Total Energy Output Research Articles

Utilizing waste compost to improve the atmospheric CO2 capturing in the rice-wheat cropping system and energy-cum‑carbon credit auditing for a circular economy

The study aimed to manage industrial wastes and create a module for using compost from waste for crops cultivation to conserve energy, reduce fertilizer use and Greenhouse gas (GHG) emissions, and improve the atmospheric CO2 capturing in agriculture for a green economy. In the main-plot, the experiment's results using NS3 found 50.1 and 41.8 % more grain yield and total carbon dioxide (CO2) sequestration in the wheat-rice cropping sequence, respectively, compared to the NS0. Moreover, the treatment CW + TV in the sub-plot observed 24.0 and 20.3 % higher grain yield and total CO2 sequestration than B + PS. Based on interaction, the NS3× CW + TV resulted in a maximum total CO2 sequestration and C credit of 47.5 Mg ha−1 and US$ 1899 ha−1, respectively. Further, it was 27.9 % lower in carbon footprints (CFs) than NS1 × B + PS. Regarding another parameter, the treatment NS3 observed a 42.4 % more total energy output in the main-plot than that of NS0. Further, in the sub-plot, the treatment CW + TV produced 21.3 % more total energy output than B + PS. Energy use efficiency (EUE) and net energy return in the interaction of NS3× CW + TV were 20.5 and 138.8 % greater than the NS0 × B + PS, respectively. In the main-plot, the treatment NS3 obtained a maximum of 585.0 MJ US$−1 and US$ 0.24 MJ−1 for energy intensity in economic terms (EIET) and eco-efficiency index in terms of energy (EEIe), respectively. While in the sub-plot, the CW + TV was observed at a maximum of 571.52 MJ US$−1 and US$ 0.23 MJ−1 EIET and EEIe, respectively. The correlation and regression study showed a perfect positive correlation between grain yield and total C output. Moreover, a high positive correlation (0.75 to 1) was found with all other energy parameters for grain energy use efficiency (GEUE). The variability in the wheat-rice cropping sequence's energy profitability (EPr) was 53.7 % for human energy profitability (HEP). Based on principal component analysis (PCA), the eigenvalues of the first two principal components (PCs) had been greater than two, explaining 78.4 and 13.7 % of the variability. The experiment hypothesis was to develop a reliable technology for safely using industrial waste compost, minimizing energy consumption and CO2 emissions by reducing chemical fertilizer input in agriculture soils.

Investigation on nano-absorbing precursors in the picosecond regime via the comparative study of HfO2/SiO2 and Ta2O5/SiO2 high-reflectivity coating damage

Laser-induced damage to the final reflective and diffractive optics limits the total output energy of petawatt laser systems with pulse durations ranging from a few hundred femtoseconds (fs) up to a few tens of picoseconds (ps). In this study, the laser damage to HfO2/SiO2 and Ta2O5/SiO2 multilayer dielectric high-reflectivity (HR) coatings induced by a 1053 nm laser with a pulse width of 8.6 ps was studied to investigate the nano-absorbing precursors in ps regimes. The HfO2/SiO2 HR coating exhibited stronger laser resistance than the Ta2O5/SiO2 HR coating. Flat-bottom pits, pinpoints, and funnel pits were the three typical damage morphologies for the experimental HR coatings. The damage to the HfO2/SiO2 HR coating was primarily dominated by flat-bottom pits, whereas dense pinpoints were the most significant damage for the Ta2O5/SiO2 HR coating. The nano-absorbing precursors introduced by the ion-assisted deposition process were proved to be the damage precursors that trigger pinpoints under a strong electric field intensity (EFI). The nano-absorbing precursors located in the second EFI peak of the SiO2 top layer induced the funnel pits. The funnel pits were expected to be the previous stage of the flat-bottom pits. After they grew along the upward-sloping crack and separated from the interface, the flat-bottom pits were formed. In addition, poor-binding interfaces promoted the formation of flat-bottom pits.

