Solar and other renewable power sources are becoming an integral part of the electrical grid in the United States. In the Southwest US, solar and wind power plants already serve over 20% of the electrical load during the daytime on sunny days in the Spring. While solar power produces fewer emissions and has a lower carbon footprint than burning fossil fuels, solar power is only generated during the daytime and it is variable due to clouds blocking the sun. Electric utilities that are required to maintain a reliable electricity supply benefit from anticipating the schedule of power output from solar power plants. Forecasting the irradiance reaching the ground, the primary input to a solar power forecast, can help utilities understand and respond to the variability. This dissertation will explore techniques to forecast irradiance that make use of data from a network of sensors deployed throughout Tucson, AZ. The design and deployment of inexpensive sensors used in the network will be described. We will present a forecasting technique that uses data from the sensor network and outperforms a reference persistence forecast for one minute to two hours in the future. We will analyze the errors of this technique in depth and suggest ways to interpret these errors. Then, we will describe a data assimilation technique, optimal interpolation, that combines estimates of irradiance derived from satellite images with data from the sensor network to improve the satellite estimates. These improved satellite estimates form the base of future work that will explore generating forecasts while continuously assimilating new data.

Renewable energy resources (RES) are becoming more popular for electricity generation due to their easy installation, flexibility, low cost, environmental compatibility, etc. However, their fluctuating nature is a major drawback, which decreases the power quality and makes them less trusty in the power system. To mitigate this problem, battery energy storage (BES) has been widely used with renewable energy sources. Because batteries are designed to handle “steady fluctuations” of power, the “sudden and peak” fluctuating power levels of renewable energy sources may cause shorter life spans for them, which may cause dramatic economic loss or negatively impact the power quality. Also, even though batteries have been used as a backup for RES, high power quality cannot be guaranteed when there is a rapid and peak fluctuations on source/load.

A heliostat is a motorized mirror used in a Solar Power Tower plant. The technology has been around since the 1970’s, and involves hundreds or thousands of heliostats reflecting the sun’s rays to the top of a high tower, where the incident solar energy is converted to heat energy, which in turn is used to drive steam turbines and produce electricity. Demonstration plants have been built in the U.S.A. and Spain, and a number of new facilities have been added since 2005. To achieve a commercial breakthrough, the technology must be made more efficient so that electricity can be produced at prices comparable with other options such as wind, photovoltaic, nuclear and coal. A critical component in the economics of the Solar Power Tower plant is the cost of the heliostat, which is estimated to account for approximately 50 % of the investment cost of the total plant. This report deals with the heliostat from a multifaceted perspective. Different design approaches are explained. First, mirror geometries, with manufacturing dimensions, for a rotation-symmetric paraboloid-shaped mirror-assembly are obtained for mirrors with different sizes with a Matlab code. Investigating wind loads are among the most important tasks in a heliostat development project, as large wind loads radically complicates the design work. A wind load calculation-method based on previous work by Sandia National Laboratories and finite element method (FEM) is used in this work to design heliostats to withstand expected wind loading. The design of the geometry and the structure to withstand wind loading is illustrated with two azimuth elevation heliostats (25 m 2 and 49 m2). Finally, a number of innovative technical solutions are suggested. These are a new mirror facet mounting technique, sliding bearings, elevation drive, and a very unique azimuth motor module, which uses steel wires as belts with an integrated brake. It is hoped that the results and designs presented in this thesis will be a good foundation for further research in the heliostat structures and heliostat controls at the Robotics lab in IISc and elsewhere. Keywords: Solar Power, Heliostat, Thermal solar power, Solar Power Tower, Central Receiver System / En heliostat är en motordriven spegel som används i tornsolkraftverk, kända som Solar Power Tower, även kallade Central Receiver system. Tekniken har funnits sedan 1970-talet och går ut på att hundratals eller tusentals heliostater speglar solstrålarna till toppen av ett högt torn, där stålningsenergin omvandlas