Maximizing Vanadium Redox Flow Battery Efficiency: Strategies of Flow Rate Control

Vanadium redox flow batteries (VRFBs) are one of the most promising technologies for large-scale energy storage due to their flexible energy and power capacity configurations. The energy losses evaluation assumes a very important rule on the VRFB characterization in order increase the efficiency of the battery. Very few papers describe the relations between hydraulic, electrical and chemical contributions to the system energy losses, especially in a large size VRFB system. In the first part a fluid dynamics characterization of a 9kW / 27 kWh VRFB test facility has been conducted. In particular, we will consider the internal resistance as the sum of an ohmic and a transport resistance. Secondly, an overall loss assessment based on both numerical and experimental results has been carried out. Finally, some improvements in the battery management strategy and in stack engineering are proposed, that results from this work and can help the future designer to develop more efficient VRFB stack with a compact design

Enhancing the efficiency of kW-class vanadium redox flow batteries by flow factor modulation: An experimental method

he paper presents a control method of the electrolyte flow factor in kW-class Vanadium Redox Flow Batteries that minimizes transport losses without affecting the battery's electrical performance. This method uses experimental data acquired on a 9 kW/27 kWh test facility at varying operating conditions. The effects of overpotentials on the polarization curves are then modeled as non-linear electrical resistances that vary with the stack current, state of charge and electrolyte flow rates. Our analysis of these variables shows that the optimal performance is found if the flow factor is modulated during operation according to stack current and the battery state, so as to minimize the overall flow-dependent losses. The optimal profiles have been identified as functions of the battery's operating conditions. Based on these results, a dynamic control for the electrolyte flow rates has been implemented at a software level (i.e. without modifying the hardware of the test facility), which is capable of maximizing the round-trip efficiency and exceeds the performance achieved with a constant flow factor strategy, as proposed in previous literature. The implementation of the optimal flow rate control requires a preliminary test campaign to collect performance data, which are then used in the control protocol to manage the battery's operation. This scheme is easily implementable at a software level in other industrial redox flow batteries

A validated dynamical model of a kW-class Vanadium Redox Flow Battery

The development of redox flow batteries depends on the research on new materials as well as on the technological development, but also on appropriate models which allow to simulate their performance in operative conditions. Very few investigations are reported in the literature concerning the technology, modeling and simulation of large-scale Vanadium Redox Flow Battery systems, built around multi-cell stacks. This paper regards the modeling of an industrial-sized 9 kW test facility. In particular, a complete dynamic model is presented, that takes into account all thermal effects occurring inside the stack, resulting in a complex non-linear coupled formulation, that allows to simulate the battery operation in any realistic conditions. The model is able to simulate the thermal behavior both in standby, i.e. without power and reactant flow, as well as in load operation, i.e. in charge and discharge. The numerical implementation of the model is described in detail. The model validation is also described, consisting in comparing computed data with experimental measurements taken on the available test facility

RI-abitare l’oggi : intorno al progetto di riuso

Interi paesi fantasma, un patrimonio demaniale in disuso e in cerca di valorizzazione, caserme e carceri obsolete o abbandonate collocate all’interno dei centri urbani, capannoni industriali vuoti e un numero crescente di centri commerciali poco o per niente frequentati nelle aree di connessione tra città e campagna, interi complessi industriali abbandonati, palazzi pubblici e privati di dimensione, organizzazione e dotazione di servizi non adeguati alle esigenze odierne. E ancora, chiese, barchesse, scuole, ex colonie ma anche edifici residenziali del tessuto storico urbano e non, architetture storiche e monumentali dal grande valore culturale da rendere funzionali per i diversi usi attuali: sono diversi e sempre più evidenti gli esempi di un patrimonio da riconsiderare, in un’ottica di riutilizzo sostenibile del costruito inteso come risorsa da non sprecare, su cui convergono molteplici obiettivi europei, quali l’incremento dell’efficienza energetica legata al Green New Deal e il raggiungimento del traguardo di zero consumo di suolo, mediante un riuso selettivo e appropriato dell’esistente. In Italia, per la storia plurimillenaria e la forte tradizione identitaria caratterizzata dal ruolo significativo del costruito storico, in cui affondano le radici culturali del Paese, queste sfide richiedono lo sviluppo di un pensiero evoluto sul progetto, in cui l’innovazione e la continuità possano integrarsi, confrontandosi con i principi della Dichiarazione di Davos 2018 Verso una Baukultur di alta qualità per l’Europa e del New European Bauhaus. Sono questi i nuovi temi – o temi noti da riconsiderare – che l’architettura contemporanea deve affrontare, sollecitando una riflessione sui modi di intervenire sul patrimonio costruito e sul ruolo esercitato dalle diverse discipline

Yield genetic gain at national level of carioca common beans from the Embrapa Breeding Program - 1993 to 2008.

The objective of this work was to estimate the genetic gain of the commercial type carioca dry beans breeding program carried out by Embrapa Rice and Beans Research Center in a period of 16 years, from 1993 to 2008

Prostate Cancer Treatment-Related Toxicity: Comparison between 3D-Conformal Radiation Therapy (3D-CRT) and Volumetric Modulated Arc Therapy (VMAT) Techniques

Objective: This paper illustrates the results of a mono-institutional registry trial, aimed to test whether gastrointestinal (GI) and genitourinary (GU) toxicity rates were lower in localized prostate cancer patients treated with image-guided volumetric modulated arc therapy (IG-VMAT) compared to those treated with IG-3D conformal radiation therapy (IG-3DCRT). Materials and Methods: Histologically proven prostate cancer patients with organ-confined disease, treated between October 2008 and September 2014 with moderately hypofractionated radiotherapy, were reviewed. Fiducial markers were placed in the prostate gland by transrectal ultrasound guide. The prescribed total dose was 70 Gy in 28 fractions. The mean and median dose volume constraints for bladder and rectum as well as total volume of treatment were analyzed as potentially prognostic factors influencing toxicity. The Kaplan–Meier method was applied to calculate survival. Results: Overall, 83 consecutive patients were included. Forty-two (50.6%) patients were treated with 3D-CRT and 41 (49.4%) with the VMAT technique. The median follow-up for toxicity was 77.26 months for the whole cohort. The VMAT allowed for a dose reduction to the rectum and bladder for the large majority of the considered parameters; nonetheless, the only parameter correlated with a clinical outcome was a rectal dose limit V66 > 8.5% for late GI toxicity G ≥ 2 (p = 0.045). Rates of G ≥ 2 toxicities were low among the whole cohort of these patients treated with IGRT. The analysis for rectum dose volume histograms (DVHs) showed that a severe (grade ≥ 2) late GI toxicity was related with the rectal dose limit V66 > 8.5% (p = 0.045). Conclusions: This study shows that moderate hypofractionation is feasible and safe in patients with intermediate and high-risk prostate cancer. Daily IGRT may decrease acute and late toxicity to organs at risk and improve clinical benefit and disease control rate, cutting down the risk of PTV geographical missing. The adoption of VMAT allows for promising results in terms of OAR sparing and a reduction in toxicity that, also given the small sample, did not reach statistical significance