Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: One of the areas of the fluid dynamic design of solar chimney power plants that has not been investigated sufficiently is the collector-to-chimney transition section of a single turbine layout. The transition section contains the turbine inlet guide vanes (IGVs) that support the whole chimney and guide the flow entering the turbine. The primary objective of the study was to determine the dependence of the loss coefficient of the section on inlet guide vane stagger angle and collector roof height. Experiments were done on a nominal 900 mm chimney diameter rig, with four combinations of two collector roof heights and two IGV stagger angles. Velocity components and pressures in the transition section were measured in three conical planes, respectively at the IGV exit and midway to, and just below the turbine position, using a five-hole pneumatic pressure probe. Very good agreement was found between experimental values and commercial CFD code predictions of flow angles, velocity components and internal and wall static pressures. The agreement between measured and predicted total pressure loss coefficient was reasonable when considering that most of the loss occurred in the weak wakes of the IGVs and in the very thin transition section wall boundary layers. The CFD code served to extend the predictions to a proposed full scale geometry. The losses are less than previously assumed. The study led to correlations between respectively loss and turning angle as dependent variables, and collector roof height and IGV stagger angle as independent variables. / AFRIKAANSE OPSOMMING: Een van die gebiede van vloeidinamiese ontwerp van sonskoorsteen kragstasies wat nog nie voldoende navorsing geniet het nie is die kollektor-tot-skoorsteen oorgangs gedeelte van `n enkel turbine opstelling. Die oorgangs gedeelte bevat die turbine se inlaat lei lemme (ILL) wat die hele skoorsteen dra en die vloei lei wat by die turbine ingaan. Die hoof doel van hierdie studie was om die verlies koëffisiënt van hierdie oorgangs gedeelte te bepaal as afhanklike van die ILL stel hoek en die hoogte van die kollektor se dak hoogte. Die eksperimente het op `n nominale 900mm deursnee skoorsteen skaal model geskied, met vier kombinasies van twee dak hoogtes en twee ILL stel hoeke. Snelheidskomponente en drukke is met `n pneumatiese 5-punt buis in drie koniese vlakke in die oorgangs gedeelte gemeet. Die vlakke was by die ILL se stert, halfpad deur die oorgangs gedeelte en by die turbine se inlaat. Baie goeie ooreenstemming is gevind met die eksperimentele waardes en `n kommersiële CFD kode se voorspellings van vloei hoeke, snelheidskomponente en interne- en wand statiese drukke. Die ooreenstemming tussen die gemete waardes en die berekende waardes vir die totale druk verlies koëffisiënt was redelik siende dat die meeste verliese van die klein versteurings van die ILL en die oorgangs gedeelte se dun-wand grenslae kom. Die CFD kode is toe ingespan om verdere voorspellings te maak vir `n voorgestelde volskaal geometrie. Die verliese is minder as wat daar van te vore voorspel is. Hierdie studie het gelei tot korrelasies tussen onderskeidelik verlies en draai hoeke as afhanklike veranderlikes, en kollektor dak hoogte en ILL plasings hoek as onafhanklike veranderlikes.

Current concentrated solar power plants (CSP) use molten salt at 565°C as a heat transfer and energy storage fluid. Due to thermal energy storage (TES), these solar plants can deliver dispatachable electricity to the grid; however, the levelized cost of electricity (LCOE) for these plants is 12-15 c/kWh, about 2.5 times as high as fossil fuel electricity generation. Molten salt technology limits peak operating temperatures to 565°C and a heat engine efficiency of 40%. Liquid metal (LM), however, can reach >1350°C, and potentially utilize a more efficient (60%) heat engine and realize cost reductions. A 1350 °C LM-CSP plant would require ceramic containment, inert atmosphere containment, additional solar flux concentration, and redesigned internal receiver. It was initially unclear if these changes and additions for LM-CSP were technically feasible and could lower the LCOE compared to LS-CSP. To answer this question, a LM-CSP plant was designed with the same thermal input as a published LS-CSP plant. A graphite internal cavity receiver with secondary concentration heated liquid Sn to 1400°C and transferred heat to a 2-phase Al-Si fluid for 9 hours of thermal energy storage. Input heat to the combined power cycle was 1350°C and had 60% thermal efficiency for a gross output of 168 MW. The cost of this LM-CSP was estimated by applying material cost factors to the designed geometry and scaling construction costs from published LS-CSP estimates. Furthermore, graphite was experimentally tested for reactivity with liquid Sn, successful reaction bonds, and successful mechanical seals. The result is switching to molten metal can reduce CSP costs by 30% and graphite pipes, valves, and seals are possible at least at 400°C.

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.

Thesis (MEng (Civil Engineering))--University of Stellenbosch, 2005. / Previous studies on the solar chimney have shown that its structural integrity might be compromised by the occurrence of resonance. A structure may displace excessively when a load of the same frequency as a structural eigen-frequency is applied. The wind gust spectrum peaks near the solar chimney’s fundamental resonance frequency. This phenomenon poses a reliability threat, not only to the solar chimney, but also to all high-rise, slender structures. Structural dynamics describe the response of a structure to a varying load. The dynamic equation incorporates four terms that bind the factors responsible for resonance: kinetic energy, dissipated energy (damping), stiffness energy and input energy (loading). After a brief literature study on classical chimney design procedures, the study scrutinises each of these terms individually in the context of the solar chimney as designed to date. A dynamic analysis is undertaken with all the above-mentioned parameters as defined and estimated by the study. The results from the analysis show amplifications of approximately three times the static displacements. In load cases where the wind direction inverts along the height, higher eigen-modes are excited. However, the most severe dynamic amplification occurs at the fundamental eigen-mode. In the context of solar chimney research, this study brings valuable new insights regarding the dynamic behaviour of the chimney structure to the fore.