till värmeenergi, som t.ex. kan användas till att driva ångturbiner och producera elektricitet. Demonstrationsanläggningar har byggts i bland annat USA och Spanien, och ett flertal nya installationer har tillkommit sedan år 2005. För att verkligen nå ett kommersiellt genombrott måste tekniken göras billigare så att solelen kan produceras till minst lika bra pris som andra alternativ, så som t.ex. solceller, kärnkraft och kolkraft. En kritisk komponent för tornsolkraftverkens ekonomi är kostnaden för heliostaterna, som beräknas stå för ungefär 50 % av anläggningens totala investeringskostnad. Den här rapporten avhandlar heliostaten ur ett mångfacetterat perspektiv där olika konstruktionsspår förklaras. Vidare behandlar rapporten spegelgeometrier, och en Matlab-kod som genererar tillverkningsmått för en rotationssymmetrisk paraboloidformad spegelyta finns bifogad. Att undersöka vindlaster är bland det viktigaste i ett heliostatutvecklingsprojekt, eftersom dessa är de dimensionerande lasterna för designarbetet. Här används en vindlastberäkningsmetod utgiven av Sandia National Laboratories, som kortfattat går ut på att man multiplicerar det dynamiska vindtrycket med en korrigeringsfaktor som baserats på emiriska studier av heliostatmodeller i vindtunnel. En dimensioneringsprocess för heliostater föreslås och utvecklingsgången för två Azimut-Elevation heliostater i storlek 25 m 2 resp. 49 m2 demonstreras. FEM-mjukvara nyttjas som det främsta verktyget för att dimensionera heliostatkonstruktioner som kan stå emot vindlasterna. Slutligen ges förslag på innovativa tekniska lösningar för spegelmontering, glidlager, montering av elevation-motorerna, och en unik azimut-motormodul, vilken använder stålvajrar som remmar och har en integrerad broms. Med all denna information bör Robotics Lab på IISc ha en god grund att stå på inför vidare forskning inom konstruktion och styrning av heliostater. Nyckelord: Solenergi, Heliostat, Termisk solenergi, Solar Power Tower, Tornsolkraftverk

In this thesis we consider design methodology and resource allocation for IEEE 802.11 ESS mesh networks. In such networks, solar powered access points can be used to significantly reduce the installation cost of outdoor WLAN hotzones. SolarMESH is a network of this kind and is currently in its second year of an operational deployment. In SolarMESH, the cost of the solar panel/battery can be a significant fraction of the total, and therefore reducing AP power consumption is very important. Unfortunately, access point power saving is not currently supported under IEEE 802.11, but this would be very useful in future versions of the standard. A design methodology is presented for sustainable solar powered ESS mesh networks, assuming a power saving version of IEEE 802.11. First, a load profile for each network node is determined. The load profile is a time function which represents the average workload for which the node in question is designed. For a given geographic location, public meteorological data is then used together with the averaged offered capacity profile to provision each node subject to a target outage probability. The design is statistical since future load conditions and solar insolation may not exactly match that for which the node was designed. For this reason, a control algorithm is introduced which attempts to maintain outage-free operation of the node by introducing a capacity deficit under certain conditions. Results are presented showing that significant resource reductions are possible using the proposed resource allocation methodology. The results also give a strong motivation for including access point power saving in outdoor ESS mesh networks. / Thesis / Master of Science (MS)

Thesis (MScIng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: This study investigates energy generation by large-scale solar tower power plants. The performance characteristics of a so-called reference plant with a 4000 m diameter glass collector roof and a 1500 m high, 160 m diameter tower are determined for a site located in South Africa. The relevant draught and conservation equations are derived, discretized and implemented in a numerical model which solves the equations using speci ed meteorological input data and determines the power delivered by the plant. The power output of a solar tower power plant over a twenty-four hour period is presented. Corresponding temperature distributions in the ground under the collector are shown. Variations in seasonal generation are evaluated and the total annual electrical output is determined. The dependency of the power output on collector diameter and tower height is illustrated, while showing that greater power production can be facilitated by optimizing the roof shape and height. The minor in uence of the tower shadow falling across the collector is evaluated, while the e ect of prevailing winds on the power generated is found to be signi cant. / AFRIKAANSE OPSOMMING: Hierdie studie ondersoek elektrisiteitsopwekking