Predicting how increasing atmospheric carbon dioxide concentration will affect the hydrologic cycle is of utmost importance for water resource management, ecological systems and for human life and activities. A typical perspective is that the water cycle will mostly be altered by atmospheric effects of climate change, precipitation and radiation, and that the land surface will adjust accordingly. Terrestrial processes can however feedback significantly on the hydrologic changes themselves. Vegetation is indeed at the center of the carbon, water and energy nexus. This work investigates the processes, the timing and the geography of these feedbacks. Using Earth System Models simulations from the Coupled Model Intercomparison Project, Phase 5 (CMIP5), with decoupled surface (vegetation physiology) and atmospheric (radiative) responses to increased atmospheric carbon dioxide concentration, we first evaluate the individual contribution of precipitation, radiation and physiological forcings for several key hydrological variables. Over the largest fraction of the globe the physiological response indeed not only impacts, but also dominates the change in the continental hydrologic cycle compared to either radiative or precipitation changes due to increased atmospheric carbon dioxide concentration. It is however complicated to draw any conclusion for the soil moisture as it exhibits a particularly nonlinear response. The physiological feedbacks are especially important for extreme temperature events. The 2003 European heat wave is an interesting and crucial case study, as extreme heat waves are anticipated to become more frequent and more severe with increasing atmospheric carbon dioxide concentration. The soil moisture and land-atmosphere feedbacks were responsible for the severity of this episode unique for this region. Instead of focusing on statistical change, we use the framework of Regional Climate Modeling to simulate this specific event under higher levels of surface atmospheric carbon dioxide concentration and to assess how this heat wave could be altered by land-atmosphere interactions in the future. Increased atmospheric carbon dioxide concentration modifies the seasonality of the water cycle through stomatal regulation and increased leaf area. As a result, the water saved during the growing season through higher water use efficiency mitigates summer dryness and the heat wave impact. Land-atmosphere interactions and carbon dioxide fertilization together synergistically contribute to increased summer transpiration if rainfall does not change. This, in turn, alters the surface energy budget and decreases sensible heat flux, mitigating air temperature rise during extreme heat periods. This soil moisture feedback, which is mediated and enabled by the vegetation on a seasonal scale is a European example of the impacts the vegetation could have in an atmosphere enriched in carbon dioxide. We again use Earth System Models to systematically and statistically investigate the influence of the vegetation feedbacks on the global and regional changes of extreme temperatures. Physiological effects typically contribute to the increase of the annual daily maximum temperature with increasing atmospheric carbon dioxide concentration, accounting for around 15% of the full trend by the end of the XXIth Century. Except in Northern latitudes, the annual daily maximum temperature increases at a faster pace than the mean temperature, which is reinforced by vegetation feedbacks in Europe but reduced in North America. This work highlights the key role of vegetation in influencing future terrestrial hydrologic responses. Accurate representation of the response to higher atmospheric carbon dioxide concentration levels, and of the coupling between the carbon and water cycles are therefore critical to forecasting seasonal climate, water cycle dynamics and to enhance the accuracy of extreme event prediction under future climates in various regions of the globe.

