Energies, Volume 8, Issue 11 (November 2015) – 55 articles

In this paper we develop an agent-based model to explore a feasible way of simultaneously providing sufficient food and bioenergy feedstocks in China. Concerns over the competition for agricultural land resources between food and bioenergy supply hinder the further development of bioenergy, especially in China, the country that needs to feed the world’s largest population. Prior research has suggested the introduction of energy crops and reviewed the resulting agricultural land use change in China. However, there is a lack of quantitative studies which estimate the value, contribution, and impact of bioenergy for specific conditions at the county level and provide adequate information to guide local practices. To fill this gap, we choose the Jiangsu Province in China as a case study, build up a spatial-agent dynamic model of agricultural land use, and perform a sensitivity analysis for important parameters. The simulation results show that straw from conventional crops generally dominates Jiangsu’s biomass supply with a contribution above 85%. The sensitivity analyses reveal severe consequences of bioenergy targets for local land use. For Jiangsu Province, reclaimed mudflats, an alternative to arable lands for energy crop plantation, help to secure the local biomass supply and to alleviate the land use conflict between food and biomass production. Full article

In China, the power sector is currently the largest carbon emitter and the transportation sector is the fastest-growing carbon emitter. This paper proposes a model of solar-powered charging stations for electric vehicles to mitigate problems encountered in China’s renewable energy utilization processes and to cope with the increasing power demand by electric vehicles for the near future. This study applies the proposed model to Shenzhen City to verify its technical and economic feasibility. Modeling results showed that the total net present value of a photovoltaic power charging station that meets the daily electricity demand of 4500 kWh is $3,579,236 and that the cost of energy of the combined energy system is $0.098/kWh. In addition, the photovoltaic powered electric vehicle model has pollutant reduction potentials of 99.8%, 99.7% and 100% for carbon dioxide, sulfur dioxide, and nitrogen oxides, respectively, compared with a traditional gasoline-fueled car. Sensitivity analysis results indicated that interest rate has a relatively strong influence on COE (Cost of Energy). An increase in the interest rate from 0% to 6% increases COE from $0.027/kWh to $0.097/kWh. This analysis also suggests that carbon pricing promotes renewable energy only when the price of carbon is above $20/t. Full article

In the ten years since committing to clean energy transition, China has formulated a large number of policies and programs to achieve some very ambitious targets. This paper argues that the dearth of empirical studies concerning the implementation of these new policies and programs has created a knowledge gap between official policy documents, which are vague and lacking in specifics, and official policy outcomes, which are unreliable. In particular, the merits and limitations of flexible implementation with regard to desirable outcomes need to be debated and clarified. This paper calls for more empirical investigation in four areas as a starting point: (1) the nature and extent of flexibility in the implementation; (2) implementation strategies and their impacts; (3) factors that shape the behavior of local officials responsible for implementation; and (4) the relationship between the central-local relation and policy implementation. Full article

This work focuses on a steady-state model developed for an integrated planar solid oxide fuel cell (IP-SOFC) bundle. In this geometry, several single IP-SOFCs are deposited on a tube and electrically connected in series through interconnections. Then, several tubes are coupled to one another to form a full-sized bundle. A previously-developed and validated electrochemical model is the basis for the development of the tube model, taking into account in detail the presence of active cells, interconnections and dead areas. Mass and energy balance equations are written for the IP-SOFC tube, in the classical form adopted for chemical reactors. Based on the single tube model, a bundle model is developed. Model validation is presented based on single tube current-voltage (I-V) experimental data obtained in a wide range of experimental conditions, i.e., at different temperatures and for different H₂/CO/CO₂/CH₄/H₂O/N₂ mixtures as the fuel feedstock. The error of the simulation results versus I-V experimental data is less than 1% in most cases, and it grows to a value of 8% only in one case, which is discussed in detail. Finally, we report model predictions of the current density distribution and temperature distribution in a bundle, the latter being a key aspect in view of the mechanical integrity of the IP-SOFC structure. Full article