deur grootskaalse sontoringkragstasies. Die uitsetkarakteristieke van 'n sogenaamde verwysings-kragstasie met 'n 4000 m deursnee glas kollektor en 'n 1500 m hoë, 160 m deursnee toring word ondersoek vir 'n spesi eke ligging in Suid-Afrika. Die toepaslike trek- en behoudsvergelykings word afgelei, gediskretiseer en geimplementeer in 'n numeriese rekenaarmodel. Die rekenaarmodel los die betrokke vergelykings op deur gebruik te maak van gespesi seerde meteorologiese invoerdata en bepaal dan die uitset gelewer deur die kragstasie. Die uitset van 'n sontoring-kragstasie oor 'n periode van vier-en-twintig uur word getoon. Ooreenstemmende temperatuurverdelings in die grond onder die kollektor word geïllustreer. Die variasie in seisoenale elektrisiteitsopwekking word ondersoek en die totale jaarlikse elektriese uitset bepaal. Die invloed wat die kragstasie dimensies (kollektor deursnee en toring hoogte) op die uitset het, word bestudeer en resultate getoon. Daar is ook bevind dat verhoogde uitset meegebring kan word deur die vorm en hoogte van die kollektordak te optimeer. Die geringe e ek van die toringskadu op die kollektor word bespreek, terwyl bevind is dat heersende winde 'n beduidende e ek op die kragstasie uitset het.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Most rural African villages enjoy high levels of sunlight, but rolling out solar power generation technology to tap into this renewable energy resource at remote rural sites in Africa pose a number of design challenges. To meet these challenges, a project has been initiated to design, build and test/evaluate a knock down 3 kW peak electrical stand-alone self-tracking dual-axis concentrating solar power system. This study focusses on the mechatronic engineering aspects in the design and development of a dynamic mechatronic platform and digital electronic control system for the stand-alone concentrating solar power system. Design specifications require an accurate automatic positioner and control system for a motorized parabolic solar reflector with an optical solar harnessing capacity of 12 kWt at solar noon. It must be suitable for stand-alone rural power generation. This study presents a conceptual design and engineering prototype of a balanced cantilever tilt-and-swing dual-axis slew drive actuation means as mechatronic solar tracking mobility platform for a ∼12 m2 lightweight parabolic solar concentrator. Digital automation of the concentrated solar platform is implemented using an industrial Siemens S7-1200 programmable logic controller (PLC) with digital remote control interfacing, pulse width modulated direct current driving, and electronic open loop/closed loop solar tracking control. The design and prototype incorporates off-the-shelf components to support local manufacturing at reduced cost and generally meets the goal of delivering a dynamic mechatronic platform for a concentrating solar power system that is easy to transport, assemble and install at remote rural sites in Africa. Real-time experiments, conducted in the summer of South Africa, validated and established the accuracy of the engineering prototype positioning system. It shows that the as-designed and -built continuous solar tracking performs to an optical accuracy of better than 1.0◦ on both the azimuth and elevation tracking axes; and which is also in compliance with the pre-defined design specifications. Structural aspects of the prototype parabolic dish are evaluated and optimized by other researchers while the Stirling and power handling units are under development in parallel projects. Ultimately, these joint research projects aim to produce a locally manufactured knock down do-it-yourself concentrated solar power generation kit, suitable for deployment into Africa. / AFRIKAANSE OPSOMMING: Landelike gebiede in Afrika geniet hoë vlakke van sonskyn, maar die ontwerp van betroubare sonkrag tegnologie vir die benutting van hierdie hernubare energie hulpbron by afgeleë gebiede in Afrika bied verskeie uitdagings. Om hierdie uitdagings te oorkom, is ’n projek van stapel gestuur om ’n afbreekbare 3 kW piek elektriese alleenstaande selfaangedrewe dubbel-as son-konsentreeder te ontwerp, bou en te toets. Hierdie studies fokus op die megatroniese ingenieurs-aspekte in die ontwerp en ontwikkeling van ’n dinamiese megatroniese platform en ’n digitale elektroniese beheerstelsel vir die alleenstaande gekonsentreerde sonkrag stelsel. Ontwerp spesifikasies vereis ’n akkurate outomatiese posisionering en beheer stelsel vir ’n motor aangedrewe paraboliese son reflekteerder met ’n optiesekollekteer- kapasiteit van 12 kWt by maksimum sonhoogte, en veral geskik wees vir afgeleë sonkrag opwekking. Hierdie studie lewer ’n konsepsuele ontwerp en ingenieurs-prototipe van ’n gebalanseerde dubbelas swaai-en-kantel swenkrat aandrywingsmeganisme as megatroniese sonvolg platform vir ’n ∼12 m2 liggewig paraboliese son konsentreerder. Digitale outomatisering van die son konsentreerder platform is geimplementeer op ’n