Showing papers in "Energies in 2012"
TL;DR: More than two hundred publications have been reviewed, discussed and summarized, with the emphasis being placed on the current status of pyrolysis technology and its potential for commercial applications for bio-fuel production as mentioned in this paper.
Abstract: There has been an enormous amount of research in recent years in the area of thermo-chemical conversion of biomass into bio-fuels (bio-oil, bio-char and bio-gas) through pyrolysis technology due to its several socio-economic advantages as well as the fact it is an efficient conversion method compared to other thermo-chemical conversion technologies. However, this technology is not yet fully developed with respect to its commercial applications. In this study, more than two hundred publications are reviewed, discussed and summarized, with the emphasis being placed on the current status of pyrolysis technology and its potential for commercial applications for bio-fuel production. Aspects of pyrolysis technology such as pyrolysis principles, biomass sources and characteristics, types of pyrolysis, pyrolysis reactor design, pyrolysis products and their characteristics and economics of bio-fuel production are presented. It is found from this study that conversion of biomass to bio-fuel has to overcome challenges such as understanding the trade-off between the size of the pyrolysis plant and feedstock, improvement of the reliability of pyrolysis reactors and processes to become viable for commercial applications. Further study is required to achieve a better understanding of the economics of biomass pyrolysis for bio-fuel production, as well as resolving issues related to the capabilities of this technology in practical application.
1,020 citations
TL;DR: The potential of lipid induction techniques in microalgae and their application at commercial scale for the production of biodiesel are discussed and several genetic strategies for increased triacylglycerides production and inducibility are developed.
Abstract: Oil-accumulating microalgae have the potential to enable large-scale biodiesel production without competing for arable land or biodiverse natural landscapes. High lipid productivity of dominant, fast-growing algae is a major prerequisite for commercial production of microalgal oil-derived biodiesel. However, under optimal growth conditions, large amounts of algal biomass are produced, but with relatively low lipid contents, while species with high lipid contents are typically slow growing. Major advances in this area can be made through the induction of lipid biosynthesis, e.g., by environmental stresses. Lipids, in the form of triacylglycerides typically provide a storage function in the cell that enables microalgae to endure adverse environmental conditions. Essentially algal biomass and triacylglycerides compete for photosynthetic assimilate and a reprogramming of physiological pathways is required to stimulate lipid biosynthesis. There has been a wide range of studies carried out to identify and develop efficient lipid induction techniques in microalgae such as nutrients stress (e.g., nitrogen and/or phosphorus starvation), osmotic stress, radiation, pH, temperature, heavy metals and other chemicals. In addition, several genetic strategies for increased triacylglycerides production and inducibility are currently being developed. In this review, we discuss the potential of lipid induction techniques in microalgae and also their application at commercial scale for the production of biodiesel.
779 citations
TL;DR: A detailed review of the current state-of-the-art for wind turbine blade design is presented in this paper, including theoretical maximum efficiency, propulsion, practical efficiency, HAWT blade design, and blade loads.
Abstract: A detailed review of the current state-of-art for wind turbine blade design is presented, including theoretical maximum efficiency, propulsion, practical efficiency, HAWT blade design, and blade loads. The review provides a complete picture of wind turbine blade design and shows the dominance of modern turbines almost exclusive use of horizontal axis rotors. The aerodynamic design principles for a modern wind turbine blade are detailed, including blade plan shape/quantity, aerofoil selection and optimal attack angles. A detailed review of design loads on wind turbine blades is offered, describing aerodynamic, gravitational, centrifugal, gyroscopic and operational conditions.
379 citations
TL;DR: The use of gas fermentation for the production of low carbon biofuels such as ethanol or butanol from lignocellulosic biomass is an area currently undergoing intensive research and development, with the first commercial units expected to commence operation in the near future as discussed by the authors.
Abstract: The use of gas fermentation for the production of low carbon biofuels such as ethanol or butanol from lignocellulosic biomass is an area currently undergoing intensive research and development, with the first commercial units expected to commence operation in the near future. In this process, biomass is first converted into carbon monoxide (CO) and hydrogen (H2)-rich synthesis gas (syngas) via gasification, and subsequently fermented to hydrocarbons by acetogenic bacteria. Several studies have been performed over the last few years to optimise both biomass gasification and syngas fermentation with significant progress being reported in both areas. While challenges associated with the scale-up and operation of this novel process remain, this strategy offers numerous advantages compared with established fermentation and purely thermochemical approaches to biofuel production in terms of feedstock flexibility and production cost. In recent times, metabolic engineering and synthetic biology techniques have been applied to gas fermenting organisms, paving the way for gases to be used as the feedstock for the commercial production of increasingly energy dense fuels and more valuable chemicals.
