4E Analysis Research Articles

Dynamic 4E (energy, exergy, economic and environmental) analysis and tri-criteria optimization of a building-integrated plant with latent heat thermal energy storage

The buildings energy sector is expected to account for 40% of total world energy consumption and 40% participation on total carbon dioxide emissions, according to the International Energy Agency reports. The present study proposes a novel integrated system to meet all loads of the house's energy requirements. The system employs a heat storage tank rather than pricey batteries, which helps to keep the total cost of the system as low as feasible. Also, the system is developed for an on-grid operation, being capable to sell surplus energy to the grid helping to reduce the payback time. Dynamic modeling is conducted to analyze the system performance to provide heating, cooling and power demands of a case study building, for which two scenarios of with and without Phase Change Material (PCM) incorporation is considered. The influence of critical design factors is investigated, after which a tri-objective optimization is carried out. It was found that, the integration of PCM energy storage would reduce the annual heating and cooling demands of the building by 25.6%. As a result, the exergy efficiency of the proposed system increases by 13 % and the product cost is reduced by 8.57%. Based on the obtained yearly average results, the proposed building energy system yields exergy efficiency, unit product cost, and CO2 emission of 64.3 %, 0.26 $/kWh, and 0.21 kg/kWh, respectively.

4E analysis and thermodynamic optimization of flaring associated gas recovery using external firing recuperative gas turbine

Associated gas with oil extraction is usually burning through the flaring process. This process destroys a valuable natural resource that should be either recovered or stored. The process also pollutes the environment by emitting greenhouse gasses. The current study presents a novel external firing gas turbine cycle to recover the associated gas. The external firing prevents corrosion within gas turbine components due to the corrosive nature of the associated gas. To find an optimal design of the cycle, the comprehensive 4E analysis including Energy, Exergy, Environment and Economic analysis is carried out. The sensitivity analysis is employed to investigate the influence of the key parameters such as the compressor pressure ratio and fuel cost on the evaluation criteria of the system i.e., energy efficiency, exergy efficiency, total cost and environmental impact. Moreover, the net present value and payback period criteria are applied to analyze the whole system economically. The results of the proposed system modeling show that at the base condition for fixed output electricity of 1200 kW, values of the principal parameters are as the 27.6%, 35.8%, 6553 $/kW, 269020 kg/kW, 12.3e7 $, 3.8 year for energy efficiency, exergy efficiency, total cost, environmental impact, net present value and payback period, respectively. As another activity, Multi-objective optimization using the NSGAII method is performed to achieve the optimal value of three selective objective functions as well as decision variables. Results reveal that there is a conflict between objective functions (total cost and environmental impact) and the other one i.e., exergy efficiency. It indicates that any effort to increase the system efficiency causes relatively higher costs and environmental issues. The final optimum values of the objective functions i.e. total cost, environmental impact and exergy efficiency are found to be 5864.6 $/kW, 241374.5 kg/kW and 33.4%, respectively.

Energy, exergy, economic and environmental (4E) analysis of a parabolic trough solar collector using MXene based silicone oil nanofluids

A bstract The present study is a 4E (Energy, Exergy, Economic, and Environmental) analysis of a nanofluid-based parabolic trough collector (PTC) which is conducted with a developed model in MATLAB. MXene (Ti 3 C 2 ) nanoparticles were added to the silicon oil at weight concentrations of 0.05, 0.08, and 0.1%. The result was the important enhancement of the thermal conductivity of the nanofluid on the rand of 70%–89% for the highest concentration. According to the results, the PTC's optical efficiency was estimated at 79%, while thermal and exergy efficiencies of 74.71% and 22.44% with 0.10 wt% concentration were recorded on July 17, 2019. It is found that the MXene based silicone oil can reduce the system's cost by 0.021 M$ and enhance the energy gained by 1.51% at 0.10 wt% concentration compared to pure oil. Also, the annual CO 2 mitigation from the energy side varies from 2.25 to 2.30-ton CO 2 /year, while the annual environmental gain ranged between 32.73 and 33.28 $/year and 9.065 to 9.102 $/year for the energy and exergy studies respectively. • A nanofluid-based parabolic trough collector is studied with MXene. • The collector thermal efficiency enhancement is found up to 1.1%. • For the day July 17, 2019, the exergy efficiency was improved from 0.07% to 15.16%. • For energy analysis, the annual CO 2 mitigation varies from 2.26 to 2.30 ton CO 2 . • The environmental gain from the energy analysis varies from 32.73 to 33.28 $/year.