industriële Siemens S7-1200 programmeerbare logiese beheerder (PLB) met ’n digitale afstandbeheer koppelvlak, puls-wydte-gemoduleerde gelykstroom aandrywing en elektroniese ooplus en geslote-lus sonvolg beheer. Die ontwerp en prototipe maak gebruik van beskikbare komponente om lae-koste plaaslike vervaardiging te ondersteun en slaag in die algemeen in die doel om ’n dinamiese megatroniese platform vir ’n gekonsentreerde sonkrag stelsel te lewer wat maklik vervoer, gebou en opgerig kan word op afgeleë persele in Afrika. Intydse eksperimente is gedurende die somer uitgevoer om die akkuraatheid van die prototipe posisionering sisteem te evalueer. Dit toon dat die sisteem die son deurlopend volg met ’n akkuraatheid beter as 1.0◦ op beide die azimut en elevasie sonvolg asse, wat voldoen aan die ontwerp spesifikasies. Strukturele aspekte van die prototipe paraboliese skottel word deur ander navorsers geëvalueer en verbeter terwyl die Stirling-eenheid en elektriese sisteme in parallelle projekte ontwikkel word. Die uiteindelike doel met hierdie groepnavorsing is om ’n plaaslik vervaardigde doen-dit-self sonkrag eenheid te ontwikkel wat in Afrika ontplooi kan word.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Up to this point in time research on the South African solar chimney, proposed for a site in the Northern Cape, comprised of determining the structural integrity of the chimney structure, as well as airflow calculation, finding the optimal shape for the airflow channels. Not much work had been done on the realisation of the foundation of the global structure, i.e. how the cardinal parts are optimized in an integrated system. The inlet guide vanes (IGV's) should be central in such research efforts, being the main support of gravitational and lateral wind load on the chimney structure, as well as its important role in channelling air and creating pre-swirl of the airflow onto the turbine blades. However, little detailed research - research to actually determine and fix the many variables of the IGV's and integration with surrounding parts - had been performed! In this thesis as many of these variables as possible are investigated - ranging from structural integrity with regard to compressive and shear strength through optimizing structure eigenfrequency to economic feasibility. The outcome of this study is conceptual solutions regarding the geometry of the IGV structures in order for it to support the chimney while minimizing material volume. Finite element methods are used to create insight into the behaviour of the IGV's and force transferring structures, incorporating external factors such as lateral wind and gravitational loadsto determine the optimal shape of these structures. This study is valuable for researchers on the solar chimney, serving as a reference from where to design and secure the variables of the global structure, and eventually building the solar chimney. Keywords: Solar chimney, inlet guide vanes, solar power, massive concrete structures, structural realisation, finite element application, structure optimisation. / AFRIKAANSE OPSOMMING: Tot op hede het die navorsing op die Suid Afrikaanse sonskoorsteen, wat beplan word vir konstruksie in die Noordkaap, bestaan uit die bepaling van die integriteit van die struktuur asook lugvloei berekeninge om die optimale vorm van die lugvloei kanale te lewer. Min werk is gedoen om die fondasies van die globale struktuur, dus hoe die kardinale dele geïntegreer is in die gesamentlike sisteem, te ondersoek. Die inlaat lei lemme behoort sentraal te lê in sulke navorsingspogings aangesien dit die hoof ondersteuner en verspreider van gravitasie en laterale windlaste op die skoorsteen struktuur is. Dit speelook 'n integrale rol in die kanalisering van invloeiende lug om dit vooraf 'n vorteks beweging te gee vir 'n optimale invalshoek op die turbine lemme. Min gedetaileerde navorsing - navorsing om die verskeie onbekende faktore rondom die inlaat lei lemme en die omliggende strukture te bepaal - is tot op hede gedoen. Hierdie tesis mik om soveel moontlik van hierdie veranderlikes - wat reik van struktuur integriteit met betrekking tot die samedrukkings- en skuifsterktes in die materiaal tot die eie-frekwensies en ekonomiese vatbaarheid van die struktuur - vas te stel. Die uitkoms van hierdie studie is konseptueie oplossings vir die geometrie van die inlaat lei lem strukture wat terselfdertyd die totale struktuur se materiaal volume minimiseer. Eindige element metodes word gebruik om insig in die gedrag van die inlaat lei lemme en ander strukture wat krag oordra, te genereer. Die metodes inkorporeer soveel as moontlik van die eksterne faktore soos gravitasie en laterale windlas om die optimale geometrie vir die betrokke struktuur te bepaal. Hierdie studie is waardevol vir navorsers oor die sonskoorsteen en dien as 'n bron waaruit verdere ontwerp en die vasstel van veranderlikes in die globale struktuur gedoen kan word met die oog op die uiteindelike daarstelling van 'n sonskoorsteen.