357 citations
TL;DR: A summary of different aspects of the design and operation of small-scale, household, biogas digesters can be found in this article, where different digester designs and materials used for construction, important operating parameters such as pH, temperature, substrate, and loading rate, applications of the biogAS, the government policies concerning the use of household digesters, and the social and environmental effects of the digesters.
Abstract: This review is a summary of different aspects of the design and operation of small-scale, household, biogas digesters. It covers different digester designs and materials used for construction, important operating parameters such as pH, temperature, substrate, and loading rate, applications of the biogas, the government policies concerning the use of household digesters, and the social and environmental effects of the digesters. Biogas is a value-added product of anaerobic digestion of organic compounds. Biogas production depends on different factors including: pH, temperature, substrate, loading rate, hydraulic retention time (HRT), C/N ratio, and mixing. Household digesters are cheap, easy to handle, and reduce the amount of organic household waste. The size of these digesters varies between 1 and 150 m 3 . The common designs include fixed dome, floating drum, and plug flow type. Biogas and fertilizer obtained at the end of anaerobic digestion could be used for cooking, lighting, and electricity.
297 citations
TL;DR: In this article, a numerical study of atmospheric turbulence effects on wind-turbine wakes is presented, where the structure and characteristics of turbine wakes in the cases where the incident flows to the turbine have the same mean velocity at the hub height but different mean wind shears and turbulence intensity levels.
Abstract: A numerical study of atmospheric turbulence effects on wind-turbine wakes is presented. Large-eddy simulations of neutrally-stratified atmospheric boundary layer flows through stand-alone wind turbines were performed over homogeneous flat surfaces with four different aerodynamic roughness lengths. Emphasis is placed on the structure and characteristics of turbine wakes in the cases where the incident flows to the turbine have the same mean velocity at the hub height but different mean wind shears and turbulence intensity levels. The simulation results show that the different turbulence intensity levels of the incoming flow lead to considerable influence on the spatial distribution of the mean velocity deficit, turbulence intensity, and turbulent shear stress in the wake region. In particular, when the turbulence intensity level of the incoming flow is higher, the turbine-induced wake (velocity deficit) recovers faster, and the locations of the maximum turbulence intensity and turbulent stress are closer to the turbine. A detailed analysis of the turbulence kinetic energy budget in the wakes reveals also an important effect of the incoming flow turbulence level on the magnitude and spatial distribution of the shear production and transport terms.
273 citations
TL;DR: In this article, an extensive review of the scientific literature associated with various microwave pyrolysis applications in waste to energy engineering is presented, and it is concluded that more work is needed to extend existing understanding of these aspects in order to develop improvements to the process to transform it into a commercially viable route to recover energy from waste materials in an environmentally sustainable manner.
Abstract: This paper presents an extensive review of the scientific literature associated with various microwave pyrolysis applications in waste to energy engineering. It was established that microwave-heated pyrolysis processes offer a number of advantages over other processes that use traditional thermal heat sources. In particular, microwave-heated processes show a distinct advantage in providing rapid and energy-efficient heating compared to conventional technologies, and thus facilitating increased production rates. It can also be established that the pyrolysis process offers an exciting way to recover both the energetic and chemical value of the waste materials by generating potentially useful pyrolysis products suitable for future reuse. Furthermore, this review has revealed good performance of the microwave pyrolysis process when compared to other more conventional methods of operation, indicating that it shows exceptional promise as a means for energy recovery from waste materials. Nonetheless, it was revealed that many important characteristics of the microwave pyrolysis process have yet to be raised or fully investigated. In addition, limited information is available concerning the characteristics of the microwave pyrolysis of waste materials. It was thus concluded that more work is needed to extend existing understanding of these aspects in order to develop improvements to the process to transform it into a commercially viable route to recover energy from waste materials in an environmentally sustainable manner.
272 citations
TL;DR: In this article, a novel ANN model using statistical feature parameters (ANN-SFP) for short-term solar irradiance forecasting (STSIF) is proposed, where the input vector is reconstructed with several statistical feature parameter parameters of irradiance and ambient temperature.
Abstract: Short-term solar irradiance forecasting (STSIF) is of great significance for the optimal operation and power predication of grid-connected photovoltaic (PV) plants. However, STSIF is very complex to handle due to the random and nonlinear characteristics of solar irradiance under changeable weather conditions. Artificial Neural Network (ANN) is suitable for STSIF modeling and many research works on this topic are presented, but the conciseness and robustness of the existing models still need to be improved. After discussing the relation between weather variations and irradiance, the characteristics of the statistical feature parameters of irradiance under different weather conditions are figured out. A novel ANN model using statistical feature parameters (ANN-SFP) for STSIF is proposed in this paper. The input vector is reconstructed with several statistical feature parameters of irradiance and ambient temperature. Thus sufficient information can be effectively extracted from relatively few inputs and the model complexity is reduced. The model structure is determined by cross-validation (CV), and the Levenberg-Marquardt algorithm (LMA) is used for the network training. Simulations are carried out to validate and compare the proposed model with the conventional ANN model using historical data series (ANN-HDS), and the results indicated that the forecast accuracy is obviously improved under variable weather conditions.
