Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Concentrating solar power promises to be a potential solution for meeting the worlds energy needs in the future. One of the key features of this type of renewable energy technology is its ability to store energy effectively and relatively cheaply. An air-rock bed thermal energy storage system promises to be an effective and reasonably inexpensive storage system for concentrating solar power plants. Currently there is no such storage system commercially in operation in any concentrating solar power plant, and further research is required before such a system can be implemented. The main research areas to address are the thermal-mechanical behaviour of rocks, rock bed pressure drop correlations and effective and practical system designs. Recent studies have shown that the pressure drop over a packed bed of rocks is dependant on various aspects such as particle orientation relative to the flow direction, particle shape and surface roughness. The irregularity and unpredictability of the particle shapes make it difficult to formulate a general pressure drop correlation. Typical air-rock bed thermal design concepts consist of a large vertical square or cylindrical vessel in which the bed is contained. Such system designs are simple but susceptible to the ratcheting effect and large pressure drops. Several authors have proposed concepts to over-come these issues, but there remains a need for tools to prove the feasibility of the designs. The purpose of this paper is to investigate aDEM-CFD coupled approach that can aid the development of an air-rock bed thermal energy storage system. This study specifically focuses on the use of CFD. A complementary study focusses on DEM. The two areas of focus in this study are the pressure drop and system design. A discrete CFD simulation model is used to predict pressure drop over packed beds containing spherical and irregular particles. DEM is used to create randomly packed beds containing either spherical or irregularly shaped particles. This model is also used to determine the heat transfer between the fluid and particle surface. A porous CFD model is used to model system design concepts. Pressure drop and heat transfer data predicted by the discrete model, is used in the porous model to describe the pressure drop and thermal behaviour of a TES system. Results from the discrete CFD model shows that it can accurately predict the pressure drop over a packed bed of spheres with an average deviation of roughly 10%fromresults found in literature. The heat transfer between the fluid and particle surface also is accurately predicted, with an average deviation of between 13.36 % and 21.83 % from results found in literature. The discrete CFD model for packed beds containing irregular particles presented problems when generating a mesh for the CFD computational domain. The clump logic method was used to represent rock particles in this study. This method was proven by other studies to accurately model the rock particle and the rock packed bed structure using DEM. However, this technique presented problems when generating the surface mesh. As a result a simplified clump model was used to represent the rock particles. This simplified clump model showed characteristics of a packed bed of rocks in terms of pressure drop and heat transfer. However, the results suggest that the particles failed to represent formdrag. This was attributed to absence of blunt surfaces and sharp edges of the simplified clumpmodel normally found on rock particles. The irregular particles presented in this study proved to be inadequate for modelling universal characteristics of a packed bed of rocks in terms of pressure drop. The porous CFD model was validated against experimental measurement to predict the thermal behaviour of rock beds. The application of the porous model demonstrated that it is a useful design tool for system design concepts. / AFRIKAANSE OPSOMMING: Gekonsentreerde sonkrag beloof om ’n potensiële toekomstige oplossing te wees vir die wêreld se groeiende energie behoeftes. Een van die belangrikste eienskappe van hierdie tipe hernubare energie tegnologie is die