Energy Efficient Option Research Articles

Passive House Design: A Possible Energy Efficient Option in the Building Sector of Nepal

The diversified geography of Nepal creates huge variations in the country's climatic zones; however, the building industry has so far used standardized methods that tend to neglect local climate conditions. Most of these standards then rely on energy-intensive mechanical systems to maintain indoor thermal comfort, without considering more viable and climate-responsive design methods. In this light, the development of a climate classification related to building design will help develop and encourage energy- and climate-effective building architecture in Nepal. The existing energy-saving practice in the building sector of the country is reviewed in this paper, and it outlines ways to improve the adaptation of energy-efficient methodology. It shows that passive houses are performing much better in comparison with modern constructions that are behind in terms of energy efficiency when compared with traditional homes. The study outlines the climate-specific design criteria and methodologies for various regions and sets the path for exploration of the passive house design process challenges and opportunities that might exist for wider diffusion. Also discussed are strategies to overcome the barriers and promote passive house construction, offering a pathway toward sustainable building practices in Nepal.

Analysis of fly-around mission with spinning tether system for space station observation

This paper presents the mission scenarios of using spinning tether system to conduct space stations fly-around mission and validates its feasibility. The main challenge of fly-around mission lies in the difficulty of balancing low fuel consumption and long-term fly-around observation. To deal with this problem, a novel spinning tether system is proposed. Firstly, the fly-around process with spinning tether system is introduced, and the tether system is modeled based on Newton-Euler method with a novel description of spinning motion. Secondly, Given the unique structural limitations of space stations, two fly-around schemes and referenced fly-around trajectories are detailed. Thirdly, a backstepping controller is proposed for tracking the reference motion of fly-around satellites, and the fuel consumption among different fly-around schemes is compared and analyzed. In the end, numerical results validate that under the proposed control strategy, the spinning tether system can maintain a stable fly-around configuration in both the planar and vertical plane, the symmetrical formation configuration prevents the central space station from being affected by the motion of fly-around satellites. Moreover, energy consumption analysis indicates that tethered system can save 62.8 % of impulse compared to traditional schemes when flying in the planar plane, making it the most energy-efficient option.

Highly insulated hydrogen powered vacuum gasochromic smart windows for energy-efficient buildings

Switchable active hydrogen powered gasochromic smart windows present an appealing option for energy-efficient building integration, offering two controllable transparencies between ON and OFF states compared to traditional windows. Implementing such glazing in cold-climate buildings requires minimizing the total heat transfer across the glazing, achievable through vacuum-insulated glazing resulting in the retrofitting to obtain energy efficient building. This study investigates the potential of vacuum gasochromic (VGC) windows to enhance the energy efficiency of buildings in diverse climatic conditions, focusing on London, UK, and New Delhi, India. Comparing traditional single-glazing and double-glazing windows with vacuum-gasochromic windows in terms of thermal performance, energy demand, and dynamic control over solar heat gain and visible light transmission are evaluated using advanced simulation techniques with SketchUp, OPTICS6, WINDOW 7.8 and EnergyPlus 9.6. Results reveal that vacuum gasochromic windows exhibit superior thermal insulation with significantly lower U-values of 1.559W/m2K, reducing heat transfer and energy demand for heating and cooling. Vacuum gasochromic opaque states demonstrate exceptional performance in minimizing energy transfer, making them the most energy-efficient option, especially in warm climates like New Delhi with 9544.4 kWh. Conversely, vacuum gasochromic transparent state shows promise in reducing heating demand in London's cold climate by 9.43 %, highlighting their adaptability. Moreover, vacuum gasochromic windows allow dynamic control over solar heat gain and visible light transmission, enabling occupants to adjust transparency based on weather conditions and preferences.

