Total Energy Output Research Articles

Maize intercropping in the milpa system. Diversity, extent and importance for nutritional security in the Western Highlands of Guatemala

We present an assessment of the extent, diversity, and nutritional contribution of the milpa through a quantitative analysis of data from a survey conducted in 989 small scale farm households in the Western Highlands of Guatemala (WHG). The milpa is a traditional agricultural system in which maize is intercropped with other species, such as common beans, faba beans, squashes or potatoes. Our study shows that more than two-thirds of the 1,205 plots recorded were under the milpa system, with a great diversity of crop combinations. As shown with the 357 plots for which specific yields were available, milpa systems present higher total productivity than monocropped maize, expressed as total energy yield of the harvested crops in the respective system, and were also better at providing the recommended daily allowances of fourteen essential nutrients, based on a Potential Nutrient Adequacy (PNA) indicator. Maize-bean-potato, maize-potato, and maize-bean-faba intercrops had the highest PNAs, and monocropped maize, the lowest. These results support the implementation of milpa systems tailored to different agro-ecologies in order to improve nutrition in the WHG and a variety of similar regions.

Comparative assessment of energy flow, carbon auditing and eco-efficiency of diverse tillage systems for cleaner and sustainable crop production in eastern India

Identification of the appropriate tillage production system having lower energy use and carbon-emission, and better crop productivity is becoming increasingly important to maintain the environmental sustainability. In the present study, a comprehensive system analysis was performed for four consecutive years (2016–2019) in three major agroecosystems of eastern India: eastern Indo-Gangetic plain, coastal agroecosystem and hill & plateau region. Six rice-based production systems with different levels of farm mechanization viz., a) fully mechanized tillage, b) partly mechanized tillage and c) traditional tillage were considered in the analysis. The main aim was to assess the energy flow and carbon-balance of diverse tillage production systems. Among the different sources of total input energy, chemical fertilizer accounted for the highest energy used in partly mechanized tillage (44%) and mechanized tillage (38%) followed by diesel, irrigation water, plant protection chemical, seed and electricity. Seed, human, animal energy and farmyard manure accounted for 21, 20, 16 and 16%, respectively, of the total energy input in traditional tillage. Maximum energy input (52161 MJ ha−1) was noted in mechanized tillage and minimum with traditional tillage (16879 MJ ha−1). Cropping systems followed in eastern Indo-Gangetic plain were more energy-intensive (50908 MJ ha−1) compared to coastal-ecosystem (27459 MJ ha−1). On an average, the total energy output in mechanized tillage (395245 MJ ha−1) were 0.3 and 2.4 times higher over partly mechanized and traditional tillage, respectively. Overall, the present results indicated that partly mechanized tillage and coastal agroecosystem were the most energy-efficient with an energy ratio of 8.88 and 9.81, respectively. Mechanized tillage was 0.24 and 1.66 times more carbon-intensive in comparison to partly mechanized and traditional tillage system. Mechanized tillage had higher carbon efficiency (3.75), carbon-sustainability index (2.75), carbon-footprint in spatial scales (4342 kg CO2eq. ha−1), but had 34% less carbon-footprint in yield scales compared to traditional tillage. Mechanized tillage showed 22 and 73% higher system productivity compared to partly mechanized and traditional tillage, respectively. Partly mechanized tillage had a 23% lower cultivation cost than mechanized tillage. Thus, the present study suggests that partly mechanize tillage was the most appropriate energy and carbon-efficient production system in eastern India.

Energy Use Efficiency of Mandarin Production: A Case Study from Adana Province

In this research was aimed to define the energy use efficiency of mandarin production for the 2017 production seasons in Adana province in Turkey. A survey data were compiled in 2017 and the farms were chosen according to the simple random sampling method and the survey were done to these farms. In order to define the energy use efficiency in the production of mandarin, a survey was done with 142 farmers in Adana province. According to results of research, human labour energy, machinery energy, chemical fertilizers energy, chemicals energy, farmyard manure energy, diesel fuel energy, irrigation water energy and lime energy were calculated as energy inputs. Mandarin fruit was calculated as output. In mandarin production, total input energy was calculated as 38,303.09 MJ ha−1 and total energy output was calculated as 59,850 MJ ha−1. The energy inputs in mandarin production were calculated respectively as chemical fertilizers energy 15,568.80 MJ ha−1 (40.65%), farmyard manure energy 5781 MJ ha−1 (15.09%), diesel fuel energy 5034.11 MJ ha−1 (13.14%), irrigation water energy 4095 MJ ha−1 (10.69%), machinery energy 3207.60 MJ ha−1 (8.37%), human labour energy 3039.18 MJ ha−1 (7.93%), chemicals energy 1518 MJ ha−1 (3.96%) and lime energy 59.40 MJ ha−1 (0.16%). The energy use efficiency, specific energy, energy productivity and net energy calculations were calculated in mandarin production respectively as 1.56, 1.22 MJ kg−1, 0.82 kg MJ−1 and 21,546.91 MJ ha−1.