vermoë om energie doeltreffend en relatief goedkoop te stoor. ’n Lug-klipbed termiese energie stoorstelsel beloof om ’n doeltreffende en redelik goedkoop stoorstelsel vir gekonsentreerde sonkragstasies te wees . Tans is daar geen sodanige stoorstelsel kommersieël in werking in enige gekonsentreerde sonkragstasie nie. Verdere navorsing is nodig voordat so ’n stelsel in werking gestel kan word. Die belangrikste navorsingsgebiede om aan te spreek is die termies-meganiese gedrag van klippe, klipbed drukverlies korrelasies en effektiewe en praktiese stelsel ontwerpe. Onlangse studies het getoon dat die drukverlies oor ’n gepakte bed van klippe afhanklik is van verskeie aspekte soos partikel oriëntasie tot die vloeirigting, partikel vormen oppervlak grofheid. Die onreëlmatigheid en onvoorspelbaarheid van die klip vorms maak dit moeilik om ’n algemene drukverlies korrelasie te formuleer. Tipiese lug-klipbed termiese ontwerp konsepte bestaan uit ’n groot vertikale vierkantige of silindriese houer waarin die gepakte bed is. Sodanige sisteem ontwerpe is eenvoudig, maar vatbaar vir die palrat effek en groot drukverliese. Verskeie studies het voorgestelde konsepte om hierdie kwessies te oorkom, maar daar is steeds ’n behoefte aanmetodes om die haalbaarheid van die ontwerpe te bewys. Die doel van hierdie studie is om ’n Diskreet Element Modelle (DEM) en numeriese vloeidinamika gekoppelde benadering te ontwikkel wat ’n lug-klipbed termiese energie stoorstelsel kan ondersoek. Hierdie studie fokus spesifiek op die gebruik van numeriese vloeidinamika. ’n Aanvullende studie fokus op DEM. Die twee areas van fokus in hierdie studie is die drukverlies en stelsel ontwerp. ’n Diskrete numeriese vloeidinamika simulasie model word gebruik om drukverlies te voorspel oor gepakte beddens met sferiese en onreëlmatige partikels. DEM word gebruik om lukraak gepakte beddens van óf sferiese óf onreëlmatige partikels te skep. Hierdie model is ook gebruik om die hitte-oordrag tussen die vloeistof en partikel oppervlak te bepaal. ’n Poreuse numeriese vloeidinamika model word gebruik omdie stelsel ontwerp konsepte voor te stel. Drukverlies en hitte-oordrag data, voorspel deur die diskrete model, word gebruik in die poreuse model om die drukverlies- en hittegedrag van ’n TES-stelsel te beskryf. Resultate van die diskrete numeriese vloeidinamikamodel toon dat dit akkuraat die drukverlies oor ’n gepakte bed van sfere kan voorspel met ’n gemiddelde afwyking van ongeveer 10%van die resultatewat in die literatuur aangetref word. Die hitte-oordrag tussen die vloeistof en partikel oppervlak is ook akkuraat voorspel, met ’n gemiddelde afwyking van tussen 13.36%en 21.83%van die resultate wat in die literatuur aangetref word. Die diskrete numeriese vloeidinamika model vir gepakte beddens met onreëlmatige partikels bied probleme wanneer ’n maas vir die numeriese vloeidinamika, numeriese domein gegenereer word. Die "clump"logika metode is gebruik om klip partikels te verteenwoordig in hierdie studie. Hierdiemetode is deur ander studies bewys om akkuraat die klip partikel en die klip gepakte bed-struktuur te modelleer deur die gebruik van DEM. Hierdie tegniek het egter probleme gebied toe die oppervlak maas gegenereer is. As gevolg hiervan is ’n vereenvoudigde "clump"model gebruik om die klip partikels te verteenwoordig. Die vereenvoudigde "clump"model vertoon karakteristieke eienskappe van ’n gepakte bed van klippe in terme van drukverlies en hitte oordrag. Die resultate het egter getoon dat die partikels nie vorm weerstand verteenwoordig nie. Hierdie resultate kan toegeskryf word aan die afwesigheid van gladde oppervlaktes en skerp kante, wat normaalweg op klip partikels gevind word, in die vereenvoudigde "clump"model. Die oneweredige partikels wat in hierdie studie voorgestel word, blykomnie geskik tewees vir die modellering van die universele karakteristieke eienskappe van ’n gepakte bed van klippe in terme van drukverlies nie. Die poreuse numeriese vloeidinamika model is met eksperimentele metings bevestig omdie termiese gedrag van klipbeddens te voorspel. Die toepassing van die poreuse model demonstreer dat dit ’n nuttige ontwerp metode is vir stelsel ontwerp konsepte.

