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Abstract This paper addresses the importance of the probabilistic analysis in determining the wave energy potential to support the design of electrical generators for wave energy conversion. The irregular activity of ocean waves induces variable frequencies and amplitudes of operation for point absorbers electrical generators, which may lead to the construction of inefficient electrical machines. Applying probabilistic models to describe the ocean wave's behavior allows the determination of the values most likely to be sampled for ocean-state parameters. Knowing these values, the most expected ocean wave potential can be determined and a proper device design can be performed. This work also refers to the importance of using the joint probability models instead of the marginal ones. Seven locations at the Portuguese coast are evaluated in order to determine their wave energy resource potential.

Abstract High power pseudocapacitors are extremely relevant to answer specific needs in the current energy transition arena and to implement an efficient renewable energy society. However, literature shows that are still open gaps concerning improvement of their energy density at high power, conversion efficiency, cost and cycle life. Electrodes based on active transition metal compounds, and in particular metal sulphides, evidence high potential to meet these objectives. This work discusses the dependence on the synthesis route of the charge storage mechanism of manganese sulphide-based materials and relates the pseudocapacitive response of these electrodes with their polycrystalline nature. Results reveal that a manganese oxy-sulphide mixture can achieve a high specific capacitance of 231 F.g−1 at 0.5 A/g in a 0.65 V active window. These values represent a 31.5 % increase compared to pure rambergite, γ-MnS, and 436 % compared to pure hausmannite Mn3O4 prepared under the same conditions. Moreover, the results show that manganese oxy-sulphide electrodes are characterized by good charge retention (73%), and superior long term capacity retention (above 86%) after 5000 cycles, evidencing potential for high power energy storage applications.

This paper presents a methodology to address reactive power compensation using Evolutionary Particle Swarm Optimization (EPSO) technique programmed in the MATLAB environment. The main objective is to find the best operation point minimizing power losses with reactive power compensation, subjected to all operational constraints, namely full AC power flow equations, active and reactive power generation constraints. The methodology has been tested with the IEEE 14 bus test system demonstrating the ability and effectiveness of the proposed approach to handle the reactive power compensation problem.

Often the several stakeholders involved in the agricultural sector place a greater emphasis on the negative externalities from farming production rather than on the solutions and approaches to mitigate, namely impacts from pollution. The scientific literature, in certain circumstances, follows this tendency leaving a vast chasm of enormous potential left to be explored. It is important to contribute towards the reduction of this gap, highlighting the best management practices implemented across the agricultural sector around the world, specifically to make them more visible and give incentive to the several agents in adopting and spreading their use. In this way, the main objective is to stress the best management practices presented by the global scientific literature from the farming sector. To achieve this objective methodology based on bibliometric analysis-factor-analysis-literature survey approach was considered, applied to 150 documents obtained from the Web of Science (core collection) related with the following topics: best management practice; agricultural economics; air, soil and water pollution. As main insights, it is worth referring the best management practices to deal with problems from agricultural production, such as, for example, the use of agricultural residues as feedstock for renewable energies. With regard to sustainable development in the agricultural sector, concepts such as "sustainable remediation" have their place. On the other hand, the agricultural and environmental policies and the agricultural costs associated with the several farming practices also play a determinant role here. Finally, only fraction of the scientific documents analysed (16 papers) belong to the group of studies related to policies, showing that there are potential subjects to be addressed here in future studies related with these topics. The same happens for cost-benefit analyses (24 documents).

A methodology for the sizing of domestic hot water heating and storage systems is defined, by assuming an extreme operating condition cycle composed of only two parts, a water consumption period and a system repositioning period. In both parts to respond to the extreme hot water demanding conditions, the heating is always on. The subsequent exergy analysis of this domestic hot water production system compares the irreversibility and the exergy efficiency of the water storage and the tankless situation. To carry out such analysis, some basic assumptions were made: a constant temperature heat source, a short duration operating cycle and a constant thermal energy supply. Under these circumstances it is shown that the hot water storage system leads to lower exergy losses while the tankless system is more exergy efficient, but requiring a higher instantaneous thermal power input. The use of the joule effect electricity, as the system heat source, be it a water storage one or a tankless one, maximizes the system irreversibility losses and minimizes the system exergy efficiency. The tankless system, with the joule effect electricity heat source is the worst situation.

Factors such as uncertainty associated to fuel prices, energy demand and generation availability, are on the basis of the agents major concerns in electricity markets. Facing that reality, price forecasting has an increasing impact in agents' activity. The success on bidding strategies or on price negotiation for bilateral contracts is directly dependent on the accuracy of the price forecast. However, taking decisions based only on a single forecasted value is not a good practice in risk management. The work presented in this paper makes use of artificial neural networks to find the market price for a given period, with a certain confidence level. Historical information was used to train the neural networks and the number of neural networks used is dependent of the number of clusters found on that data. K-Means clustering method is used to find clusters. A study case with real data is presented and discussed in detail

This paper describes a solid-state asymmetric bridge resonant topology to increase the energy efficiency of switching pulse modulators. The solid-state resonant topology will replace an existing pulse transformer and thyratron-based resonant modulator to supply the 60-kV target potential for the ion acceleration of the On-Line Isotope Mass Separator ISOLDE accelerator. An experimental prototype is tested in order to validate the proposed concept, including a low auxiliary voltage power supply to compensate the losses in the circuit. The design of the circuit components and the experimental results for a 6-kV prototype are presented and discussed, as well as the design procedure and parameters for the 60-kV modulator, including a high-voltage gapped coil core.

The artistic production can play a role of reflection and alert to the recovery of waste and end-of-life materials, with the consequent circular economy implementation, minimizing the use of new natural resources. The contest “Reciclar é uma arte” was organized in the framework of a Portugal partnership between Instituto Politécnico do Porto (IPP)/Instituto Superior de Engenharia do Porto (ISEP) and Laboratório Associado REQUIMTE-LAQV/GRAQ (Grupo de Reação e Análises Químicas). The main objectives were the dissemination of the concepts of recycling, green chemistry, sustainability and to show to the younger generations that Science can be accessible and fun. All products used by mankind originated from raw materials, which, during their possible transformation, use and consequent disposal will give rise to waste that will be discarded. This paper aims to demonstrate the connection between environmental education and ecological art, and how this association can help students to develop their creativity and critical thinking.