Energy Efficiency of Continuous Rye, Rotational Rye and Barley in Different Fertilization Systems in a Long-Term Field Experiment

A goal in sustainable agriculture is to use fossil energy more efficiently in crop production. This 60-year-old experiment on a silt loam chernozem investigated effects of fertilization (unfertilized control, mineral fertilizer (NPK) and farmyard manure (FYM)) and rotation (continuous winter rye (CR), winter rye in rotation (RR), spring barley in rotation (SB) on diesel fuel consumption, total energy input (made of both direct and indirect inputs), crop yield, energy output, net-energy output, energy intensity, energy productivity and energy use efficiency. The input rates of fertilizer, herbicides and seeds were set constant during the experiment. Soil tillage was done with a moldboard plough with subsequent combined seedbed preparation and seeding. The mean calculated total energy input was highest in NPK with 11.28 GJ ha−1 and lowest in the unfertilized control with 5.00 GJ ha−1. Total energy input for FYM was intermediate with 6.30 GJ ha−1. With energetic consideration of NPK nutrients in FYM the total energy input increased to the level of NPK. The share of the fertilizer energy on the total energy input was 49% for NPK. Fertilization with FYM and NPK increased yield and energy output considerably, especially of CR and SB which attained about doubled values. Crop rotation also increased the yield and energy output, especially of unfertilized rye, which attained values increased by about 75%. Fertilization with FYM resulted in the highest energy efficiency as the net-energy output, the energy productivity and the energy use efficiency were higher but the energy intensity was lower compared to unfertilized controls and NPK. When the nutrients in FYM were also energetically considered, the energy efficiency parameters of FYM decreased to the level of the NPK treatment. Crop rotation increased the energy efficiency of winter rye compared to the monoculture.

Post-anaerobic treatability and residual biogas potential of digestate

Anaerobic digestion is a well-established method of stabilizing various organic wastes. However, effective and low-cost methods need to be developed and applied for digestate management to realize the full benefits of anaerobic digestion. The post-treatment of the digestate does not only reduce the greenhouse gas emissions due to storage or land application of digestates but also leads to an increase in the recovery of methane. The objective of this study was to quantify anaerobic treatability and biogas formation from the digestates of three full-scale anaerobic digesters fed with fruit processing and brewery wastewater and animal manure and food waste. Biochemical methane potential assays were conducted to determine the residual biogas production and yields achievable in the digestate samples investigated. The methane yields for the digestates investigated ranged between 0.055 and 0.147 l CH4/g VS which agree well with the relevant values from the literature. Anaerobic treatability assessment of digestates indicated chemical oxygen demand (COD), total solids (TS), and volatile solids (VS) removals of up to 62, 35, and 41%, respectively. Very low removals were observed for nitrogen and phosphorus as expected. The total potential energy yield and electricity production based on anaerobic digestion of the digestates of the three full-scale digesters are calculated as 35.3 GJ/day and 3.4 MWh, respectively. Moreover, a significant reduction in the greenhouse gas production will be achieved by anaerobically digesting the digestates of the three full-scale anaerobic digesters investigated in this study. If these findings are projected for all 127 biogas systems in Michigan, the significance of digestate treatment and valorization becomes clearer.