Удельные энергетические затраты на измельчение древесины при подготовке композита для 3D-печати

The Northwestern Federal District is a region of Russia rich in a variety of wood species. The properties of wood in this region differ significantly from the properties of wood grown in other countries or in the eastern part of Russia, which leads to differences in energy costs of grinding wood. The aim of this research has been to estimate the specific energy costs of grinding wood to the state of wood flour, which will be used as the basis for wood polymer composite consumables in additive technologies. Wood flour has been obtained by grinding wood in a laboratory disk mill, repeatedly reducing the particle size. The granulometric composition has been analyzed for beech, oak, larch, alder and pine wood at 1, 3, 5 and 10 grinding cycles. Particle sizes have been determined by analyzing images obtained using an optical microscope and processed in the ImageJ graphic program. The specific energy costs of grinding have been estimated by recording the power with a wattmeter every second with repeated feeding of wood flour for the known mill productivity. When calculating the specific energy consumption, the moisture content of each wood species has been taken into account, as well as productivity losses associated with the adhesion of wood particles to the working surfaces of the dispersing set and the inner area of the disk mill body. The research has revealed a relationship between the specific energy costs and the particle size of wood flour obtained from various wood species. Regression analysis of curves corresponding to different wood species has made it possible to obtain exponential and power-law dependencies that do not contradict the fundamental theoretical laws of grinding solid particles. Based on these results, pine wood flour has been recognized as the most energy-efficient option. The established dependencies can be used to predict the specific energy consumption for grinding beech, oak, larch, alder and pine wood in disk mills.

Limestone calcined clay cement (LC³) coating mortars as an energy-efficient option for construction

LC³ coating mortars have been developed by replacing 45 – 60 % of Portland cement with metakaolin and limestone (2:1) and using a 1:4.5 binder-to-sand ratio to create an energy-saving and environmentally friendly alternative. Their thermal conductivity was reduced by up to 51 %, and the thermal insulation was improved by up to 4 °C with just a 2 cm layer application compared to a mortar with 100 % cement. By increasing the water content by just 12 %, the consistency index of the mortar was maintained without using any additives. LC³ coating mortars with less cement and more sand still resemble traditional mortars, complying with all regulations.

Pots to Plots: Microshock Weed Control Is an Effective and Energy Efficient Option in the Field

Seeking low environmental impact alternatives to chemical herbicides that can be integrated into a regenerative agriculture system, we developed and tested flat-plate electrode weeding equipment applying ultra-low-energy electric shocks to seedlings in the field. Better than 90% control was achieved for all species, with energy to treat 5 weeds m−2 equivalent to 15 kJ ha−1 for L. didymum and A. powellii, and 363 kJ ha−1 (leaf contact only) and 555kJ ha−1 (plants pressed to soil) for in-ground L. multiflorum, all well below our 1 MJ ha−1 target and a fraction of the energy required by any other weeding system. We compared applications to the leaves only or to leaves pressed against the soil surface, to seedlings growing outside in the ground and to plants growing in bags filled with the same soil. No previous studies have made such direct comparisons. Our research indicated that greenhouse and in-field results are comparable, other factors remaining constant. The in-ground, outdoor treatments were as effective and efficient as our previously published in-bag, greenhouse trials. The flat-plate system tested supports sustainable farming by providing ultra-low-energy weed control suitable for manual, robotic, or conventional deployment without recourse to tillage or chemical herbicides.

Thermal Analysis of Building Roofs with Latent Heat Storage for Reduction in Energy Consumption and CO2 Emissions: An Experimental and Numerical Research

In green energy buildings, air conditioning charges can be lowered through careful planning of the building’s envelope. This article investigates several strategically designed phase change material (PCM) roof envelopes for savings on air conditioning prices, CO2 emission abatement, and payback timeframes in hot–arid and warm-temperate climates, taking into account unsteady heat transfer characteristics, cooling, and heating degree–hours. This is accomplished by using six different PCMs–RCC (reinforced cement concrete) roof envelope cases (RCC roof with PCM layer on the outer side, RCC roof with PCM layer on the center (middle), RCC roof with PCM layer on the inside, RCC roof with PCM layers placed on the outside and center, RCC roof with PCM layers placed on the center and inside, and RCC roof with PCM layers placed on the outer side and inside) with three PCMs (FS29 (form stable mixture), HS29 (hydrated salt), and OM29 (organic mixture)). PCM thermophysical characteristics are experimentally measured. The analytical results are experimentally validated. In hot–arid and warm-temperate regions, the layer of PCM installed on the outside of the RCC with HS29 saved the most on air conditioning expenses, at 6.29 and 6.61 $/m2, respectively. They also reported the greatest carbon mitigation of 300.55 kg of CO2/year and 281.58 kg of CO2/year with the faster payback periods. PCM roof envelopes are the most energy-efficient option for green buildings.

