Nowadays, concerns about climate change have contributed significantly to changing the paradigm in the urban transportation sector towards vehicle electrification, where purely electric or hybrid ...vehicles are increasingly a new reality, supported by all major automotive brands. Nevertheless, new challenges are imposed on the current electrical power grids in terms of a synergistic, progressive, dynamic and stable integration of electric mobility. Besides the traditional unidirectional charging, more and more, the adoption of a bidirectional interconnection is expected to be a reality. In addition, whenever the vehicle is plugged-in, the on-board power electronics can also be used for other purposes, such as in the event of a power failure, regardless if the vehicle is in charging mode or not. Other new opportunities, from the electrical grid point of view, are even more relevant in the context of off-board power electronics systems, which can be enhanced with new features as, for example, compensation of power quality problems or interface with renewable energy sources. In this sense, this paper aims to present, in a comprehensive way, the new challenges and opportunities that smart grids are facing, including the new technologies in the vehicle electrification, towards a sustainable future. A theoretical analysis is also presented and supported by experimental validation based on developed laboratory prototypes.
This paper presents the main operation modes for an electric vehicle (EV) battery charger framed in smart grids and smart homes, i.e., present-day and new operation modes that can represent an asset ...toward EV adoption are discussed and proposed, respectively. Apart from the well-known grid-to-vehicle (G2V) and vehicle-to-grid (V2G) operation modes, this paper proposes two new operation modes: home-to-vehicle (H2V), where the EV battery charger current is controlled according to the current consumption of the electrical appliances of the home (this operation mode is combined with G2V and V2G), and vehicle-for-grid (V4G), where the EV battery charger is used for compensating current harmonics or reactive power, simultaneously with the G2V and V2G operation modes. The vehicle-to-home (V2H) operation mode, where the EV can operate as a power source in isolated systems or as offline uninterruptible power supply to feed priority appliances of the home during power outages of the electrical grid, is presented in this paper and framed with the other operation modes. These five operation modes were validated through experimental results using a developed 3.6-kW bidirectional EV battery charger prototype, which was specially designed for these operation modes. This paper describes the developed EV battery charger prototype, detailing the power theory and the voltage and current control strategies used in the control system. This paper also presents experimental results for the various operation modes, both in steady state and during transients.
We show that fused deposition modelling (FDM) 3D-printed electrodes can be used for quality control of fuel bioethanol. 3D-printing using carbon black/polylactic acid (CB-PLA) filaments resulted in ...conductive and biodegradable electrodes for biofuel analysis. As a proof-of-concept, copper determination in fuel bioethanol was performed, as such ions catalyse oxidation processes during storage and transport. Square-wave anodic-stripping voltammetry (SWASV) of copper was achieved after sample dilution in 0.1 mol L
−1
HCl as supporting electrolyte (resulting in 30:70%
v
/
v
ethanol:water). The linear responses were in the range between 10 and 300 μg L
−1
(
R
= 0.999), inter-day precision was lower than 8% (
n
= 10, for 20 μg L
−1
) and limits of detection (LOD) and quantification (LOQ) using 180 s as deposition time were 0.097 μg L
−1
and 0.323 μg L
−1
, respectively. Recovery values between 95 and 103% for the analysis of bioethanol spiked with known amounts of copper were obtained. These results show great promise of the application of 3D-printed sensors for the quality control of biofuels.
Graphical abstract
Transparent conductive oxides (TCOs) constitute a class of materials that combine high electrical conductivity and optical transparency. These features led to the development of the transparent ...electronics applications, such as flat panel displays, “smart” windows or functional glasses.
N
-type TCOs dominate the applications market, and the lack of a suitable p-type counterpart limits the fabrication of a completely transparent active device, which might be considered as a technological breakthrough. Among the wide range of p-type candidates, delafossite CuCrO
2
(and its out-of-stoichiometry derivatives) is a promising material to achieve the desired p-type TCO properties as, up to date, it is presenting the foremost trade-off between optical and electrical properties. The present paper covers the research work and the major achievements related to copper chromium delafossite. A comprehensive overview of fabrication methods and opto-electronic properties is presented. The source of doping and the charge carriers transport mechanism are also thoroughly discussed.
Graphical abstract
The main contribution of this paper is the proposal of new modulation techniques for three-phase transformerless neutral point clamped inverters to eliminate leakage currents in photovoltaic systems ...without requiring any modification on the multilevel inverter or any additional hardware. The modulation techniques are capable of reducing the leakage currents in photovoltaic systems by applying three medium vectors or using only two medium vectors and one specific zero vector to compose the reference vector. In addition, to increase the system utilization, the three-phase neutral point clamped inverter can be designed to also provide functions of active filter using the p - q theory. The proposed system provides maximum power point tracking and compensation of current harmonics and reactive power. To validate the simulation models, an experimental three-phase inverter is used to evaluate leakage currents and the dc link voltage control.