Energy Budgeting of Paddy-Pulse Cropping System in Bhadrak District of Odisha and Assessment of Emission from Paddy Straw Burning

Energy auditing of an existing production system helps to assess its energy-use and energy efficiency. The average input energy of paddy-black gram (PB) cropping system (19,862.01 MJ.ha-1) was higher than paddy-green gram (PG) (18,972.34 MJ.ha-1) cropping system in Bhadrak, Odisha. Harvesting and transport operation required highest operational energy for PG (35.57%) and PB (41.20%) farms; while, threshing and winnowing consumed the second highest input energy with 21.34% and 22.71% for PG and PB farms, followed by land preparation with 21.87% and 20.10% respectively. Linear regression data of PG and PB systems showed significant effect (p<0.05) of predictors with R2 values of 87.70% and 82.20% for total output energy and grain energy, respectively; confirming a good fit among the data. The output energy of PB cropping system was 13.91% higher than that of PG cropping system. The PB cropping system, with energy utilisation efficiency (EUE) of 10.31 and 11.82, was more energy-efficient than PG system with EUE of 9.32 and 11.01 for “NC” and “C” farms, respectively. The net energy return of PBC farm was highest with 2,04,505.31 MJ.ha-1. Amongst various pollutants emitted from paddy straw burning in Odisha; CO2 (5,51,296.0 Mg.yr-1), CO (13,102.72 Mg.yr-1), and TPM (4,908.80 Mg.yr-1) had highest share. The quantity of major GHGs (N2O, CH4) released into the atmosphere through paddy straw burning was estimated as 26.43 Mg.yr-1 and 453.12 Mg.yr-1, respectively. Use of straw baler can prevent straw burning, and reduce emission from paddy fields by 2805.54 kg.ha-1 of CO2 and 66.69 kg.ha-1 of CO, 5.96 kg.ha-1 of NOx, 24.98 kg.ha-1 of TPM. Alternatively, use of mulcher can also reduce emission from paddy fields by 2924.44 kg.ha-1 of CO2 and 69.51 kg.ha-1 of CO, 6.21 kg.ha-1 of NOx, 26.04 kg.ha-1 of TPM. The cost of operation of a baler and mulcher were 8,617.0 ₹ ha-1 and 2,543.0 ₹ ha-1, respectively. Input energy and energy saved in paddy fields by baler were 820.0 MJ.ha-1 and 16,928.0 MJ.ha-1; and 266.0 MJ.ha-1 and 24,458.0 MJ.ha-1 by mulcher, respectively.

Energy and environmental footprints of flywheels for utility-scale energy storage applications

Flywheel energy storage systems are feasible for short-duration applications, which are crucial for the reliability of an electrical grid with large renewable energy penetration. Flywheel energy storage system use is increasing, which has encouraged research in design improvement, performance optimization, and cost analysis. However, the system's environmental impacts for utility applications have not been widely studied. Evaluating the life cycle environmental performance of a flywheel energy storage system helps to identify the hotspots to make informed decisions in improving its sustainability; to make reasonable comparisons with other energy storage technologies, such as pumped hydro, compressed air, electro-chemical batteries, and thermal; and to formulate environmental policy in the energy sector. In this study, an engineering principles-based model was developed to size the components and to determine the net energy ratio and life cycle greenhouse gas emissions of two configurations of flywheel energy storage: steel rotor flywheel and composite rotor flywheel. The net energy ratio is a ratio of total energy output to the total non-renewable energy input over the life cycle of a system. Steel rotor and composite rotor flywheel energy storage systems were assessed for a capacity of 20 MW for short-duration utility applications. A consistent system boundary was considered for both systems with the life cycle stages of material production, operation, transportation, and end-of-life. Electricity from solar and wind was considered separately in the operation phase. The net energy ratios of the steel rotor and composite rotor flywheel energy storage systems are 2.5–3.5 and 2.7–3.8, respectively. The corresponding life cycle greenhouse gas emissions are 75.2–121.4 kg-CO2eq/MWh and 48.9–95.0 kg-CO2eq/MWh, depending on the electricity source. The net energy ratio and greenhouse gas emissions are highly influenced by the operation phase, which includes charging and standby modes. Uncertainty analysis shows that the life cycle greenhouse gas emissions are most sensitive to the solar, wind, and grid electricity mix emission factors. The results of this study will help to understand the carbon footprints of the various utility-scale energy storage systems.

Optimal Placement of Wind Turbines in Wind Farm Layout Using Particle Swarm Optimization

An optimal geographical location of wind turbines can ensure the optimum total energy output of a wind farm. This study introduces a new solution to the optimization of wind farm layout (WFLO) problem based on a three-step strategy and particle swarm optimization as the main method. The proposed strategy is applied to a certain WFLO to generate highly efficient optimal output power. Three case scenarios are considered to formulate the non-wake and wake effects at various levels. The required wind turbine positions within the wind farm are determined by the particle swarm optimization method. The rule of thumb, which determines the wind turbine spacing, is thoroughly considered. The MATLAB simulation results verify the proposed three-step strategy. Moreover, the results are compared with those of existing research works, and it shows that the proposed optimization strategy yields a better solution in terms of total output power generation and efficiency with a minimized objective function. The efficiencies of the three case studies considered herein increase by 0.65%, 1.95%, and 1.74%, respectively. Finally, the simulation results indicate that the proposed method is robust in WFLO design because it further minimizes the objective function.