Wind Energy Conversion System Using Advanced Speed Control and Model-Based Loss Minimization

This paper presents a new optimization strategy for a stand-alone wind energy conversion system (WECS). The WECS is comprised of a variable-speed wind turbine (WT) with a vector-controlled self-excited induction generator (SEIG), a three-phase full-bridge converter, and a DC-bus containing the excitation capacitor, batteries, and a load. The control strategy incorporates an advanced model-based SEIG loss minimization and fuzzy-logic WT optimization. The latter utilizes a hedge-algebra speed controller to ensure fast response with practically no overshoot in the whole WT operating range, which cannot be achieved with the conventional proportional-integral (PI) controller. Consequently, the WT optimization time step is shortened and its convergence accelerated. The proposed SEIG loss minimization is based on the corresponding mathematical model that accounts for magnetic saturation and variable stray load and iron losses. Simultaneous optimization of the WT and SEIG is enabled, which results in greater total energy output compared to the successive WT-SEIG optimization. The proposed control strategy is run in real-time using the DS1103 board (dSpace) with a 1.5 kW SEIG driven by an emulated WT. It is experimentally evaluated over a wide WT operating range and compared with several competing strategies involving successive optimization, PI speed control and/or less elaborate SEIG models.

The sustainable treatment of chemical polishing wastewater under low-carbon economy: Pollutants removal, resource recovery and energy generation

A two-step approach, first by iron-air fuel cell and then by adjusting pH, was developed to treat chemical polishing wastewater, aiming at resource recovery and energy generation. The removal efficiencies of main pollutants, i.e. PO43− and Al3+ were 77.87% and 100%, the corresponding volumetric removal rates were 1.81 and 0.36 kg/(m3·d). The approach also showed removal abilities to COD, SS, NO3− and NH4+ with 77.87%, 100%, 22.96%, 16.67%, 100% and 61.53%, respectively. Nearly all of Al3+ was precipitated by PO43− in step I. Meanwhile, plenty of Fe2+ was accumulated for the following PO43− removal. In step II with pH being adjusted from 3.0 to 7.0, PO43− was supposed to be precipitated to form vivianite (Fe3(PO4)2·8H2O). By SEM-EDS, XRD, FITR and Mössbauer analysis, precipitate in step I was determined as AlPO4, while in step II it was mainly vivianite with a grade of 60%. The yield of AlPO4 and vivianite was 5.13 and 13.22 kg/t chemical polishing wastewater. Besides, electricity was generated by two-step approach. The total output energy was calculated as 0.33 kW h/t wastewater, with maximum output voltage at 0.19 V. This novel approach has potential economic advantages and will promote the sustainable development of chemical polishing wastewater treatment.

Techno-economic analysis of a multi-energy system for the co-production of green hydrogen, renewable electricity and heat

Renewable Multi-Energy Systems (MESs) are receiving growing attention since they represent a key step towards the decarbonization of electricity, thermal and transport sectors. This paper aims to investigate, from techno-economic perspectives, the performances of an off-grid MES that is designed for satisfying i) the electric and thermal loads of industrial utilities and ii) the energy requirements of novel refueling stations, able to supply electricity for battery electric vehicles fast charging and hydrogen for fuel cell electric vehicles. Wind power is used to meet the electric energy load and the hydrogen demand, while the thermal load is covered by burning biogas and by recovering useful heat inside the system. Two MES configurations, differing in terms of energy storage systems, have been sized by applying an optimization procedure, based on the minimization of the Net Present Cost (NPC), performed by using HOMER Pro software. The annual operations of the MES configurations have been analyzed and the levelized costs of electricity (LCOE), of hydrogen (LCOH) and of thermal energy (LCOT) have been estimated by considering the share of each produced energy stream with respect to the total energy output (or the energy served to the utilities). Results highlighted that the co-production of energy streams allows to significantly reduce their levelized costs with values that are in the range of 0.048–0.054 $/kWh (LCOE), 3.14–3.49 $/kg (LCOH) and 0.037–0.048 $/kWh (LCOT). These costs can be further reduced by connecting the MES to the grid and by delivering the excess of the electricity produced by the renewable source (on-grid configuration).