Deciphering the role of hydraulic retention time (HRT) in integrated fixed-film activated sludge (IFAS) system under aniline stress: Effects on microbial succession and communication

Integrated fixed-film activated sludge (IFAS) system offered an energy-efficient option for nitrogen removal from aniline wastewater. The regulation of hydraulic retention time (HRT) has been reported to affect the fate of functional microbial communities with different generation cycles, but the role of HRT in IFAS under aniline stress has not been sufficiently revealed. Herein, it was observed that shortening the HRT altered the mechanisms underlying the adaptation of a continuous flow micro-aerated IFAS system to aniline stress, thereby negligibly impacting the removal of aniline. The total nitrogen removal rate in Y2 (HRT = 0.5 day) was 40.28 % higher than Y1 (1 day), and 23.7 % higher than Y3 (0.25 day). This could be attributed to Y2 having an ample supply of electron donors for denitrification compared to Y1, as well as showing weaker stress to inhibit nitrification compared to Y3. Furthermore, with the progressive intensification of stress induced by HRT reduction, microorganisms gradually enhanced their adaptation to aniline. This led to an increased migration of microorganisms towards the inner layers of the biofilm, resulting in enhanced functional complementarity between the sludge and biofilm in Y2. Also, there was a distinct development of autotrophic denitrification, with arenimonas predominant in Y1, and Thauera predominant in Y2 and Y3. Moreover, Y2 possessed a high abundance of functional genes related to the production and reception of quorum sensing signal molecules, which may enhance the electron transport-dependent nitrogen metabolism reaction.

A sustainable bio-based char as emerging electrode material for energy storage applications

In the last few years, extensive research efforts have been made to develop novel bio-char-based electrodes using different strategies starting from a variety of biomass precursors as well as applying different thermochemical conversion paths. In this regard, hydrothermal carbonization method is becoming a more prevalent option among conversion procedures even if pyrolysis remains crucial in converting biomass into carbonaceous materials. The main aim of this study is to develop an innovative supercapacitor electrode from spruce bark waste through a unique low-temperature technique approach, which proved to effectively eliminate the pyrolysis step. Consequently, a hybrid spruce-bark-graphene oxide compound (HySB) was obtained as electrode material for supercapacitors. When compared to a regularly used commercial electrode material, SLC1512P graphite (reference) with 150.3 µF cm−2 capacitance, the HySB has a substantially higher capacitive performance of 530.5 µF cm−2. In contrast to the reference, the HySB polarization resistance increases by two orders of magnitude at the stationary potential and by three orders of magnitude at the optimum potential, underlying that the superior performances of HySB extend beyond static conditions. The synthesis strategy provides an appropriate energy-efficient option for converting biomass into carbonaceous materials with meaningful properties suitable for energy storage applications.

Modeling Mushrooms’ Carbon Dioxide Emission and Heat Exchange Rates for Synergistic Cultivation with Leafy Greens

The cultivation of mushrooms in controlled environments generates a significant amount of CO2 as a by-product. This presents opportunities for carbon dioxide (CO2) enrichment in leafy green production. This study aimed to develop a model for CO2 emission and heat exchange rates that can be used to support the synergistic cultivation of mushrooms and leafy greens. This was achieved by aggregating data from literature with experimental data gathered in two different testing spaces. The average CO2 emission and heat exchange rates for shiitake incubated at 21 °C were determined and a CO2 emission rate model for mixed substrate in incubation was developed based on indoor temperature variations. The results indicated that oyster mushrooms have a notable CO2 enrichment potential, twice that of shiitake in the incubation stage and five times more in fructification. Additionally, oyster mushrooms released a significant amount of heat during incubation. In contrast, shiitake mushrooms with their minimal heat exchange rate during incubation could offer an energy-efficient option for synergistic cultivation with leafy greens in environments where cooling is required year-round. Moreover, it was observed that the CO2 emission rate of a full-scale incubation chamber is strongly correlated with indoor temperature. These findings offer valuable information for modeling the CO2 emission and heat exchange rates of mushroom and leafy green farms.

