Conselheiro, Portugal
Conselheiro, Portugal
Time filter
Source Type

Camus C.,ISEL | Farias T.,University of Lisbon
2011 8th International Conference on the European Energy Market, EEM 11 | Year: 2011

Electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), which obtain their fuel from the grid by charging a battery, are set to be introduced into the mass market and expected to contribute to oil consumption reduction. In this research, scenarios for 2020 EVs penetration and charging profiles are studied integrated with different hypotheses of power sources expected in electricity generation for year 2020. Simulations of the impacts in load profiles and spot prices are obtained for the Portuguese case study as well as the emissions balance between the transportation and the electricity generation sectors. Simulations made for year 2020 in a scenario of low hydro production and high costs, estimate that the price could reach the 17 cents/kWh (including wholesale, plus the net access, plus retailer revenue) for a 2 Million EVs charging mainly at peak hours. In an off-peak recharge the price reduces to about 7 cents/kWh. In a high hydro production and low wholesale prices, an off peak recharge could reach 5.6 cents/kWh. Reductions in primary energy consumption, fossil fuels use and CO 2 emissions of 4%, 12% and 9% respectively were verified from the transportation and electricity generation sectors together when compared with a Business as usual (BAU) scenario without EVs and the same electricity production mix. In these extreme cases, EV energy prices were between 0.9€ to 2.8€ per 100 km. © 2011 IEEE.

Martins L.M.D.R.S.,ISEL | Martins L.M.D.R.S.,University of Lisbon | De Almeida M.P.,University of Porto | Carabineiro S.A.C.,University of Porto | And 2 more authors.
ChemCatChem | Year: 2013

The hydrotris(pyrazol-1-yl)methane iron(II) complex [FeCl 2{η3-HC(pz)3}] (pz=pyrazol-1-yl) (1) was immobilized on three different carbon materials (activated carbon, carbon xerogel and multi-walled carbon nanotubes) with three different surface treatments (original, treated with nitric acid, and treated with nitric acid followed by sodium hydroxide) to produce active, selective and recyclable catalysts. The heterogenisation process was more efficient for carbon nanotubes treated with nitric acid and sodium hydroxide. An outstanding improved catalytic performance of complex 1 upon heterogenisation on carbon nanotubes treated with nitric acid and sodium hydroxide (turnover numbers up to 5.6×10 3 and overall yield of 21 %), relative to the homogeneous system, was achieved for the single-pot peroxidative oxidation of cyclohexane to the cyclohexanone and cyclohexanol mixture. The heterogenised systems allowed their easy recovery and reuse, at least for five consecutive cycles, maintaining 96 % of the initial activity and concomitant rather high selectivity to cyclohexanol and cyclohexanone. An iron scorpion: A C-scorpionate FeII complex is heterogenized on carbon materials and used for peroxidative oxidation of cyclohexane to cyclohexanone and cyclohexanol (see picture). The heterogenized system allows easy recovery and reuse of the catalyst, at least for five consecutive cycles, maintaining 96 % of the initial activity and concomitant rather high selectivity. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Freire L.,University of Lisbon | Freire L.,University of Vigo | Catarino M.A.,ISEL | Godinho M.I.,ISEL | And 5 more authors.
Cement and Concrete Composites | Year: 2012

Passive films were grown in potentiodynamic mode, by cyclic voltammetry on AISI 316 and AISI 304 stainless steels. The composition of these films was investigated by X-ray photoelectron spectroscopy (XPS). The electrochemical behaviour and the chemical composition of the passive films formed by cyclic voltammetry were compared to those of films grown under natural conditions (by immersion at open circuit potential, OCP) in alkaline solutions simulating concrete. The study included the effect of pH of the electrolyte and the effect of the presence of chloride ions. The XPS results revealed important changes in the passive film composition, which becomes enriched in chromium and depleted in magnetite as the pH decreases. On the other hand, the presence of chlorides promotes a more oxidised passive layer. The XPS results also showed relevant differences on the composition of the oxide layers for the films formed under cyclic voltammetry and/or under OCP. © 2012 Elsevier Ltd. All rights reserved.

Carabineiro S.A.C.,University of Porto | Martins L.M.D.R.S.,ISEL | Martins L.M.D.R.S.,University of Lisbon | Avalos-Borja M.,National Autonomous University of Mexico | And 3 more authors.
Applied Catalysis A: General | Year: 2013

Gold (1 wt.%) was loaded on several types of carbon materials (activated carbon, polymer based carbon xerogels, multi-walled carbon nanotubes, nanodiamonds, microdiamonds, graphite and silicon carbide) using two different methods (sol immobilisation and double impregnation). Samples were characterised by N2 adsorption at -196 C, temperature programmed desorption, high-resolution transmission electron microscopy, selected area electron diffraction, energy dispersive X-ray spectrometry, high-angle annular dark-field imaging (Z-contrast), X-ray photoelectron spectroscopy and atomic absorption spectroscopy. The obtained Au/carbon materials were used as catalysts for the oxidation of cyclohexane to cyclohexanol and cyclohexanone, with aqueous H 2O2, under mild conditions. The most active catalyst was prepared by supporting gold nanoparticles on carbon nanotubes by the sol method, achieving an overall turnover number of ca. 171 and an overall yield of 3.6% after 6 h reaction time. These values are comparable to the industrial process (that uses Co catalysts and high temperature), but were obtained at ambient temperature with considerable low loads of catalyst (Au catalyst to substrate molar ratio always lower than 1 × 10-3), which is of relevance for establishing a greener catalytic process for cyclohexane oxidation. Moreover, a very high selectivity towards the formation of cyclohexanol and cyclohexanone was achieved, since no traces of by-products were detected. The promoting effect of pyrazine carboxylic acid was observed and an optimum peroxide-to-catalyst molar ratio was found to be 2 × 104. Further increase of the oxidant amount results in decreased yield due to overoxidation reactions at higher H2O2 amounts. Catalyst recycling was tested up to six consecutive cycles for the most active catalytic system (gold deposited on carbon nanotubes by sol immobilisation), and it was found that the catalyst maintains almost the original level of activity after several reaction cycles (there was only a 6% drop in activity after the sixth cycle) with a rather high selectivity to cyclohexanol and cyclohexanone and with no catalyst leaching. The differences in activity for the other samples can be explained in terms of gold nanoparticle size and the textural properties of the carbon support. © 2013 Elsevier B.V. All rights reserved.