The venting of anthropogenic CO₂ emissions into the atmosphere at increasing rates is probably influencing global warming and climate change. The Tangguh LNG development project in Papua, Indonesia will produce significant volumes of CO₂, which might be vented into the atmosphere. The LNG process will necessitate the separation of CO₂, estimated at 2.4 trillion cubic feet (TCF sc), from the natural gas reserves prior to liquefaction and shipping. This study screens and assesses the possible alternatives to atmospheric venting, and recommends subsurface CO₂ injection and sequestration/storage in saline aquifers. The study identifies specific subsurface locations for several Environmentally-Sustainable Sites for CO₂ Injection (ESSCI) in Bintuni Basin, where the Tangguh production fields are located. Alternatives to atmospheric venting of the estimated CO₂ volume at Tangguh include both non-geologic and geologic disposal options. Non-geologic options such as biosphere sinks (enhanced forest or agricultural growth), deep-ocean sinks (subsea dispersal), and direct commercial usage (e.g. use in beverage or fertilizer production, fire-retardant manufacturing) are impractical and of questionable impact in remote Papua, Indonesia. Several subsurface geological disposal options were investigated, but the most viable geologic disposal option for Tangguh CO₂ is injection into the downdip aquifer leg of the Roabiba Sandstone Formation hydrocarbon reservoir. Injected CO₂, at supercritical phase, is expected to migrate updip into the sealed structural traps at Vorwata or Wiriagar Deep, as the natural gas reserves are produced. A probabilistic ranking of data quality and quantity for five potential ESSCI reservoirs determined that the Middle Jurassic Roabiba Sandstone Formation has the highest likelihood of viable ESSCI sequestration/storage. A probabilistic ranking of data quality and quantity for eight ESSCI structural traps within the western flank of Bintuni Basin, determined that Vorwata, followed by Wiriagar Deep, are the most viable ESSCI structural traps at the Middle Jurassic reservoir level. Five potential ESSCI seals were evaluated and it was determined the best seal potential occurs in the Pre-Ayot Shales, directly overlying the Middle Jurassic reservoir at Vorwata. This unit is capable of holding a 3300 to 4660 foot (1006 to 1420 meter) CO₂_column. Seal integrity of the Pre-Ayot is very good because it is a relatively homogeneous deep-water shale that is composed primarily of ductile illite and kaolinite clays with a minor quartz and feldspar content. Sequence stratigraphy analysis suggests that the zone extends over the entire Vorwata three-way dip closure, with thickness between 17 feet (5 m) and 233 (71 m) feet. The maximum effective storage capacity of the Middle Jurassic reservoirs for each structure was calculated, taking into account irreducible water, trapped water, and trapped residual gas pore volumes. The Vorwata structure is capable of storing 19.3 TCFsc supercritical CO₂ at reservoir temperature and pressure. The Wiriagar Deep structure has potential storage capacity of 3.5 TCFsc, and Ubadari 2.8 TCFsc, at their respective reservoir temperatures and pressures. A ‘Rating Product Ranking’ was developed to quantify the results of the quality and quantity of four factors: Reservoir Data, Structure Data, Seal Data, and Storage Ratio. Each structure, and the respective top and lateral seal overlying the Middle Jurassic reservoirs, was evaluated. The net result was that Vorwata rated a 0.88 on a scale of zero to one, where 1.0 represents 100% confidence in ESSCI potential. Ubadari and Wiriagar Deep scored, respectively, 0.52 and a 0.45. Finally, the structures were evaluated for relative proximity to the proposed CO₂_source (i.e. the LNG plant location). With a weighted distance factor calculated with the Rating product for each potential injection site, Vorwata rated 0.88 on a scale of zero to one, Wiriagar scored 0.24, and Ubadari scored only 0.09. The Middle Jurassic ‘Roabiba Sandstone Formation reservoir’ at the Vorwata structure has the greatest potential as an ESSCI storage site. The Middle Jurassic ‘Aalenian Sandstone Formation reservoir’ at the Wiriagar Deep is the second-best potential ESSCI storage site. The subsurface ESSCI injection location proposed for the ‘Roabiba Sandstone Formation’ aquifer, 10 km southeast and down-dip from the known gas-water contact (GWC), is on the southeast Vorwata plunging anticlinal nose. An alternate potential ESSCI injection location proposed for the ‘Roabiba Sandstone Formation’ aquifer is 6 km south of and down-dip from the known gaswater contact (GWC) on Vorwata structure southern flank. A key issue was to determine the possible risk of fault re-activation from CO₂_ injection. NE-SW striking vertical faults have the highest risk of re-activation requiring an increase of over ~1460 psi (103 kg/cc) over hydrostatic at 14,000 ft TVDss (4267 m), for slippage to occur. The closest fault with a high risk of re- activation is 5 km northwest of the recommended ESSCI site location. Supercritical CO₂_ pressure is not expected to exceed the estimated pressure determined to cause fault re-activation. A 3D geological model of the Mesozoic interval was constructed over a large area of western Bintuni Basin. The model was constructed so as to preserve as much geological heterogeneity as possible yet still have a manageable number of active cells. Faults were incorporated into the model as strike-slip vertical fault surfaces (or indexed fault polygons) as