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Dolomite-based binders are characterised by interesting technical and environmental features. For their synthesis, sources of both CaO and MgO are required. The idea developed in this work is to couple the synthesis of dolomite-based binders, starting from a natural dolomite, through the concept of concentrated solar energy (needed to drive the endothermal dolomite calcination process) in fluidised bed reactors. To this end, a fluidised bed system, where the concentrated solar radiation is mimicked by the use of Xe-lamps (short-arc), has been set up and operated. Natural dolomite (sieved in the 420-590 ?m size range) was calcined at a nominal temperature of 850 °C, and bed temperature profiles during solar-driven calcination were investigated. Then, four binders were prepared by mixing slaked dolomite (obtained from the hydration of solar calcined dolomite) with either blast furnace slag or coal fly ash as supplementary cementitious materials. The binders were hydrated for curing times ranging from 7 to 56 days. X-ray fluorescence, X-ray diffraction and combined differential thermal and thermogravimetric analyses were employed as characterisation techniques both to analyse the chemical composition of starting materials and to investigate the evolution of the hydration in the four systems.

The influence of compost on the growth of bean plants irrigated with As-contaminated waters and its influence on the mobility of As in the soils and the uptake of As (as NaAs(III)O2) by plant components was studied at various compost application rates (3·10(4) and 6·10(4) kg ha(-1)) and at three As concentrations (1, 2 and 3 mg kg(-1)). The biomass and As and P concentrations of the roots, shoots and beans were determined at harvest time, as well as the chlorophyll content of the leaves and nonspecific and specifically bound As in the soil. The bean plants exposed to As showed typical phytotoxicity symptoms; no plants however died over the study. The biomass of the bean plants increased with the increasing amounts of compost added to the soil, attributed to the phytonutritive capacity of compost. Biomass decreased with increasing As concentrations, however, the reduction in the biomass was significantly lower with the addition of compost, indicating that the As phytotoxicity was alleviated by the compost. For the same As concentration, the As content of the roots, shoots and beans decreased with increasing compost added compared to the Control. This is due to partial immobilization of the As by the organic functional groups on the compost, either directly or through cation bridging. Most of the As adsorbed by the bean plants accumulated in the roots, while a scant allocation of As occurred in the beans. Hence, the addition of compost to soils could be used as an effective means to limit As accumulation in crops from As-contaminated waters.

In this paper a grid-tied photovoltaic (PV) cascaded H-bridge (CHB) inverter with embedded storage units is proposed. The multi-input single-output inverter architecture allows a distributed maximum power point tracking (DMPPT) approach, thus mitigating the mismatch effects. The energy storage units (ESUs) embedded at each dc-link provides more flexibility to the power circuit compensating for the inherent variability of the PV sources. The proposed power system ensures a continuous power supply to the grid also in case of PV power fluctuations due to irradiance conditions as well as to the MPPT. In particular, the presence of a storage element allows a voltage sweep on the PV source to be implemented, thus guaranteeing the maximization of PV energy harvesting, with no detrimental effect on the power delivery to the utility network. The numerical results, carried out on a single-phase nineteen-level PV CHB inverter, reveal the improved performance of the proposed design and control technique.

The safeguard of power equipments is assuming a major role in the deregulated electricity market, where a malfunctioning power system could be responsible for serious damages to a large number of system operators having access to the shared energy resource. In this context thermal monitoring of power cables represents a key issue in evaluating the risks associated with a given load management policy especially during emergency conditions. In particular this demands for reliable assessment models that should be able to predict the transient thermal behaviour when the load exceeds the nameplate value. In this connection the application of both simplified and detailed power cable thermal models is often complicated by the presence of uncertainties affecting the tolerances of the input data. The effect of these uncertainties could influence the final solution to a considerable extent. A comprehensive tolerance analysis is therefore required in order to incorporate the effect of data uncertainties into the thermal modelling process. To address this problem, in the paper the employment of interval mathematic is proposed. Several numerical results are presented and discussed in order to assess the effectiveness of the proposed methodology which offer a rough qualitative insight of the solution in a very short time, comparable to the time required for a deterministic numerical simulation.

This paper analyzes different policies that may promote the transition to sustainability, with a particular focus on the energy sector. We present a dynamic simulation model where three different strategies for sustainability are identified: reduction in GHG emissions, improvements in energy efficiency and the development of the renewable energy sector. Our aim is to evaluate the dynamics that those strategies may produce in the economy, looking at different performance indicators: rate of growth, unemployment, fiscal position, GHG emission, and transition to renewable energy sources.

Doubly-fed induction generators (DFIGs) are widely used in wind turbine systems. Traditionally, they rely on the grid voltage to operate. However, the increasing penetration of renewables necessitates wind turbines that can contribute to grid stability, and grid-forming control (GFM) has emerged as an attractive solution. Traditionally, the GFM control of DFIGs has been proposed as a single-loop control of the rotor flux magnitude and orientation, while double-loop schemes based on virtual impedance or virtual admittance have been scarcely investigated. This paper analyzes the operation and small-signal stability of a virtual-impedance-based dual-loop GFM control for DFIG. The small-signal impedance-model is derived and used to analyze the system stability in case of strong and weak grid connection. Electromagnetic transient simulations on a 1.5 MW wind turbine system are presented to validate the analysis.

Abstract In the field of innovative power sources, photovoltaic are playing an important role as new clean energy generators. The performances being dependent on instantaneous weather condition, photovoltaic sources are usually equipped with an auxiliary energy storage device. There are applications where the opportunity to couple the photovoltaic source with ultracapacitor can be taken into account. The aim of the paper is to study the performances of a hybrid system constituted by photovoltaic and ultracapacitor sources. In particular, the paper deals with the study of the ultracapacitor rate design for photovoltaic systems feeding pulsing loads. The results of the study, which can also be referred to temporary unfavourable weather conditions, have been validated by experimental data. In the final part of the paper, some considerations on economical implications about the dimensioning of a photovoltaic–ultracapacitor systems are drawn.