In this research, the design of a new electromagnetic engine valve in the limited space of combustion engine is optimized by multidisciplinary simulation using MATLAB and Maxwell. An electromagnetic engine valve actuator using a permanent magnet is a new actuator concept for overcoming the inherent drawbacks of the conventional solenoid-driven electromagnetic engine valve actuator, such as high power consumption and so on. This study aims to maximize the vibration frequency of the armature to reduce the transition time of the engine valve. The higher performance of the new actuator is demonstrated by dynamic finite element analysis. Full article

Microbial electrochemical technologies (METs) have a number of potential technological applications. In this work, we report the use of screen-printed electrodes (SPEs) as a tool to analyze the microbial electroactivity by using Geobacter sulfurreducens as a model microorganism. We took advantage of the small volume required for the assays (75 μL) and the disposable nature of the manufactured strips to explore short-term responses of microbial extracellular electron transfer to conductive materials under different scenarios. The system proved to be robust for identifying the bioelectrochemical response, while avoiding complex electrochemical setups, not available in standard biotechnology laboratories. We successfully validated the system for characterizing the response of Geobacter sulfurreducens in different physiological states (exponential phase, stationary phase, and steady state under continuous culture conditions) revealing different electron transfer responses. Moreover, a combination of SPE and G. sulfurreducens resulted to be a promising biosensor for quantifying the levels of acetate, as well as for performing studies in real wastewater. In addition, the potential of the technology for identifying electroactive consortia was tested, as an example, with a mixed population with nitrate-reducing capacity. We therefore present SPEs as a novel low-cost platform for assessing microbial electrochemical activity at the microscale level. Full article

The high temperature and high pressure supersonic jet is one of the key problems in the design of solid rocket motors. To reduce the jet temperature and noise, cooling water is typically injected into the exhaust plume. Numerical simulations for the gas-liquid multiphase flow field with mixture multiphase model were developed and a series of experiments were carried out. By introducing the energy source terms caused by the vaporization of liquid water into the energy equation, a coupling solution was developed to calculate the multiphase flow field. The temperature data predictions agreed well with the experimental results. When water was injected into the plume, the high temperature core region area was reduced, and the temperature on the head face was much lower than that without water. The relationship between the reduction of temperature on the bottom plate and the momentum ratio is developed, which can be used to predict the cooling effect of water injection in many cases. Full article

Data mining has become an essential tool during the last decade to analyze large sets of data. The variety of techniques it includes and the successful results obtained in many application fields, make this family of approaches powerful and widely used. In particular, this work explores the application of these techniques to time series forecasting. Although classical statistical-based methods provides reasonably good results, the result of the application of data mining outperforms those of classical ones. Hence, this work faces two main challenges: (i) to provide a compact mathematical formulation of the mainly used techniques; (ii) to review the latest works of time series forecasting and, as case study, those related to electricity price and demand markets. Full article

In this study, the multi-objective optimization of an indirect forced-circulation solar water heating (SWH) system was performed to obtain the optimal configuration that minimized the life cycle cost (LCC) and maximized the life cycle net energy saving (LCES). An elitist non-dominated sorting genetic algorithm (NSGA-II) was employed to obtain the Pareto optimal solutions of the multi-objective optimization. To incorporate the characteristics of practical SWH systems, operation-related decision variables as well as capacity-related decision variables were included. The proposed method was used to conduct a case study wherein the optimal configuration of the SWH system of an office building was determined. The case study results showed that the energy cost decreases linearly and the equipment cost increases more significantly as the LCES increases. However, the results also showed that it is difficult to identify the best solution among the Pareto optimal solutions using only the correlation between the corresponding objective function values. Furthermore, regression analysis showed that the energy and economic performances of the Pareto optimal solutions are significantly influenced by the ratio of the storage tank volume to the collector area (RVA). Therefore, it is necessary to simultaneously consider the trade-off and the effect of the RVA on the Pareto optimal solutions while selecting the best solution from among the optimal solutions. Full article

