A practical simulation method to estimate fusion enthalpy of phase change materials eutectic mixtures for CSP plant applications

The determination of fusion enthalpy of ternary eutectic mixtures of molten salt was crucial for the development of feasible PCM material. A simulation method was presented as a suitable and fast way to estimate a first rough value of latent heat. The approach was validated by calorimetric measurements using five eutectic mixtures composed by alkaline nitrates and nitrites. At this aim, the binary fitting parameters determined in previous works were collected and then employed to estimate the latent enthalpy of the corresponding ternary mixtures, according to a thermodynamic model based on the regular solution assumptions. The obtained values were confronted with the experimental measurements, resulting in a discrepancy of about 15%

Chemical CSP storage system based on a manganese aluminium spinel.

Chemical storage systems are a promising innovative route to overcome the issue of the solar irradiation storage, resulting as cost effective and with high energy density. A main problem with these kinds of materials is to design a synthesis method for preparing stable reactive structures, presenting at the same time a high volumetric charging/discharging enthalpy. At this purpose, a size controlled spinel was produced, characterized and investigated regarding its thermophysical and kinetics properties. The obtained powder presents an average diameter between 100 and 200 μm and an energy density of 133 J/g and an experimental test was carried out to verify the spinel morphology stability under thermal cycles. The specific heat is similar to other structured chemical storage system and makes the spinel feasible to be used also as sensible accumulation medium. Despite the relatively high particles size, and the expected small exposed reactive area, the charging, and especially discharging reaction rates resulted particularly favourable and comparable with the reported behaviour of micrometric powders. The particularly simple preparation method plus the cost effectiveness of the precursors leads to a quite convenient expected cost for the storage material, absolutely similar to commercially available accumulation systems

A general thermodynamic model for eutectics of phase change molten salts in concentrating solar power applications

The production of electric energy from solar radiation is nowadays one of the most investigated “carbon free” technologies. Concentrating solar power (CSP) plants employ thermal energy storage (TES) units in order to dispatch electrical output to match the peak demand period. Therefore, the selection of a proper heat storage material (HSM) is the key to make this technology suitable for renewable energy production. The aim of this work is to provide a general semi-predictive thermodynamic model able to detect the eutectic temperature and molar composition of phase change molten salt mixtures employed as HSM. The method is based on the experimental liquidus curves, where the non-ideal behavior of the system is expressed by the most commonly used local-composition activity coefficients models, namely Wilson and NRTL. The only conditions required are a total miscibility in the liquid phase and a quasi-total immiscibility in the solid phase. This simulation tool was validated predicting the eutectic points of several significant ternary mixtures based on nitrates, nitrites, chlorides and carbonates that are the most promising candidates as PCM in temperature range applications from 200°C to 600°C. At this purpose, the literature phase diagrams of the binary subsystems were simulated in order to obtain the fitting parameters necessary for the ternary system behaviour prediction. Then, the ternary systems were modelled and an experimental campaign was conducted to compare the experimental eutectic points with the simulated ones. The model always resulted flexible and accurate with a maximum discordance of 5% for both temperature and molar composition

Scarto vs Risorsa. Proposte per la rigenerazione dei residui urbani

Lo studio affronta il tema della rigenerazione di comparti urbani in disuso, con l’obiettivo di orientare il concetto di recupero/riuso, verso una visione più ampia e circolare delle trasformazioni. Il carattere multidisciplinare del gruppo di lavoro ha consentito di sviluppare una proposta metodologica in grado di descrivere un processo di recupero “atipico” dei “residui” urbani, visti come risorsa strategica per generare nuove economie e per [ri]attivare relazioni materiali e immateriali tra uomo e ambiente. Il processo proposto, costruito a partire dalle peculiarità del caso di via Medici del Vascello a Milano, si caratterizza per un approccio metodologico adattivo, flessibile e multiscalare, in grado di agire a diversi livelli di intervento per la riattivazione economica, ambientale e sociale dell’area. Il modello meta-progettuale è costruito a partire dalla definizione dei macro-temi di orientamento per la rigenerazione (recupero atipico, connessione reticolare, gestione/presidio ed abitare fluido), dai quali far derivare le misure-obiettivo per le linee di azione strategica. Si tratta di un metodo aperto che intende il progetto come “servizio” per l’attivazione di un modello replicabile di rigenerazione urbana, con particolare riferimento a come le tematiche dell’innovazione tecnologica, di sostenibilità e comfort ambientale, del riuso e dell’economia circolare, possano integrarsi e dialogare con le rinnovate esigenze tipologiche e sociali dell’abitare contemporaneo.The study deals with the issue of regeneration of disused urban areas, with the aim of orienting the concept of recovery/reuse towards a broader and more circular vision of transformations. The multidisciplinary nature of the working group made it possible to develop a methodological proposal, capable of describing a process of "atypical" recovery of urban "residues", seen as a strategic resource to generate new economies and to [re] activate material and immaterial relations between Man and Environment. The proposed process, built starting from the peculiarities of the case study of via Medici del Vascello in Milan, is characterized by an adaptive, flexible and multi-scale methodological approach, capable of acting at different levels of intervention for the economic, environmental and social reactivation of the area. The meta-design model is constructed starting from the definition of the macro-orientation regeneration issues (atypical recovery, reticular connection, management/supervision and fluid living), from which target measures for strategic action lines can be obtained. It is an open method that considers the “project” as a "service" for the activation of a replicable urban regeneration model, with particular reference to how the issues of technological innovation, sustainability and environmental comfort, reuse and circular economy, can integrate and dialogue with the renewed typological and social needs of contemporary living

All‐optical synchronization of self‐pulsating laser diodes

We examine the behavior of self‐pulsating laser diodes when injected with periodic optical signals. We experimentally and theoretically investigate the phase difference between the injected optical signal and the synchronized self‐pulsating laser diode emission. We explore the phase difference dependence on detuning between the laser free‐running self‐pulsation frequency and the applied signal frequency, and on the injected signal power. The determined sensitive dependence of the phase difference on these factors has important consequences when self‐pulsating lasers are used as optical signal processing elements in all‐optical communication networks, where such sensitivity may lead to timing problems