Vanadiiniakut

Nykyään monet käyttökohteet vaativat akuilta aiempaa parempaa suorituskykyä, joten on syntynyt kasvavaa tarvetta uusien akkujen kehittämiselle erilaisista uusista materiaaleista ja uusiin valmistusmenetelmiin pohjautuen. Työn tavoitteena on selvittää kirjallisuustutkimuksena litium-vanadiini-fosfaattiakun ja vanadiini-redoksi-virtausakun ominaisuuksia, saatavuutta, sovelluskohteita ja vertailla niitä muutamaan eri litiumakkutekniikkaan. Tutkimuksen perusteella litium-vanadiini-fosfaattiakkuja ei ole vielä saatavilla kaupallisesti, joten työssä tutkittiin niitä teknisten raporttien pohjalta. Raporttien pohjalta arvioituna, parhaita ominaisuuksia litium-vanadiini-fosfaattiakuilla on erinomainen kuormituksen kesto ja korkea nimellisjännite. Sähköisissä ajoneuvoissa litium-vanadiini-fosfaattiakuilla on suurimmat mahdollisuudet erilaisissa hybridiajoneuvoissa, mutta todennäköisesti ne soveltuvat täyssähköisiin ajoneuvoihin vähintään yhtä hyvin kuin esimerkiksi litium-rauta-fosfaattiakut, jos valmistuskustannukset olisivat samalla tasolla. Vanadiini-redoksi-virtausakkua on jo markkinoilla usean valmistajan toimesta. Niiden ominaisuudet poikkeavat paljon muista akkutyypeistä ja erikoisuutena on mahdollisuus akun pikalataukseen elektrolyyttinesteet vaihtamalla. Syklien kestossa päästään myös erinomaisiin arvoihin, mutta suurimmat ongelmat ovat lyijyakkuakin matalampi energiatiheys ja tehotiheys. Vanadiini-redoksi-virtausakut soveltuvat parhaiten suuren kokoluokan sähköverkkoratkaisuihin ja sähköisissä ajoneuvoissa niiden mahdollisuudet rajoittunevat täyssähköisiin linja-autoihin ja isoihin työkoneisiin.

Continuous Counter-current Solvent Extraction of Magnesium and Calcium from Lithium-rich Brine

Solvent extraction of calcium and magnesium impurities from a lithium-rich brine (Ca ~ 2,000 ppm, Mg ~ 50 ppm, Li ~ 30,000 ppm) was investigated using a continuous counter-current solvent extraction mixer-settler set-up. The literature review includes a general review about resources, demands and production methods of Li followed by basics of solvent extraction. Experimental section includes batch experiments for investigation of pH isotherms of three extractants; D2EHPA, Versatic 10 and LIX 984 with concentrations of 0.52, 0.53 and 0.50 M in kerosene respectively. Based on pH isotherms LIX 984 showed no affinity for solvent extraction of Mg and Ca at pH ≤ 8 while D2EHPA and Versatic 10 were effective in extraction of Ca and Mg. Based on constructed pH isotherms, loading isotherms of D2EHPA (at pH 3.5 and 3.9) and Versatic 10 (at pH 7 and 8) were further investigated. Furthermore based on McCabe-Thiele method, two extraction stages and one stripping stage (using HCl acid with concentration of 2 M for Versatic 10 and 3 M for D2EHPA) was practiced in continuous runs. Merits of Versatic 10 in comparison to D2EHPA are higher selectivity for Ca and Mg, faster phase disengagement, no detrimental change in viscosity due to shear amount of metal extraction and lower acidity in stripping. On the other hand D2EHPA has less aqueous solubility and is capable of removing Mg and Ca simultaneously even at higher Ca loading (A/O in continuous runs > 1). In general, shorter residence time (~ 2 min), lower temperature (~23 °C), lower pH values (6.5-7.0 for Versatic 10 and 3.5-3.7 for D2EHPA) and a moderately low A/O value (< 1:1) would cause removal of 100% of Ca and nearly 100% of Mg while keeping Li loss less than 4%, much lower than the conventional precipitation in which 20% of Li is lost.

