Open AccessArticle
Sliding Surface in Consensus Problem of Multi-Agent Rigid Manipulators with Neural Network Controller
Energies 2017, 10(12), 2127; doi:10.3390/en10122127 (registering DOI) -
Abstract
Based on Lyapunov theory, this research demonstrates the stability of the sliding surface in the consensus problem of multi-agent systems. Each agent in this system is represented by the dynamically uncertain robot, unstructured disturbances, and nonlinear friction, especially when the dynamic function of
[...] Read more.
Based on Lyapunov theory, this research demonstrates the stability of the sliding surface in the consensus problem of multi-agent systems. Each agent in this system is represented by the dynamically uncertain robot, unstructured disturbances, and nonlinear friction, especially when the dynamic function of agent is unknown. All system states use neural network online weight tuning algorithms to compensate for the disturbance and uncertainty. Each agent in the system has a different position, and their trajectory approach to the same target is from each distinct orientation. In this research, we analyze the design of the sliding surface for this model and demonstrate which type of sliding surface is the best for the consensus problem. Lastly, simulation results are presented to certify the correctness and the effectiveness of the proposed control method. Full article
Figures

Figure 1

Open AccessArticle
Wide Area Coordinated Control of Multi-FACTS Devices to Damp Power System Oscillations
Energies 2017, 10(12), 2130; doi:10.3390/en10122130 (registering DOI) -
Abstract
Aiming at damping the inter-area oscillations of power systems, the present study proposes a wide-area decentralized coordinated control framework, where the upper-level controller is designed to coordinate the lower-level multiple FACTS devices. Based on the polytopic differential inclusion method, the derived controller adopts
[...] Read more.
Aiming at damping the inter-area oscillations of power systems, the present study proposes a wide-area decentralized coordinated control framework, where the upper-level controller is designed to coordinate the lower-level multiple FACTS devices. Based on the polytopic differential inclusion method, the derived controller adopts a decentralized structure and it is guaranteed to be robust to meet the demand of operation under multiple operating conditions. Since time delay of wide area signal transmission is inevitable, in what follows, the quantum evolution algorithm (QEA) method is introduced to find an optimal solution of the time-delay coordinated controller. In this regard, the stability of the system with a prescribed time delay is guaranteed and the system damping ratio is increased. Effectiveness and applicability of the proposed controller design methods have been demonstrated through numerical simulations. Full article
Open AccessArticle
A Modified Version of the RNG kε Turbulence Model for the Scale-Resolving Simulation of Internal Combustion Engines
Energies 2017, 10(12), 2116; doi:10.3390/en10122116 (registering DOI) -
Abstract
The unsteady and random character of turbulent flow motion is a key aspect of the multidimensional modeling of internal combustion engines (ICEs). A typical example can be found in the prediction of the cycle-to-cycle variability (CCV) in modern, highly downsized gasoline direct injection
[...] Read more.
The unsteady and random character of turbulent flow motion is a key aspect of the multidimensional modeling of internal combustion engines (ICEs). A typical example can be found in the prediction of the cycle-to-cycle variability (CCV) in modern, highly downsized gasoline direct injection (GDI) engines, which strongly depends on the accurate simulation of turbulent in-cylinder flow structures. The current standard for turbulence modeling in ICEs is still represented by the unsteady form of Reynold-averaged Navier Stokes equations (URANS), which allows the simulation of full engine cycles at relatively low computational costs. URANS-based methods, however, are only able to return a statistical description of turbulence, as the effects of all scales of motion are entirely modeled. Therefore, during the last decade, scale-resolving methods such as large eddy simulation (LES) or hybrid URANS/LES approaches are gaining increasing attention among the engine-modeling community. In the present paper, we propose a scale-resolving capable modification of the popular RNG kε URANS model. The modification is based on a detached-eddy simulation (DES) framework and allows one to explicitly set the behavior (URANS, DES or LES) of the model in different zones of the computational domain. The resulting zonal formulation has been tested on two reference test cases, comparing the numerical predictions with the available experimental data sets and with previous computational studies. Overall, the scale-resolved part of the computed flow has been found to be consistent with the expected flow physics, thus confirming the validity of the proposed simulation methodology. Full article
Figures