Concentrating solar power plants can integrate cost-effective thermal energy storage systems and thereby supply controllable power on demand, an advantage against other renewable technologies. Storage integration allows a solar thermal power plant to increase its load factor and to shift production to periods of peak demand. It also enables output firmness, providing stability to the power block and to the grid. Thus, despite the additional investment, storage can enhance the performance and economic viability of the plants. However, the levelized cost of electricity of these plants yet remains higher than for other technologies, so projects today are only viable through the provision of incentives or technology-specific competitive bid tenders. It is the variability of the solar resource, the myriad roles that storage can assume, and the complexity of enhancing the synergies between the solar field, the storage and the power block, what makes the development of adequate policy instruments, design and operation of these plants a challenging process. In this thesis a comprehensive methodology for the pre-design and analysis of concentrating solar power plants is presented. The methodology is based on a techno-economic modeling approach that allows identifying optimum trade-off curves between technical, environmental, and financial performance indicators. A number of contemporary plant layouts and novel storage and hybridization concepts are assessed to identify optimum plant configurations, in terms of component size and storage dispatch strategies. Conclusions highlight the relevance between the sizing of key plant components, the operation strategy and the boundaries set by the location. The interrelation between critical performance indicators, and their use as decisive parameters, is also discussed. Results are used as a basis to provide recommendations aimed to support the decision making process of key actors along the project development value chain of the plants. This research work and conclusions are primarily meant to set a stepping stone in the research of concentrating solar power plant design and optimization, but also to support the research towards understanding the value of storage in concentrating solar power plants and in the grid. / Koncentrerad solkraft erbjuder möjligheten att integrera kostnadseffektiv termisk energilagring och därmed behovsstyrd kraftkontroll. Detta är en viktig fördel jämfört med andra förnybara energiteknologier. Lagringsintegration tillåter solkraftsanläggningar att öka sin lastfaktor och skifta produktion till tider med största efterfrågan. Vidare möjliggör lagring fast elproduktion vilket leder till förbättrad nät- och kraftturbinstabilitet. Därför kan termisk lagring öka anläggningsprestanda och ekonomiskt värde trots ökande initiala kapitalkostnader. I termer av specifik elproduktionskostnad (LCOE) ligger koncentrerade solkraftsanläggningar med lagring fortfarande högre än andra kraftteknologier och anläggningsprojekt blir endast lönsamma genom subventionsmodeller eller teknologispecifika konkurrensutsatta anbudsförfaranden. Att hitta adekvata policylösningar och optimala design och operationsstrategier är en utmanande process eftersom det gäller att hitta rätt balans mellan variabel solinstrålning, lagring av energi och tid för produktion genom optimal design och operation av solmottagarfält, kraftblock och lagringskapacitet. I denna avhandling presenteras en omfattande metodik för pre-design och analys av koncentrerande solkraftverk. Metodiken baseras på en tekno-ekonomisk modelleringsansats som möjliggör identifiering av optimala avvägningssamband för tekniska, ekonomiska och miljöprestanda indikatorer. Metodiken tillämpas på ett antal moderna anläggningslayouter  och lagrings- och hybridiseringskoncept för att identifiera optimal kraftanläggningsdesign i termer av komponentprestanda och lagringsanvändningsstrategier. I slutsatsen poängteras relevansen av att hitta rätt storlek på nyckelkomponenter i relation till lagringsstrategi och randvillkoren som ges av konstruktionsläget för optimal ekonomisk och miljömässig prestanda. Resultaten används för att formulera rekommendationer till nyckelaktörer i beslutsprocessen genom hela kraftanläggningens värdekedja från politisk beslutsfattare till anläggningsingenjör. Forskningen och slutsatserna i detta arbete skall i första hand ta ett steg framåt för optimering och design av solkraftsanläggningar men även tillhandahålla en metodik för utvärdering av lagringslösningar och dess specifika värde för solkraftsanläggningar och elnätet. / <p>QC 20160829</p>

In a northern European climate a typical solar combisystem for a single family house normally saves between 10 and 30 % of the auxiliary energy needed for space heating and domestic water heating. It is considered uneconomical to dimension systems for higher energy savings. Overheating problems may also occur. One way of avoiding these problems is to use a collector that is designed so that it has a low optical efficiency in summer, when the solar elevation is high and the load is small, and a high optical efficiency in early spring and late fall when the solar elevation is low and the load is large.The study investigates the possibilities to design the system and, in particular, the collector optics, in order to match the system performance with the yearly variations of the heating load and the solar irradiation. It seems possible to design practically viable load adapted collectors, and to use them for whole roofs ( 40 m2) without causing more overheating stress on the system than with a standard 10 m2 system. The load adapted collectors collect roughly as much energy per unit area as flat plate collectors, but they may be produced at a lower cost due to lower material costs. There is an additional potential for a cost reduction since it is possible to design the load adapted collector for low stagnation temperatures making it possible to use less expensive materials. One and the same collector design is suitable for a wide range of system sizes and roof inclinations. The report contains descriptions of optimized collector designs, properties of realistic collectors, and results of calculations of system output, stagnation performance and cost performance. Appropriate computer tools for optical analysis, optimization of collectors in systems and a very fast simulation model have been developed.