Analysis and assessment of a novel organic flash Rankine cycle (OFRC) system for low‐temperature heat recovery

AbstractIn this paper, a novel organic flash Rankine cycle (OFRC) system for low‐temperature heat recovery is analyzed and optimized using the 3E (energy, exergy, and economic) analysis method and particle swarm optimization algorithm, respectively. Five environmentally friendly organic fluids and three typical heat source conditions are simultaneously discussed during the parametric analysis and optimization process, to obtain a comprehensive understanding of the thermo‐economic characteristics of this novel system. The main analysis results show that the biggest exergy loss of the OFRC system is caused by the condenser, followed by the evaporator. About 70% of the specific power cost is caused by the capital investment of the system, and more than 60% of the capital investment is spent on purchasing the high‐pressure and low‐pressure expanders. Under the same operating conditions, the working fluids with high critical temperatures can achieve higher cycle thermal efficiency and lower specific power costs than those with low critical temperatures. The optimization results show that the OFRC system is able to achieve a better thermodynamic performance than the organic Rankine cycle (ORC) and organic flash cycle (OFC) systems, and when the heat source's inlet temperature is set to 100°C, 120°C, and 140°C, R245fa, R290, and R152a are, respectively, recommended as the best working fluid for the OFRC system. Besides this, it is found that the OFC system has the worst thermo‐economic performance, and the ORC system can achieve the lowest specific power cost. A new finding is that, for all three systems, the higher the critical temperature of the working fluid, the lower the specific power cost of the system.

Energy-exergy and environ-economic (4E) analysis while drying ivy gourd in a passive indirect solar dryer without and with energy storage system and results comparison

The energy-exergy and environ-economic (4E) analysis was conducted while drying ivy gourd in a natural convection indirect solar dryer (ISD) without and with a thermal energy storage system (TESS). The initial setup was modified with TESS by integrating a rectangular glass box holding polycarbonate tubes filled with paraffin wax. The paraffin wax was selected based on its easy availability in the market, and also the existing studies suggested that it works successfully by shortening the drying time, homogenizing the process and maintaining temperature. Mass loss, air velocity, and temperature data were recorded during experiments in both setups. The average collector and drying efficiencies of ISD were 62.56 and 61.87 (without and with TESS) and 6.62% and 13.13% (without and with TESS), respectively. The specific energy consumptions were 1.549 and 0.253 kWh/kg for without and with TESS, respectively. The exergy parameters for collector and drying cabinet such as average exergy efficiency, loss, outflow, and inflow without and with TESS were estimated. Other exergy parameters such as the ratio of waste exergy, improvement potential, sustainability index and environmental impact factor were estimated and compared for both setups. CO2 mitigation and credit were better with the TESS setup. The energy payback period of the dryer was 1.04 and 1.51 years for without and with TESS setups for a lifespan of 25 years. Comparatively, with TESS setup performed well in all the evaluated parameters.

