bluuebunny/crossref_metadata_2025 huggingface dataset:
Coproduction of Furfural, Phenolated Lignin and Fermentable Sugars from Bamboo with One-Pot Fractionation Using Phenol-Acidic 1,4-Dioxane
Authors: Ji Li , Li Pengfei , Lei Fuhou , Song Xianliang , Jiang Jianxin , Wang Kun
Published: October 2020

A one-pot fractionation method of Moso bamboo into hemicellulose, lignin, and cellulose streams was used to produce furfural, phenolated lignin, and fermentable sugars in the acidic 1,4-dioxane system. Xylan was depolymerized to furfural at a yield of 93.81% of the theoretical value; however, the prolonged processing time (5 h) led to a high removal ratio of glucan (37.21%) in the absence of phenol. The optimum moderate condition (80 °C for 2 h with 2.5% phenol) was determined through the high fractionation efficiency. Consequently, 77.28% of xylan and 84.83% of lignin were removed and presented in the hydrolysate, while 91.08% of glucan was reserved in the solid portion. The formation of furfural from xylan remained high, with a yield of 92.92%. The extracted lignin was phenolated with an increasing content of phenolic hydroxyl. The fractionated lignin yield was 51.88%, which suggested this could be a low-cost raw material to product the activated carbon fiber precursor. The delignified pulp was subjected to enzymatic hydrolysis and the glucose yield reached up to 99.03% of the theoretical.
Automatic Optimization of the Compensation Networks of a Wireless Power Transfer System
Authors: Bertoluzzo Manuele , Giacomuzzi Stefano , Sieni Elisabetta
Published: October 2020

This paper addresses the optimization of the compensation networks of a wireless power transfer system. Optimization is performed by means of a genetic algorithm that looks for the reactances of the elements of the compensation networks that maximize the power transfer efficiency and the power transferred to the load. In addition, the algorithm selects the solutions that are less sensitive to the difference between the theoretical and actual reactances. The last part of the paper describes the prototypal setup used for the tests and supports the theoretical findings by reporting experimental results.
Carrier Transmission Mechanism-Based Analysis of Front Surface Field Effects on Simplified Industrially Feasible Interdigitated Back Contact Solar Cells
Authors: Li Xiaoxuan , Liu Aimin
Published: October 2020

Interdigitated back contact (IBC) n-type silicon solar cells with a different front surface layer doping concentration were fabricated and studied and the influence of the front surface doping level was analyzed via simulation (PC1D). The IBC cells were processed by industrially feasible technologies including laser ablation and screen printing; photolithography was not used. A maximum efficiency of up to 20.88% was achieved at an optimal front surface field (FSF) peak doping concentration of 4.8 × 1019 cm−3 with a sheet resistance of approximately 95 Ω/square, corresponding to Jsc = 40.05 mA/cm2, Voc = 671 mV and a fill factor of 77.70%. The effects of the front surface doping level were studied in detail by analyzing parameters related to carrier transmission mechanisms such as minority carrier concentration, minority carrier lifetime and the saturation current density of the FSF (J0e). The influence of the front surface recombination velocity (FSRV) on the performance of IBC solar cells with different FSF layer doping concentrations was also investigated and was verified by examining the variation in the minority carrier density as a function of the distance from the front surface. In particular, the impact of the FSF doping concentration on the Jsc of the IBC cells was clarified by considering carrier transmission mechanisms and the charge-collection probability. The trends revealed in the simulations agreed with the corresponding experimental data obtained from the fabricated IBC solar cells. This study not only verifies that the presented simulation is a reasonable and reliable guide for choosing the optimal front surface doping concentration in industrial IBC solar cells but also provides a deeper physical understanding of the impact that front surface layer doping has on the IBC solar cell performance considering carrier transmission mechanisms and the charge-collection probability.
Energy Efficiency Package for Tenant Fit-Out: Laboratory Testing and Validation of Energy Savings and Indoor Environmental Quality
Authors: Mathew Paul , Regnier Cindy , Shackelford Jordan , Walter Travis
Published: October 2020

Approximately 40% of the total U.S. office floor space of 1.5 billion sq.m (16 billion sq.ft.) is leased space occupied by tenants. Tenant fit-out presents a key opportunity to incorporate energy efficiency within the real estate business cycle. We designed a package of energy efficiency measures tailored to the scope of a tenant fit-out. This tenant fit-out package (TFP) includes advanced lighting and heating, ventilating and air-conditioning (HVAC) controls as core measures, with ceiling fans, automated shading, and plug load controls as additional optional measures. We conducted laboratory testing of six configurations of the package to evaluate energy savings, indoor environmental quality, and identify installation, commissioning, and operational issues. Combined savings for HVAC, lighting, and plug loads ranged from 33–40%. Lighting savings ranged from 69–83%, and HVAC savings from 20–40%. The laboratory testing also revealed some minor but tractable challenges with installation and commissioning of HVAC controls. Overall, the results demonstrate that significant savings can be realized in existing office buildings by incorporating relatively low-risk, proven measures at the time of a tenant fit-out.
Estimating the Energy Demand and Growth in Off-Grid Villages: Case Studies from Myanmar, Indonesia, and Laos
Authors: Pandyaswargo Andante Hadi , Ruan Mengyi , Htwe Eiei , Hiratsuka Motoshi , Wibowo Alan Dwi , Nagai Yuji , Onoda Hiroshi
Published: October 2020

