The Future Prospect of PV and CSP Solar Technologies: An Expert Elicitation Survey

In this paper we present and discuss the results of an expert elicitation survey on solar technologies. Sixteen leading European experts from the academic world, the private sector and international institutions took part in this expert elicitation survey on Photovoltaic (PV) and Concentrated Solar Power (CSP) technologies. The survey collected probabilistic information on (1) how Research, Development and Demonstration (RD&D) investments will impact the future costs of solar technologies and (2) the potential for solar technology deployment both in OECD and non-OECD countries. Understanding the technological progress and the potential of solar PV and CPS technologies is crucial to draft appropriate energy policies. The results presented in this paper are thus relevant for the policy making process and can be used as better input data in integrated assessment and energy models.Expert Elicitation, Research, Development and Demonstration, Solar Technologies

Process parameters affecting quality of high-pressure die cast aluminium alloys

High pressure die casting (HPDC) is a widely used process for manufacturing components with high production rate and complex geometries. However, high pressure die casting is still considered a “defect generating process”, since an amount of 5-10% of scrap is usually detected in castings. For this reason, the availability of new standards and tools for optimizing the process is one of the prominent needs of foundry field. Both these issues are tackled in this Thesis. First, a new classification of defects and reference dies for estimating the static mechanical properties of aluminium alloys have been developed and then published as CEN Technical Reports, satisfying the need for new standards. Then, a novel and comprehensive methodology has been developed for optimizing HPDC process through the definition of meaningful behavioural models. Some newly defined process parameters have been hence introduced, by representing the most important physical phenomena affecting casting quality and the integral nature of HPDC, and an original approach is outlined. In particular, in order to provide an effective representation of the different process stages, the following parameters have been found to be more influential and effective in representing transmitted forces, mechanical energy exchange and heat removal: the root mean square acceleration in the second stage, the energy associated to the flow forces in the whole cycle, the work of the pressure forces in the third stage and the normalized thermal gradient. The first two parameters embody the plunger motion time-history, the third parameter represents the hydraulic pressure time-history, while the last one concentrates on some thermal aspects. These parameters take advantage from signal processing techniques of the measured position and pressure profiles. Four experimental campaigns (in the whole 210 castings) using different injection machines, different alloys and different geometries of the die have been carried out to validate the novel process parameters and to prove the general validity of the approach. The statistical correlation with the measured static mechanical properties, density and percentage of porosity, as well as the metallographic analysis (percentage of oxides on fracture surfaces, analysis of different kinds of internal defect) prove the soundness of the developed method. Given the significance of the plunger motion profile in explaining the casting quality, analytical models for computing the root mean square acceleration and the energy associated to the flow forces have been developed. These analytical models permit selecting in advance the best plunger motion profile, which guarantees reliability and soundness of castings, thus satisfying the need expressed by foundries for effective optimization tools