This paper presents a novel lightning search algorithm (LSA) using quantum mechanics theories to generate a quantum-inspired LSA (QLSA). The QLSA improves the searching of each step leader to obtain the best position for a projectile. To evaluate the reliability and efficiency of the proposed algorithm, the QLSA is tested using eighteen benchmark functions with various characteristics. The QLSA is applied to improve the design of the fuzzy logic controller (FLC) for controlling the speed response of the induction motor drive. The proposed algorithm avoids the exhaustive conventional trial-and-error procedure for obtaining membership functions (MFs). The generated adaptive input and output MFs are implemented in the fuzzy speed controller design to formulate the objective functions. Mean absolute error (MAE) of the rotor speed is the objective function of optimization controller. An optimal QLSA-based FLC (QLSAF) optimization controller is employed to tune and minimize the MAE, thereby improving the performance of the induction motor with the change in speed and mechanical load. To validate the performance of the developed controller, the results obtained with the QLSAF are compared to the results obtained with LSA, the backtracking search algorithm (BSA), the gravitational search algorithm (GSA), the particle swarm optimization (PSO) and the proportional integral derivative controllers (PID), respectively. Results show that the QLASF outperforms the other control methods in all of the tested cases in terms of damping capability and transient response under different mechanical loads and speeds. Full article

This paper presents a new soft switching boost converter with a passive snubber cell without additional active switches for battery charging systems. The proposed snubber finds its application in the front-end ac-dc converter of Plug-in Hybrid Electric Vehicle (PHEV) battery chargers. The proposed auxiliary snubber circuit consists of an inductor, two capacitors and two diodes. The new converter has the advantages of continuous input current, low switching stresses, high voltage gain without extreme duty cycle, minimized charger size and charging time and fewer amounts of cost and electricity drawn from the utility at higher switching frequencies. The switch is made to turn ON by Zero Current Switching (ZCS) and turn OFF by Zero Voltage Switching (ZVS). The detailed steady state analysis of the novel ac-dc Zero Current- Zero Voltage Switching (ZC-ZVS) boost Power Factor Correction (PFC) converter is presented with its operating principle. The experimental prototype of 20 kHz, 100 W converter verifies the theoretical analysis. The power factor of the prototype circuit reaches near unity with an efficiency of 97%, at nominal output power for a ±10% variation in the input voltage and ±20% variation in the snubber component values. Full article

Manufacturing processes are responsible for climate change due to the emissions produced as result of energy consumption. This paper analyzes the influence of the cutting conditions and the characteristics of cutting tools on the energy required in machining processes and the carbon dioxide equivalent (CO₂-eq) emissions generated per material removed ratio (MRR) in an effort to define common criteria for using cutting inserts in a sustainable manner. Consequently, four cutting inserts were evaluated during the turning of Ti6Al4V alloy. An experimental and statistical methodology that combined the orthogonal array L36, the signal-to-noise ratio under the “small is better” criterion of Taguchi, and a multifactor analysis of variance was used. The effects of the geometry, material and coating of the tool and the cutting conditions on the energy and the carbon footprint during the manufacturing process were analyzed. The results show that a high tool cutting length and a high cutting depth are significant common factors, whereas the coating-cutting depth and cutting length-cutting speed are significant common interactions for both the energy/MRR ratio and the CO₂-eq emissions/MRR ratio, and the coating-cutting speed exhibits a significant interaction for emissions. The outcomes show that the lifespan of the tool has little influence on the total emissions, at the time that the methodology is able to identify the most appropriate manner to calculate energy. Full article

Among the various renewable energy sources, biohydrogen is gaining a lot of traction as it has very high efficiency of conversion to usable power with less pollutant generation. The various technologies available for the production of biohydrogen from lignocellulosic biomass such as direct biophotolysis, indirect biophotolysis, photo, and dark fermentations have some drawbacks (e.g., low yield and slower production rate, etc.), which limits their practical application. Among these, metabolic engineering is presently the most promising for the production of biohydrogen as it overcomes most of the limitations in other technologies. Microbial electrolysis is another recent technology that is progressing very rapidly. However, it is the dark fermentation approach, followed by photo fermentation, which seem closer to commercialization. Biohydrogen production from lignocellulosic biomass is particularly suitable for relatively small and decentralized systems and it can be considered as an important sustainable and renewable energy source. The comprehensive life cycle assessment (LCA) of biohydrogen production from lignocellulosic biomass and its comparison with other biofuels can be a tool for policy decisions. In this paper, we discuss the various possible approaches for producing biohydrogen from lignocellulosic biomass which is an globally available abundant resource. The main technological challenges are discussed in detail, followed by potential solutions. Full article

