Experimental Investigation of Unconfined Compression Strength and Microstructure Characteristics of Slag and Fly Ash-Based Geopolymer Stabilized Riverside Soft Soil

To solve the issues of insufficient early strength of cement stabilized soil and high resource cost, high reduction cost, and high environmental cost induced by the application of cement, the slag and fly ash-based geopolymer was adopted as the stabilizer to treat riverside soft soil. This study mainly investigated the effects of stabilizer content, slag-to-fly ash ratio, and alkaline activator content on the strength of geopolymer stabilized soils with different curing ages. Unconfined compressive strength (UCS), scanning electron microscope (SEM), and X-ray energy spectrum analysis (EDS) tests were carried out. The results show that the stabilizer content, slag–fly ash ratio, and alkaline activator content have a decisive influence on the UCS of geopolymer-stabilized soil. The mix-proportions scheme of geopolymer stabilized riverside soft soil, with a geopolymer content of 15%, a slag–fly ash ratio of 80:20, and an alkaline activator content of 30%, is considered optimum. It is proven by SEM that the uniformly distributed gelatinous products formed in the geopolymer-stabilized soil bind the soil particles tightly. Moreover, the EDS analysis confirms that the gelatinous products are mainly composed of C-S-H gel and sodium-based aluminosilicate (N-A-S-H).

Cost-Effectiveness of Energy Efficiency and Renewable Energy Technologies for Reducing Peak Demand

This paper describes an optimization-based approach to evaluate measures providing peak electricity demand reduction cost benefits for Saudi residential buildings. These measures can be categorized as energy efficiency (EE) and renewable energy (RE) measures. Specifically, this paper models the existing Saudi building stock using 56 housing prototypes based on types, vintages and locations.

Optimasi Kombinasi Biaya Bahan Bakar dan Emisi Pembangkit Energi Listrik menggunakan Teknik Reduksi Tempat Kedudukan

ABSTRAKDalam pengoperasian pembangkit energi listrik bukan saja untuk mendapatkan biaya yang minimal, namun juga meminimalkan emisi yang dihasilkan atau dikenal dengan Combined Economic Emission Dispatch (CEED), karena emisi merupakan bagian dari permasalahan energi. Makalah ini mengusulkan teknik reduksi tempat kedudukan untuk memecahkan masalah CEED. Prinsip dasar dari teknik ini adalah menebarkan sejumlah kandidat pada tempat kedudukan, S0 yang dibentuk dari limit daya generator, dan ditentukan sebuah kandidat terbaik. S0 diperkecil dan proses diulangi hingga didapatkan tempat kedudukan yang sangat kecil dimana kandidat terbaiknya dapat dianggap sebagai titik optimal. Teknik ini lebih akurat dibandingkan dengan metoda lain seperti Gradient Method (GM), Ant Colony Optimization (ACO), Particle Swarm Optimization (PSO), JAYA Algorithm dan Whale Optimization Algorithm (WOA). Hasilnya memberikan penghematan biaya tanpa melibatkan emisi masing-masing terhadap GM, ACO, PSO, WOA dan JAYA sebesar 9,24%, 3,91%, 0,56%, 0,47% dan 0,21%, serta bila melibatkan emisi sebesar 21,28%, 16,09%, 5,52%, 5,31% dan 5,04%.Kata kunci: CEED, reduksi tempat kedudukan, penghematan biaya, optimal, akurat. ABSTRACTIn an operating, generator units not only to get minimal costs but also to consider the emissions produced, known as the Combined Economic Emission Dispatch (CEED), because emission is part of the energy problem. This paper proposes a feasible area reduction technique for solving CEED problems. The basic principle of this technique is to spread number of candidates on a feasible area, S0 which is formed by generator limits from n generator units and the best candidate is determined. S0 is reduced and the process is repeated until a very small area is found, where the best candidate can be considered the solution. This technique is more accurate than other methods such as GM, ACO, PSO, JAYA Algorithm and WOA. The result provides cost savings without involving emission of GM, ACO, PSO, WOA and JAYA of 9.24%, 3.91%, 0.56%, 0.47% and 0.21% respectively, as well as when it involves emissions amounted to 21.28%, 16.09%, 5.52%, 5.31% and 5.04% respectively.Keywords: CEED, feasible area reduction, cost saving, optimal, accurate