Figure 1

Open AccessArticle
Environmental Impact of End-of-Life Tires: Life Cycle Assessment Comparison of Three Scenarios from a Case Study in Valle Del Cauca, Colombia
Energies 2017, 10(12), 2117; doi:10.3390/en10122117 (registering DOI) -
Abstract
Life Cycle Assessment methodology has been applied to estimate diverse environmental impacts of different usage alternatives for worn-out tires at the end of their useful life in a case study at the Department of Valle del Cauca, Colombia. Different real scenarios were compared,
[...] Read more.
Life Cycle Assessment methodology has been applied to estimate diverse environmental impacts of different usage alternatives for worn-out tires at the end of their useful life in a case study at the Department of Valle del Cauca, Colombia. Different real scenarios were compared, which allowed for the assessment of the best environmental option for the management of worn-out tires. A method developed in the Institute of Environmental Sciences at University of Leiden, better known as CML-2001, was used to calculate the environmental impact indicators. The results show that the incineration of whole tires in cement plants, and the activities of grinding and floor manufacturing from granulated rubber, exhibited the best indicators, especially in terms of environmental load avoidance through the recovery of materials. Finally, the categories of depletion of the ozone layer, acidification, global warming potential, depletion of abiotic resources, and photochemical ozone formation revealed that the strongest environmental impacts are associated with retreading and the production of multipart asphalt. This is due to the use of synthetic rubber in the former alternative, and of liquid asphalt, gravel, and diesel consumption in the latter. Full article
Figures

Figure 1

Open AccessArticle
Potential of Tropical Fruit Waste Biomass for Production of Bio-Briquette Fuel: Using Indonesia as an Example
Energies 2017, 10(12), 2119; doi:10.3390/en10122119 (registering DOI) -
Abstract
Within developing countries, there is an appeal to use waste biomass for energy generation in the form of bio-briquettes. This study investigated the potential use of bio-briquettes that are produced from the waste biomass of the following tropical fruits: durian (Durio zibethinus
[...] Read more.
Within developing countries, there is an appeal to use waste biomass for energy generation in the form of bio-briquettes. This study investigated the potential use of bio-briquettes that are produced from the waste biomass of the following tropical fruits: durian (Durio zibethinus), coconut (Cocos nucifera), coffee (Coffea arabica), cacao (Theobroma cacao), banana (Musa acuminata) and rambutan (Nephelium lappaceum). All fruit waste biomass samples exhibited an extremely high level of initial moisture content (78.22% in average). Fruit samples with the highest proportion of fruit waste biomass (of total unprocessed fruit mass) were represented by cacao (83.82%), durian (62.56%) and coconut (56.83%). Highest energy potentials (calorific value) of fruit waste biomass were observed in case of coconut (18.22 MJ∙kg−1), banana (17.79 MJ∙kg−1) and durian (17.60 MJ∙kg−1) fruit samples, whereas fruit waste biomass with the lowest level of ash content originated from the rambutan (3.67%), coconut (4.52%), and durian (5.05%) fruit samples. When investigating the energy demands to produce bio-briquettes from such feedstock materials, the best results (lowest amount of required deformation energy in combination with highest level of bio-briquette bulk density) were achieved by the rambutan, durian and banana fruit waste biomass samples. Finally, all investigated bio-briquette samples presented satisfactory levels of bulk density (>1050 kg∙m−3). In conclusion, our results indicated the practicability and viability of such bio-briquette fuel production, as well as supporting the fact that bio-briquettes from tropical fruit waste biomass can offer a potentially attractive energy source with many benefits, especially in rural areas. Full article
Figures

Figure 1

Open AccessArticle
Measuring Renewable Energy Development in the Eastern Bloc of the European Union
Energies 2017, 10(12), 2120; doi:10.3390/en10122120 (registering DOI) -
Abstract
This paper aims to investigate the energy development in terms of renewable energy in the Eastern Bloc European Union member states. Energy is a topic of planetary implications and the analysis of the development of renewable energy sources (RES) in parts of the
[...] Read more.
This paper aims to investigate the energy development in terms of renewable energy in the Eastern Bloc European Union member states. Energy is a topic of planetary implications and the analysis of the development of renewable energy sources (RES) in parts of the world where the fossil fuels are scarce is of tremendous importance. In the first section, the paper concisely explores the energy landscape of the European Union (EU), revealing important concerns. The second section introduces an index of renewable energy development (IRED) which captures the complexity of the development of RES and is based on two components, each containing three factors built on efforts and outcomes in RES development. IRED is further applied on a cross-country analysis based on the Eastern Bloc of the EU member states for 2005–2015 interval, revealing the best and worst performers. The application of IRED might contribute to a better understanding of the needed efforts required by different countries in their quest towards energy security, efficient energy use and emissions control. The findings of this paper might conduct to the identification of the best practices which could be spread throughout EU and might contribute to a more rigorous development of policymaking in the energy area. Full article
Figures