The challenge for our paper consists in controlling the performance of the future state of a microgrid with energy produced from renewable energy sources. The added value of this proposal consists in identifying the most used criteria, related to each modeling step, able to lead us to an optimal neural network forecasting tool. In order to underline the effects of users’ decision making on the forecasting performance, in the second part of the article, two Adaptive Neuro-Fuzzy Inference System (ANFIS) models are tested and evaluated. Several scenarios are built by changing: the prediction time horizon (Scenario 1) and the shape of membership functions (Scenario 2). Full article

Several studies have quantified the energy consumption associated with crop production in various countries. However, these studies have not compared the energy consumption from a broad range of farming practices currently in practice, such as zero tillage, conventional tillage and irrigated farming systems. This study examines direct on-farm energy use for high value grain crops grown under different farming practices in Australia. Grain farming processes are identified and “typical” farming operation data are collected from several sources, including published and unpublished literature, as well as expert interviews. The direct on-farm energy uses are assessed for 27 scenarios, including three high value grain crops―wheat, barley and sorghum―for three regions (Northern, Southern and Western Australia) under three farming conditions with both dryland (both for conventional and zero-tillage) and irrigated conditions. It is found that energy requirement for farming operations is directly related to the intensity and frequency of farming operations, which in turn is related to tillage practices, soil types, irrigation systems, local climate, and crop types. Among the three studied regions, Western Australia requires less direct on-farm energy for each crop, mainly due to the easily workable sandy soils and adoption of zero tillage systems. In irrigated crops, irrigation energy remains a major contributor to the total on-farm energy demand, accounting for up to 85% of total energy use. Full article

To study the effects of inherent and external alkali and alkaline earth metallic species (AAEMs, i.e., K, Ca and Mg) on the behavior of N-containing species release during rice straw (RS) pyrolysis, different pretreatments were applied in numerous experiments. Results indicate that ammonia (NH₃) and hydrogen cyanide (HCN) are the major N-containing species and that the yields of isocyanic acid (HNCO) and nitric oxide (NO) are relatively low. The removal of inhert AAEMs shifts N-containing species release to a high-temperature zone according to volatile release behavior because of the increase in activation energy. The formation selectivity of NH₃, HNCO, and NO increases by demineralized pretreatment, whereas HCN selectivity decreases. The formation of HNCO is mainly affected by alkaline earth metal. N-containing species release occurs in low temperatures with the addition of external AAEMs. The activation energy of samples impregnated with CaCl₂ and MgCl₂ sharply decreases compared to the original RS. The total yields of N-containing species are reduced significantly in the presence of KCl, CaCl₂, and MgCl₂ as additives. The inhibition ability of AAEMs follows the sequence MgCl₂ > CaCl₂ > KCl. The inhibition effect of MgCl₂ can be improved by solution immersion compared with solid powder mixing. The clean biomass pyrolysis and gasification technology with low N-containing species content may be developed according to the results. Full article

I use energy cost share to characterize the role of energy in the economy. Specifically, I use an estimate of monetary expenditures for primary energy on an annualized basis for forty-four countries from 1978 to 2010 for natural gas, coal, petroleum, and electricity. I show that global energy cost share is significantly correlated to a one-year lag in the change in gross domestic product as well as measures of total factor productivity. Given the historical reduction in the relative cost of energy (including food and fodder for animate power) since the start of the Industrial Revolution, combined with a global energy cost share estimate, I conclude that the turn of the 21st Century represents the time period with the cheapest energy in the history of human civilization (to date). This potential historical nadir for energy expenditures around 2000 has important ramifications for strategies to solve future social, economic, and environmental problems such as reducing annual emissions of greenhouse gases (GHGs). Rapidly decreasing annual GHG emissions while internalizing their costs into the economy might feedback to increase energy expenditures to such a degree as to prevent economic growth during that transition. Full article

