effect on some performance parameters could be lost due to the averaging effect of the internal irreversibility parameter.

Cost optimization of heat exchanger inventory for mechanical subcooling refrigeration cycles

In this paper, thermoeconomic considerations are given to heat exchanger inventory allocation in vapor compression cycles with mechanical subcooling. Investigation is made with respect to constant work rate, heat rejection and cooling rates as well as heat transfer in the subcooler. It was found that no minima exist for any of the cost functions with respect to the absolute temperature ratio (ξ) and the average subcooling absolute temperature ratio (θ3). The derivatives for the integrated subcooling cycle can be generated from the derivatives of the dedicated subcooling cycle. It was concluded that the cost optimization of the integrated mechanical subcooling system is qualitatively the same as the dedicated subcooling system.

Multi-objective optimization of a cogeneration plant for supplying given amount of power and fresh water

Today, the required energy of thermal desalination is widely supplied by power generation cycles as dual-purpose plants. One of the most considerable issues in combining gas turbine cycle (GT) with thermal desalination is how the operating parameters of GT affect technical and economic aspects of power and water production. Therefore, some researchers have studied dual-purpose plants from the thermodynamic point of view without economic or thermoeconomic considerations. According to the lack of studies in this area, in this paper, a dual-purpose plant is modeled which consisted of a GT with and without an air preheater (APH), heat recovery steam generator (HRSG) and multi-effect evaporation thermal vapor compression desalination (METVC). The system is supposed to supply 40 MW of power and 14,000 m 3/day of fresh water for an industrial plant near the seashore in the south of Iran. After the simulation stage, a thermoeconomic analysis is performed and, then, a heuristic optimization algorithm, namely, multi-objective genetic algorithm (MOGA) is applied in order to achieve the optimal design. Eventually, it could be concluded that, by applying the optimization approach and using APH, the total cost of products decreases by 19% while the exergy efficiency of the combined cycle increases by 19%.

Thermoeconomic considerations in the design and analysis of a finned heat sink array: the effect of material cost

A detailed second-law based thermoeconomic optimisation is presented for a finned heat sink array. This involves including costs associated with material and irreversible losses due to heat transfer and pressure drop. The influence of important physical, geometrical and unit cost parameters on the overall finned array are optimised for some typical operating conditions that are representative of electronic cooling applications. The cost optimised results are presented in terms of ReD, ReL, ?P/?H, ?m/λH, and q for a finned system. Furthermore, the methodology of obtaining optimum design parameters for a finned heat sink system that will result in minimum total cost is explained.

Thermoeconomic Considerations in the Optimum Allocation of Heat Transfer Inventory for Refrigeration and Heat Pump Systems

Abstract Thermoeconomics is defined as attaching monetary values to heat exchanger conductances of a given plant. In this study, optimum allocation of heat transfer inventory for heat exchangers in a refrigeration system with specified power input or cooling capacity, and for a heat pump with specified heating capacity is investigated. The ratio of hot- to cold-end conductance unit cost ratio, G, was considered in the analysis as an additional parameter of considerable importance to the designer. A closed-form expression is given in terms of unit cost of conductances of both the heat exchangers. The results show a strong dependence of the total cost on the absolute temperature ratios as well as the hot- to the cold-end conductance cost ratio. It is demonstrated in the illustrative example that for G=0.1, the conductance of the hot-end heat exchanger is about three times the cold-end heat exchanger.

Thermoeconomic considerations in the optimum allocation of heat exchanger inventory for a power plant

Thermoeconomics is defined as the integration of thermodynamics with economics of thermal systems. In this paper, we discuss the thermoeconomics of heat exchanger units in a power plant for cost based optimal design conditions. In this regard, unit cost parameters of hot and cold end heat exchangers in distributing the heat transfer surface area of the power plant are considered for minimum total cost of the heat exchangers. A closed form expression is given in terms of unit costs of the conductances of both heat exchangers, and the results are presented in terms of a unit cost ratio, G, and the hot and cold end heat exchangers costs. The results demonstrate a strong dependence of the total cost function on the absolute temperature ratios as well as the hot to cold end conductance cost ratio. It is also shown that for the case of equal unit costs of the hot and cold end heat exchangers, the total conductance is equally divided between the two heat exchangers.

Thermoeconomic considerations in the design and rating of two-phase heat exchangers

We discuss a closed-form model for thermoeconomic design and analysis of two-phase heat exchangers used as condensers and evaporators. The results are presented in terms of the optimum number of heat-transfer units (NTUs) as a function of the dimensionless unit-cost ratio and the exit-to-inlet absolute temperature ratio of the single-phase fluid. The sensitivities of various unit-cost parameters (UCPs) are presented. It is demonstrated that the selection of UCPs play a significant role in sizing heat exchangers.

The maximum cooling density of a realistic Stirling refrigerator

The maximum cooling density of a Stirling refrigerator operating in a closed regenerative thermodynamic cycle is presented in this paper. The cooling density is the cooling load per unit volume of the refrigerator. Since the size of the refrigerator is involved in the cooling density, the maximization of the cooling density has given a critical compression ratio. The maximum cooling density serves as a better comparison criterion for thermoeconomic considerations.

Heat transfer in a multi-stage flash/ fluidized bed evaporator (MSF/FBE).

The MSF/FBE process in which a fluidized bed heat exchanger is used represents an attractive process for water distillation. High heat transfer coefficients obtained at low fluid velocities allow for vertical long-tube condenser configuration with short stage heights. In an MSF/FBE vapour production takes place in the vapour space and causes a high interfacial heat transfer. Flash chamber volume is reduced with a factor 6 comparing with the conventional MSF. Fouling factor is drastically reduced by the mechanical abrasive action of the solid fluidized particles. Hence there is a more urgent need to know the wall-to-liquid heat transfer coefficient in fluidized beds. Correlations from literature are in some cases contradictory. Ruckenstein's correlation agreed best with indirect measuring of the coefficient. A test programme was started to investigate heat transfer and to measure values in a direct method test module. Data-aquisition is reported. Independent variables as particle size, porosity, particle density and tube diameter allow for application of a large variety in heat and mass transfer. This enables a optimum unit design based on thermo-economic considerations. Such an optimum design is only possible with the aid of a flexible computer program. Part of this paper is devoted to calculation procedures, while in the last part the test module for determination of the wall-to-liquid heat transfer is reflected.