Experimental analysis of energy consumption of building roof energy-saving technologies based on time difference comparison test

The roof plays a pivotal role as it directly engages with solar radiation absorption and external heat exchange, significantly influencing the building’s overall energy dynamics. To assess the performance of green roofs and cool roofs, a roof performance test facility was established in Nanjing. Time-difference comparison experiments were conducted to measure and analyze the energy-saving effects of cool roofs, green roofs, and conventional roofs during both summer and winter conditions. The study aimed to investigate how their thermal performance impacts building energy consumption. The study’s findings reveal that under summer conditions, the incorporation of a cool roof system leads to a substantial enhancement in energy efficiency, achieving an impressive 13.2% energy savings compared to conventional roofing solutions. In contrast, the implementation of a green roof system results in a more modest energy-saving rate of 4.1%. Transitioning to winter conditions, the adoption of a cool roof system shows a marginal increase of 2.8% in energy consumption compared to conventional roofs. Interestingly, the green roof system stands out as an energy-efficient option during winter, demonstrating a significant 4.9% reduction in energy consumption. This approach ensured reliable and valid results to provide a comprehensive view of how different roof types respond to varying climatic conditions.

RisCO2: Implementation and Performance Evaluation of RISC-V Processors for Low-Power CO2 Concentration Sensing.

In the field of embedded systems, energy efficiency is a critical requirement, particularly for battery-powered devices. RISC-V processors have gained popularity due to their flexibility and open-source nature, making them an attractive choice for embedded applications. However, not all RISC-V processors are equally energy-efficient, and evaluating their performance in specific use cases is essential. This paper presents RisCO2, an RISC-V implementation optimized for energy efficiency. It evaluates its performance compared to other RISC-V processors in terms of resource utilization and energy consumption in a signal processing application for nondispersive infrared (NDIR) CO2 sensors.The processors were implemented in the PULPino SoC and synthesized using Vivado IDE. RisCO2 is based on the RV32E_Zfinx instruction set and was designed from scratch by the authors specifically for low-power signal demodulation in CO2 NDIR sensors. The other processors are Ri5cy, Micro-riscy, and Zero-riscy, developed by the PULP team, and CV32E40P (derived from Ri5cy) from the OpenHW Group, all of them widely used in the RISC-V community. Our experiments showed that RisCO2 had the lowest energy consumption among the five processors, with a 53.5% reduction in energy consumption compared to CV32E40P and a 94.8% reduction compared to Micro-riscy. Additionally, RisCO2 had the lowest FPGA resource utilization compared to the best-performing processors, CV32E40P and Ri5cy, with a 46.1% and a 59% reduction in LUTs, respectively. Our findings suggest that RisCO2 is a highly energy-efficient RISC-V processor for NDIR CO2 sensors that require signal demodulation to enhance the accuracy of the measurements. The results also highlight the importance of evaluating processors in specific use cases to identify the most energy-efficient option. This paper provides valuable insights for designers of energy-efficient embedded systems using RISC-V processors.

Testing of a custom, portable drill press to minimize probe misalignment in sap flow sensors.

The accurate estimation of plant transpiration is critical to the fields of hydrology, plant physiology and ecology. Among the various methods of measuring transpiration in the field, the sap flow methods based on head pulses offers a cost-effective and energy-efficient option to directly measure the plant-level movement of water through the hydraulically active tissue. While authors have identified several possible sources of error in these measurements, one of the most common sources is misalignment of the sap flow probes due to user error. Though the effects of probe misalignment are well documented, no device or technique has been universally adopted to ensure the proper installation of sap flow probes. In this paper we compare the magnitude of misalignment errors among a 5mm thick drilling template (DT), a 10mm thick DT, and a custom designed, field-portable drill press. The different techniques were evaluated in the laboratory using a 7.5cm wood block and in the field, comparing differences in measured sap flow. Based on analysis of holes drilled in the wood block, we found that the portable drill press was most effective in assuring that drill holes remained parallel, even at 7.5cm depth. In field installations, nearly 50% of holes drilled with a 5mm template needed to be redrilled while none needed to be when drilled with the drill press. Widespread use of a portable drill press when implementing the heat pulse method would minimize alignment uncertainty and allow a clearer understanding of other sources of uncertainty due to variability in tree species, age, or external drivers or transpiration.