Under the Sustainable Development Goals (SDGs), the world has pledged to “leaving no one behind”. Responding to goal No. 7 on the agenda, efforts to provide modern energy to all the world population must be pushed forward. This is important because electrification in the rural area can indirectly support opportunities for social and economic development resulting in an acceleration of the eradication of poverty. The research goal of this study is to contribute insights about the scale of energy demand in unelectrified villages in the Southeast Asian countries and to discuss some factors that might influence the energy demand growth. This is done by making projections based on surveys and interviews, including a time-use survey, in three off-grid villages located in Myanmar, Indonesia, and Laos. Our analysis presented the living condition, highlight the types of energy sources, how, and in what rhythms people use energy on a daily basis in those villages. The demands in each case study villages were then projected based on several constructed scenarios. It was found that the factors of household size, proximity to the city, climate, and topography may influence the present and future growth of energy demands in the villages. The estimated energy demand may be useful for project managers to design a pilot off-grid energy system project in a similar environment and pointed out important factors to consider when formulating off-grid energy policies in the region.
Calorific Power Improvement of Wood by Heat Treatment and Its Relation to Chemical Composition
Authors: Domingos Idalina , Ayata Umit , Ferreira José , Cruz-Lopes Luisa , Sen Ali , Sahin Sirri , Esteves Bruno
Published: October 2020

Chemical composition influences the calorific power of wood, mainly due to the calorific power of structural compounds and extractives. Heat treatment changes the chemical composition of treated wood. This work studies the relationship between chemical composition and calorific power improvement by heat treatment. Samples were heat-treated by the ThermoWood process ® for 1 h and 2 h. High heating value (HHV) and chemical composition; lignin, cellulose, hemicelluloses and extractives in dichloromethane, ethanol, and water were determined. The HHV of untreated wood ranged between 18.54–19.92 MJ/kg and increased with heat treatment for all the tested species. A positive linear correlation was found between HHV and Klason lignin (R2 = 0.60). A negative trend was observed for holocellulose, cellulose, and hemicelluloses content against HHV, but with low determination coefficients for linear regression. The best adjust for polysaccharides was found for hemicelluloses content. A positive correlation could be found for dichloromethane extractives (R2 = 0.04). The same was obtained in relation to ethanol extractives with R2 = 0.20. For water and total extractives, no clear positive or negative trends could be achieved. The results showed that the HHV of wood increased with heat treatment and that this increase was mainly due to the increase in lignin content.
A Single Scalable LSTM Model for Short-Term Forecasting of Massive Electricity Time Series
Authors: Alonso Andrés M. , Nogales Francisco J. , Ruiz Carlos
Published: October 2020

Most electricity systems worldwide are deploying advanced metering infrastructures to collect relevant operational data. In particular, smart meters allow tracking electricity load consumption at a very disaggregated level and at high frequency rates. This data opens the possibility of developing new forecasting models with a potential positive impact on electricity systems. We present a general methodology that can process and forecast many smart-meter time series. Instead of using traditional and univariate approaches, we develop a single but complex recurrent neural-network model with long short-term memory that can capture individual consumption patterns and consumptions from different households. The resulting model can accurately predict future loads (short-term) of individual consumers, even if these were not included in the original training set. This entails a great potential for large-scale applications as once the single network is trained, accurate individual forecast for new consumers can be obtained at almost no computational cost. The proposed model is tested under a large set of numerical experiments by using a real-world dataset with thousands of disaggregated electricity consumption time series. Furthermore, we explore how geo-demographic segmentation of consumers may impact the forecasting accuracy of the model.
Nonlinear Active Disturbance Rejection Control of VGT-EGR System in Diesel Engines
Authors: Zhang Pingyue , Zhang Jingyu , Li Yingshun , Wu Yuhu
Published: October 2020

In this paper, a nonlinear active disturbance rejection control (NLADRC) strategy based on nonlinear extended state observer (NLESO) is proposed to solve the unmodeled dynamics, coupling and disturbance due to change of working point in the variable geometry turbine (VGT) and exhaust gas recirculation (EGR) system, so as to achieve accurate control of intake manifold pressure and mass air flow in a diesel engine. To achieve decoupling, the double-input double-output (DIDO) VGT-EGR system is decomposed into two single-input single-output (SISO) subsystems, and each subsystem has a separate nonlinear active disturbance rejection controller. At the same time, the convergence proof of the designed NLESO is also given theoretically. Finally, the NLADRC controller is compared with linear active disturbance rejection controller and proportional–integral–derivative (PID) controller. Through simulation, it is indicated that the proposed NLADRC controller has better transient response performance, resistance to external disturbance and robustness to the change of engine operating point.
Impact of Passive Cooling on Thermal Comfort in a Single-Family Building for Current and Future Climate Conditions
Authors: Grygierek Krzysztof , Sarna Izabela
Published: October 2020