Exergoeconomic analysis and multi-objective optimization of a CCHP system based on SOFC/GT and transcritical CO2 power/refrigeration cycles

A CCHP (Combined Cooling, Heating and Power) system based on SOFC/GT (Solid Oxide Fuel Cell/Gas Turbine) and transcritical CO2 power/refrigeration cycles is proposed to efficiently provide cooling, heating and power for users under the principle of energy cascade utilization. The energy, exergy and exergoeconomic analysis is conducted to assess the effects of key parameters on the system’s thermal-economic performance. The simulation results demonstrate that the cooling, heating and net electricity outputs could reach 48.37 kW, 240.65 kW and 250.95 kW with a trigeneration cost per unit exergy of 37.12$/GJ, while the power generation and exergetic efficiencies could reach 62.65% and 62.27%. The annualized capital cost, O&M cost and fuel cost are 131 549$, 90 532$ and 162 375$, respectively. The NPV and payback period of the CCHP system are 502 824$ and 12.5 years. The effects of SOFC pressure, air flowrate, refrigerant flowrate and CO2 flowrate of the transcritical CO2 power cycle on the CCHP system characteristics are discussed. Furthermore, exergoeconomic and multi-objective optimization methods are used to find the final optimum operation condition with best results. A solution set in Pareto frontier with each fitness value superior to that of the design condition is obtained after optimization. Through the decision-making process, the total energy output and the exergy efficiency increase by 35.58 kW and 0.20%, respectively, while the unit exergy cost of trigeneration rises by 0.21$/GJ.

Green roof effects on urban building surface processes and energy budgets

Green roofs, as a nature-based solution, can be an effective tool for cities to improve the thermal environment, save energy, and combat climate change. However, it remains unclear how green roofs change the energy budget of urban building surfaces. Therefore, we modeled the surface energy balance of bare and green roofs based on experimental observations over a full calendar year to compare the physical transport processes of energy flows on bare and green roofs. Observational data were used to quantify the seasonal influence of green and bare roof surfaces on the energy flows and to document how roof vegetation alteres surface energy flow via physical and biochemical processes. On the bare roof, the incident solar radiation was partitioned largely into heating the building structure, with approximately 32.3% of the solar radiation absorbed. The green roof intercepted and consumed nearly 89% of incident solar radiation. The green roof effectively reduced convective energy by 6.7% compared to the bare roof, while longwave radiation emitted by green roof surfaces was reduced by 24.89 Wm−2. Evapotranspiration was the primary form of energy consumption on the green roof, accounting for 23.7% of the energy output. Results show that seasonal green roof evapotranspiration ranks as follows: winter > summer > spring > autumn. Reflected solar radiation, upward longwave radiation, and latent heat flux accounted for almost 95% of the total energy output of the green roof. Quantifying the energy balance impacts of green roofs on urban building surfaces improves the accuracy of urban climate models and supports adopting green roofs to foster sustainable urban development.

An investigation of spatial wind direction variability and its consideration in engineering models