a separate attribute. The geo-cellular model was built suitable for importation into a reservoir simulator (VIP), and a 25-year simulation run for natural gas production from the Vorwata Middle Jurassic reservoir, with concurrent CO₂ injection downdip into the Vorwata Middle Jurassic aquifer at the primary recommended ESSCI site location. The simulation verified the recommended location with the CO₂ slowly migrating into the Vorwata structural trap within the Middle Jurassic reservoir, and not compromising the hydrocarbon reserves or production. It is recommended that additional data be acquired such as conventional core, formation water samples, and specific logs such as dipole-sonic, multi-chambered dynamic formation testers (MDT), and mechanical rotary sidewall coring tools (MSCT). Lastly, several CO₂ monitoring methods and techniques are recommended for Tangguh to monitor CO₂ migration, pressures, and potential leakages. One such method is a vertical monitoring well at the recommended injection site. Other monitoring techniques include smart well completions, detection monitors at production wells with tracers injected prior to CO₂ injection. In addition, crosswell seismic surveys, electromagnetic methods, and electrical-resistance tomography techniques are suggested during the injection phase. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1174414 / Thesis (Ph.D.) -- University of Adelaide, Australian School of Petroleum, 2005

I investigated the utility of Br- as a chemical ionization mass spectrometry (CIMS) reagent ion for the detection and measurement of both atmospheric trace gases and aerosol species. The primary goals of this study are to obtain fast, very sensitive measurements of nitrate and sulfate and to ascertain if gas phase PAN and HNO3 could be measured simultaneously with the same chemical ionization scheme. Gas-phase measurements of PAN and nitric acid were conducted and the sensitivities of these measurements to temperature and relative humidity were determined. The potential for measuring aerosol composition by CIMS was assessed by comparison with PILS (particle-into-liquid sampler) measurements.

No description available.

This study has provided a landscape level estimate of leaf area index (LAI) and net primary productivity (NPP) for a temperate broadleaf forest ecosystem in south-central Indiana. The estimates were compared with the Moderate Resolution Imaging Spectroradiometer (MODIS) biophysical products LAI and NPP from both spatial and temporal perspectives. The evidence suggests that field-based estimates were poorly correlated with global MODIS data due to the simplifying assumptions of the MODIS global applicability, saturation problems of the red reflectance in highly vegetated areas, homogeneous land cover types of the study area, and other design assumptions of the field-based estimates. To improve the localized applicability of MODIS product algorithms, an empirical and localized algorithm combining in-situ measurements, the buildup of a localized biophysical model, and remote sensing-derived data were suggested for each local-scaled ecosystem. / Department of Natural Resources and Environmental Management

Symbiotic nitrogen fixation is the greatest potential input of nitrogen into terrestrial ecosystems. As a result, nitrogen fixation is critical to the functioning of the land carbon sink and its capacity to offset anthropogenic CO2 emissions and climate change. However, our understanding of the controls over nitrogen fixation rates and nitrogen fixing tree abundance is limited, resulting in paradoxes such as the relative absence of nitrogen fixing trees at high latitudes (where nitrogen is most limiting and it seems that nitrogen fixation should be most beneficial) and tropical forest nitrogen saturation, a mechanistically poor representation of nitrogen fixation in terrestrial biosphere models, and incomplete theory for variation in the successional trajectories of nitrogen fixing trees. This dissertation consists of four chapters that examine the drivers of symbiotic nitrogen fixation rates and the abundance of nitrogen fixing trees as they pertain to latitude, climate, and nitrogen fixation strategies. In chapter 1, I develop a method to measure coupled nitrogen fixation and plant carbon exchange in real-time, non-destructively, continuously, and at the whole plant scale. This permits a study of the controls of nitrogen fixation rates over timescales that range from seconds to months. In chapter 2 and 3, I apply the method developed in chapter 1 to determine the temperature response of nitrogen fixation rates and the timescales over which nitrogen fixation is regulated. For chapter 2 and 3, I grew nitrogen fixing tree species of tropical and temperate origin and representing the two types of nitrogen fixing symbioses (rhizobial and actinorhizal) across a 10 °C gradient of growing temperatures. In chapter 2, I show that nitrogen fixation depends on growing temperature and geographic origin and peaks at 30-38 °C, which is 5-13 °C higher than previous estimates based on other nitrogen fixing symbioses and 3-7 °C higher than net photosynthesis. These findings have direct implications for how nitrogen fixation is represented in terrestrial biosphere models and are in direct contrast to terrestrial biosphere model predictions of a decline in tropical nitrogen fixation with warming associated with climate change. In chapter 3, I show that nitrogen fixation takes 1-3 weeks to be down-regulated by 50% following an alleviation of nitrogen limitation, 