Figure 1

Open AccessArticle
Boolean Network-Based Sensor Selection with Application to the Fault Diagnosis of a Nuclear Plant
Energies 2017, 10(12), 2125; doi:10.3390/en10122125 (registering DOI) -
Abstract
Fault diagnosis is crucial for the operation of energy systems such as nuclear plants, and heavily relies on various types of sensors for temperature, pressure, concentration, etc. Due to the redundancy of sensors in each energy system, the sensor selection scheme can deeply
[...] Read more.
Fault diagnosis is crucial for the operation of energy systems such as nuclear plants, and heavily relies on various types of sensors for temperature, pressure, concentration, etc. Due to the redundancy of sensors in each energy system, the sensor selection scheme can deeply influence the diagnostic efficiency. In this paper, a Boolean network (BN) with its linear representation is proposed for describing the fault propagation among sensors. Both the sufficient condition of fault detectability and that of fault discriminability are given. Then, a sensor selection method for fault detection and discrimination is proposed. Finally, the theoretic result is applied to realize the diagnosis oriented sensor selection for a nuclear steam supply system based on a modular high temperature gas-cooled reactor (MHTGR). The computation and simulation results verify the correctness of the theoretical results. Full article
Open AccessArticle
Effect on Vehicle Turbocharger Exhaust Gas Energy Utilization for the Performance of Centrifugal Compressors under Plateau Conditions
Energies 2017, 10(12), 2121; doi:10.3390/en10122121 (registering DOI) -
Abstract
This paper is focused on the performance of centrifugal compressors for vehicle turbochargers operating at high altitude. The reasons for turbocharged diesel engine power loss increases and bad economy performance caused by exhaust gas energy utilization are investigated. The atmosphere’s impact on the
[...] Read more.
This paper is focused on the performance of centrifugal compressors for vehicle turbochargers operating at high altitude. The reasons for turbocharged diesel engine power loss increases and bad economy performance caused by exhaust gas energy utilization are investigated. The atmosphere’s impact on the turbocharger centrifugal compressor’s energy distribution characteristics under the plateau is discussed. The key parameters that affect compressor characteristics are concluded in a theoretical method. A simulation calculation model is established to accurately predict compressor performance at high altitude. By comparing the experimental results, the calculation results are validated. The details of the internal flow fields analysis, including critical parameters of a compressor operating at high altitude, are analyzed. The results show that with the increase of altitude from 0 m to 4500 m, the peak efficiency of the compressor is reduced by 2.4%, while the peak pressure ratio is increased by 7%. The main influence characters of the plateau environment on the turbocharger centrifugal compressor performance, such as blade loads, exergy utilization and entropy distribution are concluded. The key factors for compressor performance and compressor energy flow control design method operated at high altitude are obtained. Full article
Figures

Figure 1

Open AccessArticle
An Improved Lubrication Model between Piston Rings and Cylinder Liners with Consideration of Liner Dynamic Deformations
Energies 2017, 10(12), 2122; doi:10.3390/en10122122 (registering DOI) -
Abstract
The friction pair of piston rings and cylinder liner is one of the most important friction couplings in an internal combustion engine. It influences engine efficiency and service life. Under the excitation of piston slaps, the dynamic deformation of cylinder liner is close
[...] Read more.
The friction pair of piston rings and cylinder liner is one of the most important friction couplings in an internal combustion engine. It influences engine efficiency and service life. Under the excitation of piston slaps, the dynamic deformation of cylinder liner is close to the surface roughness magnitudes, which can affect the friction and lubrication performance between the piston rings and cylinder assemblies. To investigate the potential influences of structural deformations to tribological behaviours of cylinder assemblies, the dynamic deformation of the inner surface due to pistons slaps is obtained by dynamic simulations, and then coupled into an improved lubrication model. Different from the traditional lubrication model which takes the pressure stress factor and shear stress factor to be constant, the model proposed in this paper calculated these factors in real time using numerical integration to achieve a more realistic simulation. Based on the improved piston rings and cylinder liner lubrication model, the minimum oil film thickness and friction force curves are obtained for an entire work cycle. It shows that the friction force obtained from the improved model manifests clear oscillations in each stoke, which is different from the smoothed profiles predicted traditionally. Moreover, the average amplitude of the friction forces also shows clear reduction. Full article
Figures

