Environmental Impact Rate Research Articles

Exergoenvironmental analysis of a ultra-supercritical coal-fired power plant

This paper presents an exergoenvironmental analysis for a coal-fired ultra-supercritical technology. The study was carried out for a generating unit of 800 MWe of power, which uses bituminous coal as fuel. The environmental impact rates associated with: the destruction of exergy, to the life cycle of the components, to pollutants formation, besides the indicator of relative difference and the exergoenvironmental factor for each of the components of the system are evaluated. It was identified that the flow of cooling water and exhaust gas has a significant environmental impact rate (349.39 mPts/s and 702.26 mPts/s, respectively), which represents an impact rate per kWh of generated electricity of 1.57 and 3.16 mPts/kWh, respectively. The impact rate for the electricity generated by the ultra-supercritical system is 40.78 mPts/kWh. The environmental impact rate associated with the component (production, operation and maintenance, and disposal) is not significant in the analysis of this system. The environmental impact rate related to the destruction of exergy is representative in system (35.36%), together with the formation of pollutants which is the main source of environmental impact of system (64.55%) due to the large contribution of emissions provided by the combustion of coal. The system with ultra-supercritical technology presents itself as an alternative to less efficient coal generation systems, such as subcritical and even supercritical, but it promotes a high environmental impact rate when compared to other generation systems. The incorporation of exhaust gas treatment equipment, such as to particulate removal, gas desulphurisation, and removal of nitrogen oxides, can significantly reduce the environmental impact of the system.

Biopower and biofertilizer production from organic municipal solid waste: An exergoenvironmental analysis

In this study, the environmental performance of a genset-coupled anaerobic digestion plant is analyzed at component-level using an exergoenvironmental method. The plant digests organic municipal solid waste (MSW) while producing two main products, i.e., biopower and biofertilizer. A comprehensive exergoenvironmental modeling of the plant is conducted using actual operating data in order to highlight the main units consuming exergy and causing environmental burdens. The exergoenvironmental indicators of all units of the system are computed by integrating exergy and environmental impact balances. The unitary exegetic environmental impact of biopower and biofertilizer are determined at 11.10 and 0.36 mPts/GJ, respectively. This means that the biofertilizer generation causes less environmental burden over the biopower due to the ease of its production. The highest total environmental impact rate (37.05 mPts/h) is caused by the genset followed far behind by the digester (8.56 mPts/h). Although the genset has the highest operation-related environmental impact rate (36.97 mPts/h), the highest component-related environmental impact rate (7.87 mPts/h) is associated with the digester. Therefore, the exergoenvironmental performance of the plant can be boosted by minimizing the rate of exergy dissipation of the genset while mitigating the environmental impacts related to the development and construction of the digester.

Enhancement of mixture pollutant biodegradation efficiency using a bacterial consortium under static magnetic field.

One of the main challenges of bioremediation is to define efficient protocols with low environmental impact and high removal rates, such as static magnetic field (SMF). The aim of this study was to evaluate the effect of SMF exposure on the biodegradation rate of a mixture of pollutants using three bacterial strains which were isolated and identified from the Bizerte lagoon: Pseudomonas stutzeri LBR (KC157911), Cupriavidus metallidurans LBJ (KU659610) and Rhodococcus equi LBB (KU743870). To recognize the improvement role of SMF, the culture was submitted to a pre-treatment with SMF with an induction equal to 200 mT for 5 hours, after that the degradation experiment was followed with individual strains and with a consortium. Results showed an increase by 20% in the growth of the exposed bacterial population compared to controls, and 98% of biodegradation of DDT and 90% for BaP after 30 days of follow-up. This encouraging data opens new perspectives for a bioremediation bioprocess using SMF.