Deciphering the role of granular activated carbon (GAC) in anammox: Effects on microbial succession and communication

Anaerobic ammonium oxidation (anammox) offered an energy-efficient option for nitrogen removal from wastewater. Granular activated carbon (GAC) addition has been reported that improved biomass immobilization, but the role of GAC in anammox reactors has not been sufficiently revealed. In this study, it was observed that GAC addition in an upflow anaerobic sludge blanket (UASB) reactor led to the significantly shortened anammox enrichment time (shortened by 45 days) than the reactor without GAC addition. The nitrogen removal rate was 0.83 kg N/m3/day versus 0.76 kg N/m3/day in GAC and non-GAC reactors, respectively after 255 days’ operation. Acyl-homoserine lactone (AHL) quorum sensing signal molecule C8-HSL had comparable concentrations in both anammox reactors, whereas the signal molecule C12-HSL was more pervasive in the reactor containing GAC than the reactor without GAC. Microbial analysis revealed distinct anammox development in both reactors, with Candidatus Brocadia predominant in the reactor that did not contain GAC, and Candidatus Kuenenia predominant in the reactor that contained GAC. Denitrification bacteria likely supported anammox metabolism in both reactors. The analyses of microbial functions suggested that AHL-dependent quorum sensing was enhanced with the addition of GAC, and that GAC possibly augmented the extracellular electron transfer (EET)-dependent anammox reaction.

Experimental investigations on thermo-stamping of carbon fiber reinforced polyamide 6 hat-shaped components with self-resistance electrical heating: Influence on microscopic and macroscopic properties from temperature related processing parameters

Thermo-stamping is a widely used forming process for automotive components made from fiber reinforced thermoplastic composites, but it still suffers from a variety of challenges such as long cycle time and high energy consumption. In this paper, self-resistance electrical (SRE) heating, an internal efficient heating method with the advantages of rapid heating speed and low energy consumption, was introduced into thermo-stamping for the rapid manufacturing of carbon fiber reinforced polyamide 6 (CFR-PA6) hat-shaped components. The impacts of the temperature related process parameters, preheating temperature (90 °C ∼ 220 °C) and mold temperature (20 °C ∼ 130 °C) on the shape accuracy, surface quality, microscopic morphology and mechanical properties of obtained hat-shaped components were investigated through experimental characterization. Besides, the energy-saving effect of SRE heating was also revealed compared with radiant heating, an external heating method. It is found that the defects such as fiber bundle cracks, matrix cracks and interface cracks caused by SRE heating are more serious than those caused by radiant heating, which is attributed to the effect of Joule heating, Lorentz force and dielectric breakdown. However, a high mold temperature can reduce these defects owing to the reconsolidation behavior of the hat-shaped component during the thermo-stamping process. The results show that the hat-shaped components possess a good formability and forming quality at a preheating temperature at 200 °C and mold temperature at 130 °C. Moreover, the total cycle time of thermo-stamping with SRE heating is less than 1 min and the energy consumption by SRE heating is about 9.86 % ∼12.09 % compared with radiant heating, which provides a more energy-efficient option for industrial production.

Deep-learning optimization and environmental assessment of nanomaterial's boosted hydrogen and power generation system combined with SOFC

Renewable energy sources are unquestionably required, given that the world's energy consumption is anticipated to increase significantly in the next decades. Besides, fuel cell converts chemical energy directly into electricity, making it the most efficient and environmentally friendly power source. This study examines the viability of producing electricity using a supercritical CO2 cycle, a methane digester, and a gas turbine. Applying the principles of exergetic balance, mass, energy conservation, and component-specific exergetic balance to each part of the power unit allow for a simulation of the power unit's efficiency. Furthermore, a parametric analysis is performed to establish how the relevant factors will affect the unit's functioning. The optimization algorithms are generated with the help of deep learning methods. It was found that the ratio of the compressor's pressure to the current density was the most crucial element in determining output power. Nanoparticles are used in fuel cells to enhance heat transfer and, thus, the generated power. Through optimization, one might find a product that is both the most cost-effective and energy-efficient option available. Artificial neural networks may be used as a mediator to help expedite the process of reaching optimum performance across several criteria. The optimal settings for the planned power plant are now being determined by studying the correlation between design factors and objective functions. Therefore, the second law's efficiency at its sweet spot was calculated at 61.8%. In the end, the system at its optimum point was found to have an exergo-environmental index of 0.436.

Energy-Efficient Small-Scale Ammonia Synthesis Process with Plasma-Enabled Nitrogen Oxidation and Catalytic Reduction of Adsorbed NOx.