Energy, exergy, economic and environmental analysis of a novel steam-driven vapor recompression and organic Rankine cycle intensified dividing wall column

The dividing wall column (DWC) is a typical thermal coupled distillation column to separate the ternary mixture instead of the conventional two-column sequence. However, the energy utilization of DWC is the same as the conventional distillation column with large energy consumption. The current energy intensification measures for DWC is to use the vapor recompression (VRC) technology for retrofitting the stream cycle and use organic Rankine cycle (ORC) for waste heat recovery. The large top and bottom temperature difference of DWC limits the energy and economic benefit of VRC and also the production of ORC is not high. In this paper, unlike the general electric-driven VRC and waste heat recovery to save the energy consumption of the DWC (VRC-WHRS-DWC), a novel steam-driven VRC and waste heat recovery assisted DWC (SD-VRC-WHRS-DWC) is proposed to form a new energy utilization mode of DWC. As comparison, DWC and VRC-DWC are also developed. The single- and multi-objective genetic algorithms are used to optimize the different processes. All the processes are evaluated by energy, exergy, economic and environmental (4E) analysis. The result shows the cascade utilization of the steam in steam-driven system can effectively increase the economic benefit and decrease the energy consumption of DWC with the large temperature difference between top and bottom.

A combined cycle power plant integrated with a desalination system: Energy, exergy, economic and environmental (4E) analysis and multi-objective optimization

A combined cycle power plant integrated with a desalination system: Energy, exergy, economic and environmental (4E) analysis and multi-objective optimization

A 4E analysis of a novel coupling process of syngas purification and CO2 capture, transcritical CO2 power and absorption refrigeration

To achieve the goal of CO2 emission peak and carbon neutrality, a novel process coupling syngas purification and CO2 capture, transcritical CO2 power and absorption refrigeration is proposed. The purpose is to realize energy conservation and CO2 emission reduction by coupling medium and low-grade waste heat, electricity and cold water in the process. Based on verifying the accuracy of the model and simulation, the proposed system is studied from four aspects: energy, exergy, economy and environment (4E). The results show that the process can meet the industrial requirements of syngas purification and CO2 products. The thermal efficiency and exergy efficiency are 35.58% and 35.96% respectively. The annual total cost is 2.45 million dollars, and the annual CO2 emission reduction is 113.6 kt. By exploring the exergy destruction and cost distribution of components, the parts that need attention and improvement in the process are determined. In addition, the effects of heat transfer temperature difference and refrigeration temperature on the performance of the process are also studied. This provides a reference for the comprehensive performance analysis and application feasibility of the coupling process of syngas purification, CO2 capture and waste heat utilization.

Assessing benefits in the flexibility of refined oil logistics from pipeline network integration reform: A case from South China

• Propose a framework for flexibility quantification of oil logistics flexibility. • The framework based on MILP model contains both quantitative and qualitative parts. • Build a calculation method for the flexibility indicator of refined oil logistics. • Quantify the impact of the reform on logistics flexibility in South China. The pipeline network integration reform enables unified management of pipelines from different entities. For refined oil logistics, this paper proposes a framework based on the MILP optimization model to quantify its flexibility. Considering the uncertainty, three disturbances occur in the logistics concurrently, and 10,000 simulations are performed to obtain the turnover cost. The ratio of pipeline transportation cost to the calculated average turnover cost is defined as the flexibility indicator. Taking China's largest refined oil pipeline network as an example, the results show that the flexibility rises 8.9% after the reform. The paper also quantifies the impact of the reform on logistics flexibility in South China, which is embodied in achieving lower freights and GHG emissions, lower impact by fluctuations, higher pipeline utilization, more efficient oil product turnover, and the avoiding of depot shortages when facing logistical disturbances. The underlying reasons for the results and 3E analysis are analyzed.

Coupled CFD and 3E (Energy, Exergy and Economical) analysis of using windbreak walls in heller type cooling towers

Generally, Montazer Ghaem Combined Cycle Power Plant (MGCCPP) is equipped with natural draft dry cooling towers (NDDCT) and its performance strongly depends on environmental conditions such as wind speed. Thus, the present study aims to evaluate the effects of wind blowing on the cooling towers (CTs) efficiency and propose methods to improve their performance. It can help increase plant efficiency and decrease energy loss, which leads to cleaner production. For this purpose, the cycle of MGCCPP is modeled simultaneously using CFD and energy-exergy analyses for the first time. Moreover, the effect of windbreak walls (WBWs) on CT performance and CCPP are addressed. The results of CFD analyses are used to recognize the behavior of the towers in different wind speeds and deriving heat rejection. Based on obtained results, using the WBW in the prevailing wind leads to about 6.5 MW excess power in each unit. According to the economic analysis, the payback period of the three proposed plans is 14, 15.5, and 16 months, which is fully justified.