Figure 1

Open AccessArticle
Chip Temperature-Based Workload Allocation for Holistic Power Minimization in Air-Cooled Data Center
Energies 2017, 10(12), 2123; doi:10.3390/en10122123 (registering DOI) -
Abstract
Minimizing the energy consumption is a dominant problem in data center design and operation. To cope with this issue, the common approach is to optimize the data center layout and the workload distribution among servers. Previous works have mainly adopted the temperature at
[...] Read more.
Minimizing the energy consumption is a dominant problem in data center design and operation. To cope with this issue, the common approach is to optimize the data center layout and the workload distribution among servers. Previous works have mainly adopted the temperature at the server inlet as the optimization constraint. However, the inlet temperature does not properly characterize the server’s thermal state. In this paper, a chip temperature-based workload allocation strategy (CTWA-MTP) is proposed to reduce the holistic power consumption in data centers. Our method adopts an abstract heat-flow model to describe the thermal environment in data centers and uses a thermal resistance model to describe the convective heat transfer of the server. The core optimizes the workload allocation with respect to the chip temperature threshold. In addition, the temperature-dependent leakage power of the server has been considered in our model. The proposed method is described as a constrained nonlinear optimization problem to find the optimal solution by a genetic algorithm (GA). We applied the method to a sample data center constructed with computational fluid dynamics (CFD) software. By comparing the simulation results with other different workload allocation strategies, the proposed method prevents the servers from overcooling and achieves a substantial energy saving by optimizing the workload allocation in an air-cooled data center. Full article
Figures

Figure 1

Open AccessArticle
Power Swing Generated in Francis Turbines by Part Load and Overload Instabilities
Energies 2017, 10(12), 2124; doi:10.3390/en10122124 (registering DOI) -
Abstract
Hydropower plays a key role in the actual energy market due to its fast response and regulation capacity. In that way, hydraulic turbines are increasingly demanded to work at off-design conditions, where complex flow patterns and cavitation appear, especially in Francis turbines. The
[...] Read more.
Hydropower plays a key role in the actual energy market due to its fast response and regulation capacity. In that way, hydraulic turbines are increasingly demanded to work at off-design conditions, where complex flow patterns and cavitation appear, especially in Francis turbines. The draft tube cavitation surge is a hydraulic phenomenon that appears in Francis turbines below and above its Best Efficiency Point (BEP). It is a low frequency phenomenon consisting of a vortex rope in the runner outlet and draft tube, which can become unstable when its frequency coincides with a natural frequency of the hydraulic circuit. At this situation, the output power can significantly swing, endangering the electrical grid stability. This study is focused on the detection of these instabilities in Francis turbines and their relationship with the output power swings. To do so, extensive experimental tests for different operating conditions have been carried out in a large prototype Francis turbine (444 MW of rated power) within the frame of the European Project Hyperbole (FP7-ENERGY-2013-1). Several sensors have been installed in the hydraulic circuit (pressure sensors in the draft tube, spiral casing, and penstock), in the rotating and static structures (vibration sensors, proximity probes, and strain gauges in the runner and in the shaft), as well as in the electrical side (output power, intensity, and voltage). Moreover, a numerical Finite Element Method (FEM) has been also used to relate the hydraulic excitation with the output power swing. Full article
Figures