Today, there is a great deal of emphasis on reducing energy use in buildings for both economic and environmental reasons. Investors strongly encourage the insulating of buildings. Buildings without cooling systems can lead to a deterioration in thermal comfort, even in transitional climate areas. In this article, the effectiveness of natural ventilation in a passive cooling building is analyzed. Two options are considered: cooling with external air supplied to the building by fans, or by opening windows (automatically or by residents). In both cases, fuzzy controllers for the cooling time and supply airflow control are proposed and optimized. The analysis refers to a typical Polish single-family building. Simulations are made with the use of the EnergyPlus program, and the model is validated based on indoor temperature measurement. The calculations were carried out for different climate data: standard and future (warmed) weather data. Research has shown that cooling with external air can effectively improve thermal comfort with a slight increase in heating demand. However, to be able to reach the potential of such a solution, fans should be used.
Study of Visualization Experiment on the Influence of Injector Nozzle Diameter on Diesel Engine Spray Ignition and Combustion Characteristics
Authors: Tang Yuanzhi , Lou Diming , Wang Chengguan , Tan Pi-qiang , Hu Zhiyuan , Zhang Yunhua , Fang Liang
Published: October 2020

The elementary research of spray and combustion is of great significance to the development of compactness of modern diesel engines. In this paper, three injectors with different nozzle orifice diameters (0.23 mm, 0.27 mm and 0.31 mm) were used to study the diesel spray, ignition and flame-wall impingement visualization experiment. This paper studied the influence of different nozzle sizes on the trends of spray, ignition and flame diffusion under the flame-wall impinging combustion and used the flame luminosity to characterize the soot generation in combustion. By analyzing the quantitative data, such as spray penetration, ignition delay, flame area and flame luminosity systematically, it was shown that the smaller nozzle benefitted diesel combustion to some extent. The 0.23 mm nozzle injector in these experiments had the best fuel-air mixing effect under 800 K. The length of the spray liquid under the 0.23 mm nozzle condition was 19% and 23% shorter than that of 0.27 and 0.31 mm, respectively. Smaller orifice size of the nozzle can help to reach the gas ignition conditions more effectively. Without liquid fuel impingement, the simple flame-wall impingement will not change the trend of the nozzle influence on combustion. The total amount of accumulated soot according to the approximate luminosity spatial integral calculation in the combustion process was reduced by 37% and 43% under 0.27 mm and 0.23 mm nozzles, respectively, which is favorable for the clean combustion of diesel engines.
Numerical Investigation of the Effect of Partially Propped Fracture Closure on Gas Production in Fractured Shale Reservoirs
Authors: Yan Xia , Huang Zhaoqin , Zhang Qi , Fan Dongyan , Yao Jun
Published: October 2020

Nonuniform proppant distribution is fairly common in hydraulic fractures, and different closure behaviors of the propped and unpropped fractures have been observed in lots of physical experiments. However, the modeling of partially propped fracture closure is rarely performed, and its effect on gas production is not well understood as a result of previous studies. In this paper, a fully coupled fluid flow and geomechanics model is developed to simulate partially propped fracture closure, and to examine its effect on gas production in fractured shale reservoirs. Specifically, an efficient hybrid model, which consists of a single porosity model, a multiple porosity model and the embedded discrete fracture model (EDFM), is adopted to model the hydro-mechanical coupling process in fractured shale reservoirs. In flow equations, the Klinkenberg effect is considered in gas apparent permeability, and adsorption/desorption is treated as an additional source term. In the geomechanical domain, the closure behaviors of propped and unpropped fractures are described through two different constitutive models. Then, a stabilized extended finite element method (XFEM) iterative formulation, which is based on the polynomial pressure projection (PPP) technique, is developed to simulate a partially propped fracture closure with the consideration of displacement discontinuity at the fracture interfaces. After that, the sequential implicit method is applied to solve the coupled problem, in which the finite volume method (FVM) and stabilized XFEM are applied to discretize the flow and geomechanics equations, respectively. Finally, the proposed method is validated through some numerical examples, and then it is further used to study the effect of partially propped fracture closures on gas production in 3D fractured shale reservoir simulation models. This work will contribute to a better understanding of the dynamic behaviors of fractured shale reservoirs during gas production, and will provide more realistic production forecasts.
Driving Mode Optimization for Hybrid Trucks Using Road and Traffic Preview Data
Authors: Chen Yutao , Rozkvas Nazar , Lazar Mircea
Published: October 2020