Recent research advances in sensors, wireless communications, network protocols, microelectronics, cloud computing, and machine learning, among others, are driving the growth of the Internet of ...Things (IoT) ...
•Incorporation of natural antioxidants in chitosan improves film’s physical properties.•Hydro-alcoholic extracts (HAE’s) improve the light barrier of films.•HAE’s increase film’s moisture content and ...solubility while decreasing the swelling degree.•Essential Oils (EO’s) improve the mechanical properties of chitosan films.
In the past decades, as alternative to the petroleum based products, biodegradable polymers, such as chitosan, have undergone extensive investigation in order to minimize waste disposal problem. Yet, biopolymers face some constraints, namely regarding their poor mechanical and barrier properties. Thus, the purpose of this work was to test the incorporation of several natural antioxidants, both oil and water based, in the chitosan matrix and to evaluate the effect on the physical properties of the resulting biopolymers. Five essential oils (EO) (ginger, rosemary, sage, tea tree and thyme EO) and six different hydro-alcoholic extracts (HAE) (ginger, rosemary, sage, black tea, green tea and kenaf leaves HAE) were used. Thickness of films produced did not change statistically with incorporation of the natural antioxidants tested (values were found in the range 52–71μm, including pristine chitosan with 67μm). The color of EO films was similar to control samples, but HAE turned the material to a more saturated color and less bright. EO’s and (especially) HAE’s (which reduced by 15–80% the transmittance compared to pristine chitosan) improved the light barrier of films, conferring to chitosan an extra protection against oxidative processes. In general, incorporation of HAE in the chitosan increased the moisture content (from 13% in the chitosan to 25% on average of the HAE films) and solubility (from 17% in the chitosan to 22% on average of the HAE films) while swelling degree decreased (from 191% in the chitosan to 139% on average of the HAE films), due to the interaction of water, chitosan and polyphenols present on extracts used. The same trend, although with less significance, was also observed in the EO’s films. HAE’s and (especially) EO’s (which increased the tensile strength of chitosan from 20MPa to 26MPa, on average) active compounds changed the mechanical properties of chitosan films. To conclude, chitosan films incorporated with natural antioxidants have shown, generally, modified physical properties. Among the tested extracts, black tea and green tea HAE’s and sage, thyme and rosemary EO’s can be highlighted as the most promising due to the resulting mechanical properties of the prepared films. Yet, in order to identify if these novel materials can be used by the food packaging industry, further research is demanded to evaluate the behaviour of these biopolymers when in contact with food matrices.
The decentralization in the electrical power grids has gained increasing importance, especially in the last two decades, since transmission system operators (TSO), distribution system operators (DSO) ...and consumers are more aware of energy efficiency and energy sustainability issues. Therefore, globally, due to the introduction of energy production technologies near the consumers, in residential and industrial sectors, new scenarios of distributed energy resources (DER) are emerging. In order to guarantee an adequate power management in the electrical power grids, incorporating producers, consumers and producers-consumers (prosumers) together, it is important to adopt intelligent systems and platforms that allow the provision of information on energy consumption and production in real time, as well as for obtaining a fair price for the sale and purchase of energy. In this paper, we analyze the literature to identify the appropriate solutions to implement a decentralized electrical power grid based on sensors, blockchain and smart contracts, evaluating the current state of the art and pilot projects already in place. We also discuss a proposal for a power grid model, with renewable energy production, combining Internet of Things, blockchain and smart contracts.
Power grids are progressing, and the possibility of incorporating DC grids toward hybrid AC/DC grids is gaining increasing relevance, as several technologies available nowadays are operating natively ...in DC. This paper proposes a topology of a full-controlled bidirectional dual-stage interleaved converter for interfacing hybrid AC/DC grids. The topology is based on a dual-stage architecture, constituted by an AC/DC converter and by a DC/DC converter, both based on interleaved power converters. On the AC side, which is connected to the main AC power grid, the proposed dual-stage architecture operates with sinusoidal current in phase or phase opposition with the voltage, meaning a bidirectional operation. In addition, it has the possibility of interfacing with other AC loads, such as domestic electrical appliances, or with an AC microgrid. The DC link, formed by the AC/DC power stage, is interfaced with a DC power grid, which provides numerous advantages, e.g., for interfacing battery electric vehicles directly charged in DC, as well as other DC loads, such as renewable energy sources. The DC/DC power stage is considered for interfacing with an energy storage system, which is capable of bidirectional power exchange with the DC grid or with the AC grid through the AC/DC power stage. A complete laboratory prototype was designed and developed, with the unified control algorithms implemented on a digital signal processor. The experimental results validated the operation of the full-controlled bidirectional dual-stage interleaved converter based on the specifications for the hybrid AC/DC grid, such as bidirectional operation, synchronization with the AC power grid, predictive current control, interleaved operation on both AC/DC and DC/DC power stages, DC-link voltage control for the DC grid, as well as the operation with different power levels.
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