Abstract. We propose that considering mesoscale wind direction changes in the computation of wind farm cluster wakes could reduce the uncertainty of engineering wake modeling tools. The relevance of mesoscale wind direction changes is investigated using a wind climatology of the German Bight area covering 30 years, derived from the New European Wind Atlas (NEWA). Furthermore, we present a new solution for engineering modeling tools that accounts for the effect of such changes on the propagation of cluster wakes. The mesoscale wind direction changes relevant to the operation of wind farm clusters in the German Bight are found to exceed 11∘ in 50 % of all cases. Particularly in the lower partial load range, which is associated with strong wake formation, the wind direction changes are the most pronounced, with quartiles reaching up to 20∘. Especially on a horizontal scale of several tens of kilometers to 100 km, wind direction changes are relevant. Both the temporal and spatial scales at which large wind direction changes occur depend on the presence of synoptic pressure systems. Furthermore, atmospheric conditions which promote far-reaching wakes were found to align with a strong turning in 14.6 % of the cases. In order to capture these mesoscale wind direction changes in engineering model tools, a wake propagation model was implemented in the Fraunhofer IWES wind farm and wake modeling software flappy (Farm Layout Program in Python). The propagation model derives streamlines from the horizontal velocity field and forces the single turbine wakes along these streamlines. This model has been qualitatively evaluated by simulating the flow around wind farm clusters in the German Bight with data from the mesoscale atlas of the NEWA and comparing the results to synthetic aperture radar (SAR) measurements for selected situations. The comparison reveals that the flow patterns are in good agreement if the underlying mesoscale data capture the velocity field well. For such cases, the new model provides an improvement compared to the baseline approach of engineering models, which assumes a straight-line propagation of wakes. The streamline and the baseline models have been further compared in terms of their quantitative effect on the energy yield. Simulating two neighboring wind farm clusters over a time period of 10 years, it is found that there are no significant differences across the models when computing the total energy yield of both clusters. However, extracting the wake effect of one cluster on the other, the two models show a difference of about 1 %. Even greater differences are commonly observed when comparing single situations. Therefore, we claim that the model has the potential to reduce uncertainty in applications such as site assessment and short-term power forecasting.

Analysis of Energy Use Efficiency and Greenhouse Gas Emissions of Lemon (Citrus lemonL.) Production in Turkey.

The purpose of this study was to determine the energy use efficiency and greenhouse gas emissions of lemon production. It was performed during the 2019-2020 production period in Turkey. The agricultural inputs and outputs used in lemon production were calculated to determine the energy use efficiency and greenhouse gas emissions. According to study findings, the energy inputs in lemon production were calculated respectively as 16,046.98 MJha-1 (55.43%) chemical fertilizers energy, 4168.93 MJha-1 (14.40%) chemicals energy, 2815.20 MJha-1 (9.72%) electricity energy, 2740.42 MJha-1 (9.47%) diesel fuel energy, 1864.80 MJha-1 (6.44%) irrigation water energy, 705.67 MJha-1 (2.44%) machinery energy and 610.20 MJha-1 (2.11%) human labour energy. Total input energy and output energy were calculated as 28,952.20 MJha-1 and 60,165.40 MJha-1, respectively. Energy use efficiency, specific energy, energy productivity and net energy values were calculated respectively as 2.08, 0.91 MJkg-1, 1.09 kgMJ-1 and 31,213.20 MJha-1. The consumed total energy inputs in lemon production can be categorized as 27.74% direct, 72.26% indirect, 8.55% renewable and 91.45% non-renewable. Total greenhouse gas emissions were calculated as 2650.96 kgCO2‑eqha-1 for lemon production, with the greatest share for nitrogen 950.62 kgCO2‑eqha-1 (35.86%). Based on the study findings, it was concluded that lemon production in 2019-2020 production season was profitable in terms of energy use efficiency (2.08). Greenhouse gas emission ratio (per kg) was calculated as 0.08. This study is important since there is no study on the energy balance and greenhouse gas emissions in lemon production in Muğla province, Turkey.

Hydrogen and Methane Production in a Two-Stage Thermophilic Anaerobic Digestion System by Co-Digestion of Kitchen Waste and Municipal Sewage Sludge with a High Solid Content

The thermophilic anaerobic fermentation of mixed materials for simultaneously producing biohydrogen and methane has become a research hotspot. In this study, thermally treated kitchen waste (KW) and municipal sewage sludge (MSS) were used as substrates for a thermophilic two-stage anaerobic digestion process. The effects on gas production performance were investigated in both the hydrogen-producing stage and methane-producing stage under different organic load rates (OLRs). The production rates, volume, removal rates, and energy yields of volatile solids (VS) were optimal under higher OLRs for both the hydrogen (OLR = 12.5 g VS/L·day) and methane stages (OLR = 5 g VS/L·day). These conditions also provided the optimal average removal rate and total energy yield of VS for the entire anaerobic fermentation system (65.4% and 30.9 kJ/g VS, respectively). Overall, the results demonstrate the superior efficiency of VS removal and hydrogen and methane production in a two-stage thermophilic anaerobic co-digestion of KW and MSS with a high solid content under proper material mix ratio and higher OLRs. This study provides the basis for material mass ratio, mixtures' pretreatment, and operation control for future pilot tests.