263 citations
TL;DR: In this article, an ensemble of simulations of regional patterns of changes in runoff, computed from global circulation models (GCM) simulations with 12 different models, were used to evaluate the changes in global hydropower generation resulting from predicted changes in climate.
Abstract: Currently, hydropower accounts for close to 16% of the world’s total power supply and is the world’s most dominant (86%) source of renewable electrical energy. The key resource for hydropower generation is runoff, which is dependent on precipitation. The future global climate is uncertain and thus poses some risk for the hydropower generation sector. The crucial question and challenge then is what will be the impact of climate change on global hydropower generation and what are the resulting regional variations in hydropower generation potential? This paper is a study that aims to evaluate the changes in global hydropower generation resulting from predicted changes in climate. The study uses an ensemble of simulations of regional patterns of changes in runoff, computed from global circulation models (GCM) simulations with 12 different models. Based on these runoff changes, hydropower generation is estimated by relating the runoff changes to hydropower generation potential through geographical information system (GIS), based on 2005 hydropower generation. Hydropower data obtained from EIA (energy generation), national sites, FAO (water resources) and UNEP were used in the analysis. The countries/states were used as computational units to reduce the complexities of the analysis. The results indicate that there are large variations of changes (increases/decreases) in hydropower generation across regions and even within regions. Globally, hydropower generation is predicted to change very little by the year 2050 for the hydropower system in operation today. This change amounts to an increase of less than 1% of the current (2005) generation level although it is necessary to carry out basin level detailed assessment for local impacts which may differ from the country based values. There are many regions where runoff and hydropower generation will increase due to increasing precipitation, but also many regions where there will be a decrease. Based on this evaluation, it has been concluded that even if individual countries and regions may experience significant impacts, climate change will not lead to significant changes in the global hydropower generation, at least for the existing hydropower system.
248 citations
TL;DR: The accumulation of methane hydrate in marine sediments is controlled by a number of physical and biogeochemical parameters including the thickness of the gas hydrate stability zone (GHSZ), the solubility of methane in pore fluids, the accumulation of particulate organic carbon at the seafloor, the kinetics of microbial organic matter degradation and methane generation in marine sediment, sediment compaction and the ascent of deep-seated pore fluid and methane gas into the GHSZ as mentioned in this paper.
Abstract: The accumulation of methane hydrate in marine sediments is controlled by a number of physical and biogeochemical parameters including the thickness of the gas hydrate stability zone (GHSZ), the solubility of methane in pore fluids, the accumulation of particulate organic carbon at the seafloor, the kinetics of microbial organic matter degradation and methane generation in marine sediments, sediment compaction and the ascent of deep-seated pore fluids and methane gas into the GHSZ. Our present knowledge on these controlling factors is discussed and new estimates of global sediment and methane fluxes are provided applying a transport-reaction model at global scale. The modeling and the data evaluation yield improved and better constrained estimates of the global pore volume within the modern GHSZ ( ≥ 44 × 1015 m3), the Holocene POC accumulation rate at the seabed (~1.4 × 1014 g yr−1), the global rate of microbial methane production in the deep biosphere (4−25 × 1012 g C yr−1) and the inventory of methane hydrates in marine sediments ( ≥ 455 Gt of methane-bound carbon).
246 citations
TL;DR: In this article, Nannochloropsis salina was subjected to ranges of light intensity (5-850 μmol m−2 s−1) and temperature (13-40 °C) and its exponential growth rate, total fatty acids (TFA) and fatty acid composition were measured.
Abstract: Accurate prediction of algal biofuel yield will require empirical determination of physiological responses to the environment, particularly light and temperature. One strain of interest, Nannochloropsis salina, was subjected to ranges of light intensity (5–850 μmol m−2 s−1) and temperature (13–40 °C) and its exponential growth rate, total fatty acids (TFA) and fatty acid composition were measured. The maximum acclimated growth rate was 1.3 day−1 at 23 °C and 250 μmol m−2 s−1. Fatty acids were detected by gas chromatography with flame ionization detection (GC-FID) after transesterification to corresponding fatty acid methyl esters (FAMEs). A sharp increase in TFA containing elevated palmitic acid (C16:0) and palmitoleic acid (C16:1) during exponential growth at high light was observed, indicating likely triacylglycerol accumulation due to photo-oxidative stress. Lower light resulted in increases in the relative abundance of unsaturated fatty acids; in thin cultures, increases were observed in palmitoleic and eicosapentaenoic acids (C20:5ω3). As cultures aged and the effective light intensity per cell converged to very low levels, fatty acid profiles became more similar and there was a notable increase of oleic acid (C18:1ω9). The amount of unsaturated fatty acids was inversely proportional to temperature, demonstrating physiological adaptations to increase membrane fluidity. These data will improve prediction of fatty acid characteristics and yields relevant to biofuel production.
