• Energy Research

AbstractThe increasing global demands for fossil fuels have resulted in the release of large quantity of pollutants and reduction of the available resources. Owing to this fact, alternatives to fossil fuels, like biodiesel, are essential for the survival of the existing resources and the decrease of environmental contamination. In the current study, the technical assessment of five continuous biodiesel production processes was designed and simulated with the Aspen Plus v8.6 software. In order to convert virgin vegetable oil (VVO) as well as waste cooking oil (WCO) to biodiesel, alkali‐catalyzed and acid‐catalyzed processes were utilized in the first three processes. In the fourth and fifth processes, the two‐step supercritical methanol method (noncatalytic) and the acid‐catalyzed process were adopted by hexane extraction to transform the WCO to biodiesel. According to the technical assessment, the two‐step supercritical methanol process has the lowest number of operating units; however, it has the lowest purity of FAME (98.47%). The highest purity of glycerol (99.98%) and FAME (99.7%) belong to Processes 3 and 1, respectively. As a result, the homogeneous acid catalytic process of WCO and the two‐step supercritical methanol process are the best choices in terms of technical evaluation among all the examined processes.

Abstract The consequences of water crisis in terms of political, social and environmental impacts have been motivated in this paper to recognize the hybrid wet/dry cooling systems of power plant in Iran. The existence of temperature constraints for consumers connected to the hybrid cooling tower, Space constraints for the construction of auxiliary system, devoting attention to high Net Present Value (NPV) of the project over the course of 25 years, Returning the appropriate capital, Optimal Design of air cooler and it's desirable performance over the course of a year were the reasons led to use of the genetic algorithm (GA) in this paper. The GA should optimize the design of the air cooler, according to that, at one functional point of a year, the lowest investment costs and the lowest cost of utilization in one year will happen. The cost of utilization in this project including: water consumption (makeup water of the cycle), fan power consumption (wet and dry block of hybrid cooling system), as well as chemical additives to water. The results illustrated that the proposed algorithm usage, applying a proper control system, taking into account the standards in the written code and determining the optimization intervals according to the manufacturer's data could conclude to the design of an air cooler, which can be constructed by inquiring from the manufacturing companies. The results also indicated that optimized design of hybrid cooling tower could reduce water consumption about 63% over the course of one year, return on investment by 5 years, develop NPV up to 40 M€ and enhance steam turbine power.

The high energy consumption in Iran, particularly in the transportation sector, has contaminated large cities and jeopardized the society health. Therefore, in this study technical and economic features of the production of biodiesel plant in Iran from various wastes are investigated. Based on the Analytic Hierarchy Process (AHP) method’s findings, the southern area of Iran is selected for establishing the biodiesel plant in Iran. The biorefinery, which includes three units of sewage sludge, edible waste oil and microalgae. The results of the economic evaluation show that the lowest costs of investment and production of biodiesel are related to microalgae units ($0.375/kg) and edible waste oil ($0.53/kg), respectively. Also, among all units, the lowest break even prices are related to biodiesel production ($1.17/kg) and the highest ATROR rate (29.16%) belongs to the microalgae unit. This indicates that this unit is more profitable than other units and the invested cost is returned to the investor in a shorter period of time (3.43 years). On the other hand, the results of sensitivity analysis show that the highest sensitivity of changes in the selling price of biodiesel and the cost of raw materials to ATROR to the microalgae and sludge unit. Therefore, the construction of a biorefinery in Iran has an economic justification.

The purpose of this paper is to propose a novel combined cooling, heating, and power generation system driven by evacuated tube solar collectors for residential applications. Accordingly, evacuated tube collectors are employed to provide sufficient heat for cooling and power generation purposes, while the waste heat of the evacuated tube collectors is then exploited for heating. The proposed system is comprehensively analyzed from various standpoints i.e., energy, exergy, and exergoeconomic. Afterward, the multi-objective genetic algorithm optimization – as a suitable tool – is applied to the system to extract a trade-off between the competing objective functions. The results showed that R124 results in better exergetic efficiency compared to other refrigerants. The parametric study outcomes indicate that with increasing the collector area, total product cost reduces but the total cost rate increases dramatically. The results also show that input parameters can directly affect the exergetic sustainability index to be cautiously designed. The optimization results show that the system’s maximum exergy efficiency is 10.06% while the minimum total cost rate is obtained as 0.4835 $/h. Further, the decision factors’ scatter plots show that LiBr mass fraction should be around 25% for optimal operation. Overall, the proposed system can be employed for cooling, heating, and power generation as a potential cycle.