Published Article / The world is increasingly being misused by its inhabitants by the wasteful manner that its resources are utilized and the amount of pollution that is generated in the environment. This practice is unsustainable and it is incumbent on the present generation of decision-makers to rectify this phenomenon if our descendants are to have an opportunity to live life in the same manner as we do. Special emphasis should be placed on a reduction in the amount of air pollution that is created by electrical power generating plants, as well as the manner in which potable water is utilized and wasted. In this article the local situation with respect to the generation and use of electrical energy and water is discussed. It is encouraging to see that the National Government is taking strong steps to address these problems. Yet, it might not have the required ability to finance these efforts fully.

The electrification of passenger vehicles has been a step towards the reduction of greenhouse gas emissions by automobiles; however, in the United States many plug-in hybrid electric vehicles (PHEVs) and battery electric vehicles (BEVs) must still be plugged in to a grid that is heavily reliant on the burning of fossil fuels to charge. The goal of this thesis is to investigate how to develop a system capable of fully charging a PHEV using only alternative and/or regenerative energy sources. In developing such a system, various alternative and regenerative energy sources were investigated with the intent of reaching a specified daily energy goal; sufficient to charge a PHEV. These energy sources were evaluated based upon criteria such as novelty, ability to reach desired daily energy goal, applicability to BEV/PHEV, etc. The primary technological categories considered include but are not limited to regenerative and solar technologies. The evaluation of technologies indicated that a major opportunity lies in solar technologies, and in particular concentrated photovoltaics. Design alternatives for a concentrated photovoltaic system capable of reaching the desired energy goal are described. The design alternatives utilize Fresnel lenses as a means of concentrating a large area of sunlight onto an array of photovoltaics affixed to a vehicle. Various tracking mechanisms for the concentrating systems have been outlined to meet given design criteria. 3-D ray tracing algorithms have been developed to determine the path of the tracking mechanisms depending upon the time of year and on the geographic location. The same algorithms have been used in conjunction with typical meteorological year data to determine the expected output of the concentrating systems based upon the solar resource and solar angles at a specific place and time. The findings suggest that a concentrated photovoltaic system designed specifically for charging an electrified vehicle may generate sufficient energy over the course of a day to power a typical driver’s trips. However, for such a concentrating system to be commercially feasible there are still many design challenges to be overcome. Design limitations and implications for further research are discussed.

The purpose of this study is to investigate the effects of stochastic dust accumulations and rain events on the cleaning schedule of the parabolic trough collectors that are used to generate power at concentrated solar power (CSP) plants. The level of cleanliness is proportional to the power produced, and thus it affects the economic pay off at CSP plants. Current practice to address this dust problem, termed as conventional cleaning, is to follow a periodic cleaning schedule that entails a fixed setup cost for each cleaning event. The frequency of cleaning under such conventional (periodic schedule) policy is selected based upon a tradeoff between the set up cost and the payoff from improving the cleanliness factor. The conventional practice is to have a constant and periodic cleaning schedule over an entire season (e.g. either severe or mild combination of the dust and rain over a 180-day cleaning season, with either 8 or 4 cycles scheduled for the severe and mild seasons respectively). This thesis draws upon evidence from recent literature to show that presence of random rain events improves the cleanliness of parabolic troughs in CSP plants. Upon analyzing such evidence, this study models rain event as a compound Poisson process that replenishes the level of cleanliness. In this scenario, it is possible to establish an adaptive threshold policy for scheduling plant cleaning that analogous to the formulation of a (s,S) inventory management policy, subject to random replenishment of inventory. The study offers a review of related literature to establish that such formulations are not amenable to a close form solution. The second half of the thesis describes a numerical study that has been conducted using Arena Simulation package for characterizing the adaptive cleaning policy. The parameter of interest for assessing system performance is the average payoff over the average cost of cleaning for a 180-day cleaning season. Numerical study shows that adaptive cleaning policy outperforms the conventional (periodic) cleaning policy under reasonable assumptions for dust and rain event distributions. As an extension, the simulation study also examines the use of alternative cleaning system, known as electrodynamic screening (EDS), for different rain scenarios that may be used in conjunction with either conventional or adaptive cleaning policies to improve the overall system performance. / 2019-07-09T00:00:00Z