In this work a spectrum splitting micro-scale concentrating PV system is evaluated to increase the conversion efficiency of flat panel PV systems. In this approach, the dispersed spectrum splitting concentration systems is scaled down to a small size and structured in an array. The spectrum splitting configuration allows the use of separate single bandgap PV cells that increase spectral overlap with the incident solar spectrum. This results in an overall increase in the spectral conversion efficiency of the resulting system. In addition other benefits of the micro-scale PV system are retained such reduced PV cell material requirements, more versatile interconnect configurations, and lower heat rejection requirements that can lead to a lower cost system. The system proposed in this work consists of two cascaded off-axis holograms in combination with a micro lens array, and three types of PV cells. An aspherical lens design is made to minimize the dispersion so that higher concentration ratios can be achieved for a three-junction system. An analysis methodology is also developed to determine the optical efficiency of the resulting system, the characteristics of the dispersed spectrum, and the overall system conversion efficiency for a combination of three types of PV cells.

O hormônio concentrador de melanina (MCH) foi inicialmente identificado em peixes teleósteos por regular a mudança de coloração, agregando os grânulos de pigmentos nas células pigmentares, levando ao clareamento dos animais. Possui dois receptores conhecidos: MCHR1, encontrado em todas as espécies, e o MCHR2, no SNC de alguns mamíferos e em outros tecidos de teleósteos. Devido a sua ampla distribuição, diversos estudos tem investigado o papel do MCH como um peptídeo que exerce diversas funções fisiológicas: regulação da ingestão de alimentos em mamíferos e peixes, regulação da resposta ao stress e à ansiedade, comportamento, locomoção, reprodução, sono, memória, inflamação. O objetivo desse trabalho foi investigar a possível participação do MCH na ativação das vias de sinalização para oxido nítrico em células de eritroforoma de Carassius auratus (GEM-81). Adicionalmente, incluímos o hormônio estimulador de melanócitos - ?-MSH no estudo, pois este é antagônico ao MCH nas mais diversas funções. Demonstramos que em GEM-81 ocorre a expressão da isoforma iNOS sem o estimulo de lipopolissacarídeos; e que com o tratamento de MCH e Soro Fetal Bovino (SFB) reduzido a 0,5%, sua expressão foi aumentada com o decorrer do tempo, com o máximo alcançado com 180 min e 360 min. Na produção de nitrito foi observado um aumento muito discreto nos mesmos tempos. O &alpha;-MSH não apresentou nenhuma diferença de expressão de iNOS e na produção de nitrito. Nossos dados apontam a existência da via do óxido nítrico em células de eritroforoma de Carassius auratus e sugerem que o MCH possa induzir a produção de oxido nítrico pelo aumento de expressão da iNOS / The melanin -concentrating hormone (MCH) was first identified in teleost fish by regulating the color change, aggregating the pigment granules in pigment cells, leading to bleaching of animals. It has two known receptors: MCHR1, found in all species, and MCHR2, in the CNS of mammals and some other tissues of teleosts. Because of their widespread distribution, various studies have investigated the role of MCH as a peptide that exerts various physiological functions: regulation of food intake in mammals and fish, regulation of stress responses and anxiety, behavior, locomotion, reproduction, sleep, memory and inflammation. The aim of this study was to investigate the possible involvement of MCH in the activation of signaling pathways for nitric oxide in cells of Carassius auratus eritroforoma (GEM -81). Additionally, we include the melanocyte stimulating hormone - &alpha; - MSH in the study, as this is antagonistic to MCH in various functions. We demonstrated that GEM -81 isoform expression of iNOS without lipopolysaccharide stimulation occurs, and the treatment with MCH and Fetal Bovine Serum (FBS) reduced to 0.5% increased the expression with the passage of time, the maximum reached at 180 min and 360 min. Regarding nitrite production, it was observed a very modest increase at the same time. The &alpha;-MSH showed no difference in the expression of iNOS or production of nitrite. Our data indicate the presence of the nitric oxide pathway in cells of eritroforoma Carassius auratus, suggesting that MCH could induce nitric oxide production by increasing the expression of iNOS .