We translate between energetic and economic metrics that characterize the role of energy in the economy. Specifically, we estimate monetary expenditures for the primary energy and net external power ratio (NEPR direct ; NEPR, net external power ratio), a power return ratio of annual energy production divided by annual direct energy inputs within the energy industry. We estimate these on an annualized basis for forty-four countries from 1978 to 2010. Expressed as a fraction of gross domestic product (GDP), f e , GDP , the forty-four country aggregate (composing >90% world GDP) worldwide expenditures on energy decreased from a maximum of 10.3% in 1979 to a minimum of 3.0% in 1998 before increasing to a second peak of 8.1% in 2008. While the global f e , GDP fluctuates significantly, global NEPR direct declined from a value of 34 in 1980 to 17 in 1986 before staying in a range between 14 and 16 from 1991 to 2010. In comparing both of these metrics as ratios of power output over power input, one economic ( f e , GDP - 1 ) and one biophysical (NEPR direct ), we see that when the former divided by the latter is below unity, the world was in a low-growth or recessionary state. Full article

We translate between biophysical and economic metrics that characterize the role of energy in the economy. Specifically, using data from the International Energy Agency, we estimate the energy intensity ratio (EIR), a price-based proxy for a power return ratio (PRR ∼ P out / P invested ). The EIR is a useful metric, because for most countries and energy commodities, it can indicate the biophysical trends of net energy when data are too scarce to perform an original net energy analysis. We calculate EIR for natural gas, coal, petroleum and electricity for forty-four countries from 1978 to 2010. Global EIR values generally rise from 1978 to 1998, decline from 1998 to 2008 and then slightly rebound. These trends indicate one interpretation of the net energy of the world economy. To add perspective to our recent, but short, time series, we perform the same calculations for historical England and United Kingdom energy prices to demonstrate that a given energy price translates to different PRRs (EIR in this case) depending on the structure of the economy and technology. We review the formulation of PRRs and energy return ratios (ERR ∼ E out / E invested ) to indicate why PRRs translate to (the inverse of) energy prices and ERRs translate to (the inverse of) energy costs. We show why for any given value of an ERR or PRR, there is not a single corresponding energy cost or price, and vice versa. These principles in turn provide the basis to perform better modeling of future energy scenarios (e.g., low-carbon transition) by considering the relationship between economic metrics (cost and price) and biophysical metrics (energy and power return ratios) based on energy, material and power flows. Full article

Microgrid is a new power system concept consisting of small-scale distributed energy resources; storage devices and loads. It is necessary to employ a simplified model of microgrid in the simulation of a distribution network integrating large-scale microgrids. Based on the detailed model of the components, an equivalent model of microgrid is proposed in this paper. The equivalent model comprises two parts: namely, equivalent machine component and equivalent static component. Equivalent machine component describes the dynamics of synchronous generator, asynchronous wind turbine and induction motor, equivalent static component describes the dynamics of photovoltaic, storage and static load. The trajectory sensitivities of the equivalent model parameters with respect to the output variables are analyzed. The key parameters that play important roles in the dynamics of the output variables of the equivalent model are identified and included in further parameter estimation. Particle Swarm Optimization (PSO) is improved for the parameter estimation of the equivalent model. Simulations are performed in different microgrid operation conditions to evaluate the effectiveness of the equivalent model of microgrid. Full article

Osmotic energy, as a sustainable energy source with little environmental impact, has drawn much attention in both academia and industry in recent years. Osmotically driven membrane processes can harvest the osmotic energy and thus have great potential to produce sustainable clean water or electric energy. The draw solution, as an osmotic component, has been more and more explored by scientists in recent years in order to achieve a high osmotic pressure and suitable molecular size. In this work, a novel draw solute—sodium tetraethylenepentamine heptaacetate (STPH)—is synthesized and identified by nuclear magnetic resonance spectroscopy (¹H-NMR) and Fourier transform infrared (FTIR). Its solution properties are optimized in terms of the solution pH and concentration, and related to the forward osmosis (FO) performance. A water flux of 28.57 LMH and a low solute flux of 0.45 gMH can be generated with 0.5 g/mL STPH draw solution and de-ionized water (DI water) as the feed solution under pressure retarded osmosis (PRO) mode, which is superior to the FO performance with many other draw solutes reported. Further FO desalination test shows a stable water flux of 9.7 LMH with 0.3 g/mL STPH draw solution and 0.6 M NaCl feed solution. In addition, the draw solution recovery is also investigated. Full article