EXPERIMENTAL STUDIES OF A MODEL FOR OPTIMIZING THE PORTFOLIO OF A PROJECT-ORIENTED ORGANIZATION BASED ON THE ENTROPY CONCEPT

The subject of the research is the optimization of the composition of the project portfolio based on the entropy concept. The aim of the study is to experimentally test the model for optimizing the portfolio of a project-oriented organization and substantiate its applicability in practice in management processes to ensure their effectiveness. Research objectives: forming a model taking into account the accepted value of the organization; formation of initial data on the organization and alternative projects; portfolio optimization by model and interpretation of results. Research methods: system analysis, functional analysis, operations research. Results. A model has been developed for forming a portfolio structure from projects of two categories – operational and development; the optimization criterion is to minimize the discrepancy between the desired and actually provided value of the organization. The restrictions take into account the maximum allowable energy limit and the minimum allowable value limit. As a result of the study, the applicability and adequacy of the model for optimizing the portfolio structure of a project-oriented organization were substantiated. The model makes it possible to obtain solutions on the optimal structure of a portfolio of projects in terms of its value under given resource constraints (in the form of a share of total energy and output energy) and energy entropy. The studies substantiated the possibility of adjusting the model in terms of the optimization criterion (maximizing value, minimizing energy entropy) and adding restrictions on the maximum permissible border of information entropy and energy efficiency. Conclusions. The model under consideration is characterized by wide practical application, taking into account its possible adjustment without changing the basic essence, taking into account the specifics of a particular field of activity or organization. The practical use of the main indicators of the entropy concept - information entropy, temperature, energy entropy, which characterize the state of organizations, allowing to identify hidden problems before they are reflected on the traditional indicators of organizational performance is demonstrated. Taking this into account, the structure of the project portfolio is being formed within the framework of the considered approach.

Energy and exergy analysis of solar photovoltaic thermal system: experimental and numerical verification

In this study, the electrical and thermodynamic performance of a flat-plate liquid PV/T system was investigated, and the experimental results were verified with a numerical model implemented. The simulation analyses showed that the increasing inlet and ambient temperature had a negative effect on thermal efficiency and the highest thermal efficiency was obtained at 800 W/m2 solar radiation. The optical efficiency of the experimental system was verified with the simulation and reported as 45.8% and 47.9%, respectively. Hourly electrical, thermal, and total energy efficiencies obtained hourly on a daily basis were calculated and varied between 12-13.8%, 36.1-45.2%, and 49.1-58.4% respectively on daily basis. The hourly exergy analyses were also carried out and the results showed that the exergy efficiencies changed between 13.8-14.32%. The annual total thermal and electricity energy outputs were calculated as 1,912 kWh and 556.8 kWh respectively.

Analysis of the Generated Output Energy by Different Types of Wind Turbines

This study intends to analyse the generated individual output energy by different types of wind turbines. Focusing on estimating the total energy output generated by a wind farm utilizing three distinct wind turbines, Siemens Gamesa SG 3.4-132, Vesatas HTq V126, and Lagerwey L100, with rated powers of 3.465MW, 3.45 MW, and 2.5 MW respectively. Sixty turbines of each type will be installed at the elevations of 97 m, 87 m, and 99 m consecutively. For the purpose of the study, the Sorochi Gory region was chosen as an eligible location to the farm, due to its physiographic location and desirable forestry. A virtual experiment will be conducted, by testing different possible wind turbines configurations, and calculating their gross energy output, considering the output wind speed is in the ideal case, while the output energy includes the wake effect, using (WindFarmer analyst software). Thereupon, the results will be presented, including the optimal wind turbine configuration for the wind farm, in terms of efficiency, stability, and economy wise. Doi: 10.28991/HEF-2020-01-04-03 Full Text: PDF

Efficiency of Switchgrass (Panicum virgatum L.) Cultivation in the Ukrainian Forest-Steppe Zone and Development of Its New Lines