TL;DR: In this article, the authors investigated the likely environmental and technological challenges that increased ash generation may cause, and proposed sieve fractionation as a suitable method for the separation of unburnt carbon present in bottom ash obtained from a fixed-bed combustion system, followed by the application of the gasification technology to particle sizes of energy importance.
Abstract: In industrialized countries, it is expected that the future generation of bioenergy will be from the direct combustion of residues and wastes obtained from biomass. Bioenergy production using woody biomass is a fast developing application since this fuel source is considered to be carbon neutral. The harnessing of bioenergy from these sources produces residue in the form of ash. As the demand for bioenergy production increases, ash and residue volumes will increase. Major challenges will arise relating to the efficient management of these byproducts. The primary concerns for ash are its storage, disposal, use and the presence of unburned carbon. The continual increase in ash volume will result in decreased ash storage facilities (in cases of limited room for landfill expansion), as well as increased handling, transporting and spreading costs. The utilization of ash has been the focus of many studies, hence this review investigates the likely environmental and technological challenges that increased ash generation may cause. The presence of alkali metals, alkaline earth metals, chlorine, sulphur and silicon influences the reactivity and leaching to the inorganic phases which may have significant impacts on soils and the recycling of soil nutrient. Discussed are some of the existing technologies for the processing of ash. Unburned carbon present in ash allows for the exploration of using ash as a fuel. The paper proposes sieve fractionation as a suitable method for the separation of unburnt carbon present in bottom ash obtained from a fixed-bed combustion system, followed by the application of the gasification technology to particle sizes of energy importance. It is hoped that this process will significantly reduce the volume of ash disposed at landfills.
TL;DR: In this article, the performance of Li/S cells with a cathode containing 72% sulfur and 2 mg cm−2 sulfur loading was investigated. And the authors proposed an empirical method for determination of the optimized E/S ratio.
Abstract: A liquid electrolyte lithium/sulfur (Li/S) cell is a liquid electrochemical system. In discharge, sulfur is first reduced to highly soluble Li2S8, which dissolves into the organic electrolyte and serves as the liquid cathode. In solution, lithium polysulfide (PS) undergoes a series of complicated disproportionations, whose chemical equilibriums vary with the PS concentration and affect the cell’s performance. Since the PS concentration relates to a certain electrolyte/sulfur (E/S) ratio, there is an optimized E/S ratio for the cyclability of each Li/S cell system. In this work, we study the optimized E/S ratio by measuring the cycling performance of Li/S cells, and propose an empirical method for determination of the optimized E/S ratio. By employing an electrolyte of 0.25 m LiSO3CF3-0.25 m LiNO3 dissolved in a 1:1 (wt:wt) mixture of dimethyl ether (DME) and 1,3-dioxolane (DOL) in an optimized E/S ratio, we show that the Li/S cell with a cathode containing 72% sulfur and 2 mg cm−2 sulfur loading is able to retain a specific capacity of 780 mAh g−1 after 100 cycles at 0.5 mA cm−2 between 1.7 V and 2.8 V.
TL;DR: In this paper, the performances of various lithium-ion chemistries for use in plug-in hybrid electric vehicles have been investigated and compared to several other rechargeable energy storage systems technologies such as lead-acid, nickel-metal hydride and electrical double layer capacitors.
Abstract: In this paper, the performances of various lithium-ion chemistries for use in plug-in hybrid electric vehicles have been investigated and compared to several other rechargeable energy storage systems technologies such as lead-acid, nickel-metal hydride and electrical-double layer capacitors. The analysis has shown the beneficial properties of lithium-ion in the terms of energy density, power density and rate capabilities. Particularly, the nickel manganese cobalt oxide cathode stands out with the high energy density up to 160 Wh/kg, compared to 70-110, 90 and 71 Wh/kg for lithium iron phosphate cathode, lithium nickel cobalt aluminum cathode and, lithium titanate oxide anode battery cells, respectively. These values are considerably higher than the lead-acid (23-28 Wh/kg) and nickel-metal hydride (44-53 Wh/kg) battery technologies. The dynamic discharge performance test shows that the energy efficiency of the lithium-ion batteries is significantly higher than the lead-acid and nickel-metal hydride technologies. The efficiency varies between 86% and 98%, with the best values obtained by pouch battery cells, ahead of cylindrical and prismatic battery design concepts. Also the power capacity of lithium-ion technology is superior compared to other technologies. The power density is in the range of 300-2400 W/kg against 200-400 and 90-120 W/kg for lead-acid and nickel-metal hydride, respectively. However, considering the influence of energy efficiency, the power density is in the range of 100-1150 W/kg. Lithium-ion batteries optimized for high energy are at the
TL;DR: In this paper, the authors present and review practical issues of several simple and robust methods for microalgae isolation and selection for traits that maybe most relevant for commercial biodiesel production, and suggest that a combination of conventional and modern techniques is likely to be the most efficient route from isolation to large-scale cultivation.