Since the air-gap field of flux-switching permanent magnet (FSPM) machines is difficult to regulate as it is produced by the stator-magnets alone, a type of hybrid-excited flux-switching (HEFS) machine is obtained by reducing the magnet length of an original FSPM machine and introducing a set of field windings into the saved space. In this paper, the steady-state characteristics, especially for the loaded performances of four prototyped HEFS machines, namely, PM-top, PM-middle-1, PM-middle-2, and PM-bottom, are comprehensively compared and evaluated based on both 2D and 3D finite element analysis. Also, the influences of PM materials including ferrite and NdFeB, respectively, on the characteristics of HEFS machines are covered. Particularly, the impacts of magnet movement in the corresponding slot on flux-regulating performances are studied in depth. The best overall performances employing NdFeB can be obtained when magnets are located near the air-gap. The FEA predictions are validated by experimental measurements on corresponding machine prototypes. Full article

In power systems with high wind energy penetration, the conjunction of wind power fluctuations and power system inertia reduction can lead to large frequency excursions, where the operating reserves of conventional power generation may be insufficient to restore the power balance. With the aim of evaluating the demand-side contribution to frequency control, a complete process to determine critical wind oscillations in power systems with high wind penetration is discussed and described in this paper. This process implies thousands of wind power series simulations, which have been carried out through a validated offshore wind farm model. A large number of different conditions have been taken into account, such as frequency dead bands, the percentages of controllable demand and seasonal factor influence on controllable loads. Relevant results and statistics are also included in the paper. Full article

Photovoltaic (PV) systems are becoming a relevant electricity source, characterised by a growing trend in the last years. This paper analyses the economic feasibility of investments in industrial PV systems of different sizes (200 kW, 400 kW, 1 MW, and 5 MW), in the absence of subsidies, and in a mature market (Italy). The selected indicators for this kind of assessment are net present value (NPV) and discounted payback time (DPBT). Furthermore, the environmental advantage in comparison to fossil sources of energy is evaluated through the reduction of carbon dioxide emissions (ER_cd). Finally, a sensitivity analysis on critical variables (percentage of self-consumed energy, average annual insolation rate, annual electricity purchase price, annual electricity sale price, unitary investment cost and opportunity cost) is conducted. Results highlight the strategic role of self-consumption in a market characterised by an absence of public policy incentives and the presence of interesting economic opportunities for industrial applications. Full article

Coal-fired thermal power plants, which represent the largest proportion of China’s electric power system, are very sluggish in responding to power system load demands. Thus, a reasonable and feasible scheme for the medium-term optimal commitment of thermal units (MOCTU) can ensure that the generation process runs smoothly and minimizes the start-up and shut-down times of thermal units. In this paper, based on the real-world and practical demands of power dispatch centers in China, a flexible mathematical model for MOCTU that uses equal utilization hours for the installed capacity of all thermal power plants as the optimization goal and that considers the award hours for MOCTU is developed. MOCTU is a unit commitment (UC) problem with characteristics of large-scale, high dimensions and nonlinearity. For optimization, an improved progressive optimality algorithm (IPOA) offering the advantages of POA is adopted to overcome the drawback of POA of easily falling into the local optima. In the optimization process, strategies of system operating capacity equalization and single station operating peak combination are introduced to move the target solution from the boundary constraints along the target isopleths into the feasible solution’s interior to guarantee the global optima. The results of a case study consisting of nine thermal power plants with 27 units show that the presented algorithm can obtain an optimal solution and is competent in solving the MOCTU with high efficiency and accuracy as well as that the developed simulation model can be applied to practical engineering needs. Full article