Background: Switchgrass (Panicum virgatum L.) is a promising C4-photosynthetising perennial grass and an important energy crop. It is resistant to drought, cold and winter frost, endures flooding and shows high performance at minimal energy consumption for cultivation. Methods: The purpose of the work was to develop and introduce high-yielding genotypes of switchgrass and develop effective cultivation technologies for the Forest-Steppe zone of Ukraine. The objective of the study was to evaluate the introduction potential of switchgrass, to establish biologically productive parameters and energy values of different genotypes and the effectiveness of cultivation techniques in the specific geo-climatic zone of Ukraine. To achieve the objectives, a wide range of introductory, biological-morphological, breeding-biotechnological, and agronomic methods have been used. Results: The gene pool of P. virgatum was collected (33 accessions), ten of which have been investigated, including both introduced genotypes and newly developed breeding lines. The bio-morphological, ecological features, the biochemical composition of plants have been evaluated. The productivity of the above-ground biomass and seeds, as well as the energy value of plants, has been evaluated. High-performance forms with specified yield parameters, biomass sugars, total energy and biofuel output per unit area have been determined. Conclusion: A new variety of P. virgatum (cv. Zoriane) has been introduced for cultivation. Among the accessions of newly developed genotypes, the most productive lines have been identified. New efficient technologies have been developed to increase the yield potential of switchgrass as a source of raw materials for biofuel production.

Study on Energy Use Efficiency for Sugarcane Crop Production Using the Data Envelopment Analysis (DEA) Technique

This study aimed to study the energy use pattern of sugarcane crops, optimize the energy use pattern of an inefficient farmer, and study the opportunities for input energy saving in sugarcane cultivation. The input–output energy in sugarcane cultivation was audited by collecting data from 61 decision-making units (DMUs) using a face-to-face interview with sugarcane growers in Maharashtra state (India). Technical, pure technical, and scale efficiencies for farmers were calculated using the Charnes–Cooper–Rhodes and Banker–Charnes–Cooper models of the data envelopment analysis technique. The average total input (EI) and output (Eo) energy for sugarcane cultivation were 146.15 + 11.16 GJ ha−1 and 961.02 ± 83.73 GJ ha−1, respectively. The energy share of sugarcane and sugarcane trash in the total output energy was 843.18 ± 60.4 GJ ha−1 and 91.48 ± 6.5 GJ ha−1, respectively. The energy ratio (ER) and net energy gain of sugarcane cultivation were 6.57 ± 0.57 and 814.8 ± 69.9 GJ ha−1, respectively. The average technical efficiency, pure technical efficiency, and scale efficiency for sugarcane cultivation were 0.74 ± 0.03, 0.97 ± 0.006, and 0.76 ± 0.03, respectively, in the study region. The scope for energy saving in sugarcane cultivation was observed to be 19.82% as compared with the actual energy required. If the recommendation of energy saving is followed by inefficient DMUs, a total input energy of 28.98 GJ ha−1 can be saved, maintaining a constant output level of sugarcane yield.

Energy use efficiency in soybean crops in different regions of Brazil

The soybean crop in Brazil has been growing in area and productivity in recent years and the analysis of its energy efficiency is very important to guarantee the sustainability of the production system. Assessment of energy efficiency (EE) enables the evaluation of the sustainability of agrosystems, as well as decision-making regarding the reduction in production costs and negative environmental impacts. In this context, the objective of this study was to assess energy efficiency of soybean in different regions of Brazil. For this purpose, 29 areas of soybean across the major producing states were assessed. Energy inputs and outputs of agricultural operations and/or agricultural inputs were calculated by multiplying the amount used by their calorific value or energy coefficient at each stage of production. Energy efficiency was calculated as the ratio between the total output energy and the total input energy during the production process. For every MJ of energy consumed in the production of soybean crop, 6.1; 6.7; 7.1 and 7.2 MJ of energy were produced in the form of grain, respectively in the areas assessed in the Midwest, northeast, southeast and south regions of Brazil. Generally, the main energy expenditure on soybean cultivation in different regions of Brazil was with fertilizers, seeds and herbicides. The adverse weather conditions of the year / harvest evaluated in the south-central region of Brazil resulted in low soybean yields and consequently resulted in lower energy efficiency in these regions. The evaluation of energy efficiency in soybean crops to be representative must be carried out in different regions and edaphoclimatic conditions.