Synchrotron X-ray absorption spectroscopy and fluorescence spectroscopy studies of collagen type I-talc intercalated nanocomposites

We investigated the properties of collagen type I-talc intercalated nanocomposites using different techniques. Understanding the conformational changes of collagen induced by clay is noticeably lacking, which is pivotal for understanding the structure of collagen-clay hybrid nanocomposites. We aim to investigate the influence of talc clay minerals on the microstructure of collagen type I molecules. Our main goal is to understand the interaction between talc and collagen molecules and to elucidate the microstructure–property relation of intercalated hybrid nanocomposites. The FT-IR spectrum of collagen type I-talc confirmed the presence of collagen amide bands and talc silicate bonds. Also, the differential scanning calorimetry (DSC) result showed that the addition of talc to the matrix could increase the denaturation temperature (Td = 40.8 °C) compared to pure collagen (Td = 19 °C). The fluorescence intensity increased in collagen type I-talc nanocomposites, indicating that the interaction of talc with collagen chains in collagen type I-talc dispersion varies the micro-environment of the tyrosine amino acids in the collagen fibrils and its fluorescence. We also analyzed X-ray absorption spectroscopy (XAS) in total fluorescence yield (TFY) and total energy yield (TEY) modes of pure collagen and collagen type I-talc nanocomposites prepared at different concentrations of talc and at different temperatures (4 °C, 8 °C, and 14 °C). We have found that the synthesis conditions have a considerable effect on the local atomic environments of nitrogen, carbon, and oxygen atoms in collagen type I-talc nanocomposites. These results are of significance for developing new applications of talc and collagen-based biomaterials in different fields, such as cellular and molecular biology, and drug delivery that enhances the optical signals are needed.

Energy Budgeting and Carbon Footprints Estimation of Fodder Maize Varieties Sown under Different Nutrient Management Practices in Indo-Gangetic Plains of India

Inappropriate agricultural practices consume more input energy and emit higher greenhouse gases (GHGs) which cause global warming and climate change, thereby threatening environmental sustainability. To identify energy and carbon-efficient varieties and nutrient management practices, the present study was undertaken during the kharif season of 2018 and 2019 in a split-plot design with three varieties of fodder maize (African Tall, J-1006 and P-3396) and four nutrient management practices such as N0: Absolute control, N1: 100% recommended dose of fertilizers (RDF), N2: 75% RDF + plant growth promoting rhizobacteria (PGPR) + Panchagavya spray and N3: 50% RDF + 25% farmyard manure (FYM) + PGPR + Panchagavya spray). Results indicated that variety J-1006 and applying 75% RDF + PGPR + Panchagavya spray produced significantly higher dry fodder yield. Among the varieties, J-1006 recorded the highest total energy output (224,123 MJ ha−1), net energy (211,280 MJ ha−1), energy use efficiency (17.64), energy productivity (0.98 kg MJ−1), energy profitability (16.64), and lowest specific energy (1.03 MJ ha−1). Regarding nutrient management, 75% RDF + PGPR + Panchagavya spray fetched the highest total energy output (229,470 MJ ha−1) and net energy (215,482 MJ ha−1). However, energy use efficiency, energy productivity, and energy profitability were significantly higher with integrated nutrient management (N2 and N3) over 100% RDF. Concerning the carbon estimation, J-1006 resulted in a significantly higher carbon output (5479 kg CE ha−1), net carbon gain (5029 kg CE ha−1), carbon efficiency (12.46), carbon sustainability index (11.46), and significantly lower carbon footprint per unit yield (CFy) (131.3 kg CO2-e Mg−1). For nutrient management, the application of 75% RDF + PGPR + Panchagavya spray showed significantly higher carbon output (5609 kg CE ha−1) and net carbon gain (5112 kg CE ha−1). However, significantly higher carbon efficiency, carbon sustainability index, and lower CFy were reported with integrated nutrient management over 100% RDF. Overall, selecting the J-1006 variety and applying 75% RDF + PGPR + Panchagavya spray for fodder maize cultivation could be the most productive in terms of dry fodder production, energy, and carbon efficiency approach.

