We review several examples of how spectrally-selective photonic structures may be used to improve solar cell systems. Firstly, we introduce different spectrally-selective structures that are based on interference effects. Examples shown include Rugate filter, edge filter and 3D photonic crystals such as artificial opals. In the second part, we discuss several examples of photovoltaic (PV) concepts that utilize spectral selectivity such as fluorescence collectors, upconversion systems, spectrum splitting concepts and the intermediate reflector concept. The potential of spectrally selective filters in the context of solar cells is discussed.

The growing demand for petroleum, accompanied by the declining petroleum reserves and the concerns over energy security, has intensified the interest in direct coal liquefaction (DCL), particularly in countries such as China which is rich in coal resources, but short of petroleum. In addition to a general introduction on the mechanisms and processes of DCL, this paper overviews some recent advances in DCL technology with respect to the influencing factors for DCL reactions (temperature, solvent, pressure, atmospheres, etc.), the effects of coal pre-treatments for DCL (swelling, thermal treatment, hydrothermal treatment, etc.), as well as recent development in multi-staged DCL processes, DCL catalysts and co-liquefaction of coal with biomass.

Since its appearance in 1991, the Li ion battery has been the major power source driving the rapid digitalization of our daily life; however, much of the processes and mechanisms underpinning this newest battery chemistry remains poorly understood. As in any electrochemical device, the major challenge comes from the electrolyte/electrode interfaces, where the discontinuity in charge distribution and extreme disequality in electric forces induce diversified processes that eventually determine the kinetics of Li⁺ intercalation chemistry. This article will summarize the most recent efforts on the fundamental understanding of the interphases in Li ion devices. Emphasis will be placed on the formation chemistry of the so-called “SEI” on graphitic anode, the effect of solvation sheath structure of Li⁺ on the intercalation energy barrier, and the feasibility of tailoring a desired interphase. Biologically inspired approaches to an ideal interphase will also be briefly discussed.

Biodiesel, or alkyl ester, is an alternative renewable, biodegradable, and non-toxic diesel fuel produced by the catalytic transesterification of vegetable oil. Here we characterize a system for continuous transesterification of vegetable oil using five continuous stirring tank reactors (5CSTRs). We tested residence times of 16⁻43min, stirring speeds of 200⁻800rpm, a catalyst concentration (KOH) of 0.25⁻1 wt% of oil (in gram), different total flow rates of the oil and MeOH, and on the production performance of the 5 stage continuous reactor for transesterification of vegetable oil. Using a molar ratio of oil:methanol of 1:7 and a reaction temperature of 65 °C, we show that a high stirring speed increased the reaction rate, but an excessive stir speed decreased the reaction rate and conversion to biodiesel. Furthermore, a higher catalyst percentage significantly increased the reaction rate and production capacity. A catalyst percentage of 1 wt% of oil gave the best conversion; 99.04 ± 0... [more]

In single-chamber solid oxide fuel cells (SC-SOFCs), both anode and cathode are situated in a common gas chamber and are exposed to a mixture of fuel and oxidant. The working principle is based on the difference in catalytic activity of the electrodes for the respective anodic and cathodic reactions. The resulting difference in oxygen partial pressure between the electrodes leads to the generation of an open circuit voltage. Progress in SC-SOFC technology has enabled the generation of power outputs comparable to those of conventional SOFCs. This paper provides a detailed review of the development of SC-SOFC technology.

Enzyme based bioelectronics have attracted increasing interest in recent years because of their applications on biomedical research and healthcare. They also have broad applications in environmental monitoring, and as the power source for portable electronic devices. In this review, the technology developed for fabrication of enzyme electrodes has been described. Different enzyme immobilisation methods using layered structures with self-assembled monolayers (SAM) and entrapment of enzymes in polymer matrixes have been reviewed. The performances of enzymatic biofuel cells are summarised. Various approaches on further development to overcome the current challenges have been discussed. This innovative technology will have a major impact and benefit medical science and clinical research, healthcare management, energy production from renewable sources.

We surveyed more than 1,000 randomly sampled, out-of-state tourists at Delaware, USA beaches in 2007. After providing respondents with wind turbine project photo-simulations at several distances, we inquired about the effect development would have on visitation. Approximately one-quarter stated that they would switch beaches if an offshore wind project was located 10 km from the coast, with avoidance diminishing with greater distance from shore. Stated avoidance is less than: avoidance with a fossil fuel power plant located the same distance inland; attraction to a beach with offshore wind turbines; and the percentage stating they would likely pay to take a boat tour.

Since the entry into force of the Kyoto Protocol, carbon trading has been in continuous expansion. In this paper, we review the origins of carbon trading in order to understand how carbon trading works in Europe and, specifically, the functioning of the European Union Emission Trading Scheme (EU ETS) and the workings of several spot, futures and options markets where European Union Allowances are traded. As well, the linking of the EU ETS with the other United Nations carbon markets is also studied.