Monthly assessments of exergetic, economic and environmental criteria and optimization of a solar micro-CCHP based on DORC

This research performs an analyticalsimulation of a novel solar-driven combined cooling, heating and power (CCHP) system based on a dual organic Rankine cycle (DORC) using heat transport fluids of water and Copper (II) oxide (CuO)/water nanofluid. The major design parameters are encompassed to evaluate the monthly thermodynamic efficiencies, total product cost and environmental impact (EI) rates of the system for four selected organic fluid groups, namely R134a-R245fa, R1234yf-R245fa, R1234ze-R236fa and R423A-R236fa. According to results, a considerable positive influence is observed in the energy and exergy efficiencies within 16.71% and 24.34%, respectively for R1234yf-R245fa in November. The lowest EI rate is achieved by 1.2% for R1234ze-R236fa in April as turbine 1 inlet pressure increases and the highest decrement in EI rate is calculated within 2.48% for R1234yf-R245fa in September with an increase in turbine 2 back pressure. In addition, two well-known decision making techniques comprising LINAMP and TOPSIS are applied to identify the ultimate optimal performance of the system among the solutions gained from the non-dominated sorting genetic algorithm (NSGA-II) approach. Referring to the optimization results, the maximum improvement in the exergy efficiency and product cost can be obtained within 33.49% through the LINMAP method and 23.67% through the TOPSIS procedure, respectively and the highest improvement in the EI rate is calculated by about 22.7% with 0.01788 nanoparticle volume fraction for R134a-R245fa through the LINMAP method.

Evaluation of cogeneration plant with steam and electricity production based on thermoeconomic and exergoenvironmental analyses

A cogenerative system which produces 83.6 MW of steam and 119 MW of electricity was evaluated. The exergoeconomic and exergo environmental approach were carried out in order to calculate the cost rate and environmental impact per exergy unit of both products. The specific exergy costing (SPECO) approach was used in balance. The results reveal that the specific cost rate of steam and electricity are 66.6 $/GJ and 62.8 $/GJ, respectively. And the specific environmental impact rate of steam and electricity are 15,545 mPt/GJ and 14,350 mPt/GJ, respectively. The lower exergoeconomic factor and exergoenvironmental factor was in the combustor. The effect of air environmental temperature at products (electricity and steam) shown that the increase of air temperature, reduce the electrical power and exergetic efficiency. The increase of air temperature, increase the specific cost rate and the specific environmental impact rate of electricity and steam.

Multi-generation system incorporated with PEM electrolyzer and dual ORC based on biomass gasification waste heat recovery: Exergetic, economic and environmental impact optimizations

In this paper, a multi-generation system comprising a dual organic Rankine cycle equipped with an ejector refrigeration loop, a biomass gasification process and a proton exchange membrane electrolyzer is developed to produce the syngas, power, refrigeration effect, heating load, hydrogen and oxygen. R245fa-R134a, R236fa-R1234yf and R600-R290 are applied as three organic working fluid groups inside the dual organic Rankine cycle. The system concerned is modeled using the exergy, exergoeconomic and exergoenvironmental analyses. An elitist non-dominated sorting genetic algorithm is individually used to optimize the thermodynamic, economic and environmental performances of the system for each working fluid group. The LINMAP and TOPSIS decision makers are applied to select the optimum performances of the system and electrolyzer. The optimization results show that the hydrogen cost and environmental impact per unit exergy are improved within 49.18% and 34.58%, respectively through the LINMAP method for R236fa-R1234yf. In addition, the maximum improvement in the total cost rate of the system is calculated within 39.5% for R245fa-R134a through the TOPSIS procedure and the highest increment in the environmental impact rate belongs to R236fa-R1234yf by about 34.69% using the LINMAP decision maker.

Assessment and optimization of a new sextuple energy system incorporated with concentrated photovoltaic thermal - Geothermal using exergy, economic and environmental concepts