A novel design-point computational program for thermal power plants applications: energy, exergy and economic (3E) analysis

A novel design-point computational program for thermal power plants applications: energy, exergy and economic (3E) analysis

Energy, exergy, economic and environmental (4E) analysis of passive and active-modes indirect type solar dryers while drying guava slices

The present study investigated the energy, exergy, economic and environmental (4E) analysis of passive and active mode indirect solar dryers (PMISD and AMISD) while drying guava slices in Warangal, India. The AMISD was developed by attaching a divergent duct with PMISD which consist of DC fans powered by PV panels at the entrance of the collector. The energy analysis revealed that average collector efficiency, drying efficiency and energy utilization ratio were 56.05, 5.42 and 13.27% and 65.37, 6.84 and 10.57% in PMISD and AMISD, respectively. The exergy efficiencies of the collector and drying chamber were 3.74 and 50.92% and, 2.39% and 57.03% in PMISD and AMISD, respectively. The economic analysis revealed that the payback period was noticed to be 2.24 and 1.38 years for PMISD and AMISD, respectively. The energy payback periods of PMISD and AMISD are 1.01 and 1.5 years, respectively. The CO2 emission, CO2 mitigation and maximum carbon credit earned for both the dryers were estimated at a lifetime of 35 years. The 4E analysis concluded that the performance of AMISD is higher compared to PMISD and both ISDs are economically viable and sustainable with a lower impact on the environment.

4E analysis of a SOFC-CCHP system with a LiBr absorption chiller

A new system which combined cooling, heating and power (CCHP) and based on a solid oxide fuel cell (SOFC) with a LiBr absorption chiller and water tank is investigated. The influence of the working conditions of the SOFC on its steady-state and dynamic performances are studied. Meanwhile, the effects of working conditions of the stack and absorption chillers on multi-criteria assessments are also studied. The result shows that the operating temperature and current density can greatly affect the performance of the stack and system, which can also be influenced by the working conditions of the absorption chiller simultaneously. Increasing the operating temperature can greatly increase the electrical power, and the thermal power will be reduced correspondingly. Increasing the mass flows of the cooling, chilled and hot waters increase the cooling power and coefficient of performance (COP), thereby reducing the heating power.

Developing a novel gasification-based sludge-to-methanol utilization process and exergy-economic-environmental (3E) analysis

Sewage sludge is a common waste from wastewater treatment plants in Hong Kong and conventional treatment ways like the landfilling method has been gradually abandoned considering the environmental impacts and costly land. Searching for integrating processes to well treat the sludge simultaneously achieve the energy recovery can be a good alternative way. Therefore, process design and simulation of a gasification-based sludge to methanol (STM) production was proposed in this work. It considered major subsections such as gasification, power generation, absorption, methanol synthesis, and distillation. Followed by the sensitivity analysis to optimize operational parameters, economic, environmental, and exergy (3E) analysis of STM process was conducted. The economic estimation revealed the methanol production cost is 579.62$/ton and the sludge disposal cost is 39.58$/ton. The calculated internal rate of return (IRR) of the process is 10.20% and 5.48%, respectively with a subsidy of 20$/ton sludge and without any support. Moreover, it was found the greenhouse gas (GHG) emission was 3.21 kg eq.CO2/kg methanol and overall exergy efficiency was 37.92%. The current work implies the great potential of STM treatment strategy, which can serve as a reference for the future sludge treatment planning.