Strategies of Two-Level Green Technology Investments for Coal Supply Chain under Different Dominant Modes

We consider a coal supply chain with a coal enterprise and a manufacturer, where the coal enterprise invests in clean coal technology, and the manufacturer invests in carbon reduction technology. The government offers subsidies for the investments of clean coal technology and carbon reduction technology. We examine optimal clean coal technology inputs in a coal enterprise and carbon reduction quantity in a manufacturer under the modes of coal-enterprise-led and manufacturer-led, respectively, using a Stackelberg game theory model. We obtain some interesting results. First, carbon reduction by the manufacturer is restrained when clean coal technology cost and carbon reduction cost are increased, regardless of the dominant modes, and clean coal technology input decreases when clean coal technology cost increases; however, a high carbon reduction cost has no effect on clean coal technology input when the manufacturer leads. Second, the clean coal technology subsidy for coal enterprises promotes clean coal technology inputs and carbon reductions, and the carbon reduction subsidy encourages carbon reduction without supporting clean coal technology input. Last, carbon reduction performance is better achieved under the manufacturer-led model than the coal-enterprise-led model. However, it should be noticed that the capital resource only relies on government subsidy in this article. In the future, this study could be used for green supply chain investment, and could be helpful for sustainability development.

Arsenic removal from water by nanofiltration membrane: potentials and limitations

Arsenic, in addition to being a confirmed carcinogen, is one of the most toxic elements found in nature, and should therefore be removed if the concentration is greater than 10 μg/L. Nanofiltration (NF) membranes have succeeded in arsenate As (V) ions removal from water almost completely. It is reported in this review that, like reverse osmosis (RO) membranes, NF membranes have not yet performed alone arsenite As (III) ion rejection without being associated with another technology. Commercial NF membranes exhibited a rejection between 86 and 99% towards arsenate As (V) while As (V) removal reached 99.8% for synthesized NF membranes. Since commercial NF membranes have shown their limit, scientists have prepared novel NF membranes that demonstrated long-term efficiency, fouling reduction, cost reduction, an increase in separation of multivalent ions, rejection performance, or a high flux achievement, depending on the area of use. For small treatment plants, NF is a more cost-effective method. The review succinctly reported arsenic as a serious global contamination issue and focused on novel nanofiltration processes for arsenic rejection to safeguard water security. This article also developed a comparative study of nanofiltration and reverse osmosis techniques concerning arsenic removal. Finally, future trends and perspectives have been highlighted with particular emphasis on emerging synthesis techniques of NF membranes without hiding the unpleasant fouling issue that limits its competitiveness.

EFFECT OF DRY DEFIBRATION OF RECOVERED PAPER ON MULTILAYER CARDBOARD PROPERTIES

The article focuses on the relevant for the pulp and paper industry in the direction of reduction of energy consumption for the production of cardboard from recovered paper with the preservation of its mechanical parameters. The reduction cost is due to the partial replacement of the technology of traditional conventional preparation of the recovered paper with dry defibration. The dry defibration method affects the structural, mechanical and deformation properties of the cardboard. The purpose of the work is to obtain dependencies, listed characteristics on recovered paper content prepared by dry method. In order to maintain the mechanical and deformation properties of the cardboard when adding dry-defibrated fibers, it is necessary to correctly distribute them in the test liner layers and to set the stage of supply of dry-defibrated recovered paper into the process flow. To this end, various applications of the dry recovered paper preparation technique were experimentally analyzed, fed to and ground in an aqueous medium, and dry fibers were used to form a two-layer and three-layer test-liner cardboard. The maximum content of fibers prepared by the dry method to obtain a multilayer test-liner was 50% by weight of the cardboard, even though the main mechanical parameters, including tensile strength, bending stiffness, and short-span compression strength (SCT), changed slightly. Established optimal composition of cardboard, allowed using the results of experimental studies for industrial development. The article also provides a technical and economic estimation of different ways of dry defibration technology.