Abstract: Biodiesel production from microalgae is being widely developed at different scales as a potential source of renewable energy with both economic and environmental benefits. Although many microalgae species have been identified and isolated for lipid production, there is currently no consensus as to which species provide the highest productivity. Different species are expected to function best at different aquatic, geographical and climatic conditions. In addition, other value-added products are now being considered for commercial production which necessitates the selection of the most capable algae strains suitable for multiple-product algae biorefineries. Here we present and review practical issues of several simple and robust methods for microalgae isolation and selection for traits that maybe most relevant for commercial biodiesel production. A combination of conventional and modern techniques is likely to be the most efficient route from isolation to large-scale cultivation.
TL;DR: In this article, the authors proposed transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation.
Abstract: Energy management systems strive to use energy resources efficiently, save energy, and reduce carbon output. This study proposes transient feature analyses of the transient response time and transient energy on the power signatures of non-intrusive demand monitoring and load identification to detect the power demand and load operation. This study uses the wavelet transform (WT) of the time-frequency domain to analyze and detect the transient physical behavior of loads during the load identification. The experimental results show the transient response time and transient energy are better than the steady-state features to improve the recognition accuracy and reduces computation requirements in non-intrusive load monitoring (NILM) systems. The discrete wavelet transform (DWT) is more suitable than short-time Fourier transform (STFT) for transient load analyses.
TL;DR: In this article, a simple algorithm was developed to determine the required number of generating units of wind-turbine generator and photovoltaic array, and the associated storage capacity for stand-alone hybrid microgrid.
Abstract: In this paper, we develop a simple algorithm to determine the required number of generating units of wind-turbine generator and photovoltaic array, and the associated storage capacity for stand-alone hybrid microgrid. The algorithm is based on the observation that the state of charge of battery should be periodically invariant. The optimal sizing of hybrid microgrid is given in the sense that the life cycle cost of system is minimized while the given load power demand can be satisfied without load rejection. We also report a case study to show the efficacy of the developed algorithm.
TL;DR: In this paper, a conceptual process design for methane hydrate production and pelletisation has been developed, and a hydrate carrier has been designed, featuring amongst other technical solutions a pivoted cargo system with the potential to mitigate sintering, an actively cooled containment and cargo distribution system and a dual fuel engine allowing the use of the boil-off gas.
Abstract: Within the German integrated project SUGAR, aiming for the development of new technologies for the exploration and exploitation of submarine gas hydrates, the option of gas transport by gas hydrate pellets has been comprehensively re-investigated. A series of pVT dissociation experiments, combined with analytical tools such as x-ray diffraction and cryo-SEM, were used to gather an additional level of understanding on effects controlling ice formation. Based on these new findings and the accessible literature, knowns and unknowns of the self-preservation effect important for the technology are summarized. A conceptual process design for methane hydrate production and pelletisation has been developed. For the major steps identified, comprising (i) hydrate formation; (ii) dewatering; (iii) pelletisation; (iv) pellet cooling; and (v) pressure relief, available technologies have been evaluated, and modifications and amendments included where needed. A hydrate carrier has been designed, featuring amongst other technical solutions a pivoted cargo system with the potential to mitigate sintering, an actively cooled containment and cargo distribution system, and a dual fuel engine allowing the use of the boil-off gas. The design was constrained by the properties of gas hydrate pellets, the expected operation on continental slopes in areas with rough seas, a scenario-defined loading capacity of 20,000 m3 methane hydrate pellets, and safety as well as environmental considerations. A risk analysis for the transport at sea has been carried out in this early stage of development, and the safety level of the new concept was compared to the safety level of other ship types with similar scopes, i.e., LNG carriers and crude oil tankers. Based on the results of the technological part of this study, and with best knowledge available on the alternative technologies, i.e., pipeline, LNG and CNG transportation, an evaluation of the economic competitiveness of the methane hydrate transport technology has been performed. The analysis considers capital investment as well as operational costs and comprises a wide set of scenarios with production rates from 20 to 800 103 Nm3·h−1 and transport distances from 200 to 10,000 km. In contrast to previous studies, the model calculations in this study reveal no economic benefit of methane hydrate transportation versus competing technologies.
TL;DR: In this paper, the authors present a concise overview of ash deposition in combustion or co-firing of biomass (woody biomass, agricultural residues, peat, etc.) with other fuels for power/heat generation.