Figure 1

Open AccessArticle
Distribution and Presence of Polymers in Porous Media
Energies 2017, 10(12), 2118; doi:10.3390/en10122118 (registering DOI) -
Abstract
In order to better utilize the residual polymers formed after polymer flooding, the distribution and the presence of the polymers after polymer flooding were studied. This paper studied the vertical and plane distribution of the hydrophobically-associating polymer in addition to measuring the parameters
[...] Read more.
In order to better utilize the residual polymers formed after polymer flooding, the distribution and the presence of the polymers after polymer flooding were studied. This paper studied the vertical and plane distribution of the hydrophobically-associating polymer in addition to measuring the parameters after polymer flooding, which is important for numerical reservoir simulation. The results showed that the polymers mainly enter into the high permeability zone and distribute in the mainstream line area with only a small portion in the wing area. Based on the comparison of various experimental methods, double-slug experiments were chosen to measure the inaccessible pore volume and retention, which is considered to be the most accurate, most time-consuming and most complex method. Following this, we improved the processing method of experimental data by reducing it to one experiment with two parameters. At the same time, we further enhanced the accuracy of the experimental results. The results show that at 1750 mg/L, the inaccessible pore volume of the polymer is 25.8%. When the detention is 68.2 µg/g, the inaccessible pore volume constituted 22% of the total polymer, with the other 77.7% being the dissolved polymer. Moreover, the static adsorption and dynamic detention were measured, with the results showing that the static adsorption is larger than dynamic detention. Therefore, in the numerical reservoir simulation, using the static adsorption capacity instead of the dynamic detention is unreasonable. The double-slug method was chosen since it is more accurate for the determination of various parameters. Meanwhile, in order to enhance the accuracy of results, we improved the treatment of data. Full article
Figures

Figure 1

Open AccessReview
Utilization of Microalgal Biofractions for Bioethanol, Higher Alcohols, and Biodiesel Production: A Review
Energies 2017, 10(12), 2110; doi:10.3390/en10122110 -
Abstract
Biomass is a crucial energy resource used for the generation of electricity and transportation fuels. Microalgae exhibit a high content of biocomponents which makes them a potential feedstock for the generation of ecofriendly biofuels. Biofuels derived from microalgae are suitable carbon-neutral replacements for
[...] Read more.
Biomass is a crucial energy resource used for the generation of electricity and transportation fuels. Microalgae exhibit a high content of biocomponents which makes them a potential feedstock for the generation of ecofriendly biofuels. Biofuels derived from microalgae are suitable carbon-neutral replacements for petroleum. Fermentation is the major process for metabolic conversion of microalgal biocompounds into biofuels such as bioethanol and higher alcohols. In this review, we explored the use of all three major biocomponents of microalgal biomass including carbohydrates, proteins, and lipids for maximum biofuel generation. Application of several pretreatment methods for enhancement the bioavailability of substrates (simple sugar, amino acid, and fatty acid) was discussed. This review goes one step further to discuss how to direct these biocomponents for the generation of various biofuels (bioethanol, higher alcohol, and biodiesel) through fermentation and transesterification processes. Such an approach would result in the maximum utilization of biomasses for economically feasible biofuel production. Full article
Figures

Open AccessArticle
Optimal Design of a Multi-Carrier Microgrid (MCMG) Considering Net Zero Emission
Energies 2017, 10(12), 2109; doi:10.3390/en10122109 -
Abstract
In this paper, a two-stage optimum planning and design method for a multi-carrier microgrid (MCMG) is presented in the targeted operation period considering energy purchasing and the component’s maintenance costs. An MCMG is most likely owned by a community or small group of
[...] Read more.
In this paper, a two-stage optimum planning and design method for a multi-carrier microgrid (MCMG) is presented in the targeted operation period considering energy purchasing and the component’s maintenance costs. An MCMG is most likely owned by a community or small group of public and private sectors comprising loads and distributed energy resources (DERs) with the ability of self-supply to regulate the flows of various energies to local consumers. The operation cost is undoubtedly reduced by selecting the proper components. In the proposed model, the investment and operation and maintenance costs of MCMG are simultaneously carried out in order to choose the right component and its size in the given period. Moreover, in this innovative model, net zero emission (NZE) is regarded as an environmental constraint. The genetic algorithm of MATLAB and the mixed-integer nonlinear programming (MINLP) technique of GAMS (general algebraic modeling system) software are used to solve the optimization problem. Illustrative examples show the efficiency of the proposed model. Full article
Figures