Industrial ammonia production without CO2 emission and with low energy consumption is one of the technological grand challenges of this age. Current Haber-Bosch ammonia mass production processes work with a thermally activated iron catalyst needing high pressure. The need for large volumes of hydrogen gas and the continuous operation mode render electrification of Haber-Bosch plants difficult to achieve. Electrochemical solutions at low pressure and temperature are faced with the problematic inertness of the nitrogen molecule on electrodes. Direct reduction of N2 to ammonia is only possible with very reactive chemicals such as lithium metal, the regeneration of which is energy intensive. Here, the attractiveness of an oxidative route for N2 activation was presented. N2 conversion to NOx in a plasma reactor followed by reduction with H2 on a heterogeneous catalyst at low pressure could be an energy-efficient option for small-scale distributed ammonia production with renewable electricity and without intrinsic CO2 footprint.

3D FINITE ELEMENT ANALYSIS OF THE TILLAGE AND STRAW CUTTING PERFORMANCE OF A CURVED-EDGED TOOTHED DISC

The management of crop residues together with compacted soil under intensive farming systems requires highly efficient and well-adapted tools. The performance assessment of such tools requires proper definition of their technical designs as well as the tool-induced soil-straw dynamic interactions. Few studies have characterized the performance of toothed discs based on their design considerations and mechanical responses. This study evaluated the tillage forces, structural strength, straw-cutting performance, and tillage-depth uniformity of a curved-edged toothed disc in comparison to a straight-edged toothed disc. The design of the curved-toothed disc was inspired by the arc-shaped structure of the mole-rat's claw. 3D finite element analysis (FEA) was used to simulate the discs’ interactions with soil and straw. Field experiments were conducted to validate the FEA results. It was revealed that the curved disc reduced the tillage forces by up to 22.8%, and significantly reduced the stresses on the tool. The disc also achieved uniform tillage depths and improved the straw-cutting efficacy by up to 26.31%. Bionic curved cutting-profiles on toothed discs thus provide a structurally enhanced, energy-efficient option for effectively managing crop residues and improving seeding performance in no-till conservation farming.

Converter Design for High Temperature Superconductive Degaussing Coils

Detection of the magnetic signature of ships can be avoided by using a degaussing system; a set of on-board copper coils that compensates for the magnetic signature. High temperature superconductors (HTS) are currently investigated as a replacement for copper degaussing coils. By using HTS, we have to deal with higher currents and therefore with higher power supply losses. Also, large current leads are needed which introduces extra losses. This paper investigates different possible solutions to minimize these losses. Four H-bridge-based MOSFET topologies are presented that were designed to reduce the power supply and current lead losses. The first topology uses an H-bridge configuration so that the degaussing current can freewheel through the low-resistance MOSFETs. The second topology places the H-bridge inside the cryostat so that the current leads can be made smaller. The third topology includes a smoothing capacitor in the cryostat so that the current leads and input current are even smaller. The fourth topology uses a transformer so that the current leads can be eliminated. Measurements were done to determine the MOSFETs and capacitor performance in liquid nitrogen. The simulated losses of the four topologies are compared to determine the most energy-efficient option for supplying current to the HTS coils. It was found that by submerging multiple parallel MOSFETs in liquid nitrogen, the on-state resistance is decreased and the current supply can be made more efficient. Also, by placing a smoothing capacitor inside the cryostat, the current lead losses can be minimized significantly. The benefits of using a transformer do not outweigh the transformer losses.

Passive evaporative cooling through water-filled bricks: a preliminary investigation

Direct evaporative cooling is widely known to be an energy efficient air-conditioning option for arid and semi-arid climates. However, care must be taken on humidity ranges achieved indoors. Existing literature presents several options for integrating evaporative cooling within buildings for passive cooling applications. This work aims at expanding the current knowledge by focusing on the use of water-filled hollow bricks to implement evaporative cooling of air in contact with the brick’s surfaces. A prototype is built and experimentally characterized under controlled air velocity, air temperature and relative humidity conditions. Results on the psychrometric conditions achieved under different geometric arrangements (i.e., with one, two or three rows of four bricks each) are presented and discussed. Insights on likely building integration of the system for passive cooling purposes in farms and agriculture applications are eventually given.