Abstract
This paper focuses on single-diode photovoltaic cell models. Comprehensive simulation studies are carried out in order to adequately assess temperature dependence, solar radiation change, diode ideality factor and series resistance influence. A comparison between an ideal model single-diode solar cell and a model of single-diode solar cell with a series resistance is also presented. Finally, conclusions are duly drawn.

Abstract
Devices installed in remote places require continuously energy supply for their functionality or communication requirements. For these applications, conventional energy supply is very expensive, or unreliable, and batteries dependence is not a good solution for long-term installations. Energy harvesting can be a good solution, to increase the availability of energy. Regenerative energy sources like thermoelectric, magnetic, piezoelectric, and/or renewable sources such as photovoltaic, wind, among others, allowed the development of different powering solutions for sensor units. The purpose of this work is to characterize three photovoltaic solar panels for different power consumption sensor applications. The study is carried out taking into account the intensity of light and angle of incidence over the photovoltaic panels versus voltage generated. The energy is stored in an association of supercapacitors. This association together with the solar panel itself forms the two possible sources to supply the sensor application.

Abstract
Considering the current global economic situation and the rising energy costs, all contributions to the reduction in energy consumption will be relevant. In electrical installations, energy consumption can be reduced by reducing losses in the conductors, associated with the efficiency of equipments, allowing a better use of the installed power, which can be an important issue when using renewable energies. The losses in the conductors are proportional to the square of the resistance and current. These must be analysed in conjunction with all loads that contribute to the current in the sections of the installation. When replacing equipment in distribution boxes output by more efficient ones, the current decreases in sections covered with the most significant power loss due to proportionality with the square of the current. This decrease, often forgotten, is recorded in this work and included in the investment analysis on efficiency and sustainable electrical equipment. This analysis, combined with the features and operating parameters of electrical installation, accounts for all the gains that can make a difference in the choice of efficient equipment.

Abstract
The vertical axis wind turbines (VAWT) have been suffering an increased acceptance for urban wind turbines integration in the future smart grid for decentralized generation (DG). The VAWT have several advantages over the more conventional horizontal axis wind turbines (HAWT): the smaller number of components; low sound emissions; their insensitivity to fast changes in wind flow direction; a lower architectural visual impact; the ability to operate closer to the ground; and others. But, the VAWT aerodynamic performance is more complex to simulate and predict due to its three dimensional operation. Several mathematical models have been presented to predict the VAWT performance, such as the double multiple streamtube (DMS) model. With the aim of presenting a tool to ease the study of complex shaped VAWTs, being at the same time able to be easily integrated in computational design tools, a new approach to the DMS model is presented in this paper.

Abstract
This paper focuses on the modelling and simulation for a photovoltaic system formed by monocrystalline solar modules. The objective is to find the parameters of the nonlinear I-V equation by adjusting the curve at three points: open circuit, maximum power, and short circuit. This paper brings a novel iterative procedure to find the value of diode ideality factor, series and equivalent shunt resistances. Simulation studies are carried out in order to uncover temperature dependence, solar radiation change, and output power variation. Finally, conclusions are duly drawn.

Abstract
Due to the increase in annual electricity consumption occurring in Portugal and the rising price of fossil fuels, it is imperative to diversificate the energy sources available. The Portuguese investment in renewable energies has increased significantly in the past few years, especially in wind energy. Renewable energies are intermittent and dependent on weather conditions, so fossil fuels are still an important part of the Portuguese energy mix, but with tendency to decrease in the future. In this paper, the nuclear option has been considered alongside the renewable energies increase to reduce fossil fuels dependency, envisaging several plausible scenarios for fuel prices, installed capacity and investment costs.