Performance indicators for benchmarking solar thermochemical fuel processes and reactors

ABSTRACT: Concentrated solar energy offers a source for renewable high-temperature process heat that can be used to efficiently drive endothermic chemical processes, converting the entire spectrum of solar radiation into chemical energy. In particular, solar-driven thermochemical processes for the production of fuels include reforming of methane and other hydrocarbons, gasification of biomass, coal, and other carbonaceous feedstock, and metal oxide redox cycles for splitting H2O and CO2. A notable issue in the development of these processes and their associated solar reactors is the lack of consistent reporting methods for experimental demonstrations and modelling studies, which complicates the benchmarking of the corresponding technologies. In this work we formulate dimensionless performance indicators based on mass and energy balances of such reacting systems, namely: energy efficiency, conversion extent, selectivity, and yield. Examples are outlined for the generic processes mention above. We then provide guidelines for reporting on such processes and reactors and suggest performance benchmarking on four key criteria: energy efficiency, conversion extent, product selectivity, and performance stability.info:eu-repo/semantics/publishedVersio

Guy Boothby and the “Yellow Peril”: Representations of Chinese Immigrants in British Imperial Spaces in the Late-Nineteenth Century

By the end of the nineteenth century the pernicious racial term “yellow peril” had entered the common parlance of Victorians across the British Empire. Ironically, this insidious imperial myth that China would overrun the West owed its genesis to the impact of European, and particularly British imperial activity, on China in the late-nineteenth century, rather than to any expansionary Chinese aims or activity. The western impact was bi-faceted, involving both the physical incursion of westerners into China, and the related movement of Chinese people overseas to work in western nations and colonies. Under the international coerced labour phenomenon known as the “coolie trade,” Chinese people were brought across the British Empire as far as the settler colonies of Australia and South Africa, and even to the plantations of the British West Indies. Despite the relative powerlessness of their position as indentured or indebted immigrants, they were inevitably perceived as hostile aliens who threatened "white" society. This essay examines the impact of Australian anti-Chinese sentiment on representations of Chinese people in the works of Guy Boothby, an Adelaide-born author who emigrated to London in 1893. It explores Boothby’s representations of Chinese people in the imperial spaces of Britain’s Australian and Southeast Asian colonies, and also in the informal imperial spaces of contact in “foreign” China, in the cities and coastal locations where the British Empire was making its presence and influence felt, in works including Boothby’s travelogue, On the Wallaby (1894), the Dr Nikola series of novels (1895-1901), “The Story of Lee Ping” (1895), The Beautiful White Devil (1896) and My Strangest Case (1901). It argues that these superficially disinterested but consistently derogatory representations of the far-flung Chinese contributed to the deplorable international myth of the yellow peril, but also could not help revealing the important and largely overlooked presence of the Chinese in the spaces of the British Empire, demonstrating the impact of the coolie trade on imperial society and signalling the multifaceted nature of the British Empire’s involvement with China

Advanced timeline systems

The Mission Planning Division of the Mission Operations Laboratory at NASA's Marshall Space Flight Center is responsible for scheduling experiment activities for space missions controlled at MSFC. In order to draw statistically relevant conclusions, all experiments must be scheduled at least once and may have repeated performances during the mission. An experiment consists of a series of steps which, when performed, provide results pertinent to the experiment's functional objective. Since these experiments require a set of resources such as crew and power, the task of creating a timeline of experiment activities for the mission is one of resource constrained scheduling. For each experiment, a computer model with detailed information of the steps involved in running the experiment, including crew requirements, processing times, and resource requirements is created. These models are then loaded into the Experiment Scheduling Program (ESP) which attempts to create a schedule which satisfies all resource constraints. ESP uses a depth-first search technique to place each experiment into a time interval, and a scoring function to evaluate the schedule. The mission planners generate several schedules and choose one with a high value of the scoring function to send through the approval process. The process of approving a mission timeline can take several months. Each timeline must meet the requirements of the scientists, the crew, and various engineering departments as well as enforce all resource restrictions. No single objective is considered in creating a timeline. The experiment scheduling problem is: given a set of experiments, place each experiment along the mission timeline so that all resource requirements and temporal constraints are met and the timeline is acceptable to all who must approve it. Much work has been done on multicriteria decision making (MCDM). When there are two criteria, schedules which perform well with respect to one criterion will often perform poorly with respect to the other. One schedule dominates another if it performs strictly better on one criterion, and no worse on the other. Clearly, dominated schedules are undesireable. A nondominated schedule can be generated by some sort of optimization problem. Generally there are two approaches: the first is a hierarchical approach while the second requires optimizing a weighting or scoring function

The 'obvious' stuff: exploring the mundane realities of students' digital technology use in school

This paper explores the ways in which students perceive digital technology as being helpful and/or useful to their schooling. Drawing upon survey data from students (n=1174) across three Australian high schools, the paper highlights seventeen distinct digital ‘benefits’ in domains such as information seeking, writing and composition, accessing prescribed work, scheduling and managing study tasks. While these data confirm the centrality of such technologies to students’ experiences of school, they also suggest that digital technology is not substantially changing or ‘transforming’ the nature of schools and schooling per se. Instead, students were most likely to associate digital technologies with managing the logistics of individual study and engaging with school work in distinctly teacher-led linear and passive ways. As such, it is concluded that educationalists need to temper enthusiasms for what might be achieved through digital technologies, and instead develop better understandings of the realities of students’ instrumentally-driven uses of digital technology

Recentes avanços na literatura de reactores termoquímicos para produção de combustíveis solares

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia SolarRESUMO: Este trabalho visa apresentar os principais resultados obtidos na revisão da literatura científica sobre “reactores termoquímicos para produção de combustíveis solares com recurso à energia solar de concentração”. Esta informação resulta da participação do LNEG no projeto SFERA-III mais especificamente na Subtask 8.2 - Protocols for monitoring and evaluating the performance of solar reactors. Para tal foram analisadas detalhadamente mais de 200 publicações científicas, desenvolvido um formulário personalizado em Visual Basic for Applications (VBA), desenvolvida uma base de dados em Excel para manipulação, organização e sistematização da informação. Esta informação foi agrupada em função das áreas: a) gaseificação, b) pirólise e c) reacções redox. Para cada área, a informação foi sistematizada considerando o tipo de trabalho: i) Experimental (E), ii) Modelação (M), iii) Simulador Solar (SS) e iv) Modelação em Simulador Solar (M+SS). Foi ainda desenvolvida uma análise estatística para os parâmetros experimentais temperatura, pressão, tempo, concentração solar e número de ciclos.ABSTRACT: The purpose of this work is to present the main results obtained in the review of the scientific literature on the topic of thermochemical reactors for the production of solar fuels using solar energy of concentration. This information results from LNEG's participation in the SFERA-III project, more specifically in the Subtask 8.2 - Protocols for monitoring and evaluating the performance of solar reactors. For that, more than 200 scientific publications were thoroughly analyzed, developed a customized form in Visual Basic for Applications (VBA), and developed an Excel database in order to organize accordingly all information. This information was then grouped according to the following main areas: a) gasification, b) pyrolysis, and c) redox reactions. For each area, the information was structured considering the type of work: i) Experimental (E), ii) Modeling (M), iii) Solar Simulator (SS) and iv) Modeling in Solar Simulator (M + SS). A statistical analysis was also carried out for the experimental parameters temperature, pressure, time, solar concentration and number of cycles.info:eu-repo/semantics/publishedVersio

Making ‘MOOCs’: the construction of a new digital higher education within news media discourse

One notable ‘disruptive’ impact of massive open online courses (MOOCs) has been an increased public discussion of online education. While much debate over the potential and challenges of MOOCs has taken place online confined largely to niche communities of practitioners and advocates, the rise of corporate ‘xMOOC’ ventures such as Coursera, edX and Udacity has prompted popular mass media interest at levels not seen with previous educational innovations. This article addresses this important societal outcome of the recent emergence of MOOCs as an educational form by examining the popular discursive construction of MOOCs over the past 24 months within mainstream news media sources in United States, Australia and the UK. In particular, we provide a critical account of what has been an important phase in the history of educational technology—detailing a period when popular discussion of MOOCs has far outweighed actual use/participation. We argue that a critical analysis of MOOC discourse throughout the past two years highlights broader societal struggles over education and digital technology—capturing a significant moment before these debates subside with the anticipated normalization and assimilation of MOOCs into educational practice. This analysis also sheds light on the influences underpinning how many people perceive MOOCs thereby leading to a better understanding of acceptance/adoption and rejection/resistance amongst various professional and popular publics

Left to their own devices: the everyday realities of one-to-one classrooms

The past decade has seen the expansion of personal digital technologies into schools. With many students and teachers now possessing smartphones, tablets, and laptops, schools are initiating one-to-one and ‘Bring Your Own Device’ (BYOD) policies aiming to make use of these ‘personal devices’ in classrooms. While often discussed in terms of possible educational benefits and/or organisational risks, the actual presence of personal devices in schools tends to be more mundane in nature and effect. Drawing upon ethnographic studies of three Australian high schools, this paper details ways in which the proliferation of digital devices has come to bear upon everyday experiences of school. In particular, the paper highlights the ways in which staff and students negotiate (in)appropriate technology engagement; the ordinary (rather than extraordinary) ways that students make use of their devices in classrooms; and the device-related tensions now beginning to arise in schools. Rather than constituting a radically ‘transformational’ form of schooling, the paper considers how the heightened presence of personal technologies is becoming subsumed into existing micro-politics of school organisation and control

Experimental and Numerical analysis of a Solar Rotary Kiln for Continuous Treatment of Particle Material

Several energy intensive industrial processes, such as cement production, require particulate material to be treated at high temperatures. Renewable energy could be used to remove the reliance upon fossil fuels in such processes, and of the available technologies concentrated solar energy is perfectly adapted to provide a high temperature energy source. With this objective, the present study focuses on a solar reactor continuously transferring concentrated solar radiation to a bed of flowing particles. Rotary kilns are the chosen concept due to their technical maturity, easy control and simple design. The feasibility of a solar driven rotary kiln has already been proven at lab-scale, with the successful calcination of materials up to a scale of kg/h. The present work describes a large solar rotary kiln able to heat particles to over 1000 °C at flow rates of up to 20 kg/h. The thermal performance of the reactor was evaluated through an on-sun experimental campaign, performed in the high flux solar simulator at the DLR. During one test, 17 kg/h of particles were heated up to 990 °C, with a thermal efficiency of 45 %. An improvement of the efficiency can be obtained by optimizing the reactor. To do this, a numerical model was developed and its parameters fit to the measured data. Simulations were used to quantify the different heat loss mechanisms, and to explore ways of reducing them. The promising experimental results, together with the mprovements suggested by the model, provide the basis for an upcoming chemical campaign, where the calcination of CaCO3 and the effect of endothermic reactions on the temperature distribution will be investigated