Process parameters affecting quality of high-pressure die cast aluminium alloys

High pressure die casting (HPDC) is a widely used process for manufacturing components with high production rate and complex geometries. However, high pressure die casting is still considered a “defect generating process”, since an amount of 5-10% of scrap is usually detected in castings. For this reason, the availability of new standards and tools for optimizing the process is one of the prominent needs of foundry field. Both these issues are tackled in this Thesis. First, a new classification of defects and reference dies for estimating the static mechanical properties of aluminium alloys have been developed and then published as CEN Technical Reports, satisfying the need for new standards. Then, a novel and comprehensive methodology has been developed for optimizing HPDC process through the definition of meaningful behavioural models. Some newly defined process parameters have been hence introduced, by representing the most important physical phenomena affecting casting quality and the integral nature of HPDC, and an original approach is outlined. In particular, in order to provide an effective representation of the different process stages, the following parameters have been found to be more influential and effective in representing transmitted forces, mechanical energy exchange and heat removal: the root mean square acceleration in the second stage, the energy associated to the flow forces in the whole cycle, the work of the pressure forces in the third stage and the normalized thermal gradient. The first two parameters embody the plunger motion time-history, the third parameter represents the hydraulic pressure time-history, while the last one concentrates on some thermal aspects. These parameters take advantage from signal processing techniques of the measured position and pressure profiles. Four experimental campaigns (in the whole 210 castings) using different injection machines, different alloys and different geometries of the die have been carried out to validate the novel process parameters and to prove the general validity of the approach. The statistical correlation with the measured static mechanical properties, density and percentage of porosity, as well as the metallographic analysis (percentage of oxides on fracture surfaces, analysis of different kinds of internal defect) prove the soundness of the developed method. Given the significance of the plunger motion profile in explaining the casting quality, analytical models for computing the root mean square acceleration and the energy associated to the flow forces have been developed. These analytical models permit selecting in advance the best plunger motion profile, which guarantees reliability and soundness of castings, thus satisfying the need expressed by foundries for effective optimization tools.La pressocolata è un processo ampiamente utilizzato per produrre componenti con elevata produttività e geometria complessa. Comunque, la pressocolata è ancora considerata un “processo generatore di difetti”, dal momento che una percentuale del 5-10% di scarto è rilevata di solito nei getti. Per questa ragione, la disponibilità di nuovi standard e strumenti per l’ottimizzazione di processo è uno dei bisogni più importanti del settore della fonderia. Entrambe queste criticità sono affrontate in questa Tesi. Per prima cosa, è stata sviluppata e successivamente pubblicata come Report Tecnici riconosciuti dal CEN una nuova classificazione dei difetti e degli stampi di riferimento per stimare le proprietà meccaniche statiche delle leghe di alluminio, rispondendo al bisogno di nuovi standard. Poi, è stata sviluppata una metodologia nuova e completa per ottimizzare il processo di pressocolata attraverso la definizione di metamodelli significativi. Quindi, sono stati introdotti dei nuovi parametri di processo, che rappresentano i più importanti fenomeni fisici che influenzano la qualità dei getti e la natura integrale del processo di pressocolata, ed è stato delineato un approccio originale. In particolare, allo scopo di fornire una rappresentazione efficace delle diverse fasi del processo, si è dimostrato che i seguenti parametri sono i più influenti ed efficaci nel rappresentare le forze trasmesse, il flusso di energia meccanica e l’asportazione del calore: il valore quadratico medio dell’accelerazione in seconda fase, l’energia associata alle forze di flusso nell’intero ciclo, il lavoro delle forze di pressione nella terza fase e il gradiente termico normalizzato. I primi due parametri descrivono l’effetto del profilo di moto del pistone; il secondo è invece legato anche alla pressione esercitata dal pistone stesso, mentre l’ultimo rappresenta esclusivamente fenomeni di natura termica. Lo sviluppo ed il calcolo di questi parametri sfrutta le tecniche di elaborazione numerica dei segnali, al fine di estrarre le informazioni dai profili misurati di posizione e di pressione del pistone. La validazione del metodo proposto è stata condotta attraverso quattro diverse campagne sperimentali, con un totale di 210 getti analizzati, nelle quali sono state utilizzate diverse macchine di iniezione, diversi stampi e diverse leghe, al fine di ottenere risultati generali ed estendibili. La correttezza del metodo proposto è confermata dalla correlazione statistica dei parametri proposti con la resistenza meccanica statica, con la densità, la porosità, e da alcune significative analisi metallografiche (percentuale di ossidi sulle superfici di frattura, analisi dei difetti interni). Data l’efficacia dimostrata dei parametri proposti, ed in particolare di quelli legati al profilo di moto del pistone, l’approccio è stato esteso tramite lo sviluppo di alcune relazioni analitiche per calcolare i due parametri cinematici. Ciò rappresenta uno strumento efficace per sintetizzare a priori il profilo di moto ottimale del pistone che, nel rispetto dei vincoli di macchina, consenta di ottimizzare la qualità dei getti

Methods to neutralize the effects of iron in Al-Si foundry alloys

In questo lavoro sono sistematicamente presentate le diverse tecniche utilizzate per neutralizzare gli effetti deleteri prodotti dal Fe in leghe Al-Si da fonderia. Partendo dalle tecniche tradizionali di alligazione, vengono prese in considerazione le aggiunte di elementi quali Mn, Co, Be, Cr e K, i quali risultano efficaci nello stabilizzare la precipitazione di una fase \u3b1 poligonale, o a scrittura cinese, con minor effetto infragilente rispetto alle lamelle di fase \u3b2-Al5FeSi. L\u2019utilizzo di metodi di neutralizzazione alternativi, senza cio\ue8 l\u2019aggiunta di elementi alliganti, in particolare i trattamenti termici di non-equilibrio e il surriscaldamento del bagno liquido prima della colata, sembrano mostrare buoni risultati nella dissoluzione e frammentazione della fase \u3b2. Tali metodologie vengono descritte in termini di impatto sulle caratteristiche microstrutturali, difettologiche e meccaniche del materiale

