Carbon Capture and Storage (CCS) is a suite of technologies available to directly reduce carbon dioxide (CO2) emissions to the atmosphere from fossil fuelled power plants and large industrial point sources. For a safe deployment of CCS it is important that CO2 injected into deep geological formations does not migrate out of the storage site. Characterising and understanding possible migration mechanisms and pathways along which migration may occur is therefore crucial to ensure secure engineered storage of anthropogenic CO2. In this thesis naturally occurring CO2 accumulations in the subsurface are studied as analogue sites for engineered storage sites with respect to CO2 migration pathways and mechanisms that ensure the retention of CO2 in the subsurface. Geological data of natural CO2 reservoirs world-wide has been compiled from published literature and analysed. Results show that faults are the main pathways for migration of CO2 from subsurface reservoirs to the surface and that the state and density of CO2, pressure of the reservoir, and thickness of the caprock influence the successful retention of CO2. Gaseous, low density CO2, overpressured reservoirs, and thin caprocks are characteristics of insecure storage sites. Two natural CO2 reservoirs have been studied in detail with respect to their fault seal properties. This includes the first study of how fault rock seals behave in CO2 reservoirs. It has been shown that the bounding fault of the Fizzy Field reservoir in the southern North Sea can with hold the amount of CO2 trapped in the reservoir at current time. A initially higher gas column would have led to across fault migration of CO2 as the fault rock seals would not have been able to withhold higher pressures. Depending on the present day stress regime the fault could be close to failure. At the natural CO2 reservoir of St. Johns Dome, Arizona, migration of CO2 to the surface has been occurring for at least the last 500 ka. Fault seal analysis shows that this migration is related to the fault rock composition and the orientation of the bounding fault in the present day stress field. Using the U-Th disequilibrium method the ages of travertine deposits of the St. Johns Dome area have been determined. The results illustrate that along one fault CO2 migration took place for at least 480 ka and that individual travertine mounds have had long lifespans of up to ~350 ka. Age and uranium isotope trends along the fault have been interpreted as signs of a shrinking CO2 reservoir. The amount of CO2 calculated to have migrated out of the St. Johns Dome is up to 113 Gt. Calculated rates span from 5 t/yr to 30,000 t/yr and indicate that at the worst case large amounts of CO2 can migrate rapidly from the subsurface reservoir along faults to the surface. This thesis highlights the importance of faults as fluid pathways for vertical migration of CO2. It has been also shown that they can act as baffles for CO2 migration and that whether a fault acts as pathway or baffle for CO2 can be predicted using fault seal analysis. However, further work is needed in order to minimise the uncertainties of fault seal analysis for CO2 reservoirs.

Higher penetration of volatile renewable sources and increasing load demand are putting a strain on the current utility grid structure. Energy storage solutions are required to maintain grid stability and are vital components to future smart grid designs. Flywheel energy storage can be a strong part of the solution due to high cycle life capabilities and flexible design configurations that balance power and energy capacity. This dissertation focuses on developing design methodologies for advanced flywheel energy storage, with an emphasis on sizing flywheel energy storage and developing lumped parameter modeling techniques for low loss, high temperature superconducting. The first contribution of this dissertation presents a method for using an optimal control law to size flywheel energy storage and develops a design space for potential power and energy storage combinations. This method is a data driven technique, that utilizes power consumption and renewable generation data from a particular location where the storage may be placed. The model for this sizing technique includes the spinning losses, that are unique to flywheel energy storage systems and have limited this technology to short term storage applications, such as frequency and voltage regulation. For longer term storage solutions, the spinning losses for flywheels must be significantly reduced. One potential solution is to use high temperature superconducting bearings, that work by the stable levitation of permanent magnet materials over bulk superconductors. These advanced bearing systems can reduce losses to less than 0.1% stored energy per hour. In order to integrate high temperature superconducting bearings into flywheel system designs, accurate and reduced order models are needed, that include the losses and emulate the hysteretic, non-linear behavior of superconducting levitation. The next two contributions of this dissertation present a lumped parameter axissymmetric model and a 3-D lumped parameter transverse model, which can be used to evaluate bearing lifting capabilities and transverse stiffness for flywheel rotor designs. These models greatly reduce computational time, and were validated against high level finite element analysis, and dynamic experimental tests. The validation experiments are described in detail. / text