This paper proposes a predictive driver coaching (PDC) system for fuel economy driving for hybrid electric trucks using upcoming static map and dynamic traffic data. Unlike traditional methods that optimize over engine torque and brake to obtain a speed profile, we propose to optimize over driving modes of trucks to achieve a trade-off between fuel consumption and trip time. The optimal driving mode is provided to the driver as a coaching recommendation. To obtain the optimal solution, the truck dynamics are firstly modeled as a hybrid controlled switching dynamical system with autonomous subsystems and then a hybrid optimal control problem (HOCP) is formulated. The problem is solved using an algorithm based on discrete hybrid minimum principle. A warm-start strategy to reduce algorithmic iterations is used by employing a shrinking horizon strategy. In addition, an extensive analysis of the proposed algorithm is provided. We prove that the the coasting mode is never optimal given the truck configuration and and we provide a guideline for tuning parameters to maintain the optimal mode sequence. Finally, the algorithm is validated using real-world data from baseline driving tests using a DAF hybrid truck. Significant reduction in fuel consumption is achieved when the data is perfectly available.
Evaluating the Struvite Recovered from Anaerobic Digestate in a Farm Bio-Refinery as a Slow-Release Fertiliser
Authors: Szymańska Magdalena , Sosulski Tomasz , Bożętka Adriana , Dawidowicz Urszula , Wąs Adam , Szara Ewa , Malak-Rawlikowska Agata , Sulewski Piotr , van Pruissen Gijs W. P. , Cornelissen René L.
Published: October 2020

Biogas production in agricultural biogas plants generates digestate—liquid waste containing organic matter and mineral nutrients. Utilisation of the digestate on farm fields adjacent to the biogas plants is limited. Therefore, bio-refineries implement advanced forms of digestate processing, including precipitation of struvite (MgNH4PO4.6H2O). Struvite can be transported over long distances and dosed precisely to meet the nutritional needs of the plants. Divergent opinions on the fertilising value of struvite and its function over time call for further research on its effects on crop yields in the first and subsequent years after application. This study investigates the effects of struvite (STR), struvite with ammonium sulphate (STR + N), and commercial ammonium phosphate (AP) on the yields, nutrient concentration in the crops, nutrient uptake by the crops, and soil N, P, and Mg content in the second growing period after the application of fertilisers to silty loam (SL) and loamy sand (LS) soils under grass cultivation. Struvite was recovered from the liquid fraction of digestate obtained from a bio-refinery on the De Marke farm (Netherlands). The soils investigated in the pot experiment originated from Obory (SL) and Skierniewice (LS) (Central Poland). The results obtained over the first growing period following fertilisation were published earlier. In our prior work, we showed that the majority of the struvite phosphorus remains in the soil. We hypothesised that, in the second year, the yield potential of the struvite might be higher than that of commercial P fertiliser. Currently, we have demonstrated that, in the second growing period following the application, struvite causes an increase in grass yield, nutrient uptake by the crops, and P and Mg content in the soil. On SL and LS soils, the yields of the four grass harvests from the STR and STR + N treatments were higher than those from AP by approximately 8% and 16.5%, respectively. Our results confirm that struvite is more effective as a fertiliser compared to commercial ammonium phosphate. Struvite can be, therefore, recommended for fertilising grasslands at higher doses once every two years.
Crop Residue Removal: Assessment of Future Bioenergy Generation Potential and Agro-Environmental Limitations Based on a Case Study of Ukraine
Authors: Kyryzyuk Sergii , Krupin Vitaliy , Borodina Olena , Wąs Adam
Published: October 2020

This study assesses the bioenergy generation potential of crop residues in Ukraine for the year 2030. Projections of agricultural development are made based on the Global Biosphere Management Model (GLOBIOM) and verified against available Agricultural Member State Modeling (AGMEMOD) results in regard to the six main crops cultivated in Ukraine (wheat, barley, corn, sunflower, rape and soya). Two agricultural development scenarios are assessed (traditional and innovative), facilitating the projection of future crop production volumes and yields for the selected crops. To improve precision in defining agro-environmental limitations (the share of crop residues necessary to be kept on the fields to maintain soil fertility for the continuous cultivation of crops), yield-dependent residue-to-product ratios (RPRs) were applied and the levels of available soil nutrients for regions of Ukraine (in regard to nitrogen, phosphorus, potassium and humus) were estimated. The results reveal the economically feasible future bioenergy generation potential of crop residues in Ukraine, equaling 3.6 Mtoe in the traditional agricultural development scenario and 10.7 Mtoe in the innovative development scenario. The projections show that, within the latter scenario, wheat, corn and barley combined are expected to provide up to 81.3% of the bioenergy generation potential of crop residues.
Optimization of Year-End Water Level of Multi-Year Regulating Reservoir in Cascade Hydropower System Considering the Inflow Frequency Difference
Authors: Jiang Zhiqiang , Song Peibing , Liao Xiang
Published: October 2020