The shift to a bio-based economy for the Netherlands is not only required because of climate change, but also for industrial strategy reasons. Traditional strongholds of the Dutch economy like the Rotterdam harbour, the agricultural sector (including the greenhouse sector, and food and feed industries) and the petrochemical industry will be affected by the new economic realities, and it is precisely to these sectors that a bio-based economy will offer new opportunities.

The interaction of guest molecules ranging from pentan-1-ol to octan-1-ol with α-cyclodextrin (α-CD) in water of has been studied calorimetrically at 283.15, 288.15, 293.15, 298.15 and 308.15 K with an isoperibolic titration calorimeter designed in our laboratory. The calorimetric method employed allows the determination of the thermodynamic parameters characterizing the binding process, ΔG°m, ΔH°m, ΔS°mand ΔCp°, namely free energy, enthalpy, and calorific capacity. These results show that in the temperature range investigated, the entropy change increased with chain length. This is in line with what is expected for a hydrophobic dehydration process. However, that effect is not expected to lead to the more pronounced negative CH₂-increment observed for nc > 5 or 6. As for many other ligand binding processes, we can observe a significant enthalpy - entropy compensation for this system, both with respect to temperature and structure.

The production of biodiesel from low-cost raw materials which generally contain high amounts of free fatty acids (FFAs) is a valuable alternative that would make their production costs more competitive than petroleum-derived fuel. Currently, the production of biodiesel from this kind of raw materials comprises a two-stage process, which requires an initial acid-catalyzed esterification of the FFA, followed by a basecatalyzed transesterification of the triglycerides. Commonly, the acid H₂SO₄ is the catalyst on the first step of this process. It must be said, however, that major drawbacks such as substantial reactor corrosion and the great generation of wastes, including the salts formed due to neutralization of the mineral acid, are negative and virtually unsurmountable aspects of this protocol. In this paper, tin(II) chloride dihydrate (SnCl₂·2H₂O), an inexpensive Lewis acid, was evaluated as catalyst on the ethanolysis of oleic acid, which is the major component of several fat and veg... [more]

The rapidly growing world population and rising consumption of biofuels are increasing demand for both food and biofuels. This exaggerates both food and fuel shortages. Using food crops such as corn grain to produce ethanol raises major nutritional and ethical concerns. Nearly 60% of humans in the world are currently malnourished, so the need for grains and other basic foods is critical. Growing crops for fuel squanders land, water and energy resources vital for the production of food for human consumption. Using corn for ethanol increases the price of U.S. beef, chicken, pork, eggs, breads, cereals, and milk more than 10% to 30%.

The International Energy Agency, headquartered in Paris, was founded in the early 1970s and is an energy policy advisor to 27 countries.[...]

Crops for biofuels squanders cropland, water, and energy resources vital for food production needed for people.

It is customary, for convenience, to use relative permeability data produced at room temperature. This paper shows that this practice underestimates oil recovery rates and ultimate recovery from chalk rocks for high temperature reservoirs. Above a certain temperature (80°C in this work) a reduction of oil recovery was observed. The reduction in oil recovery is reflected by the shift of relative permeability data towards more oil-wet at high temperature (tested here 130°C). However, both IFT and contact angle measurements indicate an increase in water wetness as temperature increases, which contradict the results obtained by relative permeability experiments. This phenomenon may be explained based on the total interaction potential, which basically consists of van der Waals attractive and short-range Born repulsive and double layer electrostatic forces. The fluid/rock interactions is shown to be dominated by the repulsive forces above 80°C, hence increase fine detachment enhancing oil t... [more]

As crude oil price reach a new high, the need for developing alternate fuels has become acute. Alternate fuels should be economically attractive in order to compete with currently used fossil fuels. In this work, biodiesel (ethyl ester) was prepared from waste cooking oil collected from a local restaurant in Halifax, Nova Scotia, Canada. Ethyl alcohol with sodium hydroxide as a catalyst was used for the transesterification process. The fatty acid composition of the final biodiesel esters was determined by gas chromatography. The biodiesel was characterized by its physical and fuel properties including density, viscosity, acid value, flash point, cloud point, pour point, cetane index, water and sediment content, total and free glycerin content, diglycerides and monoglycerides, phosphorus content and sulfur content according to ASTM standards. The viscosity of the biodiesel ethyl ester was found to be 5.03 mm²/sec at 40oC. The viscosity of waste cooking oil measured in room temperature (... [more]

As a scientist with a long-standing research interest in thermodynamics, information theory and diversity preservation, I would like to start publishing the journal Energies (ISSN 1996-1073).[...]

Transformerless grid-connected inverters, due to their advantages of high efficiency, small volume and light weight, have been the subject of more research and interest in recent years. Due to the asymmetrical driving signal in pulse width modulation (PWM) caused by time-delay, zero-drift of the current sensors and imparities of the power transistors, output of the grid current contains dc component. As a result, power quality of the grid is degraded. In this paper, a dc (direct current) component suppression scheme with adaptive back-propagation (BP) neural network proportional-integral-differential (PID) control is proposed for dc component minimization. Moreover, sliding-window-double-iteration-method (SWDIM) is utilized for fast dc component extraction. Compared with the conventional method, the proposed scheme shows better performance, and the dc component can be attenuated to be within 0.5% of the rated current.