Sequential biofuel production from seaweeds enhances the energy recovery: A case study for biodiesel and bioethanol production

SummaryIn the present study, eight seaweeds (five red, two brown and one green) were collected and evaluated for dual biodiesel and/or bioethanol production. The highest significant lipid and carbohydrate contents were recorded in the brown seaweed Dilophus fasciola (4.92 and 37.97%dw, respectively). Three routes were investigated, namely R1 and R2 for direct production of biodiesel and bioethanol, respectively, from the whole biomass, in addition to R3 representing the sequential biodiesel and bioethanol production. D. fasciola showed a biodiesel yield of 35.04 mg g−1 dw, composed mainly of C16‐C18 fatty acids with a high saturation degree. All biodiesel characteristics complied with the recommended values of international standards. The maximum reducing sugar content (37.2 g L−1) and bioethanol productivity at 72 hours (0.165 g L−1 h−1) were recorded in the lipid‐free biomass (R3), which were 16.3% and 27.9%, respectively, higher than that of R2. Therefore, a maximum estimated total energy output of 9.96 MJ kg−1 was recorded in R3, which represented 6‐times and 28.3% higher than R1 and R2, respectively.

Energy Efficiency and Economic Analysis of Walnut Production in Turkey

Turkey is one of the countries that is the gene center and the homeland of walnuts. The purpose of the study was to determine the energy uses of walnut production in Turkey. In the study, the energy efficiency of walnut production, net energy, energy productivity, and specific energy were examined. In addition, the benefit-cost ratio, the use of direct and indirect energy, renewable and non-renewable energy were determined. Data was obtained from walnut producers in the Istanbul province of Turkey by using a survey. Surveys were performed with 48 walnut producers. Total energy input and total energy output of the surveyed orchards were calculated as 12,605 MJ ha−1 and 23,300 MJ ha−1 respectively. The energy use efficiency was calculated as 1.85 for the walnut production. While specific energy was calculated as 5.95 MJ kg−1 energy productivity was calculated 0.17 kg MJ−1 in the study. According to economic analysis, it was determined that the walnut producers had 4850 US$ ha−1 net return per year. The benefit-cost ratio was calculated as 1.51. As a result of the study, it was determined that the walnut production was preferable in the region.

Biomass, Seed and Energy Yield of Cynara cardunculus L. as Affected by Environment and Season

Cynara cardunculus is a perennial plant that adapts well to Mediterranean climate conditions. The possibility of cultivating C. cardunculus with low or zero input and in low productivity or marginal lands makes it one of the most promising crops for bioenergy production in the Mediterranean areas. The objective of the research was to study the effects of two marginal and contrasting southern Italian environments (plain, 42 m a.s.l. and hilly area, 419 m a.s.l.) during a three-year period on biomass, seed, energy yield, and oil composition of two genotypes of C. cardunculus (cultivated cardoon and wild cardoon). When compared to the plain, plants that were grown in the hills gave higher biomass yield (10.9 vs. 9.7 t DM ha−1 year−1), higher seed yield (0.46 vs. 0.44 t DM ha−1 year−1) and, consequently, higher total energy yield (190 vs. 172 GJ ha−1 year−1), attributable to higher average annual rainfall (680 vs. 565 mm year−1). The season, although only evaluated for three years (short cycle), showed a different effect based on the genotype, highlighting a greater over-time production constancy of wild cardoon (though less yielding) as compared to cultivated cardoon. Oil yield and composition were only slightly affected by environment and genotype. Overall, the results of this research suggest using C. cardunculus in marginal hilly areas, where, in addition to the production of bioenergy, it may represent a good chance to fight erosion and improve soil fertility, without competing with food crops.

Effects of microwave irradiation on impact comminution and energy absorption of magnetite ore

The severe mechanical wear and high-energy consumption in the comminution process of high hardness iron ore have always restricted the efficient and economic development of an enterprise. On the basis of the basic principle that microwave irradiation can induce rock damage, the magnetic ore specimens were subjected to microwave heating treatment with different heating paths and cooling paths; the uniaxial impact comminution test was conducted by the drop hammer impact equipment. This study analyzed the effect of the heating and cooling paths on the crack propagation process, dynamic mechanical strength, and energy consumption of magnetite ore. The results show that microwave irradiation causes obvious microwave-induced cracks in ore, and in the subsequent impact cracking process, the new cracks gradually penetrate the microwave-induced cracks and form the macroscopic fracture surface. With the increase of irradiation power and time, the ore dynamic strength decreased, and the absorption energy increased. Therefore, increasing the total output energy of microwave can effectively alleviate the mechanical wear and enhance the comminution effect of ores. Among the factors that affect the mechanical properties and absorption energy of ore, power has a higher priority than time. With the increase in the heat exchange rate between the ore and the external environment, the ore comminution becomes more intense, leading to the best comminution effect of ores. The research results have an important reference for the practical application of microwave irradiation technology in hard rock comminution.