Figure 1

Open AccessArticle
Chance-Constrained Real-Time Dispatch with Renewable Uncertainty Based on Dynamic Load Flow
Energies 2017, 10(12), 2111; doi:10.3390/en10122111 -
Abstract
In this paper, a comprehensive real-time dispatch model considering renewable uncertainty based on dynamic load flow (DLF) is proposed. Through DLF, the primary and secondary frequency regulation amount caused by the variation of renewable energy as well as the line flow when primary
[...] Read more.
In this paper, a comprehensive real-time dispatch model considering renewable uncertainty based on dynamic load flow (DLF) is proposed. Through DLF, the primary and secondary frequency regulation amount caused by the variation of renewable energy as well as the line flow when primary and secondary regulation are deployed can be obtained easily. Not only the frequency constraints, but also the regular constraints like generator production limits and line flow limits are respected under both primary and secondary frequency regulation. To solve the dispatch problem with renewable uncertainty, chance-constrained programming based on cumulants and Cornish-fisher expansions (CCP-CMCF) is adopted to get the probability of holding the chance constraints and then the real-time dispatch model can be transformed into a quadratic programming. The simulation results show that the dispatch model proposed in this paper can deal with both primary and secondary regulation well and has a fast computation speed. Full article
Figures

Figure 1

Open AccessArticle
Reducing WCET Overestimations by Correcting Errors in Loop Bound Constraints
Energies 2017, 10(12), 2113; doi:10.3390/en10122113 -
Abstract
In order to reduce overestimations of worst-case execution time (WCET), in this article, we firstly report a kind of specific WCET overestimation caused by non-orthogonal nested loops. Then, we propose a novel correction approach which has three basic steps. The first step is
[...] Read more.
In order to reduce overestimations of worst-case execution time (WCET), in this article, we firstly report a kind of specific WCET overestimation caused by non-orthogonal nested loops. Then, we propose a novel correction approach which has three basic steps. The first step is to locate the worst-case execution path (WCEP) in the control flow graph and then map it onto source code. The second step is to identify non-orthogonal nested loops from the WCEP by means of an abstract syntax tree. The last step is to recursively calculate the WCET errors caused by the loose loop bound constraints, and then subtract the total errors from the overestimations. The novelty lies in the fact that the WCET correction is only conducted on the non-branching part of WCEP, thus avoiding potential safety risks caused by possible WCEP switches. Experimental results show that our approach reduces the specific WCET overestimation by an average of more than 82%, and 100% of corrected WCET is no less than the actual WCET. Thus, our approach is not only effective but also safe. It will help developers to design energy-efficient and safe real-time systems. Full article
Figures

Figure 1

Open AccessArticle
The Effect of Wind Forcing on Modeling Coastal Circulation at a Marine Renewable Test Site
Energies 2017, 10(12), 2114; doi:10.3390/en10122114 -
Abstract
The hydrodynamic circulation in estuaries is primarily driven by tides, river inflows and surface winds. While tidal and river data can be quite easily obtained for input to hydrodynamic models, sourcing accurate surface wind data is problematic. Inaccurate wind data can lead to
[...] Read more.
The hydrodynamic circulation in estuaries is primarily driven by tides, river inflows and surface winds. While tidal and river data can be quite easily obtained for input to hydrodynamic models, sourcing accurate surface wind data is problematic. Inaccurate wind data can lead to inaccuracies in the surface currents computed by three-dimensional hydrodynamic models. In this research, a high-resolution wind model was coupled with a three-dimensional hydrodynamic model of Galway Bay, a semi-enclosed estuary on the west coast of Ireland, to investigate the effect of wind forcing on model accuracy. Two wind-forcing conditions were investigated: (1) using wind data measured onshore on the NUI Galway campus (NUIG) and (2) using offshore wind data provided by a high resolution wind model (HR). A scenario with no wind forcing (NW) was also assessed. The onshore wind data varied with time but the speed and direction were applied across the full model domain. The modeled offshore wind fields varied with both time and space. The effect of wind forcing on modeled hydrodynamics was assessed via comparison of modeled surface currents with surface current measurements obtained from a High-Frequency (HF) radar Coastal Ocean Dynamics Applications Radar (CODAR) observation system. Results indicated that winds were most significant in simulating the north-south surface velocity component. The model using high resolution temporally- and spatially-varying wind data achieved better agreement with the CODAR surface currents than the model using the onshore wind measurements and the model without any wind forcing. Full article
Figures