Hydrogen has received significant attention throughout the past decade as the United States focuses on diversifying its energy portfolio to include sources of energy beyond fossil fuels. In a hydrogen economy, the most common use for hydrogen is in fuel cell vehicles. Advancements in on-board storage devices, investment in hydrogen production facilities nation-wide, development of a hydrogen transmission infrastructure, and construction of hydrogen fueling stations are essential to a hydrogen economy. This research proposes a novel underground storage technique to be implemented at a hydrogen fueling station. Three boreholes are drilled into the subsurface, with each borehole consisting of an outer pipe and an inner pipe. Hydrogen gas (H2) is stored in the inner tube, while the outer pipe serves to protect the inner pipe and contain any leaked gas. Three boreholes of varying pressures are necessary to maintain adequate inventory and sufficient pressure while filling vehicles to full tank capacity. The estimated cost for this storage system is $2.58 million. This dollar amount includes drilling and completion costs, steel pipe costs, the cost of a heavy-duty hydrogen compressor, and miscellaneous equipment expenses. Although the proposed design makes use of decades’ worth of experience and technical expertise from the oil and gas industry, there are several challenges—technical, economic, and social—to implementing this storage system. The impact of hydrogen embrittlement and the lack of a hydrogen transmission infrastructure represent the main technical impediments. Borehole H2 storage, as part of a larger hydrogen economy, reveals significant expenses beyond those calculated in the amount above. Costs related to delivering H2 to the filling station, electricity, miscellaneous equipment, and maintenance associated with hydrogen systems must also be considered. Public demand for hydrogen is low for several reasons, and significant misperceptions exist concerning the safety of hydrogen storage. Although the overall life-cycle emissions assessment of hydrogen fuel reveals mediocre results, a hydrogen economy impacts air quality less than current fossil-fuel systems. If and when the U.S. transitions to a hydrogen economy, the borehole storage system described herein is a feasible solution for on-site compressed H2 storage. / text

As energy systems shift away from fossil-fuel based electricity, the non-dispatchability of renewable energy converters (REC) continue to stress the grid infrastructure and conventional thermal generating units. These hybrid electricity systems require energy storage systems to buffer the variabilities of electricity supply and demand. Regenerative air energy storage (RAES) is an emerging technology that shows promise to overcome the barriers of REC variability. RAES uses a novel compressor/expander that approaches isothermal operation by spraying water into the piston/cylinder to absorb/release heat. RAES can be sized for power and energy independently, and has a high round-trip efficiency that can be boosted using low grade waste heat. Because of its novelty, new numerical models are necessary to investigate the sizing and performance of RAES systems. In this thesis a numerical simulation tool is developed to allow flexible and intuitive analysis of a range of hybrid energy systems involving RAES.

No description available.

Thesis (M.S.)--Rochester Institute of Technology, 2008. / Typescript. Includes bibliographical references (leaves 73-75).