Flexible load regulation method for a residential energy supply system based on proton exchange membrane fuel cell

To increase the use of renewable energy sources and reduce the consumption of energy and environmental pollution, a flexible load regulation method is proposed for a hybrid residential combined cooling, heating, and power system based on fuel cells and adsorption chillers. The combined cooling, heating, and power system consisted of a proton exchange membrane fuel cell stack, an adsorption refrigerator, a thermal storage tank, a wall-hanging boiler, and related accessories. A system model was established for a typical Shanghai household and a 4E (energy, exergy, environment and economy) analysis evaluation method was used to evaluate the performance of the system during winter and summer. The energy savings and CO2 emission reduction rates of the system with and without regulation were compared. The results indicated that energy and exergy efficiencies can be improved by using flexible load regulation. The energy efficiencies of the combined cooling, heating, and power system with regulation in winter and summer were 89.21% and 73.26%, respectively, and the exergy efficiencies were 58.04% and 55.47%, respectively. When compared with the traditional system, the CO2 emission reductions in the combined cooling, heating, and power system with flexible load regulation in winter and summer reached as high as 67.26% and 67.43%, respectively. Therefore, the environmental benefits of the proposed system can be significant. If the hydrogen price can drop below 1.557 $/kg and the costs of the proton exchange membrane fuel cell and adsorption chiller can be reduced, the application of the combined cooling, heating, and power system will become economically viable.

Energy, Exergy, and Economic Analysis of Cryogenic Distillation and Chemical Scrubbing for Biogas Upgrading and Hydrogen Production

Biogas is one of the most important sources of renewable energy and hydrogen production, which needs upgrading to be functional. In this study, two methods of biogas upgrading from organic parts of municipal waste were investigated. For biogas upgrading, this article used a 3E analysis and simulated cryogenic separation and chemical scrubbing. The primary goal was to compare thermoeconomic indices and create hydrogen by reforming biomethane. The exergy analysis revealed that the compressor of the refrigerant and recovery column of MEA contributed the most exergy loss in the cryogenic separation and chemical scrubbing. The total exergy efficiency of cryogenic separation and chemical scrubbing was 85% and 84%. The energy analysis revealed a 2.07% lower energy efficiency for chemical scrubbing. The capital, energy, and total annual costs of chemical absorption were 56.51, 26.33, and 54.44 percent lower than those of cryogenic separation, respectively, indicating that this technology is more economically feasible. Moreover, because the thermodynamic efficiencies of the two methods were comparable, the chemical absorption method was adopted for hydrogen production. The biomethane steam reforming was simulated, and the results indicated that this method required an energy consumption of 90.48 MJkgH2. The hydrogen production intensity equaled 1.98 kmoleH2kmolebiogas via a 79.92% methane conversion.

Energy, exergy, economic and environmental assessment of the triangular solar collector assisted heat pump

The solar air collector assisted air source heat pump is demonstrated to be an efficient clean heating technology, while the research on its working modes, and the corresponding energy, exergy, economic, environmental (4E) analysis is insufficient. In this study, a novel triangular solar air collector assisted air source heat pump (TSAHP) for building heating is proposed, and three working modes including preheating, series and parallel modes are illustrated. The energy model is established and used to determine the optimal working mode, and solved by Python environment. Four scenarios including TSAHP with three areas of triangular solar air collector (TSAC) and conventional air source heat pump (ASHP) are compared based on the optimal working mode. Thermodynamic performance of the four scenarios under different working conditions is analyzed, and result indicate that the TSAHP with 3 m2 TSAC can reduce the power consumption and exergy destruction of ASHP components by 321.9 kWh and 784.6 MJ respectively during the whole heating period. Economic evaluation shows that TSAHP has the shortest payback period with moderate TSAC area, and has economic advantages at low nominal interest rate and high electric power cost with large TSAC area. In addition, based on the whole life cycle, 1 m2 of TSAC can reduce CO2 emission by more than 4500 kg.