Influence of secondary packing on the freezing time of chiken meat in air blast freezing tunnels

Freezing of poultry cuts in continuous convective air blast tunnels is normally performed with the products protected by Low Density Polyethylene (LDPE) as a primary packaging and using Corrugated Cardboard Boxes (CCB) as secondary packaging. The objective of this work was to investigate the influence of these secondary packaging on the freezing of poultry cuts in continuous convective air blast tunnels. The study was performed by replacing CCB with Perforated Metal Boxes (PMB) in order to remove the packaging thermal resistance. The assays, performed in a industrial plant, demonstrated that CCB used commercially for meat freezing have a high heat transfer resistance. Their replacement with PMB can lead to shorter freezing times and spatially homogeneous freezing. Reductions of up to 45% in the freezing times were observed using PMB. The plateau of the temperature curve, related to the freezing time of free water, was significantly reduced using PMB, which is accepted to lead to better product quality after thawing. As the products were protected by the LDPE films as primary packaging, their appearance were not affected. The results presented in this work indicate that replacing CBB with PMB can be an excellent alternative to reduce freezing time and improve freezing homogeneity in industrial air blast tunnels, which could also be applied to other products.

Akkuvarastot omakotitaloissa

Energian varastointi on noussut keskeiseksi energia-alan teemaksi viime vuosina. Erityi-sesti uusiutuvan tuotannon lisääntyminen ja energian käytön tehostaminen ovat edesautta-neet energiavarastoratkaisuiden mukaantuloa. Työssä tarkastellaan litiumrautafosfaattiak-kujen käytön kannattavuutta omakotitaloissa. Tavoitteena on selvittää, millä reunaehdoilla näiden akkujen käyttö energiavarastoina tulee kannattavaksi Lappeenrannan olosuhteissa. Kannattavuutta selvitetään litiumrautafosfaattiakkujen markkina-analyysin ja teknistalou-dellisen analyysin sekä Matlab-simulaation avulla.

Determination of the thermal parameters of high-power batteries by local heat

A new approach to the determination of the thermal parameters of high-power batteries is introduced here. Application of local heat flux measurement with a gradient heat flux sensor (GHFS) allows determination of the cell thermal parameters in di_erent surface points of the cell. The suggested methodology is not cell destructive as it does not require deep discharge of the cell or application of any charge/discharge cycles during measurements of the thermal parameters of the cell. The complete procedure is demonstrated on a high-power Li-ion pouch cell, and it is verified on a sample with well-known thermal parameters. A comparison of the experimental results with conventional thermal characterization methods shows an acceptably low error. The dependence of the cell thermal parameters on state of charge (SoC) and measurement points on the surface was studied by the proposed measurement approach.

Performance Degradation Modelling and Techno-Economic Analysis of Lithium-Ion Battery Energy Storage Systems

Transmission system operators and distribution system operators are experiencing new challenges in terms of reliability, power quality, and cost efficiency. Although the potential of energy storages to face those challenges is recognized, the economic implications are still obscure, which introduce the risk into the business models. This thesis aims to investigate the technical and economic value indicators of lithium-ion battery energy storage systems (BESS) in grid-scale applications. In order to do that, a comprehensive performance lithium-ion BESS model with degradation effects estimation is developed. The model development process implies literature review on lifetime modelling, use, and modification of previous study progress, building the additional system parts and integrating it into a complete tool. The constructed model is capable of describing the dynamic behavior of the BESS voltage, state of charge, temperature and capacity loss. Five control strategies for BESS unit providing primary frequency regulation are implemented, in addition to the model. The questions related to BESS dimensioning and the end of life (EoL) criterion are addressed. Simulations are performed with one-month real frequency data acquired from Fingrid. The lifetime and cost-benefit analysis of the simulation results allow to compare and determine the preferable control strategy. Finally, the study performs the sensitivity analysis of economic profitability with variable size, EoL and system price. The research reports that BESS can be profitable in certain cases and presents the recommendations.