Abstract: This paper presents a concise overview of ash deposition in combustion or co-firing of biomass (woody biomass, agricultural residues, peat, etc.) with other fuels for power/heat generation. In this article, the following five research aspects on biomass combustion ash deposition are reviewed and discussed: influence of biomass fuel characteristics, deposit-related challenges, ash deposition monitoring and analysis of ash deposits, mechanisms and chemistry of fly ash deposition, and key technologies for reducing ash deposition and corrosion in biomass-involved combustion.
TL;DR: In this article, the seasonal variations of lipid content and composition in large-scale cultivation were analyzed during May 2007-May 2009 in Nannochloropsis oculata grown outdoors in closed vertical flat panels photobioreactors.
Abstract: While focus in oil-producing microalgae is normally on nutrient deficiency, we addressed the seasonal variations of lipid content and composition in large-scale cultivation. Lipid content, fatty acid profiles and mono- di- and triglycerides (MAGs, DAGs, and TAGs) were analyzed during May 2007-May 2009 in Nannochloropsis oculata grown outdoors in closed vertical flat panels photobioreactors. Total lipids (TL) ranged from 11% of dry weight (DW) in winter to 30% of DW in autumn. 50% of the variation in TL could be explained by light and temperature. As the highest lipid content was recorded during autumn indicating an optimal, non-linear, response to light and temperature we hypothesize that enhanced thylakoid stacking under reduced light conditions resulted in more structural lipids, concomitantly with the increase in glycerides due to released photo-oxidative stress. The relative amount of monounsaturated fatty acids (MUFA) increased during autumn. This suggested a synthesis, either of structural fatty acids as MUFA, or a relative increase of C16:1 incorporated into TAGs and DAGs. Our results emphasize the significant role of environmental conditions governing lipid content and
TL;DR: In this article, an EU framework for renewable energy sources (RES-E) support policies should be designed to facilitate a carbon lock-out in the electricity sector, which hampers the adoption of RES-E technologies.
Abstract: As part of its climate strategy, the EU aims at increasing the share of electricity from renewable energy sources (RES-E) in overall electricity generation. Attaining this target poses a considerable challenge as the electricity sector is “locked” into a carbon-intensive system, which hampers the adoption of RES-E technologies. Electricity generation, transmission and distribution grids as well as storage and demand response are subject to important path dependences, which put existing, non-renewable energy sources at an advantage. This paper examines how an EU framework for RES-E support policies should be designed to facilitate a carbon lock-out. For this purpose, we specify the major technological, economic and institutional barriers to RES-E. For each of the barriers, a policy review is carried out which assesses the performance of existing policy instruments and identifies needs for reform. The review reveals several shortcomings: while policies targeting generation are widely in place, measures to address barriers associated with
TL;DR: In this paper, a new approach based on the dynamic electrochemical-polarization (EP) battery model, taking into consideration constraints of current, voltage, state of charge (SoC) and power is proposed.
Abstract: Battery peak power capability estimations play an important theoretical role for the proper use of the battery in electric vehicles. To address the failures in relaxation effects and real-time ability performance, neglecting the battery’s design limits and other issues of the traditional peak power capability calculation methods, a new approach based on the dynamic electrochemical-polarization (EP) battery model, taking into consideration constraints of current, voltage, state of charge (SoC) and power is proposed. A hardware-in-the-loop (HIL) system is built for validating the online model-based peak power capability estimation approach of batteries used in hybrid electric vehicles (HEVs) and a HIL test based on the Federal Urban Driving Schedules (FUDS) is used to verify and evaluate its real-time computation performance, reliability and robustness. The results show the proposed approach gives a more accurate estimate compared with the hybrid pulse power characterization (HPPC) method, avoiding over-charging or over-discharging and providing a powerful guarantee for the optimization of HEVs power systems. Furthermore, the HIL test provides valuable data and critical guidance to evaluate the accuracy of the developed battery algorithms.
TL;DR: In this paper, the performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat using 18 organic working fluids is presented, and the results reveal that in most cases, raising the expander inlet temperature is helpful to improve the net power output and the exergy efficiency.
Abstract: The performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat using 18 organic working fluids is presented. Several parameters, such as the net power output, exergy efficiency, expander size parameter (SP), and heat exchanger requirement of evaporator and the condenser, were used to evaluate the performance of this recovery cycle and screen the working fluids. The results reveal that in most cases, raising the expander inlet temperature is helpful to improve the net power output and the exergy efficiency. However, the effect of the expander inlet pressure on those parameters is related to the expander inlet temperature and working fluid used. Either lower expander inlet temperature and pressure, or higher expander inlet temperature and pressure, generally makes the net power output more. Lower expander inlet temperature results in larger total heat transfer requirement and expander size. According to the screening criteria of both the higher output and the lower investment, the following working fluids for the supercritical ORC system are recommended: R152a and R143a.
TL;DR: A L SSVM-based annual electric load forecasting model that uses FOA to automatically determine the appropriate values of the two parameters for the LSSVM model, which outperforms other alternative methods.
