Life cycle energy and carbon footprint analysis of photovoltaic battery microgrid system in India

Electricity supply in India is from a centralized grid. Many parts of the country experience grid interruptions. Life cycle energy and environmental analysis has been done for a 27 kWp photovoltaic system which acts as grid backup for 3 h outage in an Indian urban residential scenario. This paper discusses energy requirements and carbon emission for a PV storage system for five different battery technologies in Indian context. This can be used as a metric for comparative analysis for new batteries, with an undeveloped market. The energy requirements for the components are quantified and are compared in terms of energy payback time (EPBT) and Net Energy Ratio (NER). All the calculations are done for Indian context. EPBT is found to be in the range of 2–4.5 years for all the systems, while NER is in the range of 6.6–2.52. NaS has the highest emission factor of 0.67 kgCO₂/kWh and the least for NiCd (0.091 kgCO₂/kWh). These factors can be used to select a PV battery option and to target selection of materials and systems based on the reported values.     

Valorisation of mango seed via extraction of starch: preliminary techno-economic analysis

Reducing environmental impacts and obtaining economic benefits based on utilisation of waste materials are drivers for the implementation of cleaner production policies and technologies in food processing industries. Starch is a very versatile material with a wide range of applications in the food, pharmaceutical, textile, paper, cosmetic and construction industries. In Ethiopia, starch is widely used in the textile industry. To meet the starch demand, the country imports approximately 45% of the starch used in the country. Consequently, it is imperative to find additional sources of starch that could substitute for the amount of starch that is currently being imported. Mango seeds, a waste material that is disposed of after consumption of mangos, were studied for potential use as an alternative resource for starch production. The results showed that starch extraction from mango seeds was facile and a good quality product was obtained. The present study is concerned with a techno-economic analysis for industrial production of starch from mango seeds. The study shows that extraction of starch from waste mango seeds is feasible: the project is financially viable with an accounting rate of return of 83% and a break-even analysis of 78% with a payback period of 2 years.     

Graphene quantum dots derived from hollow carbon nano-onions

Herein, carbon nano-onions (CNOs) with different structures have been investigated as precursors for the synthesis of graphene quantum dots (GQDs). It was found that hollow CNOs yield GQDs with a uniform size distribution, whereas metal encapsulation in the CNO structure is disadvantageous for the same. Furthermore, the hollow CNOs are also advantageous for the synthesis of GQDs with a yellow-green hybrid luminescence and long-ranged excitation wavelength (λ _ex)-independent photoluminescent (PL) behavior, in which the λ _ex upper limit was 480 nm. These features enable safe sensing and cell tracking applications with a longer excitation wavelength in the visible light region. The potential applications of the synthesized GQDs as fluorescent sensing probes for detecting Cu(II) ions and non-toxic cell imaging under visible light excitation have been demonstrated. This means that sensing and bioimaging can be accomplished in the natural environment with no need for UV excitation. This work provides a reference to researchers in tailoring CNO structures in terms of their inner space to synthesize GQDs with the desired luminescence behavior.

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Facile growth of homogeneous Ni(OH)<Subscript>2</Subscript> coating on carbon nanosheets for high-performance asymmetric supercapacitor applications

The growth of a Ni(OH)₂ coating on conductive carbon substrates is an efficient way to address issues related to their poor conductivity in electrochemical capacitor applications. However, the direct growth of nickel hydroxide coatings on a carbon substrate is challenging, because the surfaces of these systems are not compatible and a preoxidation treatment of the conductive carbon substrate is usually required. Herein, we present a facile preoxidation-free approach to fabricate a uniform Ni(OH)₂ coating on carbon nanosheets (CNs) by an ion-exchange reaction to achieve the in situ transformation of a MgO/C composite to a Ni(OH)₂/C one. The obtained Ni(OH)₂/CNs hybrids possess nanosheet morphology, a large surface area (278 m²/g), and homogeneous elemental distributions. When employed as supercapacitors in a three-electrode configuration, the Ni(OH)₂/CNs hybrid achieves a large capacitance of 2,218 F/g at a current density of 1.0 A/g. Moreover, asymmetric supercapacitors fabricated with the Ni(OH)₂/CNs hybrid exhibit superior supercapacitive performances, with a large capacity of 198 F/g, and high energy density of 56.7 Wh/kg at a power density of 4.0 kW/kg. They show excellent cycling stability with 93% capacity retention after 10,000 cycles, making the Ni(OH)₂/CNs hybrid a promising candidate for practical applications in supercapacitor devices.

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Single point incremental forming: state-of-the-art and prospects

Incremental sheet metal forming in general and Single Point Incremental Forming (SPIF) specifically have gone through a period of intensive development with growing attention from research institutes worldwide. The result of these efforts is significant progress in the understanding of the underlying forming mechanisms and opportunities as well as limitations associated with this category of flexible forming processes. Furthermore, creative process design efforts have enhanced the process capabilities and process planning methods. Also, simulation capabilities have evolved substantially. This review paper aims to provide an overview of the body of knowledge with respect to Single Point Incremental Forming. Without claiming to be exhaustive, each section aims for an up-to-date state-of-the-art review with corresponding conclusions on scientific progress and outlook on expected further developments.     

Numerical and experimental investigations in electromagnetic riveting with different rivet dies

In this work, the numerical simulations and electromagnetic riveting (EMR) experiments were conducted to investigate microstructure evolution and the forming mechanism of adiabatic shear bands (ASBs). And the effects of rivet dies on microstructure distributions in formed heads and mechanical properties of riveted structures were systematically explored. The impact velocity and deformation distribution results demonstrated that the proposed numerical method was accurate and reliable. The simulation results showed the slope angle of rivet dies notably affected the plastic flow of materials, and then determined the microstructure distribution in formed heads. The combined effects of inhomogeneous plastic flow and thermal softening were accounted for the forming of ASBs. The formed heads had two obvious ASBs (upper and lower ASB) for the 40° rivet die and flat rivet die. The formed heads only had the lower ASB and no clear upper for the 60° rivet die and 80° rivet die. The pull-out test results showed that the specific rivet die could improve the mechanical properties of the EMR joints, which contribute to the engineering applications of EMR riveted structures.     

Numerical and experimental investigations of laser shock forming aluminum alloy sheet with mold

Laser shock forming (LSF) technology employs shock waves to form sheet metal into three-dimensional complex parts, and has application potential in manufacturing sheet metal parts. In this paper, the forming of 2024 aluminum alloy sheet with LSF was investigated through numerical and experimental methods. The numerical model was established with the commercial code ABAQUS/Explicit. The formed conical cup was obtained from the simulation, and validated by the experiment. With the verified numerical model, the deformation behaviors, including deformation velocity, sheet thickness variation and strain distribution, were studied. In addition, the influence of different shock wave pressures on the forming precision was also investigated. The experimental and numerical results show that the metal sheet loaded by shock wave can take the shape of the mold, and the non-uniform thickness is distributed in the formed cup. The investigations also display that there exists reverse deformation at the central region of deforming sheet owing to severe collision during LSF. In order to obtain formed part with better quality, an appropriate pressure of applied shock waves is required.