Assessing the cooling/lubricating agencies for sustainable alternatives during machining of Nimonic 80: Economic and environmental impacts

Developing sustainable manufacturing methods that balance environmental and economic aspects is challenging. A comprehensive analysis of the economics of machining and carbon emissions is essential to encourage adopting sustainable practices. This work presents the machinability and comparative sustainability analysis of Nimonic 80 superalloy when it is machined utilizing a novel, environmentally friendly vegetable oil-based hybrid nanofluid-minimum quantity lubrication (MQL) and liquid carbon dioxide (LCO2) technique. The main objective is to comprehend the efficacy of the proposed approach on tool life, surface roughness, power consumption, total machining costs, and carbon emissions. Compared to other machining conditions, the use of hybrid nanofluid-MQL under 100 m/min cutting speed prevented rapid flank wear and considerably increased tool life by about 17-59 %. The change in cutting speed from 100 to 150 m/min has resulted in reduced tool life about 13-42 % under the selected environments. In addition, when compared to dry, flood, and MQL machining, the use of hybrid nanofluid-MQL and LCO2 reduced surface roughness by around 16-45 % at 150 m/min. Sustainability analysis revealed that machining at 150 m/min resulted in decreased costs ranging from 6.1 % to 36.4 % for selected cutting environments. Applying hybrid nanofluid-MQL lowered carbon emissions by 16.83 %, whereas LCO2 reduced carbon emissions by 14.6 % at 100 m/min. At 150 m/min, hybrid nanofluid-MQL and LCO2 lowered carbon emission by 22.3 % and 21.5 % at 150 m/min compared to dry machining. Compared to alternative cutting environments, hybrid nanofluid-MQL and LCO2 applications have longer tool lives, lower machining costs, and carbon emissions. As a result, they are economical and environmentally friendly.

Exergy and environmental analysis of a novel turbine inlet air cooling technique for power augmentation in a CCPP based on waste energy

Combined cycle power plant (CCPP) play a crucial role in providing electricity worldwide. Therefore, researchers and industrialists always focus on developing and improving its performance. One of the factors that affect the performance of CCPPs is weather conditions. As weather conditions change, the air density of the environment changes, which ultimately affects the production power of the gas turbine (GT) and consequently the CCPP. To mitigate the effects of weather on CCPPs' performance, power augmentation methods are developed. In the present research, a novel technique is proposed to reduce the air temperature entering the GT by recovering waste heat from the exhaust gas. The heat content of the exhaust gas is used as the heat source of an ejector refrigeration cycle (ERC), and the produced cooling capacity is used to cool down the air entering the GT. Exergy and environmental analyses are performed to investigate the proposed method's effect on exergy efficiency, environmental factors, and sustainability index. The results indicate that by the proposed method the power production of the CCPP is increased 6.26%.

Multiobjective optimization of a cogeneration system based on gas turbine, organic rankine cycle and double-effect absorbtion chiller

Combined cooling, heating and power (CCHP) is one of methods for enhancing the efficiency of the energy conversion systems. In this study a CCHP system consisting of a gas turbin (GT) as the topping cycle, and an organic Rankine cycle (ORC) associated with double-effect absorbtion chiller (DEACH) is decisioned as the bottoming cycle to recover the waste heat from GT exhaust gas. The considered CCHP system is investigated to maintain electricity, heating and cooling demand of a town. A parametric study is investigated and the effect decision variables on the performance indicators including exergy efficiency, total cost rate (TCR), cooling capacity, and ORC power generation is examined. Decision variables of the ORC system consist of HRVG pressure, and condenser pressure and the DEACH including evaporator pressure, condseser pressure, concentration of the concentrated solution, concentration of the weak solution, and solution mass flow rate. Finally a multi-objective optimization performed using Genetic Algorithm (GA) and the optimal design point is selected. It is observed at the optimum point the exergy efficiency, TCR, and sustainability index are 17.56%, 74.49 $/h, and 1.21, respectively.

Sustainability performance of bioretention systems with various designs

Bioretention systems for urban drainage are one type of blue-green infrastructure that have gained more attention in recent decades. There are numerous design options for these systems, including various construction components, filter material mixtures, and plants. However, the research focus on the impacts of these many design options has mainly been technical, i.e., how different bioretention designs affect runoff pollution treatment and hydraulic control. Knowledge of the effects of various design elements on other sustainability criteria, such as economic, social, and environmental aspects, needs to be developed. This research aimed to evaluate and compare various design elements and bioretention types to gain a better understanding of the relative sustainability of various bioretention systems. This was accomplished by identifying relevant criteria and sub-criteria, covering social, economic, and technical-environmental indicators, in a multicriteria analysis. To evaluate the sustainability performance of various bioretention designs, 12 sub-criteria were allotted -100 to 100 points in a scoring process. The main finding was that while design features had a major impact on bioretention performance, no single design configuration excelled in all criteria. High scores in the social criteria were correlated with the use of trees and smaller volumes of pumice in the filter material mixture. In the economic criteria, extensive use of concrete and a complex mixture of filter material increased the costs. The system with a water-saturated zone and a variety of plant species outperformed the other systems in the technical-environmental criteria. The results can be utilized as a reference to assess design configurations that best satisfy specific needs for each unique bioretention implementation.

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 0.111 kg/s, 0.125 kg/s, and 0.138 kg/s, respectively. The receiver's exergy efficiency is recorded at about 8.11% at 0.138 kg/s. The receiver with a maximum reduction of CO₂ emission is about 1.16 tons recorded at 0.138 kg/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.