Open AccessFeature PaperReview
Rare Earth Borohydrides—Crystal Structures and Thermal Properties
Energies 2017, 10(12), 2115; doi:10.3390/en10122115 -
Abstract
Rare earth (RE) borohydrides have received considerable attention during the past ten years as possible hydrogen storage materials due to their relatively high gravimetric hydrogen density. This review illustrates the rich chemistry, structural diversity and thermal properties of borohydrides containing RE
[...] Read more.
Rare earth (RE) borohydrides have received considerable attention during the past ten years as possible hydrogen storage materials due to their relatively high gravimetric hydrogen density. This review illustrates the rich chemistry, structural diversity and thermal properties of borohydrides containing RE elements. In addition, it highlights the decomposition and rehydrogenation properties of composites containing RE-borohydrides, light-weight metal borohydrides such as LiBH4 and additives such as LiH. Full article
Figures

Figure 1

Open AccessArticle
Bioethanol Production from Cachaza as Hydrogen Feedstock: Effect of Ammonium Sulfate during Fermentation
Energies 2017, 10(12), 2112; doi:10.3390/en10122112 -
Abstract
Cachaza is a type of non-centrifugal sugarcane press-mud that, if it is not employed efficiently, generates water pollution, soil eutrophication, and the spread of possible pathogens. This biomass can be fermented to produce bioethanol. Our intention is to obtain bioethanol that can be
[...] Read more.
Cachaza is a type of non-centrifugal sugarcane press-mud that, if it is not employed efficiently, generates water pollution, soil eutrophication, and the spread of possible pathogens. This biomass can be fermented to produce bioethanol. Our intention is to obtain bioethanol that can be catalytically reformed to produce hydrogen (H2) for further use in fuel cells for electricity production. However, some impurities could negatively affect the catalyst performance during the bioethanol reforming process. Hence, the aim of this study was to assess the fermentation of Cachaza using ammonium sulfate ((NH4)2SO4) loadings and Saccharomyces cerevisiae strain to produce the highest ethanol concentration with the minimum amount of impurities in anticipation of facilitating further bioethanol purification and reforming for H2 production. The results showed that ethanol production from Cachaza fermentation was about 50 g·L−1 and the (NH4)2SO4 addition did not affect its production. However, it significantly reduced the production of branched alcohols. When a 160 mg·L−1 (NH4)2SO4 was added to the fermentation culture, 2-methyl-1-propanol was reduced by 41% and 3-methyl-1-butanol was reduced by 6%, probably due to the repression of the catabolic nitrogen mechanism. Conversely, 1-propanol doubled its concentration likely due to the higher threonine synthesis promoted by the reducing sugar presence. Afterwards, we employed the modified Gompertz model to fit the ethanol, 2M1P, 3M1B, and 1-propanol production, which provided acceptable fits (R2 > 0.881) for the tested compounds during Cachaza fermentation. To the best of our knowledge, there are no reports of the modelling of aliphatic production during fermentation; this model will be employed to calculate yields with further scaling and for life cycle assessment. Full article
Figures

Open AccessArticle
A Multicriteria GIS-Based Assessment to Optimize Biomass Facility Sites with Parallel Environment—A Case Study in Spain
Energies 2017, 10(12), 2095; doi:10.3390/en10122095 -
Abstract
Optimizing a biomass facility site is a critical concern that is currently receiving an increased attention because of geographically spread biomass feedstock. This research presents a multicriteria GIS assessment with Weighted Linear Combination (WLC) (most suitable areas) and a sensitivity analysis (implementation strategies)
[...] Read more.
Optimizing a biomass facility site is a critical concern that is currently receiving an increased attention because of geographically spread biomass feedstock. This research presents a multicriteria GIS assessment with Weighted Linear Combination (WLC) (most suitable areas) and a sensitivity analysis (implementation strategies) applied to various disciplines using suitable criteria to optimize a biomass facility location in the context of renewable energies respecting the environment. The analyses of results with twelve criteria show the most suitable areas (9.25%) and constraints in a case study in Extremadura (Spain), where forest and agriculture are typical for land uses. Thus, the sensitivity analysis demonstrates the insight of the most influential criteria for supporting energy planning decisions. Therefore, this assessment could be used in studies to verify suitable biomass plants sites with corresponding geographical and spatial circumstances and available spatial data necessary in various governmental and industrial sectors. Full article
Figures

Figure 1