This research presents a thermodynamic, economic and environmental impact assessments of a new renewable based sextuple system made up of an organic Rankine cycle, magnetic refrigeration cycle, proton exchange membrane electrolyzer, date dryer unit and concentrated photovoltaic thermal collectors delivering power electricity, cooling and heating effects, hydrogen, oxygen and dried date productions. The impacts of the substantial design parameters on the annual thermal and exergy efficiencies, total product cost and environmental impact rates are evaluated. From parametric analysis, PEM electrolyzer current density affects the product cost rate of the system less than other parameters within 3.05% and turbine inlet pressure yields the reduction in the total product environmental impact rate by about 3.8%. Moreover, an elitist non-dominated sorting genetic algorithm and LINMAP decision maker are employed to identify the final optimum answer of the desired system. From optimization outcomes, the optimum performance of the system shows 18.3% reduction for cost and 24.9% improvement for environmental impact criteria. The annual thermal efficiency is improved about 27.4% and annual exergy efficiency gets 2.12 times. Under the optimum conditions, the isobutane mass flow rate reaches the maximum value of 35 kg/s and net power output increases within 50.25% in relation to the base point.

A comparative study on exergetic, exergoeconomic and exergoenvironmental assessments of two internal auto-cascade refrigeration cycles

This research makes a comparative study of an internal auto-cascade refrigeration system (IACRS), i.e. system 1, and a novel ejector enhanced IACRS, or system 2, employing a pressure-constant ejector at the entrance of the phase separator based on exergy, exergoeconomic and exergoenvironmental analyses. R600 is used as a convenient refrigerant in the proposed systems. Compressor mass flow rate (ṁ1), condenser inlet temperature (T3), refrigeration evaporator inlet temperature (T6) and freezer evaporator inlet temperature (T11) are chosen as substantial design parameters to evaluate the performance of both proposed systems. The simulation and comparative study show that at all ranges of selected parameters, the average energy and exergy coefficient of performance, i.e. COPEn and COPEx, respectively, obtained for system 2 have a drastic increment relative to system 1. Moreover, outcomes identify system 2 as a more economic system due to its low total product cost rate (ĊP,tot) at which ṁ1 with 20.95% decrement of ĊP,tot has a significant positive effect. Further results show that the environmental impact is improved by applying system 2 so that the total product environmental impact rate associated with exergy (ḂP,tot) for ṁ1, T3, T6 and T11 decreases within 21.52%, 10.59%, 8.96% and 8.35% respectively, as compared with system 1.

Exergo-environmental and exergo-economic analyses and multi-criteria optimization of a novel solar-driven CCHP based on Kalina cycle

The present research proposes and optimizes the performance of a novel solar-driven combined cooling, heating, and power (CCHP) Kalina system for two seasons—winter and summer—based on exergy, exergo-economic, and exergo-environmental concepts applying a Non-dominated Sort Genetic Algorithm-II (NSGA-II) technique. Three criteria, i.e. daily exergy efficiency, total product cost rate, and total product environmental impact rate associated with the exergy of the system for each season are considered simultaneously for multi-objective optimization. The outcomes reveal that increments in turbine inlet pressure and mass flow rate of the vapour generator lower the environmental impact of system products as well as the total product cost rate in both seasons. The optimum value of daily exergy efficiency, total product environmental impact rate, and total product cost rate indicate improvements by 2.56%, 15.7%, and 15.3% respectively in summer and 36.34%, 7.39%, and 4.93% respectively in winter, relative to the base point.

Multi-criteria optimization of a micro solar-geothermal CCHP system applying water/CuO nanofluid based on exergy, exergoeconomic and exergoenvironmental concepts

The main objective of the present study is to perform the thermodynamic, economic and environmental analyses of a solar-geothermal driven combined cooling, heating and power (CCHP) cycle integrated with flat plat collectors containing water/copper oxide (CuO) nanofluid as the absorbing medium. Twelve main parameters are selected as the decision variables of the desired system while the daily exergetic efficiency, total product cost rate and total product environmental impact associated with exergy rate are chosen as the three main objective functions. NSGA-II (Non-dominated Sort Genetic Algorithm-II) is individually applied to obtain the final optimal solutions in the multi-objective optimization of the desired system for four working fluids including R134a, R423A, R1234ze and R134yf from the exergy, exergoeconomic and exergoenviromental points of view. Based on the multi-objective optimization outcomes, R1234ze is the best fluid with 36.82Pts/h total product environmental impact rate so that the maximum nanoparticles volume fraction and minimum collector tilt angle are required. Moreover, R423A with the minimum total product cost rate of 4496 $/year is the best fluid at which minimum collector area is needed. Furthermore, R134a is the best fluid with 4.194% daily exergetic efficiency so that the minimum nanoparticle volume fraction is required compared with other studied fluids.