Optimization of a phase change material enhanced low-concentration photovoltaic/thermal module

This paper presents a simulation and optimization study of a nanoparticle-enhanced phase change material (PCM) assisted low-concentration photovoltaic/thermal (LCPV/T) module. An optical, electrical, and thermal model coupling finite element simulation is developed, with the thickness of the PCM, the mass fraction of nanoparticles in the heat transfer fluid and PCM, and the velocity of the heat transfer fluid as optimization parameters. To improve the efficiency of the optimization process, a response surface methodology is used to investigate the polynomial relationship between the parameters and module performance. The significance level and average error of each polynomial are found to be lower than 0.05 and 2.5%, respectively, indicating their statistical significance and accurate prediction of module performance. The fitting polynomials are used to optimize and analyze the module, and the results show maximum values of output thermal energy, output thermal exergy, output electrical energy/exergy, total output energy, and total output exergy of 573.11 W, 13.05 W, 110.40 W, 869.93 W, and 121.08 W, respectively. Comparison with the previously designed module revealed that the newly designed module demonstrated better electrical output performance, providing valuable guidance for the energy supply of zero-carbon buildings.

Standardizing Drip Irrigation Scheduling and NPK Levels on Economics and Energy use of Mentha (Mentha arvensis) Crop in Tarai Regions of Uttarakhand

To standardize the scheduling of drip irrigation and NPK levels on yield, economics and energy use of mentha crop, this field study was executed at G.B. Pant University of Agriculture and Technology, Pantnagar (Uttarakhand), India in the Norman E. Borlaug Crop Research center during the spring season of 2017. This experiment was performed in Factorial RBD having three replications. Three drip irrigation scheduling levels, 75%, 100% and 125% based on cumulative pan evaporation (CPE) loss with one control as a conventional flood and three NPK levels, 75%, 100% and 125% are taken as treatments. Experimental data conclude that drip irrigation CPE and NPK levels at 125% recorded the maximum fresh herbage (29699 and 30027 kg/ha), oil yield (260 and 274 kg/ha) and farm economics. Further the highest oil content was recorded with 125% NPK level (0.92%) but in case of CPE level, it is highest with 75% CPE (0.94%). Highest total energy input and output recorded with 125% CPE and 125% NPK levels, being 18674 and 18383 MJ/ha (input), 51988 MJ/ha and 55099 MJ/ha (output), respectively. Energy use efficiency and energy productivity increase with increase in irrigation levels and NPK dose, being highest with 125% CPE and 125% NPK dose. Again Drip irrigation and NPK level of 125% recorded maximum energy intensiveness of 0.24 MJ/Rs and 0.23 MJ/Rs and net energy gain of 33604 MJ/ha and 36425 MJ/ha, respectively.

Parametric aerodynamic and aeroelastic study of a deformable flag-based energy harvester for powering low energy devices