Abstract An innovative biomass gasifier integrated plant was proposed for combined heating and power production in the current paper. The plant consists of an s-CO2 cycle, gasifier, combustion chamber, and a domestic water heater for heating purposes. The system was studied from different perspectives, i.e., energetic, exergetic, exergo-economic, economic, and environmental (4E). For this purpose, simulation of the proposed plant was carried out by EES software; then, by utilizing COMFAR III software, the economic sensitivity investigation was conducted to detect the influence of financial parameters on the system's economic features after installation of the plant. Results of economic evaluation unfolded that installing the proposed plant is affordable from the economic point of view. Besides, a sensitivity analysis was conducted to calculate the main performance indicants, including an environmental impact indicator. The proposed system was optimized by a robust Multi-Objective Bat Optimization Algorithm . For determining the final optimum solution, TOPSIS, LINMAP, and Shannon entropy methods were used in the optimization process. Optimization results were also compared to the conventional multi-objective optimization methods to detect the suitable optimization method. The findings of the comparison confirmed that the bat algorithm's performance had been better, based on Taylor and Violin diagrams. Besides, scatter plots of effective parameters are presented to define the suitable operating ranges. The results show that the optimum exergy efficiency, Levelized CO2 emissions, and total product cost are 38.42%, 0.4757 t/MWh, and 7.517 $/GJ obtained. The total product cost was reduced significantly from 10.01 $/GJ to 7.517$/GJ at the expense of a slight diminish in exergetic efficiency of about 2% through the use of the bat algorithm. Also, the annual greenhouse gas emission made by the proposed system was reduced by about 9% after the optimization process.

Abstract This paper presents the concentration disposal index (CDI) concept extension for increasing the Water–Energy-Environmental nexus and reducing the environmental impacts of RO system brine. This non-dimensional index introduces the difference between the density of brine flow and raw water tank in recovery. This concept is utilized in main engine system of the ship. Different configurations of Organic Rankine Cycle (ORC) and working fluids are studied at the outlet of high temperature thermal source (280 °C), based on Energy analysis (1E), Exergy (2E), Economic (3E) and environmental impacts (4E) in order to produce desalinated water (4E+D). The output power from ORC is used as the driver of RO high pressure pump. Based on the waste heat in system, the sources are used for preheating of RO system pump inlet water. These sources are: Lubricating oil, air cooler and jacket cooler and ORC condenser. The key parameters in optimization are: (1) the ORC configuration choice, (2) the working fluid of Rankine cycle based on thermal source, (3) the RO system optimum design, (4) the membrane selection among the DOW company membranes, (5) the pinch and approach temperatures of the Waste Heat Recovery (WHR), (6) the reduction of environmental impacts of RO brines, (7) the selection of Energy Recovery Device (ERD). Determination of these parameters is done according to system optimization by genetic algorithm (GA). In order to consider the CDI function impact, once the system is considered with two objectives based on exergy efficiency of the entire cycle and the unit product cost (UPC) and then is considered by three objectives; the two mentioned ones and the CDI function. The results of these two optimizations indicate that, utilizing CDI reduces the ultimate concentration of the brine and increases the buoyancy force for faster mixture. In three-objective optimization, the ORC configuration is chosen with the recuperator, the R245ca working fluid, the two-stage RO system and the SW30XLE-400i membrane for both of stages.

Despite of huge effort performed in the literature encompassing the concept of hybrid solid oxide fuel cell–gas turbine (SOFC-GT), the economic and environmental superiority of this hybrid system over a conventional gas turbine (GT) has not yet been clarified. In the present study, a proper scale of solid oxide fuel cell was integrated with a GT and a comprehensive comparison analysis based on energy, exergy, exergo-economic and environmental (4E) criteria were conducted between 10 MW GT and hybrid SOFC-GT systems. Three different scenarios were considered for the comparison analysis, encompassing baseline operation, parametric behavior and optimum conditions. An appropriate artificial neural network (ANN) was utilized to model the systems, and then, the obtained ANNs were introduced to Grey Wolf optimizer. Using grey wolf optimizer, a multi-objective optimization problem was solved considering exergy efficiency, CO2 emission and unit cost of product as the objectives. The hybrid SOFC-GT system had a better performance than the GT system in terms of environmental and exergo-economic performances as the results of all three scenarios showed. However, this integration slightly increased the investment cost of the system at the baseline scenario. After optimization, at best trade-off between the objectives, the SOFC-GT exergy efficiency, CO2 emission and unit product cost were obtained to be 68.5 %, 277.7 kg/MWh, and 22.7 $/GJ, however, these values for the GT were 32.38 %, 588.4 kg/MWh, and 26.9 $/GJ, respectively.

The present study focused on the exergoenvironmental analysis via Life Cycle Assessment and emergy based evaluation of a multigeneration system of hydrogen, carbon dioxide, and power through biomass gasification (Sawdust). In this regards, energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental modeled in MATLAB software for a considered multigeneration system, is to employ hydrogen in a solid oxide fuel cell to increase power yield and to generate hydrogen and CO2 as output products. The Life Cycle Assessment for exergoenvironmental analysis has been performed in SIMA Pro based on Ecoindicator 99. Sensitivity analysis has been performed for the main decision variables of the considered multigeneration system based on energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental assessment.