Techno-economic evaluation and life cycle assessment of a biorefinery using winery waste streams for the production of succinic acid and value-added co-products

This study presents techno-economic evaluation and life cycle assessment of a novel biorefinery using the three main waste streams generated by wineries for the production of bio-based succinic acid (SA), crude phenolic-rich extract, grape-seed oil, calcium tartrate and crude tannin-rich extract. Process design has been employed for the estimation of material and energy balances and the sizing of unit operations. The Minimum Selling Price of succinic acid production within a winery waste biorefinery ranges from $1.23-2.76/kg_SA depending on the market price and the potential end-uses of the extracted fractions. The Global Warming Potential and the Abiotic Depletion Potential of winery waste valorisation through the proposed biorefinery are 1.47 kg CO₂-eq per kg dry waste and 25.2 MJ per kg dry waste, respectively. Biorefining of winery waste could lead to the development of a sustainable and novel bioeconomy business model with new market opportunities and efficient waste management.

Sustainability and efficiency analysis w.r.t adoption of climate-smart agriculture (CSA) in Pakistan: a group-wise comparison of adopters and conventional farmers

Climate change, conventional agricultural management practices, and increasing water scarcity pose a major threat to agricultural production and biodiversity as well as environmental sustainability. Climate-smart agriculture (CSA) is recognized as an efficient, sustainable, and feasible agricultural system that plays a vital role in addressing the potential impacts of climate change in Pakistan. First-hand information was collected from 450 farm households in 24 villages from Okara, Sahiwal, and Khanewal irrigation divisions, having various wheat-based cropping systems of Pakistan. This includes rice-wheat (RW), maize-wheat (MW), and cotton-wheat (CW) cropping systems in the Lower Bari Doab Canal (LBDC) irrigation system. This study estimated and compared the sustainability and efficiency analysis of CSA and conventional agricultural practices. This study also estimated the impact of water-smart practices of the CSA, technical training, and groundwater quality on agricultural production by using production function and bootstrap truncated regression. The findings of this study revealed that adopters of CSA of the wheat-based cropping systems have higher economic benefits and improved resource use efficiencies compared to the conventional farmers. The findings of the study also revealed the increased efficiency of CSA adopters over other two systems in CW cropping system. The water-smart practices of CSA, access to credit, technical training, use of groundwater of varying quality, and other inputs also showed variations in the agricultural production and resource use efficiency. It has been concluded that farmers can earn more profit, save inputs (such as water), and increase their production by adopting water-smart practices of CSA. Hence, the government and other relevant institutions should devise and implement policies that adequately addressed the importance and enhance the use of water-smart practices of CSA in Punjab and beyond.

Energy, emission, profitability, and sustainability analyses of a grid-connected solar power plant proposed in airport sites of Bangladesh: a case study

Nowadays, the aviation industry is one of the significant contributors to greenhouse gas emissions. An optimum solution to this concern is the substitution of conventional electricity consumption with clean energy sources. Barren lands are available in airport sites as buffer zones. These lands can be utilized to generate electricity from clean energy sources like solar, wind, and others. This study proposed a 5 MW grid-connected solar power plant at airport sites by utilizing the substantial barren area of the airport. The targeted airports for this study are Hazrat Shahjalal International Airport, Dhaka, and Shah Amanat International Airport, Chittagong, Bangladesh. Mathematical and simulation analyses have been performed for this purpose. Besides, sustainability analysis has also been incorporated for the grid-connected solar power plant. The energy efficiency varies from 18.74 to 7.79% for the Shah Amanat International Airport, and for the Hazrat Shahjalal International Airport, it ranges from 17.71 to 7.45%. Based on the project outcome, the revenue earned was 25% higher if the total cost was invested in power plants rather than keeping it in the bank as a deposit. On the other hand, emission analysis presented that a gross reduction of 3827.5 tons of CO₂/MWh can be achieved from the Shah Amanat International Airport, while 3926 tons of CO₂/MWh can be removed from the Hazrat Shahjalal International Airport. Based on the sustainability analysis, the energy depletion ratio for Shahjalal Airport varies from 0.82 to 0.93, while for Shah Amanat Airport, it is in the range of 0.81 and 0.92. The findings of this study suggested that investment in grid-connected solar power plants is economically viable and environmentally benign.

A multi-scale analysis of interregional sustainability: Applied to Israel's food supply

Promoting sustainability in today's world requires an understanding of the environmental burdens and social impacts of one region's consumption on other regions, both adjacent and remote. In recent years a growing body of research has quantified interregional flows of primary food crops and of embodied resources. However, most studies to date are limited to the national resolution, and mostly overlook sub- and supra-national divisions of space that emphasize varied socio-ecological circumstances. Very few recent studies have acknowledged the need to advance such interspatial analysis, and explore other relevant spatial scales, but they tend to focus on a single scale. Acknowledging the advantages and opportunities inherent in multiple scale analysis of the interactions between and within human and natural systems; this article proposes a method for a multi spatial scale analysis of the sustainability of interregional food systems, which unlike other currently available methods, enables a global and relatively complete analysis of an interregional food system. It then applies it to a case study of flows of crops and related croplands to Israel from different parts of the world, analyzed using multiple scales, such as: national, biome, ecoregion, river basin, and sub national administrative units. The findings are discussed with regards to Israel's remote environmental impact and dependency. They demonstrate how this approach can be used to provide an overview of a food system's interregional environmental interactions, identify otherwise hidden hotspots of environmental impact, and recognize interregional shared interests and trade-offs. These advantages make the method useful for national assessments of different countries' food security and food system sustainability.