Extensive wind tunnel experiments were performed to find the optimal and most influential parameters for energy harvesting from piezoelectric membranes (thin elastic cantilevered plates), herein called flags. Four different piezoelectric flags were tested in conjunction with the seven different bluff bodies at various wind speeds and streamwise gaps between the bluff body and flag. Stiffness of the flags was also varied along with its length to assess the impact on harvested power. Various flapping modes are observed for different flags which correspond to the amount of harnessed power. The results revealed that altering the stiffness of flag can produce an increase of 29 and 31 times in power generation for long and short flags, respectively. It was found that the 120-degree bluff body produced the largest power with the capability to generate a strong wake region. Further analysis of the best performing flag (short and stiff) for various bluff bodies shows a remarkable increase of 661.2 % in generated power. This membrane shows rhythmic periodic flapping with higher modes of deformation in comparison to its other flag counterparts. These alternate flags show out-of-plane and twisting motion which wastes strain energy and causes a cancelation effect, reducing total energy output. The results show that in designing an efficient and reliable energy harvester, the flag’s stiffness and length as well as the shape of the bluff body play an important role. Furthermore, in comparison with the flutter phenomenon (i.e. a dynamic instability of the flag in the absence of a bluff body), the results with a bluff body demonstrate that higher energy generation can be achieved at a lower wind speed, thus paving the way for small and practical energy harvesting devices specifically in remote areas.

Sub-nanosecond, 41 mJ pulse energy, passively Q-switched Nd:YLF laser

A sub-nanosecond, diode-stack side-pumped, passively Q-switched Nd3+:YLF4/Cr4+:YAG Laser is reported in a compact cavity design, generating one pulse of 41 mJ with a pulse width of 894 ps, achieving a peak output power of 46 MW and beam quality M2 of 5.4 × 5.9 (HxV). The number of pulses in the pulse train could be adjusted from one pulse to ten pulses of 111 mJ total output energy and 23.7 % optical efficiency by adjusting the focus distance while maintaining sub-nanosecond pulse duration. This resonator can also be used for high-power simultaneous Q-switched laser emission at 1047 nm and 1053 nm.

Thermodynamic analysis of SOFC–CCHP system based on municipal sludge plasma gasification with carbon capture

To solve the environmental problems associated with municipal sludge incineration and landfilling, a combined cooling, heating, and power (CCHP) system integrating plasma gasification, solid oxide fuel cell (SOFC), gas turbine, supercritical carbon dioxide (S-CO2) cycle, and double-effect absorption refrigeration cycle (ARC) is proposed. Additionally, the CO2 generated in the system is captured to reduce the environmental impact. Energy, exergy, and sensitivity analyses of the developed system are conducted. Key parameters such as the SOFC temperature, SOFC pressure, and fuel utilization rate affecting the system performance are studied. The results show that net electrical efficiencies of the SOFC and the system are 41.96 % and 50.00 %, respectively. The exergy efficiency and comprehensive energy utilization rate of the system are 47.04 % and 87.59 %, respectively. The system can generate a power of 175.03 kW, cooling of 45.70 kW, and heating of 85.82 kW under the design conditions, accounting for 67.46 %, 21.23 %, and 11.31 % total energy output of system, respectively. The three main sources of exergy destruction of the system are the plasma gasification, SOFC, and supercritical CO2 cycle subsystems, accounting for 36.8 %, 12.2 %, and 10.7 % exergy destruction, respectively. The system performs the best when the SOFC temperature is 910 °C and the fuel utilization rate is between 0.85 and 0.90. The SOFC pressure has little effect on the system performance. In addition, the carbon capture rate of the system can reach 97.50 %. The CCHP system has high thermodynamic efficiency and hence can convert municipal sludge efficiently into clean energy; therefore, this study provides a new concept for resource treatment of urban sludge.

Energy yield comparison between monofacial photovoltaic modules with monofacial and bifacial cells in a carport

In the photovoltaic (PV) industry, module manufacturers have begun to install bifacial cells into monofacial modules because of their lower production costs relative to monofacial cells. This is linked mainly to a 65.3% reduction in rear aluminum paste consumption and the corresponding 0.5 cent/wafer cost reduction for M4 (161.7 × 161.7 mm2) size wafers. Therefore, this study compared the performance of monofacial PV modules with the monofacial cells as a reference group and bifacial cells as the test group to determine the cost reduction potential of the latter in terms of energy yield. Fifteen modules of each type were installed in a solar carport system on the Korean Peninsula and recorded irradiance and ambient and module temperature for one year. Throughout the year, irradiance and energy yield exhibited a strong linear correlation. The total annual energy yields of the monofacial and bifacial cells were 1,093.1 and 1,098.9 kWh/kWp, respectively. The energy yield of the bifacial module was 5.8 kWh/kWp (0.53%) higher than that of the monofacial module. Thus, monofacial modules with bifacial cells may be used in the PV industry to reduce cell production costs and levelized cost of electricity while enhancing energy yields and overall product performance in carport systems on the Korean Peninsula during all four seasons.