Energy, environmental, economic, and color analysis of geo-exchange energy assisted-insulated north wall solar dryer for onion slices under relatively cloudy and rainy conditions

Preservation of onion surplus during rainy and cloudy days is a big challenge for farmers in the so-far area in northern Sahara of Algeria. Thus, available renewable energies such as geo-exchange and solar energy could be an effective solution. In the current study, an insulated north wall solar dryer (INWSD) integrated with geo-exchange heat exchanger (GHE) with inlet temperature of 80 °C was tested for drying onion slices under cloudy and rainy weather. Solar radiation and ambient temperature were in the range of 0–447 W m−2 and 9.65–26.53 °C, respectively. Drying process took 28 consecutive hours. Average diffusivity was found to be 2.81 × 10−10 m2 s−1 by considering the variation of relative humidity and temperature inside the drying chamber. Specific energy consumption varied between 0.66 and 1.75 kWh/kg with an average of 1.71 kWh/kg. Thermal efficiency was in the range of 1.48%–48.90%, with an average value of 9.52%. The low CO2 emissions of 46.69 kg/year and average payback period of 0.74 year were obtained using the INWSD. Dried onion was with low total color change at 3.79 compared to fresh samples. Therefore, INWSD is a promising technique by comprehensively considering the 3E (energy, economic, economic-environmental) and color analysis.

Energy, exergy, economy, and environmental (4E) analysis of a multi-generation system composed of solar-assisted Brayton cycle, Kalina cycle, and absorption chiller

• A combined cooling, heat, and power production system is proposed. • The system injects 4.67 MWh electricity to the grid. • The roundtrip exergy efficiency of the system is 42.1%. • Lifetime costs of the system is 2.04 million dollars. • Utilizing the system leads to 75.4% reduction in nitrogen oxides reduction. Employing multi-generation concept and renewable energy sources are two promising tools to overcome exorbitant consumption of fossil fuels. In this paper, the aforementioned techniques have been used to supply the energy demand of a commercial building. To do so, a novel tri-generation system is proposed and analyzed from energy, exergy, economic, and environmental points of view. This multilateral analysis provides a comprehensive view for the owner and decision makers whether the energy conversion system has a sustainable design from several points of view. Brayton cycle assisted with solar energy, bottoming Kalina cycle, absorption chiller, and waste heat recovery exchanger are used to supply the energy demand. Energy analysis reveals that the plant must be connected to the grid in order to meet the gap between absorption chiller production rate and the user cooling demand. The annual energy export to the grid equals to 4670 MWh while 2294 MWh electricity must be imported. Considering the exergy analysis, round-trip exergy efficiency of the plant is 42.11%. Brayton cycle has the highest share in the exergy destruction and corresponds to 93.00% of the annual exergy destruction. Based on the economic evaluation, the net system costs during its life cycle are 2.02 M$. Finally, sensitivity analysis is conducted to investigate the change in system performance by varying the key design parameters.

Examination and optimization of a novel auxiliary trigeneration system for a ship through waste-to-energy from its engine

Considering the thermal processes with the help of smart heat recovery, this study proposes a novel auxiliary trigeneration system for a ship based on the waste heat of its engine to produce electricity, cooling, and freshwater. The system consists of a regenerative organic Rankine cycle (RORC) with R600 working fluid, a lithium-bromide/water single-effect absorption chiller, and a humidification dehumidification (HDH) desalination unit. A multi-heat recovery technique is implemented in the design framework, having a well-organized waste-to-energy system. Technical 3E (energy, exergy, and exergoeconomic) analysis together with a multi-criteria optimization using a genetic algorithm is conducted. Furthermore, a parametric study is employed regarding the impact of changing design parameters, namely, pinch point temperature difference of the high recovery vapor generator (HRVG), turbine inlet pressure, and top temperature of the HDH on the thermodynamic and exergoeconomic criteria. The results indicated the high sensitivity of the outputs from varying the turbine inlet pressure. Besides, the optimum net output power, cooling, and generated freshwater are calculated to be 783.9 kW, 959.8 kW, and 98.1 m3/day, respectively. Also, the optimum energy and exergy efficiencies and total cost per unit exergy are computed to be 58.4%, 43.0%, and 0.1494 $/kWh, respectively.