A combined theoretical and experimental performance analysis of a grid-tied photovoltaic system in semi-arid climate : a case study in Ghardaia, Algeria

ABSTRACT Both theoretical study, experimental validation, and outdoor performance assessment of a single grid-connected photovoltaic plant installed on the roof of the car parking located in Renewable Energy Applied Research Unit (URAER), Ghardaia, southern of Algeria have been carried out in this paper. The plant is made up of 16 micro-amorphous modules of 125 Wp and one SMA sunny boy inverter of 3 kW. The results presented were based on experimental data recorded after about three and a half years; from May 18, 2015 to December 31, 2018. The first part of this work, modeling, and validation by the experimental data of photovoltaic array (DC side) based on the Linear Reoriented Coordinates Method (LRCM) and grid-connected inverter (AC side) based on the model developed at Sandia National Laboratories. The results show a good agreement between measured and calculated data (current, voltage, power, and efficiency). The second part of the work is to investigate the operational performance and efficiency of the PV plant from the measured daily power generation and weather as recommended in the International Electro Technical Commission IEC 61724. The performance-computed parameters are based on monthly average daily values, including DC and AC energy generated, reference yield array yield final yield temperature losses PV, inverter and system efficiency, capacity factor performance ratio, and others as defined in IEC. The total output energy PV installation generated during the measured period was of 12944, 44 kWh and the total energy output delivered into URAER internal grid was 12292, 16 kWh. Furthermore, the average daily array yield, final yield, and reference yield varied from a minimum to a maximum value of 2.62 kWh/kWp-6.41 kWh/kWp, 2.51kWh/kWp-6.29kWh/kWp, and 2.39kWh/kWp-6.06kWh/kWp, respectively. In addition, the average daily PV module efficiency, system efficiency, and inverter efficiency varied from a minimum to a maximum value of 8.21-9.00%, 7.56-8.35%, and 94-95%, respectively. The array capture losses, system losses, capacity factor, and performance ratio varied from a minimum to a maximum value of 0.053 kWh/kWp-0.42 kWh/kWp, 0.1206 kWh/kWp-0.31kWh/kWp, 10.30%-26.10%, 79.13%-82.52%, respectively. These results highlight the relatively good performance of PV plants installed in the southern region of Algeria.

Productivity, profitability, energetics and nutrient uptake of post kharif rice-cowpea preceded by rice varieties grown under different establishment methods

A field experiment was conducted at Agronomy Main Research Farm, Department of Agronomy, College of Agriculture, OUAT, Bhubaneswar, Odisha during of 2014-15 and 2015-16 to evaluate the productivity, profitability, energetics and nutrient uptake of post kharif rice-cowpea preceded by rice varieties grown in kharif under different establishment methods. The treatments comprising three establishment methods (Direct Seeded Rice, Non Puddled Transplanted Rice and Puddled Transplanted rice) and three variety/hybrids of rice (‘Arize 6129’, ‘Arize 6444’ and ‘Swarna’) were tried in split plot design with three replications. The Puddled Transplanted Rice (PTR) recorded the maximum rice equivalent yield (8.43 t ha-1) for post kharif rice-cowpea which was at par with NPTR (8.34 t ha-1) and the minimum of 6.85 t ha-1 was recorded under Direct Seeded Rice (DSR). The total cowpea biomass yield was the maximum under NPTR and the minimum under DSR. The maximum gross return of 1,20,380/-, total energy output of 2,25,045 MJ ha-1 and energy use efficiency of 8.59 was recorded under PTR, NPTR and DSR, respectively. Uptake of nitrogen was higher under NPTR while phosphorus and potassium uptake values were higher under PTR. The rice cultivar/hybrids grown in kharif had no significant effect on yield, economics, energetics and uptake of nutrient, but hybrid ‘Arize 6129’ recorded higher mean values than hybrid ‘Arize 6444’ and cv. ‘Swarna’.