In order to analyze the year-end water level of multi-year regulating reservoir of the cascade hydropower system, this paper studied the joint operation optimization model of cascade reservoirs and its solving method based on multi-dimensional dynamic programming, and analyzed the power generation impact factors of cascade system that contains multi-year regulating reservoir. In particular, taking the seven reservoirs in the middle and lower reaches of Yalong River as an example, the optimal year-end water levels of multi-year regulating reservoir under the multi-year average situation and different inflow frequencies situation were studied. Based on the optimal calculation results of multi-dimensional dynamic programming, the inflow frequency difference considered operation rule of year-end water level of Lianghekou reservoir was extracted using the least square principle. The simulation results showed that, compared with the fixed year-end water level in multi-year, the extracted rule can improve the cascade power generation by more than 400 million kWh in an average year, representing an increase of 0.4%. This result means that the extracted rule can give full play to the regulation performance of multi-year regulating reservoir and improve the conversion efficiency of hydropower resources in cascade system. This is of great significance to the practical operation of cascade reservoirs system that contains multi-year regulating reservoir.
An Optimal Peer-to-Peer Market Considering Modulating Heat Pumps and Photovoltaic Systems under the German Levy Regime
Authors: Langer Lissy
Published: October 2020

The European Commission calls for more small-scale renewable energy producers to actively participate in the energy value chain. In this study, we model an illustrative peer-to-peer (P2P) market with tariffs based on the reservation prices of market participants under the German levy regime. The study is conducted by modeling representative residential buildings with home energy management systems, modulating heat pumps, and photovoltaics, in combination with electrical and thermal storage systems. The resulting mixed-integer linear program is solved over the course of a year, using a rolling horizon approach with a time resolution of one hour. By analyzing the cost- and discomfort-minimizing behavior of the market participants, we evaluate the current levy regime and propose two additional designs. We find that in the current case, a P2P market is not economically viable. Based on feed-in tariffs (FiT) and levies no agreeable market price can be found. With no FiT or reduced levies, all participants benefit from the P2P market. The market split—where each household sources their energy from—is altered only little by the specific details of the market design when staying in the agreeable price range. As prosumagers do not consume on the P2P market, they benefit only marginally from the reduced levies—consumers are most affected. Adjusting the regime could be a measure to rebalance the distribution of renewable energy benefits towards consumers in order to foster social cohesion. Our input data and the model written in the Julia JuMP programming language are available in an open-source format.
Self-Reinforcing Electricity Price Dynamics under the Variable Market Premium Scheme
Authors: Frey Ulrich J. , Klein Martin , Nienhaus Kristina , Schimeczek Christoph
Published: October 2020

We report a potential self-reinforcing design flaw in the variable market premium scheme that occurs if variable renewable energy power plants receiving a premium become price-setting in the market. A high share of renewable energy is a goal of many countries on their transformation path to a sustainable future. Accordingly, policies like feed-in tariffs have been in place for many years in many countries to support investment. To foster market alignment, variable market premia have been introduced in at least 12 European countries and a further dozen additional countries world-wide. We demonstrate both with a mathematical model and different scenarios of an agent-based simulation that the combination of variable premia and a high share of hours in which renewables are price-setting may lead to a self-reinforcing downward spiral of prices if unchecked. This is caused by the market premium opening up the bidding space towards negative prices. We discuss possible objections and countermeasures and evaluate the severity of this market design flaw.
Three-Dimensional Geomechanical Modeling and Analysis of Refracturing and “Frac-Hits” in Unconventional Reservoirs
Authors: Masouleh Shahla , Kumar Dharmendra , Ghassemi Ahmad
Published: October 2020

Field experience has demonstrated that infill well fractures tend to propagate towards the primary well, resulting in well-to-well interference, or so-called “frac-hits”. Frac-hits are a major concern in horizontal well refracturing because they adversely affect the productivity of both wells. This paper provides a 3D geomechanical study of the problem for the first time in order to better understand frac-hits in horizontal well refracturing and its mitigating solutions. To our knowledge, this is the only refracturing study focused on fracture mechanics and within the context of coupled proroelasticity using a single model. The modeling is based on the fully coupled 3D model, GeoFrac-3D, which is capable of simulating multistage fracturing of multiple horizontal wells. The model couples pore pressure to stresses, and makes it possible to create dynamic models of fracture propagation. The modeling results show that production from production well fractures leads to a nonuniform reduction of the reservoir pore pressure around the production well and in between fractures, leading to an anisotropic decrease of the total stress, potentially resulting in stress reorientation and/or reversal. The decrease in the total stress components in the vicinity of the production fractures creates an attraction zone for infill well hydraulic fractures. The infill well fractures tend to grow asymmetrically towards the lower stress zone. The risk of frac-hits and the impact on the “parent” and “infill” well production vary according to the reservoir stress regime, in situ stress anisotropy, and production time. By optimizing well and fracture spacing, fracturing fluid viscosity, and the timing of refracturing job, frac-hit problems can be minimized. The simulation results demonstrate that the risks of frac-hits can be potentially mitigated by repressurization of the production well fractures before fracturing the infill well.
Climate Change Effects on Belgian Households: A Case Study of a Nearly Zero Energy Building
Authors: Attia Shady , Gobin Camille
Published: October 2020