Improved metamodel for the optimization of high pressure die casting process

The increasing need of improving quality in high-pressure die casting (HPDC) has been boosting the development of models to predict the final outcome and to optimize the process. It is hence promising the use of simplified behavioural models, denoted metamodels, which are abstract descriptions of HPDC. These models represent the relation between some influential process parameters and the final quality, with algebraic explicit equations obtained through least-square regression. The recent researches carried out by the Authors have identified these influential parameters, which represent the physical phenomena responsible for the casting quality. In contrast with the literature, these parameters employ physical quantities that are not instantaneous values of directly measured variables, but rather exploit signal processing and have an integral nature. These results solve the crux in the synthesis of metamodels, i.e. the definition of the correct independent parameters, which is here solved by transforming those adopted for the design of experiment (DOE), through nonlinear relations based on physical considerations. Besides showing some experimental results, the paper outlines a novel paradigm to HPDC optimization. The most influential parameters related to the plunger motion are, in turn, represented through analytical models. Then, once that these parameters are properly chosen, process control can be performed through the injection machine controller and process can be optimized by selecting in advance the best parameters

A Tool for Predicting the Effect of the Plunger Motion Profile on the Static Properties of Aluminium High Pressure Die Cast Components

The availability of tools for predicting quality in high pressure die casting is a challenging issue since a large amount of defects is detected in components with a consequent worsening of the mechanical behavior. In this paper, a tool for predicting the effect of the plunger motion on the properties of high pressure die cast aluminum alloys is explained and applied, by demonstrating its effectiveness. A comparison between two experiments executed through different cold chamber machines and the same geometry of the die and slightly different chemical compositions of the alloy is described. The effectiveness of the model is proved by showing the agreement between the prediction bounds and the measured data. The prediction model proposed is a general methodology independent of the machine and accounts for the effects of geometry and alloy through its coefficients

Guidelines for Mechanical Design of Al-alloy cast components

This Chapter is aimed at elaborating an operative support to mechanical designers, involved in the field of Al alloy components. The availability of two new CEN Technical Reports on defects & imperfections in castings (resulting from WP2) and mechanical potential of Al-Si foundry alloys (resulting from WP3) makes necessary the development of a new approach in the design stage. Such a new approach has to take into account the “mechanical potential” of Al foundry alloys (draft CEN Technical Report: Fpr TR 16748 (00132378), “Aluminium and Aluminium alloys - Mechanical Potential of Al-Si alloys for High Pressure, Low Pressure and Gravity Die Casting”, the critical role played in castings by the different types of defects, classified in the new CEN Technical Report Fpr TR 16749 (001323789), “Aluminium and aluminium alloys - Classification of Defects and Imperfections in High Pressure, Low Pressure and Gravity Die Cast Products”, the need of considering, for cast products, the interaction existing among microstructure, defects and mechanical behaviour, leading to a “distribution of mechanical properties”. These aspects will be described in the guidelines developed in this Chapter

Improved metamodels for the optimization of high-pressure die casting process

The increasing need of improving quality in high-pressure die casting (HPDC) has been boosting the development of models to predict the final outcome and to optimize the process. It is hence promising the use of simplified behavioural models, denoted metamodels, which are abstract descriptions of HPDC. These models represent the relation between some influential process parameters and the final quality, with algebraic explicit equations obtained through least-square regression. The recent researches carried out by the Authors have identified these influential parameters, which represent the physical phenomena responsible for the casting quality. In contrast with the literature, these parameters employ physical quantities that are not instantaneous values of directly measured variables, but rather exploit signal processing and have an integral nature. These results solve the crux in the synthesis of metamodels, i.e. the definition of the correct independent parameters, which is here solved by transforming those adopted for the design of experiment (DOE), through nonlinear relations based on physical considerations. Besides showing some experimental results, the paper outlines a novel paradigm to HPDC optimization. The most influential parameters related to the plunger motion are, in turn, represented through analytical models. Then, once that these parameters are properly chosen, process control can be performed through the injection machine controller and process can be optimized by selecting in advance the best parameters