Thesis (MSc Food Sc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Post-storage quality of the stone fruit, apricots and peaches, is the major factor determining their suitability for canning after cold storage in South Africa. Short harvesting periods and the limited capacity of the factory to process the large quantities of fruit within two days after delivery, necessitates cold storage until canning. Apricots develop internal breakdown, whereas peaches develop internal breakdown accompanied by loosening of the skin and adhesion of the flesh to the stone. The deterioration takes place within the fruit during a cold storage period of one to two weeks. The tendency of the fruit to develop internal defects can, to date, not be identified prior to storage and are only discovered after destoning during canning. Near infrared spectroscopy (NIRS) combined with chemometrics were investigated as a non-destructive method to predict post-storage quality in Bulida apricots and clingstone peach cultivars. Near infrared (NIR) spectra (645-1201 nm), measured on the intact fruit just after harvesting, were correlated with subjective quality evaluations performed on the cut and destoned fruit after cold storage. The cold storage periods for apricots were four weeks (2002 season) and three and two weeks for peach cultivars for the 2002 and 2003 seasons, respectively. Soft independent modelling by class analogy (SIMCA) and multivariate adaptive regression splines (MARS) were applied to the spectral and reference data to develop models for good and poor post-storage quality. The ability of these models to predict post-storage quality was evaluated in terms of recognition (sensitivity) and rejection (specificity) of the samples in independent validation sets. Total correct classification rates of 50.00% and 69.00% were obtained with Bulida apricots, using SIMCA and MARS, respectively. Classification results with apricots showed that MARS performed better than SIMCA and is thus recommended for this application. Total correct classification rates of 53.00% to 60.00% (SIMCA) and 57.65% to 65.12% (MARS) were obtained for data sets of combined peach cultivars within seasons and over both seasons. Additional aspects of fruit quality were investigated to identify possible indices of post-storage quality. Classification trees were used to find correlations between the post-storage quality and the fruit mass, diameter, firmness and soluble solids content (SSC). Among these, fruit diameter and firmness were the major indices of post-storage quality. Accurate predictions of firmness could not be achieved by near infrared spectroscopy (NlRS), making the combination of NIRS and classification trees not yet suitable for predicting post-storage quality. NIRS was further used to predict poststorage SSC within seasons in Bulida apricots and intact peach cultivars. This confirmed sufficient NIR light penetration into the intact fruit and also provided a further application of NIRS for ripeness evaluation in the canning industry. Validations on peach samples obtained correlation coefficients (r) of 0.77-0.85 and SEP-values of 1.35-1.60 °Brix using partial least squares (PLS) regression. MARS obtained r = 0.77-0.82 and SEP = 1.42-1.55 °Brix. Predictions of sse in apricots were less accurate, with r = 0.39-0.88, SEP = 1.24-2.21 °Brix (PLS) and r = 0.51-0.82, SEP = 1.54-2.19 °Brix (MARS). It is suggested that the accuracy of sse measurements, and the subsequent predictions, were affected by the cold storage periods as well as internal variation within the fruit. This study showed that a combination of NIRS and chemometrics can be used to predict post-storage quality in intact peaches and apricots. A small scale feasibility study showed that 4% (R117 720) (apricot industry) and 3% (R610 740) (peach industry) of production losses can be saved if this method is implemented in the South African canning industry. Although it was difficult to assign specific chemical components or quality attributes to the formulation of the storage potential models, important hidden information in the spectra could be revealed by chemometric classification methods. NIRS promises to be a useful and unique quality evaluation tool for the South African fruit canning industry. Several recommendations are made for the canning practices to reduce losses and for future