Overheating in residential building is a challenging problem that causes thermal discomfort, productivity reduction, and health problems. This paper aims to assess the climate change impact on thermal comfort in a Belgian reference case. The case study represents a nearly zero energy building that operates without active cooling during summer. The study quantifies the impact of climate change on overheating risks using three representative concentration pathway (RCP) trajectories for greenhouse gas concentration adopted by the Intergovernmental Panel on Climate Change (IPCC). Building performance analysis is carried out using a multizone dynamic simulation program EnergyPlus. The results show that bioclimatic and thermal adaptation strategies, including adaptive thermal comfort models, cannot suppress the effect of global warming. By 2050, zero energy buildings will be vulnerable to overheating.
CFD-DEM Simulation of Biomass Pyrolysis in Fluidized-Bed Reactor with a Multistep Kinetic Scheme
Authors: Chen Tao , Ku Xiaoke , Lin Jianzhong , Ström Henrik
Published: October 2020

The pyrolysis of biomass in a fluidized-bed reactor is studied by a combination of a CFD-DEM algorithm and a multistep kinetic scheme, where fluid dynamics, heat and mass transfer, particle collisions, and the detailed thermochemical conversion of biomass are all resolved. The integrated method is validated by experimental results available in literature and a considerable improvement in predicting the pyrolysis product yields is obtained as compared to previous works using a two-fluid model, especially the relative error in the predicted tar yield is reduced by more than 50%. Furthermore, the evolution of light gas, char and tar, as well as the particle conversion, which cannot easily be measured in experiments, are also revealed. Based on the proposed model, the influences of pyrolysis temperature and biomass particle size on the pyrolysis behavior in a fluidized-bed reactor are comprehensively studied. Numerical results show that the new algorithm clearly captures the dependence of char yield on pyrolysis temperature and the influence of heating rate on light gas and tar yields, which is not possible in simulations based on a simplified global pyrolysis model. It is found that, as the temperature rises from 500 to 700 °C, the light gas yield increases from 17% to 25% and char yield decreases from 22% to 14%. In addition, within the tested range of particle sizes (<1 mm), the impact on pyrolysis products from particle size is relatively small compared with that of the operating temperature. The simulations demonstrate the ability of a combined Lagrangian description of biomass particles and a multistep kinetic scheme to improve the prediction accuracy of fluidized-bed pyrolysis.
Automatic P2P Energy Trading Model Based on Reinforcement Learning Using Long Short-Term Delayed Reward
Authors: Kim Jin-Gyeom , Lee Bowon
Published: October 2020

Automatic peer-to-peer energy trading can be defined as a Markov decision process and designed using deep reinforcement learning. We consider prosumer as an entity that consumes and produces electric energy with an energy storage system, and define the prosumer’s objective as maximizing the profit through participation in peer-to-peer energy trading, similar to that of the agents in stock trading. In this paper, we propose an automatic peer-to-peer energy trading model by adopting a deep Q-network-based automatic trading algorithm originally designed for stock trading. Unlike in stock trading, the assets held by a prosumer may change owing to factors such as the consumption and generation of energy by the prosumer in addition to the changes from trading activities. Therefore, we propose a new trading evaluation criterion that considers these factors by defining profit as the sum of the gains from four components: electricity bill, trading, electric energy stored in the energy storage system, and virtual loss. For the proposed automatic peer-to-peer energy trading algorithm, we adopt a long-term delayed reward method that evaluates the delayed reward that occurs once per month by generating the termination point of an episode at each month and propose a long short-term delayed reward method that compensates for the issue with the long-term delayed reward method having only a single evaluation per month. This long short-term delayed reward method enables effective learning of the monthly long-term trading patterns and the short-term trading patterns at the same time, leading to a better trading strategy. The experimental results showed that the long short-term delayed reward method-based energy trading model achieves higher profits every month both in the progressive and fixed rate systems throughout the year and that prosumer participating in the trading not only earns profits every month but also reduces loss from over-generation of electric energy in the case of South Korea. Further experiments with various progressive rate systems of Japan, Taiwan, and the United States as well as in different prosumer environments indicate the general applicability of the proposed method.
How Population Age Distribution Affects Future Electricity Demand in Korea: Applying Population Polynomial Function
Authors: Jo Ha-Hyun , Jang Minwoo , Kim Jaehyeok
Published: October 2020

Mounting evidence shows that economic and climate variables such as income, energy price, and temperature impact energy demand. We examined another variable, population age distribution, which has rarely been considered, that could affect energy demand. We employ population polynomials to account for the impact of population age distribution on residential electricity consumption in Korea. Using panel data from 1990 to 2016, we verify that populations aged 20~44, and those over 60, raise residential electricity consumption. We additionally evaluate the impact of population age distribution in forecasting future electricity consumption and conclude that age distribution effects dominate total population growth effects.
Candida intermedia CBS 141442: A Novel Glucose/Xylose Co-Fermenting Isolate for Lignocellulosic Bioethanol Production
Authors: Moreno Antonio D. , Tomás-Pejó Elia , Olsson Lisbeth , Geijer Cecilia
Published: October 2020

