Development and characterisation of advanced energy storage devices for stationary applications

The growing demand for energy and increasing attention on environmental challenges outline the requirement to optimise the electrical grid, and gradually replace the current energy sources with sustainable and renewable alternatives. The electrical grid at present forms an enormous infrastructure to instantaneously transmit the primary generated energy to the end users. However, due to the lack of storage capabilities to store the primary energy, the existing grid must conform to the oscillations due to the changes in customer demand. Grid-scale energy storage devices such as redox flow batteries (RFBs) have emerged as key technologies to accommodate the transition from finite fossil fuels to renewable energies and improve the sustainability of the electricity generation sector. This thesis focuses on characterisation and development of novel RFB systems for energy storage applications. Firstly, a novel Regenerative Fuel Cell (RFC) utilising inexpensive manganese electrolyte in the cathode and facile hydrogen in the negative electrode has been examined. To understand the impact of different materials on the performance of the Regenerative Hydrogen Manganese Fuel cell (RHMnFC), various membrane electrode assemblies are tested. it was found that carbon felt as the liquid half-cell electrode, Carbon paper with Pt loading of 0.3 mg/cm2 as the hydrogen electrode and Nafion 117 as the membrane yield the highest performance in the cell. This configuration of the membrane electrode assembly yields energy efficiencies in the range of 77% and 90%, while charging and discharging the cell at current densities in the range of 20 mA/cm2 to 100 mA/cm2. Furthermore, viability of scaling-up is studied, where a techno economic study has been carried out to explore the feasibility of this novel chemistry compared to the conventional energy storage devices, with an estimated 37% reduction in the levelized cost of storage compared to the all-vanadium RFB system. RFBs with manganese redox active species have hitherto been little investigated for energy storage applications due to the instability of Mn3+. To improve the lifespan of the novel RFC, an electrolyte composition, consisting of manganese as the redox active species and Ti4+ as an additive that supresses the Mn3+ disproportionation, is presented. The performance of this electrolyte composition is tested, to identify the impact of the operating conditions, such as the operating temperature of the cell, rest time between half-cycles and overcharging the electrolyte, on the stability of the RHMnFC system. This set of experiments reveals that, although the presence of Ti4+ supresses the Mn3+ disproportionation reaction, precipitation of MnO2 is an unavoidable phenomenon. Following these findings, a method to regenerate the inevitable precipitation of MnO2 in the electrolyte is proposed and the practicality of the method is experimentally tested and proven. Secondly, an in-situ method was developed using X-ray radiography and tomography techniques to enable the visualisation and characterisation of electrodeposited zinc (Zn) in Zn-RFBs. Zn-Based RFBs are promising technologies for energy storage applications. However, there are a number of challenges that must overcome prior to the commercialisation of these systems. The main obstacle is the dendritic growth of Zn on the anode electrode. This part of the thesis focuses on developing a method to investigate the mechanisms which effect the morphology of the zinc deposit. This method consists of designing a novel three-electrode cell with the capability to operate under different conditions, to investigate the effect of current density and electrolyte flow on the morphology of the deposited Zn. By monitoring the real-time formation of Zn deposits and reconstructing the morphology of the deposits, the mechanisms which supresses the dendritic growth of Zn deposits have been found and analysed. Quantitative analysis showed that operating under dynamic flow improved the morphology of the electrodeposited Zn and gave a compact deposit.Open Acces

Recycling behaviour of italian citizens in connection with the clarity of on-pack labels. A bottom-up survey

The present work studies, through an online survey, the recycling behaviours of a representative sample of Italian end users, in connection with the effectiveness of on-pack recycling indications of different packed materials. The study has a special focus on the clarity of on-pack recycling indications to convey waste sorting information, and the impact of clear and straightforward labelling to improve the sorting result. The work took advantage of social media as the distribution platform, thus obtaining a relatively high involvement of citizens. To investigate the representativeness of the sample, some of its characteristics were subject to checks and comparisons to their corresponding values of the Italian population. According to almost three-quarters of the responders, a clear and straightforward labelling will improve the result of their waste sorting drastically. The general awareness of the answerers relative to the importance of waste recycling and willingness to improve the quality of their sorted waste is very high among the participants but the overall satisfaction of the on-pack indications is relatively low. The score of on-pack labels in conveying information on recycling and waste segregation is evaluated as improvable. A higher perception of circular economy concept leads to more re-utilisation of the packaging parts, which increases with the awareness about the importance of recycling

Effect of foot reflexology on anxiety and agitation in patients under mechanical ventilation after open heart surgery: A randomized clinical trial study