research to improve the current prediction models. / AFRIKAANSE OPSOMMING: Die kwaliteit van die steenvrugte, appelkose en perskes, is die hoof bepalende faktor vir hul geskiktheid vir inmaakdoeleindes na koelopberging in Suid-Afrika. Die vrugte moet opgeberg word by lae temperature vir een tot twee weke, aangesien die oestydperk kort is en die kapasiteit van die fabriek te beperk is om die groot hoeveeheid vrugte dadelik in te maak. Tydens hierdie opbergingstydperk vind agteruitgang in die vrugte plaas. Dit word in appelkose gekenmerk deur interne verval en in perskes gekenmerk aan interne verval, tesame met enlos skil en die vaskleef van die vrugvlees aan die pit. Tot dusver, bestaan daar geen metode om hierdie tipe agteruitgang in vrugte voor opberging te identifiseer nie. Dit word eers na opberging opgemerk wanneer die vrugte ontpit word. Naby-infrarooi spektroskopie (NIRS), gekombineerd met chemometriese metodes is gebruik om opbergingspotensiaal in Bulida appelkose en taaipitperske kultivars te bepaal. enKorrelasie is gemaak tussen naby-infrarooi (NIR) spektra, gemeet op die heel vrugte voor opberging en subjektiewe evaluering van kwaliteit, geïdentifiseer op die gesnyde vrugte na opberging. Die opbergingstydperke vir perskes was vir drie en twee weke vir die 2002 en die 2003 seisoene, onderskeldeflk, terwyl die appelkose vir vier weke opgeberg is. Twee chemometriese metodes, "soft independent modelling by class analogy" (SIMCA) en "multivariate adaptive regression splines" (MARS) is gebruik om die spektra en ooreenstemmende subjektiewe data te kombineer en modelle is ontwikkel vir goeie en swak opbergingspotensiaal. Die vermoë van die modelle om die vrugkwaliteit na die opbergingstydperk te voorspel, is geêvalueer in terme van herkenning en verwerping van vrugtemonsters in onafhanklike toetsstelle. Totale korrekte klassifikasies van 50.00% and 69.00% is verkry vir Bulida appelkose, met SIMCA en MARS, onderskeidelik. Die klassifikasie resultate het gewys dat MARS beter gevaar het as SIMCA en word dus sterk aanbeveel vir hierdie toepassing. Totale korrekte klassifikasies van 53.00% tot 60.00% (SIMCA) and 57.65% tot 65.12% (MARS) is verkry vir gekombineerde perskekultivars tussen seisoene en oor seisoene. Verdere aspekte van vrugkwaliteit is geêvalueer om enmoontlike indeks van opbergingspotensiaal te verkry. Klassifikasiebome is gebruik om en korrelasie te vind tussen kwaliteit na opberging en vrugmassa, deursnee, fermheid en totale oplosbare vastestowwe (TOV). Diameter en fermheid het die meeste gekorreleer met die kwaliteit na opberging. Voorspellings van fermheid deur die gebruik van naby infrarooi spektroskopie (NIRS) was ~gter nie akkuraat nie. Dus word die kombinasie van klassifikasiebome en NIRS om opbergingspotensiaal te voorspel nie tans aanbeveel nie. NIRS is verder gebruik om TOV te voorspel binne seisoene in heel Bulida appelkose en perskekultivars. Dit is uitgevoer om voldoende NIR ligpenitrasie in die vrugte te bevestig en ook om 'n verdere toepassing van kwaliteitsbepaling (as indeks van soetheid en rypheid) vir die inmaakindustrie te verskaf. Validasies is op perskemonsters uitgevoer en korrelasiekoêffisiente (r) van 0.77-0.85 en voorspellingsfoute van 1.35-1.60 °Brix is verkry met "partial least squares" (PLS) regressie. MARS het r = 0.77-0.82 and voorspellingsfoute = 1.42-1.55 °Brix verkry. Die akkuraatheid van die TOV meetings en gevolglike voorspellings is waarskynlik beïnvloed deur interne variasie binne die vrugte sowel as die opbergings tydperke wat verloop het tussen metings. Hierdie studie wys dat NIRS en chemometriese metodes wel gebruik kan word om opbergingspotensiaal in heel perskes in appelkose te voorspel. 'n Kosteberekening het gewys dat besparings van 4% (R117 720) (appelkoos industrie) en 3% (R610 740) (perske industrie) moontlik is indien NIRS en MARS geïmplementeer word. Alhoewel dit moeilik was om spesifieke chemiese komponente en .sekere kwaliteitsaspekte aan die ontwikkeling van die modelle te koppel, is belangrike verborge informasie in die spectra uitgebring deur chemornetriese metodes. NIRS beloof om 'n bruikbare en unieke kwaliteitskontrole maatstaf te wees vir die Suid-Afrikaanse inmaakindustrie. Verskeie aanbevelings is gemaak vir die inmaakpraktyke om verliese te voorkom en ook vir toekomstige navorsing om die huidige klassifikasiemodelle te verbeter.