Geopolymer Carbon-Based for Ultra-Wideband Absorbent Applications

Dimension reduction, cost efficiency, and environmental sustainability are important factors in absorbent designs. Geopolymers represent an eco-friendly and cost-efficient solution for such applications, and the objective of this study is to develop new geopolymer-based composites with tailored dielectric properties. To develop such composites, different formulations based on three types of carbon and various surfactants are tested. The nonionic surfactant is preferred over the anionic surfactant. Dielectric investigations between 2 and 3.3 GHz are performed. The results reveal that the carbon content and its type (origin) have significant effects on the dielectric characteristics and less on the magnetic characteristics. Indeed, an increase in permittivity from 2 to 24 and an increase from 0.09 to 0.6 for loss tangent are shown with changes in the carbon content and type. A permittivity (ε) of 2.27 and loss (tan δ) of 0.19 are obtained for a pore size of 1.6 mm, for the carbon type with the lowest purity, and with a nonionic surfactant. Finally, it is shown that the addition of magnetite has little impact on the overall magnetic properties of the geopolymer.

Decisions in Power Supply Chain with Emission Reduction Effort of Coal-Fired Power Plant under the Power Market Reform

Sustainability in power supply chain has been supported by emission reduction of coal-fired power generation and increasing renewable energy power generation. Under the power market reform of direct power purchase transactions, this paper focuses on the channel selection and emission reduction decisions of power supply chain. From the theoretical perspective, this paper develops the decision-making models of centralized and decentralized power supply chain, which consist of one renewable energy power generation enterprise, one coal-fired power plant and one power grid enterprise. The optimal strategies of power quantities and profits for power supply chain members and their corresponding numerical experiments are analyzed in different cases. The results show that there are qA1Nc*<qA1Lc* for renewable energy power generation enterprise A, qB1Nc*>qB1Lc* and eBNc*>eBLc* for coal-fired power plant B, which indicate that the direct power purchase channel in the centralized scenario is conducive to promoting the transaction quantity of renewable energy power generation, as well as the on-grid power quantity and emission reduction efforts of coal-fired power plant B. Furthermore, the profit of whole power supply chain could be enhanced by the increasing on-grid power preference coefficient of coal-fired power generation, subsidy for renewable energy power generation and preference coefficient for clean production, and by the decreasing emission reduction cost coefficient of coal-fired power plant. Additionally, the emission reduction effort of coal-fired power plant is positively relevant with preference coefficient for clean production, whereas it is negatively relevant with power grid wheeling charge, emission reduction cost coefficient and subsidy for renewable energy power generation. Our findings can provide useful managerial insights for policymakers and enterprises in the sustainability of power supply chain.

EU Emission Targets of 2050: Costs and CO2 Emissions Comparison of Three Different Solar and Heat Pump-Based Community-Level District Heating Systems in Nordic Conditions

In Finland, old apartments (1980s) contribute toward emissions. The objective is to reduce CO2 emissions to reach Europe’s targets of 2050. Three different centralized solar-based district heating systems integrated either with non-renovated or renovated old buildings in the community were simulated and compared against the reference city-level district heating system. The three proposed centralized systems were: Case 1: photovoltaic (PV) with a ground source heat pump (GSHP); Case 2: PV with an air-water heat pump (A2WHP); and Case 3: PV with A2WHPs, seasonal storage, and GSHPs. TRNSYS simulation software was used for dynamic simulation of the systems. Life cycle cost (LCC), CO2 emissions and purchased electricity were calculated and compared. The results show that the community-level district heating system (Case 3) outperformed Case 1, Case 2, and the city-level district heating. With non-renovated buildings, the relative emissions reduction was 83% when the reference energy system was replaced with Case 3 and the emissions reduction cost was 3.74 €/kg.CO2/yr. The relative emissions reduction was 91% when the buildings were deep renovated and integrated with Case 3 when compared to the reference system with non-renovated buildings and the emission reduction cost was 11.9 €/kg.CO2/yr. Such district heating systems could help in meeting Europe’s emissions target for 2050.