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Industrial boilers that produce steam or electric power represent a large capital investment as well as a crucial facility for overall plant operations. In real applications, the operation of the superheater for producing high-pressure, high-temperature steam may result in problems frequently caused by ruptured superheater tubes. To make the boiler more efficient, less emission and less prone to tube rupture problems, it is important to understand the combustion and thermal flow behaviors inside the boiler. This study performs a detailed simulation of combustion and thermal flow behaviors inside an industrial boiler. The simulations are conducted using the commercial CFD package FLUENT. The 3-D Navier-Stokes equations and five species transport equations are solved with the eddy-breakup combustion model. Calculation of NOx is performed after obtaining a converged flow, thermal and combustion solution. The results provide insight into the detailed thermal-flow and combustion in the boiler and showing possible reasons for superheater rupture

A significant number of consumer goods and building materials act as emission sources of flame retardants (FRs) in the indoor environment. As a result, FRs have become ubiquitous indoors raising concerns about human exposure and possible health implications. Once released indoors, FRs can escape to the outdoors where they can persist, be transported over long distances and present a threat to the environment. Despite the increasing number of studies reporting the occurrence of FRs in the indoor environment, the understanding of i) how and to what extent these chemicals are released from indoor sources, and ii) their subsequent fate indoors remains limited. The overarching objective of this thesis was to improve this understanding by assessing the indoor emissions and fate of FRs using a combination of multimedia modelling strategies and experimental/empirical approaches. Paper I identifies a number of knowledge gaps and limitations regarding indoor emissions and fate of FRs and the available modelling approaches. These include a limited understanding of the key emission mechanisms for low volatility FRs, uncertainties regarding indoor air/surface partitioning, poor characterization of dust and film dynamics and a significant lack of knowledge regarding indoor reaction/degradation processes. In Paper II we highlighted the serious scarcity in physicochemical property data for the alternative FRs and demonstrated the applicability of a simple QSPR technique for selecting reliable property estimates for chemical assessments. A modelling fate assessment indicated a strong partitioning to indoor surfaces and dust for most of the alternative FRs. Indications for POP (persistent organic pollutant)-like persistence and LRT (long-range transport) and bioaccumulative potential in the outdoor environment were also identified for many alternative FRs. Using an inverse modelling approach in Paper III we estimated 2 to 3 orders of magnitude higher emissions of organophosphate FRs (0.52 and 0.32 ng.h-1) than brominated FRs (0.083 μg.h-1 and 0.41 μg.h-1) in Norwegian households. An emission-to-dust signal was also identified for organophosphate FRs suggesting that direct migration to dust may be a key fate process indoors. No evidence of a direct source-to-dust transfer mechanism was seen in Paper IV where the chemical transfer between a product treated with an organophosphate FR and dust in direct contact was experimentally investigated. It was concluded though that direct contact between an FR source and dust can result in contamination hotspots indoors. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.</p>

This work is devoted to generate knowledge and high quality experimental data of catalytic combustion at operational gas turbine conditions. The initial task of the thesis work was to design and construct a high pressure combustion test facility, where the catalytic combustion experiments can be performed at real gas turbine conditions. With this in mind, a highly advanced combustion test facility has been designed, constructed and tested. This test facility is capable of simulating combustion conditions relevant to a wide range of operating gas turbine conditions and different kinds of fuel gases. The shape of the combustor (test section) is similar to a “can” type gas turbine combustor, but with significant differences in its type of operation. The test combustor is expected to operate at near adiabatic combustion conditions and there will be no additions of cooling, dilution or secondary supply of air into the combustion process. The geometry of the combustor consists of three main zones such as air/fuel mixing zone, catalytic reaction zone and downstream gas phase reaction zone with no difference of the mass flow at inlet and exit. The maximum capacity of the test facility is 100 kW (fuel power) and the maximum air flow rate is 100g/s. The significant features of the test facility are counted as its operational pressure range (1 – 35 atm), air inlet temperatures (100 – 650 °C), fuel flexibility (LHV 4 - 40 MJ/m3) and air humidity (0 – 30% kg/kg of air). Given these features, combustion could be performed at any desired pressure up to 35 bars while controlling other parameters independently. Fuel flexibility of the applications was also taken into consideration in the design phase and proper measures have been taken in order to utilize two types of targeted fuels, methane and gasified biomass. Experimental results presented in this thesis are the operational performances of highly active precious metal catalysts (also called as ignition catalysts) and combinations of precious metal, perovskites and hexaaluminate catalysts (also called as fully catalytic configuration). Experiments were performed on different catalytic combustor configurations of various types of catalysts with methane and simulated gasified biomass over the full range of pressure. The types of catalysts considered on the combustor configurations are palladium on alumina (Pd/AL2O3), palladium lanthanum hexaaluminate (PdLaAl11O19), platinum on alumina (Pt/AL2O3),and palladium:platinum bi-metal on alumina (Pd:Pt/AL2O3). The influence of pressure, inlet temperature, flow velocity and air fuel ratio on the ignition, combustion stability and emission generation on the catalytic system were investigated and presented. Combustion catalysts were developed and provided mainly by the project partner, the Division of Chemical Technology, KTH. Division of Chemical Reaction Technology, KTH and Istituto di Ricerche sulla Combustione (CNR) Italy were also collaborated with some of the experimental investigations by providing specific types of catalysts developed by them for the specific conditions of gas turbine requirements. / <p>QC 20131125</p>