Made available in DSpace on 2014-10-09T12:27:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:18Z (GMT). No. of bitstreams: 0 / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

abstract: With growing concern regarding environmental issues and the need for a more sustainable grid, power systems have seen a fast expansion of renewable resources in the last decade. The uncertainty and variability of renewable resources has posed new challenges on system operators. Due to its energy-shifting and fast-ramping capabilities, energy storage (ES) has been considered as an attractive solution to alleviate the increased renewable uncertainty and variability. In this dissertation, stochastic optimization is utilized to evaluate the benefit of bulk energy storage to facilitate the integration of high levels of renewable resources in transmission systems. A cost-benefit analysis is performed to study the cost-effectiveness of energy storage. A two-step approach is developed to analyze the effectiveness of using energy storage to provide ancillary services. Results show that as renewable penetrations increase, energy storage can effectively compensate for the variability and uncertainty in renewable energy and has increasing benefits to the system. With increased renewable penetrations, enhanced dispatch models are needed to efficiently operate energy storage. As existing approaches do not fully utilize the flexibility of energy storage, two approaches are developed in this dissertation to improve the operational strategy of energy storage. The first approach is developed using stochastic programming techniques. A stochastic unit commitment (UC) is solved to obtain schedules for energy storage with different renewable scenarios. Operating policies are then constructed using the solutions from the stochastic UC to efficiently operate energy storage across multiple time periods. The second approach is a policy function approach. By incorporating an offline analysis stage prior to the actual operating stage, the patterns between the system operating conditions and the optimal actions for energy storage are identified using a data mining model. The obtained data mining model is then used in real-time to provide enhancement to a deterministic economic dispatch model and improve the utilization of energy storage. Results show that the policy function approach outperforms a traditional approach where a schedule determined and fixed at a prior look-ahead stage is used. The policy function approach is also shown to have minimal added computational difficulty to the real-time market. / Dissertation/Thesis / Doctoral Dissertation Engineering 2016

Made available in DSpace on 2014-10-09T12:27:08Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:18Z (GMT). No. of bitstreams: 0 / O combustível nuclear queimado (CNQ) é retirado do reator nuclear após exaurir sua eficiência de geração de energia. Após ser retirado do reator, esse combustível é temporariamente armazenado em piscinas com água na própria instalação do reator. Durante esse tempo, o calor gerado e os elementos radioativos presentes, de meia-vida média e curta, caem até níveis que permitem retirar o combustível queimado da piscina e enviá-lo para depósitos temporários de via seca. Nessa fase, o material precisa ser armazenado segura e eficazmente de forma que possa ser recuperado em futuro próximo, ou disposto como rejeito radioativo. A quantidade de combustível queimado cresce anualmente e, nos próximos anos, vai aumentar mais ainda por causa da construção de novas instalações de geração de energia de origem nuclear. Nos dias de hoje, o número de instalações novas voltou a atingir os níveis da década de 1970, porque é maior que a quantidade de ações de descomissionamento de instalações antigas. Antes que seja tomada qualquer decisão, seja a de recuperar o combustível remanescente ou considerar o CNQ como rejeito radioativo, o mesmo precisa ser isolado em um dos diferentes tipos de armazenagem existentes no mundo. No presente estudo mostra-se que a armazenagem do CNQ, via seca, em cascos é a opção mais vantajosa. Propõe-se um modelo de casco autóctone para combustível de reatores de potência e de uma instalação de armazenagem para abrigar esses cascos. É um estudo multidisciplinar no qual foi desenvolvida a parte conceitual de engenharia e que poderá ser usada para que o CNQ nacional, retirado dos reatores brasileiros de potência, seja armazenado com segurança por um longo período até que as autoridades brasileiras decidam o local para deposição final. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP