A renewable copper electrode as an amperometric flow detector for nitrate determination in mineral water and soft drink samples

A novel approach was developed for nitrate analysis in a FIA configuration with amperometric detection (E=-0.48 V). Sensitive and reproducible current measurements were achieved by using a copper electrode activated with a controlled potential protocol. The response of the FIA amperometric method was linear over the range from 0.1 to 2.5 mmol L(-1) nitrate with a detection limit of 4.2 mu mol L(-1) (S/N = 3). The repeatability of measurements was determined as 4.7% (n=9) at the best conditions (flow rate: 3.0 mL min(-1), sample volume: 150 mu L and nitrate concentration: 0.5 mmol L(-1)) with a sampling rate of 60 samples h(-1). The method was employed for the determination of nitrate in mineral water and soft drink samples and the results were in agreement with those obtained by using a recommended procedure. Studies towards a selective monitoring of nitrite were also performed in samples containing nitrate by carrying out measurements at a less negative potential (-0.20 V). (C) 2009 Elsevier B.V. All rights reserved.

Have Biofuel, Will Travel: A Colorful Experiment and a Different Approach To Teach the Undergraduate Laboratory

The substitution of petroleum-based fuels with those from renewable sources has gained momentum worldwide. A UV-vis experiment for the quantitative analysis of biofuels (bioethanol or biodiesel) in (petroleum-based) diesel oil has been developed. Before the experiment, students were given a quiz on biofuels, and then they were asked to suggest a suitable UV-vis experiment for the quantification of biofuels in diesel oil. After discussing the results of the quiz, the experiment was conducted. This included the determination of lambda(max) of the medium-dependent, that is, solvatochromic, visible absorption band of the probe 2,6-bis[4-(tert-butyl)phenyl]-4-{2,4,6-tris[4-(tert-butyl)phenyl]pyridinium-1-yl}phenolate as a function of fuel composition. The students appreciated that the subject was linked to a daily situation and that they were asked to suggest the experiment. This experiment served to introduce the phenomena of solvation and solvatochromism.

Development of an Analytical Methodology for Quantification of Strong Acid in Diesel Oil

Many factors can affect the quality of diesel oil, in particular the degradation processes that are directly related to some organosulfur compounds. During the degradation process, these compounds are oxidized into their corresponding sulfonic acids, generating a strong acid content during the process. p-Toluene sulfonic acid analysis was performed using the linear sweep voltammetry technique with a platinum ultramicroelectrode in aqueous solution containing 3 mol L(-1) potassium chloride. An extraction step was introduced prior to the voltammetric detection in order to avoid the adsorption of organic molecules, which inhibit the electrochemical response. The extraction step promoted the transference of sulfonic acid from the diesel oil to an aqueous phase. The method was accurate and reproducible, with detection and quantification limits of 5 ppm and 15 ppm, respectively. Recovery of sulfonic acid was around 90%.

The Application Of Renewable Energy For Prefab Houses In Germany

Within the framework of the REBUS project the German building industry has been investigated regarding their energy concepts. The intention was to evaluatethe establishment of renewable energy sources on the German market for new built houses and prefab houses in particular. For this purpose the products of 85manufacturers of prefab houses have been analyzed. Of special interest was the applicationof heating and hot water systems driven by solar energy and biomass. The results show that both techniques are well accepted and established. Almost 90% of themanufacturers offer solar systems on request and almost 70% heating systems based on Pellets. 24% offered solar and 7% as standard options in their range. From theachieved figures the potential of the Swedish market can be worked out. Strategies to introduce renewable energy to a greater extent to Swedish house manufacturers and builders might also be found.

Renewable energy education : Report from a field trip to Melbourne, Australia, and short visits to India and New Zealand During Nov/Dec 1992

During November and December 1992 I visited several groups involved with renewable energy, most of them dealing with education. These groups and their work are described briefly in this report. The groups in Melbourne, Australia have come a long way with education in this field and we have a lot to learn from them. Government funding is needed for large scale work, but useful work can still be done at the community level with much smaller budgets.

Travel Report from the first field trip within the SIDA supported project "Mini-grids supplied by renewable energy - improving technical and social feasibility : Including visits to Ihushi Development Center, Tweyambe Secondary School and Mavuno Project in Tanzania. Conducted in April 2011

This report describes the outcome of the first visit to Tanzania, within the project "Mini-grids supplied by renewable energy - improving technical and social feasibility". The trip included visits to three different organizations; Ihushi Development Center (IDC) near Mwanza, TIDESO near Bukoba, and Mavuno Project in Karagwe. At IDC, a brief evaluation of the current power system was done and measuring equipment for long term measurements were installed. At all three locations investigations regarding the current and future electricity demand were conducted and connections to people relevant to the study were established. The report is including as well some technical specifications as some observations regarding organization and management of the technical systems. The trip was including only short visits and therefore only brief introductions to the different organizations, based on observations done by the author. The report is hence describing the author’s understanding of the technical system and social structures after only short visits to each of the organizations, and may differ from observations done at another point in time, over a different time period, or by some other person.This report describes the outcome of the first visit to Tanzania, within the project "Mini-grids supplied by renewable energy - improving technical and social feasibility". The trip included visits to three different organizations; Ihushi Development Center (IDC) near Mwanza, TIDESO near Bukoba, and Mavuno Project in Karagwe. At IDC, a brief evaluation of the current power system was done and measuring equipment for long term measurements were installed. At all three locations investigations regarding the current and future electricity demand were conducted and connections to people relevant to the study were established. The report is including as well some technical specifications as some observations regarding organization and management of the technical systems. The trip was including only short visits and therefore only brief introductions to the different organizations, based on observations done by the author. The report is hence describing the author’s understanding of the technical system and social structures after only short visits to each of the organizations, and may differ from observations done at another point in time, over a different time period, or by some other person.

Evaluation of a Micro PV-Diesel Hybrid System in Tanzania

In April 2011 a monitoring system was installed to enable studies of the performance and the usage of a micro PV-Diesel Hybrid system at the Ihushi Development Center (IDC) near Mwanza in Tanzania. Estimations of the load have been obtained by a survey of installed appliances and interviews with users of installed equipment. The load profile obtained by measurements has been analyzed and compared to estimations of the energy use. Further, the system size and performance were studied.

Dynamic whole system testing of combined renewable heating systems : the current state of the art

Objective: For the evaluation of the energetic performance of combined renewable heating systems that supply space heat and domestic hot water for single family houses, dynamic behaviour, component interactions, and control of the system play a crucial role and should be included in test methods. Methods: New dynamic whole system test methods were developed based on “hardware in the loop” concepts. Three similar approaches are described and their differences are discussed. The methods were applied for testing solar thermal systems in combination with fossil fuel boilers (heating oil and natural gas), biomass boilers, and/or heat pumps. Results: All three methods were able to show the performance of combined heating systems under transient operating conditions. The methods often detected unexpected behaviour of the tested system that cannot be detected based on steady state performance tests that are usually applied to single components. Conclusion: Further work will be needed to harmonize the different test methods in order to reach comparable results between the different laboratories. Practice implications: A harmonized approach for whole system tests may lead to new test standards and improve the accuracy of performance prediction as well as reduce the need for field tests.

A user guide to simple monitoring and sustainable operation of PV-diesel hybrid systems : Handbook for system users and operators

This report contains a suggestion for a simple monitoring and evaluation guideline for PV-diesel hybrid systems. It offers system users a way to better understand if their system is operated in a way that will make it last for a long time. It also gives suggestions on how to act if there are signs of unfavourable use or failure. The application of the guide requires little technical equipment, but daily manual measurements. For the most part, it can be managed by pen and paper, by people with no earlier experience of power systems.The guide is structured and expressed in a way that targets PV-diesel hybrid system users with no, or limited, earlier experience of power engineering. It is less detailed in terms of motivations for certain choices and limitations, but rich in details concerning calculations, evaluation procedures and maintenance routines. A more scientific description of the guide can be found in a related journal article.

O suprimento enxuto e integrado : análise dos fornecedores de uma empresa brasileira fabricante de motores diesel

Resumo não disponível.

Competitividade dos biocombustíveis no Brasil: uma comparação entre os principais biocombustíveis etanol e biodisel

As preocupações mundiais com o aquecimento global e os efeitos nocivos da utilização de combustíveis fósseis têm fomentado a busca por novos modelos energéticos, baseados em fontes limpas e renováveis, com destaque para os biocombustíveis. Sem menos importância, o esgotamento das reservas mundiais de matérias-primas fósseis, somado às instabilidades geopolíticas nas principais regiões produtoras, impulsionam, cada vez mais, o desenvolvimento destes novos modelos. Neste cenário, o Brasil tem papel de destaque. Líder mundial na produção e consumo de etanol à base de cana-de-açúcar, o país iniciou, em 2005, a inclusão de mais uma fonte de energia renovável em sua matriz energética: a mistura do biodiesel no diesel mineral. O presente trabalho tem como objetivo analisar a competitividade dos principais biocombustíveis brasileiros: o etanol e o biodiesel. Em primeiro lugar, estes produtos foram analisados quanto às suas principais características; em segundo, avaliou-se a competitividade econômica destes combustíveis frente a seus produtos substitutos diretos derivados do petróleo. Finalmente, foram analisados os benefícios (tangíveis e intangíveis) inerentes à utilização dos biocombustíveis, e como estes intangíveis deveriam ser precificados, como forma de atribuir um prêmio aos benefícios que trazem ao meio-ambiente e à sociedade. Esta dissertação pretende servir de base para uma avaliação mais profunda da real competitividade econômica dos biocombustíveis frente aos combustíveis derivados do petróleo, além de colocar em cheque as principais análises atuais e críticas sobre a utilização destes produtos. Além disso, o presente trabalho visa avaliar o potencial e as limitações da produção dos biocombustíveis no Brasil.

Resistência e prática pedagógica operária: o movimento dos operários da Fiat / Diesel e a formação da Associação Cultural de Apoio Mútuo (ACAM)

A compra da Fábrica Nacional de Motores (FNM) pela Fiat italiana, em Xerém, determina a inserção daquela unidade na linha de produção internacional da fábrica italiana, e as conseqüentes modificações no processo de trabalho. Caracterfsticas do setor moderno do processo capitalista de produção, as técnicas de organização do trabalho, complementadas pela maquinaria computadorizada, além de excludentes de mão-de-obra, visam retirar dos trabalhadores toda a atividade intelectual. Ficam, assim, reduzidas as possibilidades de controle sobre o processo de trabalho, bem como sobre as formas de desenvolvimento do potencial de libertação dos operários. Da recusa a esse estado de coisas nasce o movimento dos operários da Fiat, expresso em quatro greves (1978, 1979, 1980, 1981). Na dialética das greves, a aparência das reivindicações encobre seu aspecto essencial: a negação da opressão das relações de trabalho. A essência dos movimentos revela-se no processo de recomposição da existência coletiva em torno de um fundo comum, base objetiva da ruptura com os esquemas da organização capita lista do trabalho. Nascida com a demissão dos operários mais ativos no movimento da Fiat, a Associação Cultural de Apoio Mútuo (Acam) carregou consigo a contradição básica do ser de classe oprimida: a convivência de forças repressoras que o mantêm submisso à ordem do trabalho assalariado, de um lado, com as forças emancipatórias que o atraem para relações associativas, e possibilitam o desenvolvimento das potencial idades humanas. A reinserção dos operários na ordem do trabalho assalariado, ao fim do movimento grevista, e o fechamento da Acam, três anos depois, revelam a necessidade de se encontrar novas formas de generalização e unificação das organizações associativas esboçadas durante as greves.

O Mecanismo de transmissão de preços do petróleo para a gasolina e para o diesel nos EUA nos anos 2000

Através de um Modelo de Correção de Erros este estudo explora possíveis assimetrias no passthrough dos preços de petróleos para os preços do diesel e da gasolina no mercado dos Estados Unidos, analisando, principalmente, se as inversões das tendências das demandas destes derivados afetaram o mecanismo de transmissão de preços. A partir de dados mensais de janeiro de 2001 a dezembro de 2012, para a gasolina foram encontrados indícios de que houve alterações do passthrough em decorrência da quebra da demanda. Porém, é válido destacar que tal resultado ocorreu concomitantemente ao período de recuperação de preços presenciada após a crise de 2008. Em relação ao diesel, não há indícios de que houve alterações no passthrough. Por fim, há evidências da redução do WTI como petróleo de referência em decorrência da sua desvalorização a partir de 2010.