The present study describes the isolation of the novel strain Candida intermedia CBS 141442 and investigates the potential of this microorganism for the conversion of lignocellulosic streams. Different C. intermedia clones were isolated during an adaptive laboratory evolution experiment under the selection pressure of lignocellulosic hydrolysate and in strong competition with industrial, xylose-fermenting Saccharomyces cerevisiae cells. Isolates showed different but stable colony and cell morphologies when growing in a solid agar medium (smooth, intermediate and complex morphology) and liquid medium (unicellular, aggregates and pseudohyphal morphology). Clones of the same morphology showed similar fermentation patterns, and the C. intermedia clone I5 (CBS 141442) was selected for further testing due to its superior capacity for xylose consumption (90% of the initial xylose concentration within 72 h) and the highest ethanol yields (0.25 ± 0.02 g ethanol/g sugars consumed). Compared to the well-known yeast Scheffersomyces stipitis, the selected strain showed slightly higher tolerance to the lignocellulosic-derived inhibitors when fermenting a wheat straw hydrolysate. Furthermore, its higher glucose consumption rates (compared to S. stipitis) and its capacity for glucose and xylose co-fermentation makes C. intermedia CBS 141442 an attractive microorganism for the conversion of lignocellulosic substrates, as demonstrated in simultaneous saccharification and fermentation processes.
A Dataset for Non-Intrusive Load Monitoring: Design and Implementation
Authors: Renaux Douglas Paulo Bertrand , Pottker Fabiana , Ancelmo Hellen Cristina , Lazzaretti André Eugenio , Lima Carlos Raiumundo Erig , Linhares Robson Ribeiro , Oroski Elder , Nolasco Lucas da Silva , Lima Lucas Tokarski , Mulinari Bruna Machado , Silva José Reinaldo Lopes da , Omori Júlio Shigeaki , Santos Rodrigo Braun dos
Published: October 2020

A NILM dataset is a valuable tool in the development of Non-Intrusive Load Monitoring techniques, as it provides a means of evaluation of novel techniques and algorithms, as well as for benchmarking. The figure of merit of a NILM dataset includes characteristics such as the sampling frequency of the voltage, current, or power, the availability of indications (ground-truth) of load events during recording, the variety and representativeness of the loads, and the variety of situations these loads are subject to. Considering such aspects, the proposed LIT-Dataset was designed, populated, evaluated, and made publicly available to support NILM development. Among the distinct features of the LIT-Dataset is the labeling of the load events at sample level resolution and with an accuracy and precision better than 5 ms. The availability of such precise timing information, which also includes the identification of the load and the sort of power event, is an essential requirement both for the evaluation of NILM algorithms and techniques, as well as for the training of NILM systems, particularly those based on Machine Learning.
Cold Ironing Galvanic Corrosion Issues with Regard to a Shore-to-Ship Medium Voltage Connection
Authors: Kozak Maciej , Chmiel Jarosław
Published: October 2020

Cold ironing refers to the usage of less polluting power supply sources to deliver electricity to the moored ship. Such a shore-to-ship system is used when the ship is at a port so the auxiliary combustion engines may be turned off. This paper presents the numerical simulation results of a medium voltage cold-ironing system with regard to the currents flowing between the ship’s hull and grounding busbar. The IT electrical inland system with a neutral grounding resistor, as commonly used in shore-to-ship systems, is investigated. Parasitic capacitances present between the phase-to-hull and phase-to-ground in real-world applications can vary from each other. The direct and alternating currents flowing across the hull, seawater and the pier structure are amongst the causes that can lead to premature reinforced concrete degradation. Chosen cases of phase-to-ground or hull unequal capacitances influencing AC stray currents were considered.
A Tandem Axial-Piston Unit Based Strategy for the Reduction of Noise Sources in Hydraulic Systems
Authors: Danes Leandro , Vacca Andrea
Published: October 2020

This article presents a novel passive fluid borne noise source reduction strategy, based on tandem axial-piston unit indexing with the usage of symmetric lines. The strategy consists of setting the phase between the two synchronous units to accomplish destructive interference in targeted unit harmonics. A strategy capable of achieving destructive interference in all odd harmonics is investigated first analytically and then confirmed by a simulation study. Experiments on the proposed strategy confirmed its effectiveness at the first and third pump fundamental harmonics, and pressure ripple reduction was accomplished. The fluid borne noise source reduction in the first and third harmonic is verified to be propagated to pipe vibration and sound power. Regarding the first harmonic, pressure ripple was reduced by up to 18 dB; while for third harmonic, pressure ripple was reduced by up to 11 dB. In the experiment, however, noise cancellation is not achieved for the higher odd harmonics, as is instead found in the simulation. Conversely, transfer functions form pressure ripple to pipe wall acceleration are obtained experimentally, and a critical vibration band from 2000 Hz to 3000 Hz is identified as being crucial for effective overall sound power reduction.
Implementation of Three-Dimensional Inverse Design and Its Application to Improve the Compressor Performance
Authors: Duan Yu , Zheng Qun , Jiang Bin , Lin Aqiang , Zhao Wenfeng
Published: October 2020