A área incerto-hipotalâmica (IHy) é uma região diencefálica que atua em funções reprodutivas através da presença do hormônio concentrador de melanina (MCH). Nosso objetivo é estudar as conexões da IHy de fêmeas com áreas relacionadas ao controle neuroendócrino reprodutivo, usando traçador anterógrado dextrana amina biotinilada (BDA) e retrógrado Fluorogold (FG). Nesse sentido, destacamos que a IHy, em fêmeas, conecta-se reciprocamente com diversos núcleos hipotalâmicos da região periventricular e pré-óptica, além das áreas hipotalâmica anterior, posterior e lateral. Nosso resultados também sugerem um dimorfismo sexual das projeções da IHy, já que a área pré-óptica medial, o núcleo anteroventral periventrciular e o núcleo arqueado são mais densamente inervadas pelas IHy em fêmeas do que em machos. / The incerto-hypothalamic area (IHy) is a diencephalic region poorly studied which is characterized by two non-colocalized neurochemical groups composed by the A13 dopaminergic group intermingled with predominantly GABAergic cells co-expressing melanin-concentrating hormone (MCH) and/or cocaine and amphetamine regulated transcript (CART). Functional studies suggest that IHy is involved in the neuroendocrine control of female reproduction in specific metabolic states mediated by MCH. In this way, our aim is to study the IHy connections in female rats related to neuroendocrine control of female reproduction using neuronal anterograde Biotin Dextran Amine (BDA) and retrograde Flurogold (FG) tracers. As a result, we found that IHy projections are the lateral septal nucleus, bed nucleus of stria terminalis, paraventricular thalamic nucleus, reuniens thalamic nucleus, medial preoptic area, medial and lateral preoptic nucleus, median preoptic nucleus, periventricular hypothalamic nucleus, anteroventral periventricular nucleus, anterior, posterior and lateral hypothalamic area and precommissural nucleus. The main afferents to the IHy, in females, are the lateral septal nucleus, median preoptic nucleus and paraventricular thalamic nucleus. These results suggest sexually dimorphic projections from the IHy, since IHy more densely innervates neuroendocrine regions in female than in male rats.