Thesis (PhD (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2002. / This project investigates the performance of solar chimney power plant turbines. A solar chimney power plant consists of a tall chimney surrounded by a transparent deck or solar collector. The sun heats the air in the collector through the greenhouse effect. A turbine extracts energy from the hot air rising up the chimney. An investigation of the requirements and operation of such turbines is needed. Correct matching of the turbine to the plant requires the determination of the turbine operational range and other requirements. An air-standard cycle analysis is extended to include component and system losses. Simple steady-state and transient collector models are added to take into account the coupling effect of the collector air temperature rise and mass flow rate on the turbine operation. The predicted turbine operational range for a representative day shows that the expected pressure drop in a full-scale solar chimney turbine is significantly higher than has previously been predicted. A turbine design method is developed and used to design a turbine for the representative day. The methods can easily be extended to include more operating points for a full year of operation. A turbine layout is suggested that uses the chimney support pillars as inlet guide vanes (IGVs). These introduce pre-whirl to the turbine and reduce the amount of exit whirl thus decreasing the kinetic energy at the turbine exit. Non-radial inlet guide vanes add to the torsional stiffness of the chimney base. A matrix throughflow method is used to design the radial to axial duct between the IGVs and rotor. The turbine blade profiles are simulated using a surface-vortex method. This is coupled to an optimisation scheme that minimises both the chord length and maximum flow velocity of the profile to reduce blade drag. An experimental program investigates the performance of the turbine. Volume flow, pressure drop, torque and speed are measured on a scale model turbine to map the turbine performance over a wide range. The velocity and pressure profiles are measured at two design points to investigate the flow through the turbine in more detail. These are compared to the design predictions and used to improve the design method. The experiments show that the design of a solar chimney turbine with a total-to-total efficiency of 85 % - 90 % and total-to-static efficiency of 75 % - 80 % is possible. Analysis of the experimental results shows that the turbine efficiency can be improved.

This thesis uses the results of analysis of data recorded at a solar monitoring station in West Texas and the knowledge from an existing solar radiation estimation model to develop a methodology to predict the energy output from a panel at a site using only partial radiation data - global horizontal radiation measurements. The prediction using partial data is validated against estimates acquired using the complete radiation data and constraints are defined for accurate prediction. The methodology presented in this thesis can be used to accurately predict the solar power/energy incident on a collector at any location possessing global horizontal radiation measurements. / text

MBA Professional Report / The purpose of this MBA Project is to review existing policy of the Federal Energy Management Program under the purview of National Renewal Energy Laboratory (NREL) for Energy Savings Performance Contracts (ESPCs). This project will assess the ability for the Department of Defense to incorporate emerging technologies in alternative energy to supplement or replace existing power sources for DoD installations within the current Energy Savings Performance Contract policy. To do this the project will review previous and existing Energy Savings Performance Contracts. Further, this project will conduct a cost-benefit analysis of conventional power versus emerging photovoltaic energy for the Army’s Fort Bliss in El Paso, TX. The project will also analyze energy demands based on a new force alignment at Fort Bliss in accordance with the recent Base Realignment and Closure (BRAC) findings. The project will review current Energy Performance Contract Policy and recommend changes to allow for the use of emerging alternative energy technologies.

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>

An experimental investigation is presented on a novel High Temperature Falling Particle Receiver for Concentrated Solar Power (CSP) to quantify the extent of erosion of the receiver structural materials by the flowing particulate matter. The current receiver design uses a series of metal wire mesh screens to slow down the particulate flow through the receiver in order to increase their residence time thereby achieving the desired temperature rise within the receiver without the need for particulate recirculation. The solid particulates are gravity fed through the receiver where they absorb the incident thermal energy before flowing to a high temperature storage bin upstream of a heat exchanger where the heat stored in the particulate material is transferred to the working fluid for the power cycle. To assess the effective life of the receiver, this experimental investigation is undertaken. This thesis includes the development of an apparatus to test wire meshes under high temperature and particle abrasion conditions, and the presentation and analysis of these results.

This reports describes a master thesis project in Industrial Design Engineering at Lulea University of Technology in collaboration with Clas Ohlson.The master thesis was performed during 2015/2016 and is part of a product development project at Clas Ohlson aiming to develop a new kind of solar powered out door light. Clas Ohlson have limited experience with in house product development, and this project could be a pilot project to evaluate future in house product development.This projects main focus is the creative parts of the product development process and the detail development.The product developed resulted in a product with high customisation potential in many aspects including aesthetic, mounting, electronic and packaging.The resulting material, such as CAD-files, is handed over to Clas Ohlson for them to adjust if necessary in order to take the result in to production. The starting point is the company ́s desire to comply with one of their main objectives: provide sustainable products.The desire was for me to develop a solar powered outdoor light.The result is a module based system which can be expanded in multiple ways, from changing the function, to changing the appearance. In the chapter results you also find a suggested launch plan showing the width of the presented solution and the many opportunities the end user would have to upgrade their product without generating excessive waste.