The layout configuration of Vortex Induced Piezoelectric Energy Converters (VIPECs) is essential to improve its overall performance. Based on the formations of migrating geese, the configuration is characterized by two nondimensionalized layout parameters. A number of sampled points for different configurations are simulated with the two-dimensional Computation Fluid Dynamics (CFD) method. The influence of layout configurations on VIPECs’ lift force and wake structure is investigated and the generated open circuit output voltage is obtained through the derived output voltage equation. The response surface model of the output voltage of both the leading VIPEC and the following VIPEC and their summation are established using the Kriging surrogate model based on the obtained simulation results. Then, optimal layout parameters are found through the Particle Swarm Optimization (PSO) algorithm, and its predicted result is compared with that of the CFD simulation. The simulation and optimizat... [more]

Voltage sags result in unwanted operation stops and large economical losses in industrial applications. A dynamic voltage restorer (DVR) is a power-electronics-based device conceived to protect high-power installations against these events. However, the design of a DVR control system is not straightforward and it has some peculiarities. First of all, a DVR includes a resonant (LC) connection filter with a lightly damped resonance. Secondly, the control system of a DVR should work properly regardless of the type of load, which can be linear or non-linear, to be protected. In this paper, a digital state-feedback (SF) controller for a DVR is proposed to address these issues. The design and features of the SF controller are studied in detail. Two pole-placement alternatives are discussed and the system robustness is tested under variations in the system parameters. Furthermore, implementation aspects such as discretization not commonly addressed in the literature are described. The control... [more]

Electricity price forecasting has a paramount effect on generation companies (GenCos) due to the scheduling of the electricity generation scheme according to electricity price forecasts. Inaccurate electricity price forecasts could cause important loss of profits to the suppliers. In this paper, the financial effect of inaccurate electricity price forecasts on a hydro-based GenCo is examined. Electricity price forecasts of five individual and four hybrid forecast models and the ex-post actual prices are used to schedule the hydro-based GenCo using Mixed Integer Linear Programming (MILP). The financial effect measures of profit loss, Economic Loss Index (ELI) and Price Forecast Disadvantage Index (PFDI), as well as Mean Absolute Error (MAE) of the models are used for comparison of the data from 24 weeks of the year. According to the results, a hybrid model, 50% Artificial Neural Network (ANN)⁻50% Long Short Term Memory (LSTM), has the best performance in terms of financial effect. Furth... [more]

The permanent magnet (PM) spherical motor has been subject to growing interest from the scientific community due to its potential for applications in distinct areas, particularly in robotics, prosthetics, satellite control, sensors or camera systems. Motivated by this movement, the current work presents all the steps for the efficient design and construction of a spherical motor model, using compound deposition technology with the aid of a 3D printer. Furthermore, we report comprehensive studies on the accuracy of the positioning system of the proposed motor using only three stator coils, which jointly act to move the rotor axis toward any point in the hemisphere. Unmodeled nonlinear phenomena, such as friction, impair accurate positioning of the motor actuator, but this is solved by means of a visual servo control system, which allows the user to collect input⁻output data to train an artificial neural network model. Details on the construction of the proposed motor are reported, in ad... [more]

(no abstract)

The Free-piston linear generator (FPLG) is a novel energy converter which can generate electrical energy and is regarded as a potential technology for solving the restriction of the short driving range of electric vehicles. Getting rid of the crank and flywheel mechanism, FPLG obtains some advantages of a variable compression ratio, compact size, and highly-efficient power generation. Linear electric machine (LEM) design and piston motion control are two key technologies of FPLG. However, they are currently the main obstacles to the favorable performance of FPLG. LEM being used to drive the piston motion or generate electric energy is an integrated design including a motor/generator. Various types of LEMs are investigated, and suitable application scenarios based on advantages and disadvantages are discussed. The FPLG’s controller is used to ensure stable operation and highly-efficient output. However, cycle-to-cycle variations of the combustion process and motor/generator switching ma... [more]

Self-consumption energy facilities are presented as viable and sustainable solutions in the energy transition scenario in which many countries are immersed. However, they rely on dispersed and private investments in the territory. Given the uneven growth in the number of self-consumption facilities in Europe, the main objective of this study is to identify and measure the investment determinants in self-consumption facilities. To this end, the main influential incentives and barriers are identified through the aggregate analysis of the regulatory framework for self-consumption in several European countries, and the empirical characterization of Spanish facilities as a multiple case study, to define the common features of the investments made. The technical, economic, and financial characterization of real self-consumption facilities in climatic zones of southern Europe is a significant contribution of the present work. There are few samples of this type in the studies published to date... [more]