In order to obtain a sugar concentration of more than 100g.l-1of fermentable sugars, aspruce wood hydrolysate was subjected to high pressure and vacuum concentration andthe fermentability of each hydrolysate was assessed by fermentation experiments withflocculating S. cerevisiae. The hypothesis that high pressure evaporated hydrolysate(evaporation carried out at 108°C and 1.3 bar) would be more difficult to ferment thanvacuum evaporated hydrolysate (evaporation carried out at 80°C and 0.5 bar) was notconfirmed by the results. Minor amount of cells lost their flocculating ability afterfermentation which their ratio and their viability and vitality was assessed.By vacuum and high pressure concentration, the fermentable sugars (defined as theconcentration of glucose, mannose and galactose) in the hydrolysates reached to 120g.l-1and 129g.l-1 respectively. Compared to the initial hydrolysate the concentration factorrepresented a 3-fold increase of fermentable sugars. Furfural was evaporated in both trialsand its concentration reached to 0.03g.l-1 and 0.1g.l-1 after vacuum and high pressureevaporation respectively. Fermentation with both 0.14h-1and 0.22h-1 initial dilution rateswas possible, while more than 96% of furfural and to less extent formic and acetic acidsdisappeared from the hydrolyzates. However, HMF and levulinic acid remained in thehydrolyzates and concentrated proportionally. More than 84% of the fermentable sugarspresent in VEH were fermented by fed-batch cultivation using 12g.l-1 yeast and initialdilution rate (ID) of 0.22h-1, and resulted into 0.40±0.01g.g-1 ethanol in 21h.Fermentation of HPEH was as successful as VEH and resulted into more than 86% of thesugar consumption at the corresponding conditions. With an ID of 0.14h-1, more than97% of the total fermentable sugars were consumed, and ethanol yielded 0.44±0.01g.g-1.A viability and vitality determination from the supernatant of fermentation liquorrepresented that about 76% of the cells which lost their flocculating ability kept theirvitality. Cultivation of yeast with beet molasses was tricky in both batch and fed-batchcultivation as the concentration more than 50g.l-1 in batch cultivation prevent from yeastgrowing. / Uppsatsnivå: D

<p>This study is about inmates, who reflect upon their time in school, their experiences of school and how different things have influenced and affect them later in life. The aim with this study is to examine how different kinds of school related issues have affected the inmates in different ways. The aim is also to look at how school can spot in early years, children within the danger zone and provide for those children, so that they can be helped in different ways and so that they can be able to achieve different in life, not to end up becoming criminals later in life.</p><p>The main questions in this study are:</p><p>How did the chosen inmates experience their time in school?</p><p>Can you by looking at research tell that these persons already in their childhood were children within the danger zone?</p><p>What kind of school related issues could have contributed to a criminal lifestyle later in life?</p><p>The result of this study shows that all five have been children within the danger zone. In all five cases there have been school related issues that have affected those men. Issues such as; truancy, bullying, school defection, difficulties of concentrating and reading- and writing disorders. Issues which are to be seen as issues that could lead to a criminal lifestyle later in life.</p>

This study is about inmates, who reflect upon their time in school, their experiences of school and how different things have influenced and affect them later in life. The aim with this study is to examine how different kinds of school related issues have affected the inmates in different ways. The aim is also to look at how school can spot in early years, children within the danger zone and provide for those children, so that they can be helped in different ways and so that they can be able to achieve different in life, not to end up becoming criminals later in life. The main questions in this study are: How did the chosen inmates experience their time in school? Can you by looking at research tell that these persons already in their childhood were children within the danger zone? What kind of school related issues could have contributed to a criminal lifestyle later in life? The result of this study shows that all five have been children within the danger zone. In all five cases there have been school related issues that have affected those men. Issues such as; truancy, bullying, school defection, difficulties of concentrating and reading- and writing disorders. Issues which are to be seen as issues that could lead to a criminal lifestyle later in life.

Analysis of the genome of Anabaena sp. PCC7120 reveals that it lacks the gene, ccaA, which encodes the bonafide carboxysomal, β-class carbonic anhydrase (CA) CcaA. However, the carboxysome enriched fraction of Anabaena PCC7120 exhibits CA activity. Bioinformatic analysis reveals that the N-terminal region of the carboxysome protein CcmM has high sequence and structural similarity to the γ-class CA of Methanosarcina thermophila. Recombinantly expressed CcmM is found to be inactive in in-vitro CA assays. E. coli cell extracts containing an overexpressed form of CcmM comprised of the N-terminal 209 amino acids (CcmM209) are also inactive. However, CcmM209 displays CA activity after incubation with the thiol oxidizing agent diamide or when bound to an affinity matrix. It appears that CcmM is indeed a functional γ-CA which is active under oxidizing condition. It is hypothesized that the C-terminal RbcS like domain in CcmM may regulate activity by allowing CcmM activation only when sequestered within the carboxysome.