The challenges and successful strategies of secondary school administrators /

This study presents information gathered during personal interviews in the area of challenges that administrators have faced in their careers, and the strategies they have found to be successful in meeting those challenges. This research is a qualitative study, using an inductive approach. Five participants were chosen, based on convenience sampling, with semi-structured interviews that were audio recorded. The theoretical research found that school violence and stafS'school morale were key challenges facing administrators, with a variety of approaches suggested to foster success in meeting those challenges. Some of these approaches included knowledge, team work, an ethic of care, and having a school vision. From the interviews it became clear that the challenges administrators faced included those posed by students, including disciplinary issues, those posed by adults and those posed by government changes in education. In regards to strategies for success, the interviews revealed three key concepts that were emphasized as vital. These were the assets of craft knowledge (experience), collegiality, and the use of other professional resources and educators.

Evaluating three self-help smoking cessation interventions for post-secondary smokers : a randomized controlled trial on six Ontario campuses

Objective. Smoking prevalence is highest among the young adult cohort. Postsecondary students are no exception. Although many students intend to quit smoking, no research has established what methods best promote reductions in, or complete abstinence from smoking. This randomized controlled trial examined the effectiveness of three self-help smoking cessation interventions. Method. On six post-secondary campuses, 483 smokers who voluntarily accessed Leave The Pack Behind (a tobacco control initiative) were randomly assigned to one of three smoking cessation interventions: One Step At A Time (a 2-booklet, *gold standard' program for adults); Smoke|Quit (a newly-developed 2-booklet program for young adult students); and usual care (a 'Quit Kit' containing a booklet on stress management, information about pharmacological quitting aides and novelty items). All participants also received one proactive telephone support call from a peer counsellor. During the study, 85 participants withdrew. The final sample of 216 students who completed baseline questionnaires and 12-week follow-up telephone interviews was representative of the initial sample in terms of demographic characteristics, and smokingquitting- related variables. Results. Whether participants quit smoking depended upon treatment condition, ^(2, N=2\6) = 6.34, p = .04, with Smoke|Quit producing more successfijl quitters (18.4%) than One Step At A Time (4.5%) or the Quit Kit (1 1.4%). On average, participants had quit 53.46 days, with no significant difference across treatments. Selfefficacy also increased. Use of the intervention or other quitting aides was not associated with treatment condition. Among the 191 participants who did not quit smoking, treatment condition did not influence outcomes. Overall, 46.2% had made a quit attempt. Significant decreases in weekly tobacco consumption and increases in self-efficacy to resist smoking were observed from baseline to follow-up. Conclusion. Post-secondary institutions represent a potentially final opportunity for age-targeted interventions. Self-help resources tailored to students' social and contextual characteristics will have considerable more impact than stage-only tailored interventions. Both reduction and abstinence outcomes should be emphasized to positively support students to stop smoking.

Mentorships and co-op placements as a means of heightening the need for a secondary school diploma to the education of at-risk students.--