Alegria E.C.B.A.,ISEL | Alegria E.C.B.A.,University of Lisbon | Martins L.M.D.R.S.,ISEL | Martins L.M.D.R.S.,University of Lisbon | And 2 more authors.
Applied Catalysis A: General | Year: 2012

Rhenium (I, III-V or VII) complexes bearing N-donor or oxo-ligands catalyse the Baeyer-Villiger oxidation of cyclic and linear ketones (e.g. 2-methylcyclohexanone, 2-methylcyclopentanone, cyclohexanone, cyclopentanone, cyclobutanone and 3,3-dimethyl-2-butanone) into the corresponding lactones or esters, in the presence of aqueous H 2O 2 (30%). The effects of various reaction parameters are studied allowing to achieve yields up to 54%. © 2012 Elsevier B.V. All rights reserved.

Redondo L.M.,ISEL | Redondo L.M.,University of Lisbon
IEEE Transactions on Plasma Science | Year: 2010

The intensive use of semiconductor devices enabled the development of a repetitive high-voltage pulse-generator topology from the dc voltage-multiplier (VM) concept. The proposed circuit is based on an odd VM-type circuit, where a number of dc capacitors share a common connection with different voltage ratings in each one, and the output voltage comes from a single capacitor. Standard VM rectifier and coupling diodes are used for charging the energy-storing capacitors, from an ac power supply, and two additional on/off semiconductors in each stage, to switch from the typical charging VM mode to a pulse mode with the dc energy-storing capacitors connected in series with the load. Results from a 2-kV experimental prototype with three stages, delivering a 10-μs pulse with a 5-kHz repetition rate into a resistive load, are discussed. Additionally, the proposed circuit is compared against the solid-state Marx generator topology for the same peak input and output voltages. © 2010 IEEE.

Lopes F.,National Laboratory of Energy and Geology | Ilco C.,ISEL | Sousa J.,Polytechnic Institute of Lisbon
International Conference on the European Energy Market, EEM | Year: 2013

Two major goals of electricity markets are ensuring a secure and efficient operation and decreasing the cost of energy. To achieve these goals, three major market models have been considered: pools, bilateral contracts and hybrid markets. Pool prices tend to change quickly and variations are usually highly unpredictable. In this way, market participants can enter into bilateral contracts to hedge against pool price volatility. © 2013 IEEE.

Vieira M.A.,ISEL | Vieira M.,ISEL | Louro P.,ISEL | Garcao A.S.,CTS UNINOVA
Journal of Physics: Conference Series | Year: 2013

This paper reports on optical filters based on a-SiC:H tandem pín/pin heterostructures. The spectral sensitivity is analyzed. Steady state optical bias with different wavelengths are applied from each front and back sides and the photocurrent is measured. Results show that it is possible to control the sensitivity of the device and to tune a specific wavelength range by combining radiations with complementary light penetration depths. The transfer characteristics effects due to changes in the front and back optical bias wavelength are discussed. Depending on the wavelength of the external background and irradiation side, the device acts either as a short-or a long-pass band filter or as a band-stop filter. The output waveform presents a nonlinear amplitude-dependent response to the wavelengths of the input channels.

Vieira M.A.,ISEL | Louro P.,ISEL | Vieira M.,ISEL | Fantoni A.,ISEL | Steiger-Garcao A.,CTS UNINOVA FCT UNL
IEEE Sensors Journal | Year: 2012

Characteristics of tunable wavelength pi'n/pin filters based on a-SiC:H multilayered stacked cells are studied both experimentally and theoretically. Results show that the device combines the demultiplexing operation with the simultaneous photodetection and self amplification of the signal. An algorithm to decode the multiplex signal is established. A capacitive active band-pass filter model is presented and supported by an electrical simulation of the state variable filter circuit. Experimental and simulated results show that the device acts as a state variable filter. It combines the properties of active high-pass and low-pass filter sections into a capacitive active band-pass filter using a changing capacitance to control the power delivered to the load. © 2011 IEEE.

Domingues N.,ISEL
2012 International Conference on Smart Grid Technology, Economics and Policies, SG-TEP 2012 | Year: 2012

In order to promote energy efficiency and the use of renewable (endogenous) energy sources, the Portuguese government launched several programs and reforms, starting in 2001 with the E4 Program. This new energy policy instrument aims to improve the national competitiveness and improve the social welfare, while preserving the environment. These and other incentive programs introduce market distortions that are not fully evaluated. The present paper focus on the overall efficiency, which is divided in the following key areas: resource exploitation and ecosystems conservation (environment), innovation and competitiveness (economy) and employment and power purchase parity (social welfare). The results are focused not only on the supply side, but also on demand side (how consumers use energy), analyzing the promotion of renewable energy and the fostering of energy efficiency and savings in Portugal. © 2012 IEEE.

Loading ISEL collaborators
Loading ISEL collaborators