زمینه و هدف: رویکردهای غیر دارویی از جمله ماساژ بازتابی پا به علت کاهش عوارض و هزینه ها در کانون توجه محققین در جامعه بیماران مختلف قرار گرفته است. این مطالعه با هدف بررسی تأثیر ماساژ بازتابی پا بر اضطراب و بیقراری بیماران تحت تهویه مکانیکی پس از جراحی قلب باز انجام شد. روش بررسی: این مطالعه کارآزمایی بالینی کنترل شده، سه گروهی و دو سو کور با طراحی اندازه گیری مکرر در دو بیمارستان وابسته به دانشگاه علوم پزشکی بقیه الله (عج) تهران، از بهمن1392 تا اردیبهشت 1393 انجام شد. 96 بیمار کاندید جراحی قلب باز به روش نمونه گیری در دسترس انتخاب و به صورت تخصیص تصادفی در سه گروه آزمون (ماساژ بازتابی پا 34 نفر)، درمان نما (تماس سطحی پاشنه پا 30 نفر) و کنترل (مراقبت های معمول 32 نفر) قرار گرفتند. در گروه آزمون، ماساژ بازتابی پا به مدت20 دقیقه بر روی نقاط بازتاب قلب و ریه، انجام شد. میزان اضطراب و بیقراری بر اساس مقیاس سنجش اضطراب (FAS) و مقیاس سنجش بیقراری ریچموند (RSAS) در 6 مرحله زمانی ثبت شد. یافته ها: داده های آماری 92 بیمار (31 نفر گروه آزمون، 30 نفر گروه درمان نما و 31 نفر گروه کنترل) جمع آوری گردید. در مقایسه روند تغییرات سطح اضطراب و بیقراری، آزمون درون گروهی فریدمن نشان داد، بین میانگین سطح اضطراب و بیقراری در گروه ها در مراحل زمانی مختلف تفاوت معنی دار آماری وجود دارد. همچنین آزمون کروسکال والیس نشان داد میزان اضطراب و بیقراری بین سه گروه در مراحل مختلف زمانی تفاوت معنی دار آماری با یکدیگر ندارند. نتیجه گیری: ماساژ بازتابی پا در نقاط بازتابی مربوط به قلب و ریه تغییر معنی داری در کاهش اضطراب و بیقراری بیماران پس از جراحی ایجاد نکرد

Etched Glass Surfaces, Atomic Force Microscopy and Stochastic Analysis

The effect of etching time scale of glass surface on its statistical properties has been studied using atomic force microscopy technique. We have characterized the complexity of the height fluctuation of a etched surface by the stochastic parameters such as intermittency exponents, roughness, roughness exponents, drift and diffusion coefficients and find their variations in terms of the etching time.Comment: 5 pages, 6 figures

Stochastic Analysis and Regeneration of Rough Surfaces

We investigate Markov property of rough surfaces. Using stochastic analysis we characterize the complexity of the surface roughness by means of a Fokker-Planck or Langevin equation. The obtained Langevin equation enables us to regenerate surfaces with similar statistical properties compared with the observed morphology by atomic force microscopy.Comment: 4 pages, 7 figure

A cost-effective alkaline polysulfide-air redox flow battery enabled by a dual-membrane cell architecture

With the rapid development of renewable energy harvesting technologies, there is a significant demand for long-duration energy storage technologies that can be deployed at grid scale. In this regard, polysulfide-air redox flow batteries demonstrated great potential. However, the crossover of polysulfide is one significant challenge. Here, we report a stable and cost-effective alkaline-based hybrid polysulfide-air redox flow battery where a dual-membrane-structured flow cell design mitigates the sulfur crossover issue. Moreover, combining manganese/carbon catalysed air electrodes with sulfidised Ni foam polysulfide electrodes, the redox flow battery achieves a maximum power density of 5.8 mW cm−2 at 50% state of charge and 55 °C. An average round-trip energy efficiency of 40% is also achieved over 80 cycles at 1 mA cm−2. Based on the performance reported, techno-economic analyses suggested that energy and power costs of about 2.5 US$/kWh and 1600 US$/kW, respectively, has be achieved for this type of alkaline polysulfide-air redox flow battery, with significant scope for further reduction

Height Fluctuations and Intermittency of V2O5V_2 O_5 Films by Atomic Force Microscopy

The spatial scaling law and intermittency of the $V_2 O_5$ surface roughness by atomic force microscopy has been investigated. The intermittency of the height fluctuations has been checked by two different methods, first, by measuring scaling exponent of q-th moment of height-difference fluctuations i.e. $C_q =$ and the second, by defining generating function $Z(q,N)$ and generalized multi-fractal dimension $D_q$. These methods predict that there is no intermittency in the height fluctuations. The observed roughness and dynamical exponents can be explained by the numerical simulation on the basis of forced Kuramoto-Sivashinsky equation.Comment: 6 pages (two columns), 11 eps. figures, late

Mechanically Robust BiSbTe Alloys with Superior Thermoelectric Performance: A Case Study of Stable Hierarchical Nanostructured Thermoelectric Materials

Bismuth telluride based thermoelectric materials have been commercialized for a wide range of applications in power generation and refrigeration. However, the poor machinability and susceptibility to brittle fracturing of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with a plasma-activated sintering (MS-PAS) method is employed for commercial p-type zone-melted (ZM) ingots of Bi_0.5Sb_1.5Te_3. This fast synthesis approach achieves hierarchical structures and in-situ nanoscale precipitates, resulting in the simultaneous improvement of the thermoelectric performance and the mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS-PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS-PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in their fracture toughness, combined with an eightfold and a factor of six increase in the compressive and flexural strength, respectively. Accompanied by an excellent thermal stability up to 200 °C for the MS-PAS synthesized samples, the MS-PAS technique demonstrates great potential for mass production and large-scale applications of Bi_2Te_3 related thermoelectrics