The purpose of this study is to analyze the steady-state and transient behavior of the electrical and thermal parameters of thermoelectric generators (TEGs). The focus is on the required wait-time between measurements in order to reduce measurement errors which may appear until the system reaches steady-state. By knowing this waiting time, the total characterization time can also be reduced. The experimental characterization process is performed on a test rig known as TEGeta, which can be used to assess the output characteristics of TEG modules under different load values and temperature conditions. The setup offers the possibility to control the hot side temperature up to 1000 °C with a load variation range value between 0.22–8.13 Ω. A total of ten thermocouples are placed in the setup with the purpose of measuring the temperature in specific points between the heater and the heat sink. Based on the readings, the temperature on the hot and cold side of the modules can be extrapolated. This study provides quantitative data on the minimum waiting time of the temperatures in the surrounding system to reach equilibrium. Laboratory tests are performed on a calcium-manganese oxide module at temperatures between 400 and 800 °C to explore the high temperatures features of the setup. Full article

Multi-phase motors are gaining more attention due to the advantages of good fault tolerance capability and high power density, etc. By applying dual-rotor technology to multi-phase machines, a five-phase dual-rotor permanent magnet synchronous motor (DRPMSM) is researched in this paper to further promote their torque density and fault tolerance capability. It has two rotors and two sets of stator windings, and it can adopt a series drive mode or parallel drive mode. The fault-tolerance capability of the five-phase DRPMSM is researched. All open circuit fault types and corresponding fault tolerance techniques in different drive modes are analyzed. A fault-tolerance control strategy of injecting currents containing a certain third harmonic component is proposed for five-phase DRPMSM to ensure performance after faults in the motor or drive circuit. For adjacent double-phase faults in the motor, based on where the additional degrees of freedom are used, two different fault-tolerance current calculation schemes are adopted and the torque results are compared. Decoupling of the inner motor and outer motor is investigated under fault-tolerant conditions in parallel drive mode. The finite element analysis (FMA) results and co-simulation results based on Simulink-Simplorer-Maxwell verify the effectiveness of the techniques. Full article

In this study, biorefinery as a concept is applied to thermomechanical pulp (TMP)-based paper production to evaluate the possibility of co-production of synthetic natural gas (SNG), electricity and district heating in addition to mechanical pulp and paper. The combined heat and power plant (CHP) associated to TMP is replaced by a biomass-to-SNG (BtSNG) plant. Implementing BtSNG in a mechanical pulp production line might improve the profitability of a TMP mill and also help to commercialize the BtSNG technology by taking into account of some key issues such as biomass availability, heat utilization, etc. A TMP + BtSNG mathematical model is developed with ASPEN Plus. The model prediction shows that the scale of the TMP + BtSNG mill and SNG price are two strong factors for the implementation of BtSNG in a TMP mill. A BtSNG plant associated to a TMP mill should be built at a scale above 100 MW of biomass thermal input. For the case of Swedish economic condition, commercialization of SNG production as a transport biofuel has not matured yet. Political instruments to support commercialization of transport biofuel are necessary. Full article

We present a workflow for data sanitation and analysis of operation data with the goal of increasing energy efficiency and reliability in the operation of building-related energy systems. The workflow makes use of machine learning algorithms and innovative visualizations. The environment, in which monitoring data for energy systems are created, requires low configuration effort for data analysis. Therefore the focus lies on methods that operate automatically and require little or no configuration. As a result a generic workflow is created that is applicable to various energy-related time series data; it starts with data accessibility, followed by automated detection of duty cycles where applicable. The detection of outliers in the data and the sanitation of gaps ensure that the data quality is sufficient for an analysis by domain experts, in our case the analysis of system energy efficiency. To prove the feasibility of the approach, the sanitation and analysis workflow is implemented and applied to the recorded data of a solar driven adsorption chiller. Full article

This work investigates the possibility of providing a use to one of the major byproducts generated during biodiesel processing: glycerin. In particular, the steam gasification of water/glycerin mixtures is studied, analysing the influence of temperature (range 600–900 °C), inlet flow rate (0.5–3 mL·min⁻¹) and water/glycerin ratio (6–12 wt/wt, %) on the gas composition (H₂, CO, CH₄ and CO₂), higher heating value, and generated power. In general, a more diluted water/glycerin mixture is more interesting in order to provide a higher fraction of hydrogen in the gas produced, although it also involves a decrease in the power obtained. Higher temperatures cause a greater contribution of water gas and water gas shift reactions in all cases, thus increasing the H₂ proportion of the gas. Finally, a greater inlet flow rate increases gas production, but decreases the hydrogen proportion. Full article