Both educators and politicians appear to be quite concerned about a dropout rate in Ontario's public schools of some 30 percent. With the basic understanding that a high dropout rate is costly both in economic terms and in human terms, something quite obviously needs to be done to reduce the dropout rate in Ontario schools and, in doing so, ensuring Ontario and its graduates an active role in a growing global economy. This study is an exploratory pilot study in that it examined mentoring and the role that mentoring can play in assisting a student in staying in school and graduating from secondary school. Also incorporated in this is co-operative education and the role it can play, through mentoring, in making students aware of lifestyle level of employment, and of the skills necessary to obtain gainful, meaningful employment. In order to gain information on student attitudes, needs and expectations of a mentoring situation, a series of three questionnaires was used. Also, a questionnaire was distributed to the various co-operative education employers. The intent of this questionnaire was to probe the attitudes, needs and expectations of a mentoring situation from the perspective of an employer. The findings of this study indicated that co-operative education and mentoring are a very valuable and useful component in education. There exist certain factors in a co-operative education setting that serve to enhance and to augment the traditional or "theoretical" setting of the classroom. In addition, a mentoring situation tends to add a sense of relevance to education that students seem to require. Also, an opportunity is offered that allows a student to practice and further refine the skills that have been taught over the course of the student's academic life. Results from this study suggested that a mentoring situation, occurring through a co-operative education situation, adds relevance and a sense of "application" to the traditional or classroom schooling situation. The whole idea of mentoring bodes well for the future of education and of the student. Many advantages are identified in a mentoring situation. One of the advantages is that the schools are able to work quite closely with the community and business in order to stay current and informed on the needs and expected needs of the business community. Co-operative education has now gone beyond being an "experimental" mode of education. All students can benefit from being involved in the program. Certainly at-risk students are aided with staying in school. Those students who are said to be not at-risk can also benefit from being enrolled in the program by gaining hands-on work experience and some of the necessary skills to ensure a place in a growing world economy.

The nature of bullying among secondary school students /

The purpose of this research was to determine the prevalence and effect of bullying in a secondary school. Six hundred and fifty-nine student volunteers completed a survey which included a quantitative component of 40 questions and 3 questions which required a written response. The results suggest that approximately 1 student in 10 was involved in a bullying situation either as a bully or a victim. As age increased, physical bullying decreased whereas psychological remained high in the senior years of high school. Boys were involved more in bullying than girls, especially in the junior years. The effects of bullying could be devastating to the point of school avoidance or early school leaving. The results also indicate that much of the bullying was not being reported. The implication for the education system is that more needs to be done to prevent bullying, to encourage the reporting of bullying, and to deal with the aftermath of a bullying situation.

A qualitative study of authority from the perspective of secondary school principals /

In this research study I examined how four principals of secondary schools interpreted authority and how these interpretations affected their practice. This study involved a presentation of the literature where the concept of qualitative methodology as well as general concepts of authority were reviewed. Four principals were interviewed and asked to reflect on their feelings and experiences as they related to the practice of authority. Five major themes emerged from their reflections and stories which were: Understandings of the Concept of Authority, Principals' Enactment of Authority, Thoughts and Experiences related to Challenges to Their Authority, A View of Principals' Challenge of Authority, and Changing Views on the Authority of Principals in Ontario. The stories of these four principals demonstrated that the practice of authority is complex, dynamic, and contains personal and social tensions. The sharing of these ideas and stories provided a window into the world of these secondary school educational leaders and their experiences with, and enactment of, authority. From this research four recommendations were made to improve educators' practice related to the issue of authority. The importance of this study is that it presents an understanding of the dynamic nature of the process and enactment of authority by these secondary school principals at a unique time in the history of education in Ontario.This qualitative research provides a snapshot of a particular group of educators at a particular time and place. Others need to add to these understandings and modify these ideas through further research. Understanding the experiences of educational leaders as they negotiate concepts of authority gives a window on this very complex, yet vital, component of education.

Bridging the gap between post-secondary students with disabilities and faculty members with their perceptions of access and accommodation

The purpose of this study was to identify factors related to successful university course completion for students with disAbilities including the knowledge that faculty members and students with disAbilities have about accommodation issues; the accommodations that students with disAbilities and faculty use and find effective in the university setting; faculty members' perceptions of and attitudes toward students with disAbilities; and the attitudes that students with disAbilities have toward faculty. Fiftyseven participants were involved in the research, eight students with disabilities and forty-nine faculty members. The main objective of the research was to describe how the skills, knowledge, and attitudes of students and faculty members, and organizational supports interact to support students' academic success. The utilization and effectiveness of accommodations to overcome barriers associated with disAbility in a post-secondary setting are described in relation to students' and faculty members' perceptions of academic success.