The implementation of a three-dimensional viscous inverse design used for an axial compressor is introduced in this paper. The derivation process of the inverse design algorithm is also described in detail. Moreover, an improved blade update method and a modified relaxation factor are included to enhance the inverse design algorithm. The inverse design is built on an in-house inverse design module coupled with commercial Computational Fluid Dynamic (CFD) software NUMECATM. In contrast to analysis design, the pressure loading and the normal thickness distribution along the blade surfaces are prescribed during the process of inverse design. The numerical methods used to solve the flow field are verified using the experimental data of the transonic fan rotor NASA Rotor 67. A recovery test for the Rotor 67 is carried out to validate the developed three-dimensional inverse design tool. To explore the potential application of the inverse design system, it is then used to improve the aerodynamic performance of a transonic fan Rotor 67 and a multi-row compressor Stage 35 at a near peak efficiency point by reorganizing the pressure loading distribution on the blade surfaces.
Simulated Annealing, Differential Evolution and Directed Search Methods for Generator Maintenance Scheduling
Authors: Gubin Pavel Y. , Oboskalov Vladislav P. , Mahnitko Anatolijs , Petrichenko Roman
Published: October 2020

Generator maintenance scheduling presents many engineering issues that provide power system personnel with a variety of challenges, and one can hardly afford to neglect these engineering issues in the future. Additionally, there is vital need for further development of the repair planning task complexity in order to take into account the vast majority of power flow constraints. At present, the question still remains as to which approach is the simplest and most effective, as well as appropriate for further application in the power flow-oriented statement of the repair planning problem. This research compared directed search, differential evolution, and very fast simulated annealing methods based on a number of numerical calculations and made conclusions about their prospective utilization in terms of a more complicated mathematical formulation of the repair planning task. A comparison of results shows that the effectiveness of directed search methods should not be underestimated, and that the pure differential evolution and very fast simulated annealing approaches are not essentially reliable for repair planning. The experimental results demonstrate the perspectivity of unifying single-procedure methods in order to net out risk associated with specific features of these approaches.
Thermal and Economic Analysis of Multi-Effect Concentration System by Utilizing Waste Heat of Flue Gas for Magnesium Desulfurization Wastewater
Authors: Yan Mingwei , Shi Yuetao
Published: October 2020

Compared with limestone-based wet flue gas desulfurization (WFGD), magnesia-based WFGD has many advantages, but it is not popular in China, due to the lack of good wastewater treatment schemes. This paper proposes the wastewater treatment scheme of selling magnesium sulfate concentrate, and makes thermal and economic analysis for different concentration systems in the scheme. Comparisons of different concentration systems for 300 MW power plant were made to determine which system is the best. The results show that the parallel-feed benchmark system is better than the forward-feed benchmark system, and the parallel-feed optimization system with the 7-process is better than other parallel-feed optimization systems. Analyses of the parallel-feed optimization system with 7-process were made in 300, 600, and 1000 MW power plants. The results show that the annual profit of concentration system for a 300, 600, and 1000 MW power plant is about 2.58 million, 5.35 million, and 7.89 million Chinese Yuan (CNY), respectively. In different concentration systems of the scheme for selling magnesium sulfate concentrate, the parallel-feed optimization system with the 7-process has the best performance. The scheme can make a good profit in 300, 600, and 1000 MW power plants, and it is very helpful for promoting magnesia-based WFGD in China.
Wood vs. Canopy Allocation of Aboveground Net Primary Productivity in a Mediterranean Forest during 21 Years of Experimental Rainfall Exclusion
Authors: Ogaya Romà , Peñuelas Josep
Published: October 2020

A Mediterranean holm oak forest was subjected to experimental partial rainfall exclusion during 21 consecutive years to study the effects of the expected decrease in water availability for Mediterranean vegetation in the coming decades. Allocation in woody structures and total aboveground allocation were correlated with annual rainfall, whereas canopy allocation and the ratio of wood/canopy allocation were not dependent on rainfall. Fruit productivity was also correlated with annual rainfall, but only in Quercus ilex. In the studied site, there were two types of forest structure: high canopy stand clearly dominated by Quercus ilex, and low canopy stand with more abundance of a tall shrub species, Phillyrea latifolia. In the tall canopy stand, the allocation to woody structures decreased in the experimental rainfall exclusion, but not the allocation to canopy. In the low canopy stand, wood allocation in Quercus ilex was very small in both control and plots with rainfall exclusion, but wood allocation in Phillyrea latifolia was even higher than that obtained in tall canopy plots, especially in the plots receiving the experimental rainfall exclusion. These results highlight likely future changes in the structure and functioning of this ecosystem induced by the decrease in water availability. A serious drop in the capacity to mitigate climate change for this Mediterranean forest can be expected, and the ability of Phillyrea latifolia to take advantage of the limited capacity to cope with drought conditions detected in Quercus ilex makes likely a forthcoming change in species dominance, especially in the low canopy stands.