Development of a four-step Cu–Cl cycle for hydrogen production – Part II: Multi-objective optimization

This second part of two companion papers optimizes a four-step Cu–C cycle by considering five optimization scenarios: three single-objective functions (exergy efficiency, total cost rate, environmental impact rate), and two multi-objective functions (exergoeconomic, exergoenvironmental). Based on the single objective optimizations, it is determined that the exergy efficiency could be increased by up to 3.3% using exergy-based optimization, the cost can be reduced by up to 33% using cost-based optimization, and the environmental impact rate can be reduced by up to 39% using environmental impact-based optimization, at the expense of the non-optimized objectives. To avoid such detrimental effects, multi-objective optimization studies are undertaken. Based on the exergoeconomic optimization, a 0.80% higher exergy efficiency and 4.5% lower cost can be achieved, compared to baseline parameters. Furthermore, a 0.5% higher exergy efficiency and 30% lower environmental impact rate can be achieved based on the exergoenvironmental optimization.

Development of a four-step Cu–Cl cycle for hydrogen production – Part I: Exergoeconomic and exergoenvironmental analyses

Thermodynamic, economic and environmental impact assessments of a four-step Cu–Cl cycle developed for hydrogen production are performed using exergy, cost, exergoenvironmental and exergoeconomic analyses, and life cycle assessment. For the system considered under the baseline conditions, the total cost rate and environmental impact rate are determined to be 165 $/s and 37.6 Pt/s, respectively. The following Part II of this two companion papers leverages this paper's results to optimize the four-step Cu–Cl with respect to overall exergy efficiency, total cost rate and total environmental impact rate.

Integrated risk and multi-objective optimization of energy systems

This paper presents a risk aware energy planning model with storages as decision makers. The amount of energy bought from generators, stored in storages, and sold to users is set by storages. The paper also provides the optimal risk strategy for each storage considering energy cost, environmental impact, and failure rate as social welfare functions. A robust, simple, and verifiable framework for understanding and measuring risk scenarios for energy systems is introduced. Multiple-objective approach for integrating risk with social welfare functions is also discussed. Application of presented framework in energy industry is discussed by examples.

Multiple objective energy operation problem using Z utility theory

In this paper, we introduce an energy operation model using three objectives of cost, environmental impact, and failure rate. Developed model increases the flexibility of energy systems in coping with changes in demands and energy prices while satisfying operational constraints. We use the Midwest Independent Systems Operator as a case study to show the efficient frontier for these objectives. We apply Z utility theory to choose the best alternative in our case study. Computational results and complexity analysis show that problems with extensive number of entities can be solved efficiently in reasonable time.

Analysis and optimization of hybrid electric vehicle thermal management systems

In this study, the thermal management system of a hybrid electric vehicle is optimized using single and multi-objective evolutionary algorithms in order to maximize the exergy efficiency and minimize the cost and environmental impact of the system. The objective functions are defined and decision variables, along with their respective system constraints, are selected for the analysis. In the multi-objective optimization, a Pareto frontier is obtained and a single desirable optimal solution is selected based on LINMAP decision-making process. The corresponding solutions are compared against the exergetic, exergoeconomic and exergoenvironmental single objective optimization results. The results show that the exergy efficiency, total cost rate and environmental impact rate for the baseline system are determined to be 0.29, ¢28 h−1 and 77.3 mPts h−1 respectively. Moreover, based on the exergoeconomic optimization, 14% higher exergy efficiency and 5% lower cost can be achieved, compared to baseline parameters at an expense of a 14% increase in the environmental impact. Based on the exergoenvironmental optimization, a 13% higher exergy efficiency and 5% lower environmental impact can be achieved at the expense of a 27% increase in the total cost.