1-5 weeks to be up-regulated by 50% following the initiation of nitrogen fixation when nitrogen becomes limiting, and up to 4 months for nitrogen fixation to start following a drastic reduction in soil nitrogen supply. Theory says that time-lags in regulating nitrogen fixation start becoming important for plant competition and losses of available nitrogen from ecosystems if they are between 1 day and 1 week. Thus, time-lags on the order of multiple weeks are a significant cost of a facultative nitrogen fixation strategy and resolve the tropical nitrogen forest nitrogen paradox characterized by high losses of available nitrogen at the ecosystem scale in spite of down-regulation of nitrogen fixation at the individual scale. In chapter 4, I show that nitrogen fixing tree abundance is bimodal in all regions of the contiguous United States except the Northeast and that founder effects can explain this pattern and the persistence of nitrogen fixing trees in old forests. Using theory, I show that founder effects are most probable at intermediate soil nitrogen supply, when nitrogen fixers have a high relative capacity to uptake available nitrogen, and when nitrogen fixing trees are facultative in their nitrogen fixation strategy. These chapters provide a new tool for studying nitrogen fixation, critical data for improving terrestrial biosphere models and our understanding of how nitrogen fixation and nitrogen cycling varies across latitude and how it will change with climate change, and new theory for the successional trajectories of nitrogen fixers.

Ultramafic rocks – that are usually located deep below the Earth's surface – are occasionally exhumed by the motion of tectonic plates. The massive chemical disequilibrium that exists between these exposed rocks and the surface waters and atmosphere leads to geologically rapid reactions that consume water and CO₂, binding them to form secondary hydrated/carbonated solid minerals that are found extensively in continental exposures (ophiolites) and at the seafloor near mid-ocean ridges. Pervasive fracturing and faulting in oceanic lithosphere generates pathways for fluids to access and react with rocks that are in some cases located down to depths of tens of kilometers. Over time, the large volumes of fluids and volatiles that are bound up in crustal and upper mantle rocks via such reactions are eventually subducted to extreme depths where subsequent fluid release can trigger melting, arc volcanism and seismic activity. In addition to their geophysical importance, these reactions are also considered to be critical for the survival of organisms in deep sea hydrothermal systems, and a potential source in the origin of life hypothesis. The natural transfer of atmospheric CO₂ to stable, solid carbonate minerals has, in recent years, motivated a large research effort towards investigating its potential as a large-scale carbon sequestration alternative. Understanding the geophysical impact and environmental potential of these reactions and their related processes requires knowledge of their basic physical and chemical behavior. Because of the difficulties of observing these processes in real-time, either experimentally or in the field, there has been a heavy reliance on hypothetical arguments that have been driven by observations in natural rocks. The observations paint a very complex picture – involving an interplay between reaction, fluid flow and fracturing – that is not easily explained by simple model descriptions. Although there has been increasing interest in modeling this class of problems in recent years, to date there remains a considerable gap between the theory and computational framework that is required for a consistent model description. A major theme in said models is their omission of poro-mechanical effects and complications arising from clogging of pore space with precipitating minerals. Both of these are necessary ingredients for a consistent model; however, they require a more complex description that is based on coupled multiphase continuum mechanics, reactive transport, and potentially brittle failure. Each of these components is a technical challenge in its own right, requiring development of novel theory and computation that integrates them in a suitable manner. The overall goals and themes of this thesis are aimed at closing this gap. To this end, I develop a modeling framework and computational tools that are capable of describing reactive flow in brittle media, with a specific focus on fluid-mineral reactions in near-surface ultramafic rock environments. The exposition of this framework is split into 3 separate chapters that build on one other in increments of complexity. Specifically, Chapter 1 presents a poromechanics-based description of coupled fluid flow, mass transfer and solid deformation for a simplified hydration reaction. This model is extended in Chapter 2 to incorporate cracking by adopting modern developments in computational fracture mechanics. Finally, in Chapter 3 I extend the set of reactions to support mixed H₂O-CO₂ fluids by leveraging recently developed tools in computational thermodynamics. Along the way I present a number of numerical model simulations that develop intuition and draw comparisons with natural observations, whilst remaining mindful of its limitations and areas for improvement. Overall, this work represents progress towards better understanding of physical and chemical feedbacks of reactive-brittle processes in the Earth's near-surface and the potential for large-scale carbon sequestration.

A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. 10 February, 2017. / Climate change due to the ever-increasing emission of anthropogenic greenhouse gases arising from the use of fossil fuels for power generation and most industrial processes is now a global challenge. It is therefore imperative to develop strategies or modern technologies that could mitigate the effect of global warming due to the emission of CO2. Carbon capture and storage (CCS) is a viable option that could ensure the sustainable use of cheap fossil fuels for energy generation with less CO2 emission. Amongst existing CCS technologies, absorption technology using monoethanolamine (MEA) is very mature and widely embraced globally. However, the absorption technology has a lot of challenges such as, low CO2 loading, high energy requirement for solvent regeneration, corrosive nature etc. On this note, the adsorption technology using solid sorbents is being considered for CO2 capture due to its competitive advantages such as flexibility, low energy requirement for sorbent regeneration, non-corrosive nature etc. On the other hand, adsorbents have a very vital role to play in adsorption technology and there is need to understand the behaviour of adsorbents for CO2 capture under different operating conditions in order to adapt them for wider applications. On this note, the study contained in this dissertation investigated the adsorption behaviour of a novel polymer-based adsorbent (polyaspartamide) during post-combustion CO2 capture using experimental study and mathematical modelling approach. Polyaspartamide is an amine-rich polymer widely used in drug delivery. In addition, its rich amine content increases its affinity for CO2. Its porosity, thermal stability and large surface area make it a promising material for CO2 capture. In view of this, polyaspartamide was used as the adsorbent for post-combustion CO2 capture in this study. This dissertation investigated the kinetic behaviour, the diffusion mechanism and rate limiting steps (mass transfer limitation) controlling the CO2 adsorption behaviour of this adsorbent. Furthermore, effect of impurities such as moisture and other operating variables such as temperature, pressure, inlet gas flow rate etc. on the CO2 adsorption behaviour of polyaspartamide was also investigated. Existing mathematical models were used to understand the kinetics and diffusion limitation of this adsorbent during CO2 capture. Popularly used gas-solid adsorption models namely; Bohart- Adams and Thomas model were applied in describing the breakthrough curves in order to ascertain the equilibrium concentration and breakthrough time for CO2 to be adsorbed onto polyaspartamide. Lagergren’s pseudo 1st and 2nd order models as well as the Avrami kinetic models were used to describe the kinetic behaviour of polyaspartamide during post-combustion CO2 capture. Parameter estimations needed for the design and optimization of a CO2 adsorption system using polyaspartamide were obtained and presented in this study. The Boyd’s film diffusion model comprising of the interparticle and intra-particle diffusion models were used to investigate the effect of mass transfer limitations during the adsorption of CO2 onto polyaspartamide. Data obtained from continuous CO2 adsorption experiments were used to validate the models in this study. The experiments were conducted using a laboratory-sized packed-bed adsorption column at isothermal conditions. The packed bed was attached to an ABB CO2 analyser (model: ABB-AO2020) where concentrations of CO2 at various operating conditions were obtained. The results obtained in this study show that temperature, pressure and gas flow rate had an effect on the adsorption behaviour of polyaspartamide (PAA) during CO2 capture. Polyaspartamide exhibited a CO2 capture efficiency of 97.62 % at the lowest temperature of 303 K and pressure of 2 bar. The amount of CO2 adsorbed on polyaspartamide increased as the operating pressure increased and a decrease in the adsorption temperature resulted in increased amount of CO2 adsorbed by polyaspartamide. The amounts of CO2 adsorbed on polyaspartamide were 5.9, 4.8 and 4.1 mol CO2/kg adsorbent for adsorption temperatures of 303, 318 and 333 K, respectively. The maximum amount of CO2 adsorbed by polyaspartamide at different flow rates of 1.0, 1.5 and 2.5 ml/s of the feed gas were 7.84, 6.5 and 5.9 mmol CO2/g of adsorbent. This shows that higher flow rates resulted in decreased amount of CO2 adsorbed by polyaspartamide because of low residence time which eventually resulted in poor mass transfer between the adsorbent and adsorbate. Under dry conditions, the adsorption capacity of polyaspartamide was 365.4 mg CO2/g adsorbent and 354.1 mgCO2/g adsorbent under wet conditions. Therefore, the presence of moisture had a negligible effect on the adsorption behaviour of polyaspartamide. This is very common with most amine-rich polymer-based adsorbents. This could be attributed to the fact that CO2 reacts with moisture to form carbonic acid, thereby enhancing the CO2 adsorption capacity of the material. In conclusion, this study confirmed that the adsorption of CO2 onto polyaspartamide is favoured at low temperatures and high operating pressures. The adsorption of CO2 onto polyaspartamide was governed by film diffusion according to the outcome of the Boyd’s film diffusion model. It was also confirmed that intra-particle diffusion was the rate-limiting step controlling the adsorption of CO2 onto polyaspartamide. According to the results from the kinetic study, it can be inferred that lower temperatures had an incremental effect on the kinetic behaviour of polyaspartamide, external mass transfer governed the CO2 adsorption process and the adsorption of CO2 onto polyaspartamide was confirmed to be a physicochemical process (both physisorption and chemisorption). / MT2017

The objective of this PhD thesis is to create a Unit Commitment and Economic Dispatch (UCED) modelling tool that can used to simulate the deterministic performance of a power system with thermal and renewable generators and energy storage technologies. The model was formulated using mixed integer programing (MIP) on GAMS interface. A robust commercial solver by IBM (CPLEX) is used as solver. Emphasis on the development of the tool has been given on the following aspects. a) Technical impacts of Variable Renewable Energy (VRE) integration. The UCED model developed in this thesis is a high resolution short-term dispatch model. It captures the variability of VRE power on the intra-hour level. In addition the model considers a large number of important real world, system, unit and policy constraints. Detailed representation of a power system allows for a realistic estimation of maximum penetration levels of VRE and the related technical impacts like cycling of generators (part-loading and number of start-ups). b) CO2 emissions. High levels of VRE penetration can potentially increase consumption of fuel in thermal units per unit of electricity produced due to increased thermal cycling. The dispatch of units in the UCED model is based on minimizing system wide operational costs the most important of those being fuel, start-up costs and the cost of carbon. Fuel consumption is calculated using technical data from Input/Output curves of individual generators. The start-up cost is calculated based on times the generator units have been off and the energy requirement to bring the unit back to hot state. Thus dynamic changes on fuel consumption can be captured and reported. c) Technical solutions to facilitate VRE integration. VRE penetration can be facilitated if appropriate solutions are implemented. Energy storage is an effective way to reduce the impact of RE variability. The UCED model includes an integrated Mixed Integer Linear (MILP) compressed air energy storage (CAES) simulation sub-model. Unlike existing CAES models, the new “Thermo-Economic” (TE) CAES model developed in this thesis uses technical data from major CAES manufacturers to model the dynamic effect of cavern pressure on both the compression and expansion sides during CAES operation. More specifically the TE model takes into account that a) a compressor discharges at a pressure equal to the back-pressure developed in the cavern at each moment, b) the speed of charging can be regulated through inlet guide vanes; higher charging speed can take place at the expense of additional power consumption, c) the maximum power output during expansion can be limited by the levels of cavern pressure; there is a threshold pressure level below which the maximum output decreases linearly with pressure. Since it uses actual power curves to simulate CAES operation, the TE model can be assumed to be more accurate than conventional Fixed Parameter (FP) models that don’t model dynamic effects of cavern pressure on CAES operation. The TE model in this thesis is compared with conventional FP models using historical market prices from the Irish electricity market. The comparison was based on the ability of a CAES unit to arbitrage energy for making profit in the Irish electricity market. More specifically a “Base” scenario was created that included the operation of a 270MW CAES unit with technical characteristics obtained from a major CAES manufacturer and assumed discharge time of 13hr. Various sensitivities on discharge time, natural gas prices and system marginal prices (SMPs) were modeled. An additional scenario was created to show the benefit on CAES profitability if the unit participated in both the energy and ancillary services markets. All scenarios were modeled using both the TE and FP CAES models. The results showed that the most realistic TE model returns around 15% less profitability across more scenarios. The reduction in profitability grows to around 30% when the cavern volume (discharge time) is reduced to half (6 hours). The latter is related to the sensitivity of the TE model on cavern pressure that is being built faster when the volume is reduced. A CAES unit won’t get a positive net present value (NPV) in Ireland under any scenario unless SMPs are greatly increased. Thus, it was shown that that existing FP CAES models overestimate CAES profitability. More accurate models need to be used to estimate CAES profitability in deregulated markets. Additionally, it might deem necessary to create additional markets for energy storage units and increase the possible revenue sources and magnitude to facilitate an increase of storage capacity worldwide. The second step of analysis involved the integration of the CAES and UCED models. The UCED model developed in this thesis was validated and applied using data from the Irish grid, a power system with more than 50 thermal generators. A vast of existent data was used to create a mathematical model of the Irish system. Such data include technical specifications and variables of thermal generators, maintenance schedules and historical solar, wind and demand data. The validation exercise was deemed successful since the UCED model simulated utilization factors of 45 out of 52 generators with an absolute difference between modeled and actual results on utilization factors of less than 6% (the absolute differences are called Delta in this thesis). In addition the results of validation exercise were compared with the results of a similar exercise where PLEXOS was the modelling tool and it was found that the results of the two models were similar for the vast majority of generators. More specifically, the PLEXOS model results showed higher deltas for the coal-fired generators compared to the UCED model. On the other hand the UCED model, reported higher delta values for peat-fired generators. The results of the PLEXOS model were slightly better for the gas-fired generators while both models reported deltas nearly zero for all oil and distillate-fired generators. Finally the model was applied to study the benefits of energy storage in Ireland in 2020 when wind penetration is expected to reach 37% of total demand. The analysis involved the development of two groups of 3 scenarios each. In the first group the main scenario also called the “Reference” was used to simulate the short-term unit (30 min step) commitment within the Irish system without storage. The results of the reference scenario were compared with two additional scenarios that assumed the existence of one 270MW CAES unit in Northern Ireland by 2020 (again the first scenario involved the TE and the second the FP CAES model). The results showed –when using the TE model- that the inclusion of one 270MW CAES unit in AI can help reduce wind curtailment by 88GWh, CO2 emissions by 150,000 tonnes and system costs by € 6 million per year. If an FP model had been used instead the reductions would be: wind curtailment by 108GWh, CO2 emissions by 270,000 tonnes and annual system costs by €13 million. Two main conclusions can be obtained from the specific set of results. The first conclusion is that storage units have a financial benefit over the whole system. Thus, when a CAES unit operates to minimize the costs of the whole system can incur substantially more benefits compared to if the CAES unit operated to maximize the individual unit’s profits as in the case presented earlier. The benefits of storage over the whole system should be accounted to make policy decisions and create incentives for investors to increase energy storage capacity in national grids. The second important conclusion is that existing CAES FP models overestimate the ability of a CAES unit to facilitate VRE penetration. More accurate TE models should be used to assess a unit’s capability to increase system flexibility. A second group of scenarios was created to simulate the benefit of CAES at even higher VRE penetration levels. In the second group the “Reference” scenario again, assumed no storage however, wind production was increased by 25%. Again the “Reference” was compared with two additional scenarios that assumed integration of 3x270MW=810MW of storage capacity in AI (one scenario used the TE model and the other the FP). The results for the TE model show that each of the 3 CAES units reduces wind curtailment by 188,000MWh, total system costs by €29 million and CO2 emissions by 180,000 tonnes. The same reductions for the FP model are 217,000MWh of wind curtailment, €25.6 million on total system costs and 180,000 tonnes of CO2. Thus, the results of the second group of scenarios show that as the installed capacity of both CAES and wind increases in Ireland a) the system-wide benefits of CAES increase and b) the differences on results between the TE and FP models become much smaller.

Recent studies of the environmental Kuznets curve raise questions regarding the relationship between environmental indicators and GDP and the fundamental reasons that explain this relationship. In response, this thesis presents one-sector and two-sector models to analyze the alternative causal relationships between an environmental indicator and GDP at different stages of economic development. These models analyze how economic scale, technology, preferences, and economic structure influence the causality and shape of the relationship. These theoretical studies are followed by two empirical studies. The first tests the causal relationship between CO2 emissions and GDP in Canadian manufacturing industries. The second explores several factors as the fundamental causes that influence the CO2 emissions in the same industries. Factors, such as economic scale, preferences, technological progress, structural change, and energy input, are found to be crucial in the determination of CO2 emissions. The empirical results are positive, but there are data limitations. The empirical studies can be re-evaluated as more data becomes available.