Abstract: The accuracy of annual electric load forecasting plays an important role in the economic and social benefits of electric power systems. The least squares support vector machine (LSSVM) has been proven to offer strong potential in forecasting issues, particularly by employing an appropriate meta-heuristic algorithm to determine the values of its two parameters. However, these meta-heuristic algorithms have the drawbacks of being hard to understand and reaching the global optimal solution slowly. As a novel meta-heuristic and evolutionary algorithm, the fruit fly optimization algorithm (FOA) has the advantages of being easy to understand and fast convergence to the global optimal solution. Therefore, to improve the forecasting performance, this paper proposes a LSSVM-based annual electric load forecasting model that uses FOA to automatically determine the appropriate values of the two parameters for the LSSVM model. By taking the annual electricity consumption of China as an instance, the computational result shows that the LSSVM combined with FOA (LSSVM-FOA) outperforms other alternative methods, namely single LSSVM, LSSVM combined with coupled simulated annealing algorithm (LSSVM-CSA), generalized regression neural network (GRNN) and regression model.
TL;DR: In this paper, the feasibility of CH4 replacement is proven from the points of view of kinetics and thermodynamics, and confirmed by experiments with gaseous CO2, liquid CO2 and CO2 emulsion.
Abstract: This paper introduces the research advances on replacement of CH4 in Natural Gas Hydrates (NGHs) by use of CO2 and discusses the advantages and disadvantages of the method on the natural gas production from such hydrates. Firstly, the feasibility of replacement is proven from the points of view of kinetics and thermodynamics, and confirmed by experiments. Then, the latest progress in CH4 replacement experiments with gaseous CO2, liquid CO2 and CO2 emulsion are presented Moreover, the superiority of CO2 emulsion for replacement of CH4 is emphasized. The latest experiment progress on preparation of CO2 emulsions are introduced. Finally, the advancements in simulation research on replacement is introduced, and the deficiencies of the simulations are pointed. The factors influencing on the replacement with different forms of CO2 are analyzed and the optimum conditions for the replacement of CH4 in hydrated with different forms of CO2 is suggested.
TL;DR: In this article, a data processing system is presented to analyze energy consumption patterns in industrial parks, based on the cascade application of a Self-Organizing Map (SOM) and the clustering k-means algorithm.
Abstract: Understanding of energy consumption patterns is extremely important for optimization of resources and application of green trends Traditionally, analyses were performed for large environments like regions and nations However, with the advent of Smart Grids, the study of the behavior of smaller environments has become a necessity to allow a deeper micromanagement of the energy grid This paper presents a data processing system to analyze energy consumption patterns in industrial parks, based on the cascade application of a Self-Organizing Map (SOM) and the clustering k-means algorithm The system is validated with real load data from an industrial park in Spain The validation results show that the system adequately finds different behavior patterns which are meaningful, and is capable of doing so without supervision, and without any prior knowledge about the data
TL;DR: In this article, a biomass waste, rice husk, was inspected by thermoanalytical investigation to evaluate its capability as an adsorbent medium for tar removal, and the results showed that subsequent to high temperature pyrolysis, Rice husk char became a highly porous material, which was suitable as tar removal adorbent with the ability to remove tar effectively.
Abstract: A biomass waste, rice husk, was inspected by thermoanalytical investigation to evaluate its capability as an adsorbent medium for tar removal. The pyrolysis process has been applied to the rice husk material at different temperatures 600, 800 and 1000 °C with 20 °C/min heating rate, to investigate two topics: (1) influence of temperature on characterization of rice husk char and; (2) adsorption capability of rice husk char for tar removal. The results showed that subsequent to high temperature pyrolysis, rice husk char became a highly porous material, which was suitable as tar removal adsorbent with the ability to remove tar effectively. In addition, char characteristics and tar removal ability were significantly influenced by the pyrolysis temperature.
TL;DR: The Sea-wave Slot-cone Generator (SSG) as discussed by the authors is a Wave Energy Converter based on the wave overtopping principle; it employs several reservoirs placed on top of each other, in which the energy of incoming waves is stored as potential energy.
Abstract: The Sea-wave Slot-cone Generator (SSG) is a Wave Energy Converter based on the wave overtopping principle; it employs several reservoirs placed on top of each other, in which the energy of incoming waves is stored as potential energy. Then, the captured water runs through turbines for electricity production. The system works under a wide spectrum of different wave conditions, giving a high overall efficiency. It can be suitable for shoreline and breakwater applications and presents particular advantages, such as sharing structure costs, availability of grid connection and recirculation of water inside the harbor, as the outlet of the turbines is on the rear part of the system. Recently, plans for the SSG pilot installations are in progress at the Svaaheia site (Norway), the port of Hanstholm (Denmark) and the port of Garibaldi (Oregon, USA). In the last-mentioned two projects, the Sea-wave Slot-cone Generator technology is integrated into the outer harbor breakwater and jetty reconstruction projects. In the last years extensive studies have been performed on the hydraulic and the structural response of this converter, with the aim of optimizing the design process. The investigations have been conducted by physical model tests and numerical simulations and many results have been published on both conference proceedings and journals. The main scope of this paper is reviewing the most significant findings, to provide the reader with an organic overview on the present status of knowledge.
TL;DR: In this article, the authors compared the life-cycle greenhouse gas (GHG) intensities per megawatt-hour (MWh) of electricity produced for a range of Australian and other energy sources, including coal, conventional liquefied natural gas (LNG), coal seam gas LNG, nuclear and renewables, for the Australian export market.
Abstract: Electricity generation is one of the major contributors to global greenhouse gas emissions. Transitioning the World’s energy economy to a lower carbon future will require significant investment in a variety of cleaner technologies, including renewables and nuclear power. In the short term, improving the efficiency of fossil fuel combustion in energy generation can provide an important contribution. Availability of life cycle GHG intensity data will allow decision-makers to move away from overly simplistic assertions about the relative merits of certain fuels, and focus on the complete picture, especially the critical roles of technology selection and application of best practice. This analysis compares the life-cycle greenhouse gas (GHG) intensities per megawatt-hour (MWh) of electricity produced for a range of Australian and other energy sources, including coal, conventional liquefied natural gas (LNG), coal seam gas LNG, nuclear and renewables, for the Australian export market. When Australian fossil fuels are exported to China, life cycle greenhouse gas emission intensity in electricity production depends to a significant degree on the technology used in combustion. LNG in general is less GHG intensive than black coal, but the gap is smaller for gas combusted in open cycle gas turbine plant (OCGT) and for LNG derived from coal seam gas (CSG). On average, conventional LNG burned in a conventional OCGT plant is approximately 38% less GHG intensive over its life cycle than black coal burned in a sub-critical plant, per MWh of electricity produced. However, if OCGT LNG combustion is compared to the most efficient new ultra-supercritical coal power, the GHG intensity gap narrows considerably. Coal seam gas LNG is approximately 13–20% more GHG intensive across its life cycle, on a like-for like basis, than conventional LNG. Upstream fugitive emissions from CSG (assuming best practice gas extraction techniques) do not materially alter the life cycle GHG intensity rankings, such is the dominance of end-use combustion, but application of the most recent estimates of the 20-year global warming potential (GWP) increases the contribution of fugitives considerably if best practice fugitives management is not assumed. However, if methane leakage approaches the elevated levels recently reported in some US gas fields (circa 4% of gas production) and assuming a 20-year methane GWP, the GHG intensity of CSG-LNG generation is on a par with sub-critical coal-fired generation. The importance of applying best practice to fugitives management in Australia’s emerging natural gas industry is evident. When exported to China for electricity production, LNG was found to be 22–36 times more GHG intensive than wind and concentrated solar thermal (CST) power and 13–21 times more GHG intensive than nuclear power which, even in the post-Fukushima world, continues to be a key option for global GHG reduction.
TL;DR: In this paper, the authors show that the injection of hot, supercritical CO2 is particularly promising for the recovery of natural gas from CH4-hydrate deposits in sub-marine and sub-permafrost environments through injection of CO2, which is considered a suitable strategy towards emission-neutral energy production.
Abstract: The recovery of natural gas from CH4-hydrate deposits in sub-marine and sub-permafrost environments through injection of CO2 is considered a suitable strategy towards emission-neutral energy production. This study shows that the injection of hot, supercritical CO2 is particularly promising. The addition of heat triggers the dissociation of CH4-hydrate while the CO2, once thermally equilibrated, reacts with the pore water and is retained in the reservoir as immobile CO2-hydrate. Furthermore, optimal reservoir conditions of pressure and temperature are constrained. Experiments were conducted in a high-pressure flow-through reactor at different sediment temperatures (2 °C, 8 °C, 10 °C) and hydrostatic pressures (8 MPa, 13 MPa). The efficiency of both, CH4 production and CO2 retention is best at 8 °C, 13 MPa. Here, both CO2- and CH4-hydrate as well as mixed hydrates can form. At 2 °C, the production process was less effective due to congestion of transport pathways through the sediment by rapidly forming CO2-hydrate. In contrast, at 10 °C CH4 production suffered from local increases in permeability and fast breakthrough of the injection fluid, thereby confining the accessibility to the CH4 pool to only the most prominent fluid channels. Mass and volume balancing of the collected gas and fluid stream identified gas mobilization as equally important process parameter in addition to the rates of methane hydrate dissociation and hydrate conversion. Thus, the combination of heat supply and CO2 injection in one supercritical phase helps to overcome the mass transfer limitations usually observed in experiments with cold liquid or gaseous CO2.