Research on the Structural Optimization of the Clean Energy Industry in the Context of Dual Carbon Strategy—A Case Study of Sichuan Province, China

As a major province for hydroelectric power in China, Sichuan Province has witnessed a great amount of seasonal characteristics in its hydroelectric power, endowing the clean energy industry in Sichuan with the characteristics of unstable supply in different seasons, strong power transmission capacity, and low production capacity of other non-fossil energy sources (except hydroelectric power). In this study, the mathematical model method was used to construct a structural optimization model of the clean energy industry in Sichuan Province, and to enable a quantitative analysis of the rationalization of the clean energy industrial structure in Sichuan Province. The results are proved from the cost-effectiveness of low carbon emission that hydroelectric power > wind power > photovoltaic power > natural gas > coal > oil. This study shall find the theoretical structure of the clean energy industry in Sichuan Province in 2030 with a prediction of Sichuan Province’s total future energy output and a constraint of its industrial structure model of clean energy. This paper suggests that Sichuan Province should give priority to the development of non-fossil energy sources, increase the development and utilization of power transmission channels in wet seasons, and develop clean energy and high energy consumption industries and the construction of pumped storage power stations, so as to reduce and avoid the waste of energy resources. It is also suggested that Sichuan Province should focus on developing clean energy with the capability of peak shaving, such as hydrogen energy and natural gas, while developing smart grid and long-distance transmission technology to strengthen energy conservation and emissions-reduced power generation. On this basis, Sichuan will focus on the development and utilization of natural gas as an alternative to high-carbon energy, with a view to optimizing its industrial structure of clean energy and helping China achieve the dual-carbon goals.

Resource use efficiencies, environmental footprints and net ecosystem economic benefit of direct-seeded double-season rice in central China

Intensive cropping systems with two or three harvests per year are vital to produce sufficient food for the growing population. Improvements in the sustainability of these systems are critical for global food security. Transplanted double-season rice (TPD), an important cropping system in China, is seriously threatened by various challenges such as labor shortage, poor resource use efficiency, high environmental footprint, and low profitability. These challenges could be potentially alleviated by shifting TPD to direct-seeded double-season rice (DSD). Due to the limited thermal energy, ultrashort-duration cultivars matured within 95 days have to be used in DSD in central China. However, it is unknown whether DSD with ultrashort-duration cultivars (DSDS) can improve resource use efficiency and reduce environmental costs compared with TPD in this region. This study aimed to compare the resource use efficiency (energy, water, labor, and fertilizer), carbon and nitrogen footprints, and net ecosystem economic benefit of DSDS and TPD with ultrashort-duration (TPDS) and medium-duration cultivars (TPDM). Results showed that total energy output was 222.0 GJ ha−1 in DSDS, which was comparable to that of TPDM but was significantly increased by 9.5% compared with TPDS. Compared with TPD (i.e. both TPDS and TPDM), the total energy input, labor input, water input, and nitrogen surplus in DSDS reduced by 16.9%, 53.2%, 36.8%, and 31.4%, respectively, leading to significant increases in energy use efficiency, labor productivity, water use efficiency, and nitrogen use efficiency. Furthermore, DSDS decreased direct CH4 and NH3 emissions and indirect carbon emission and reactive nitrogen losses from agronomic inputs, and consequently reduced carbon footprint by 28.6–42.7% and nitrogen footprint by 12.9–14.8% compared with TPD. As a result, the net ecosystem economic benefit in DSDS was significantly increased by 65.9–188.2% relative to TPD. These findings suggest that DSDS is a highly promising strategy to maintain high productivity with less resource inputs and environmental pressures but high economic benefits in central China.