<p>This dissertation studies capacity investments in energy sources, with a focus on renewable technologies, such as solar and wind energy. We develop analytical models to provide insights for policymakers and use real data from the state of Texas to corroborate our findings. </p><p>We first take a strategic perspective and focus on electricity pricing policies. Specifically, we investigate the capacity investments of a utility firm in renewable and conventional energy sources under flat and peak pricing policies. We consider generation patterns and intermittency of solar and wind energy in relation to the electricity demand throughout a day. We find that flat pricing leads to a higher investment level for solar energy and it can still lead to more investments in wind energy if considerable amount of wind energy is generated throughout the day.</p><p>In the second essay, we complement the first one by focusing on the problem of matching supply with demand in every operating period (e.g., every five minutes) from the perspective of a utility firm. We study the interaction between renewable and conventional sources with different levels of operational flexibility, i.e., the possibility</p><p>of quickly ramping energy output up or down. We show that operational flexibility determines these interactions: renewable and inflexible sources (e.g., nuclear energy) are substitutes, whereas renewable and flexible sources (e.g., natural gas) are complements. </p><p>In the final essay, rather than the capacity investments of the utility firms, we focus on the capacity investments of households in rooftop solar panels. We investigate whether or not these investments may cause a utility death spiral effect, which is a vicious circle of increased solar adoption and higher electricity prices. We observe that the current rate-of-return regulation may lead to a death spiral for utility firms. We show that one way to reverse the spiral effect is to allow the utility firms to maximize their profits by determining electricity prices.</p> / Dissertation

The purpose of this paper is to investigate the causal relationship between GDP and renewable energy. In order to find a significant relationship, a literature review is first analyzed in order to select the right methods for analysis. A simple model of GDP determination is chosen to inspect the relationship of society and sustainable energy production, as well as account for externalities on the environment by including emissions as an explanatory variable. The UN framework of sustainable development is used to highlight the need for action in the renewables energy sector. Concepts of emergy and transformity are employed to give a better understanding on the nature of energy and its crucial importance to economic development. The validity of these affirmations in terms of the nexus of causality will be done through economic methods: critical tests such as Pedroni cointegration, Granger causality and others will be used. These findings lead to useful policy implications for countries attempting to promote renewable energy and energy development. Unidirectional causality running from GDP growth to growth in the percentage of renewable energy consumption is found.

Since the 1990s, advocates of policy to prevent catastrophic climate change have been divided over the appropriate economic instruments to curb CO2 emissions-carbon taxes or schemes of emission trading. Barack Obama claimed that policies implemented during his presidency set in motion irreversible trends toward a clean-energy economy, with the years 2008-2015 given as evidence of decoupling between CO2 emissions and economic growth. This is despite California being the only state in the USA that has implemented a specific policy to curb emissions, a cap-and-trade scheme in place since 2013. To assess Obama's claims and the effectiveness of policies to reduce CO2 emissions, we analyze national and state-level data from the USA over the period 1990-2015. We find: (a) annual changes in emissions strongly correlated with the growth conditions of the economy; (b) no evidence for decoupling; and (c) a trajectory of CO2 emissions in California which does not at all support the claim that the cap-and-trade system implemented there has reduced CO2 emissions. / Series: SRE - Discussion Papers

Sustained resonance in a linear oscillator is achievable with a drive whose constant frequency matches the resonant frequency of the oscillator. In oscillators with nonlinear restoring forces, i.e., Dung-type oscillators, resonant frequency changes with amplitude, so a constant frequency drive generates a beat oscillation instead of sustained resonance. Dung-type oscillators can be driven into sustained resonance, called autoresonance (AR), when drive frequency is swept in time to match the changing resonant frequency of the oscillator. It is found that near-optimal drive linear sweep rates for autoresonance can be estimated from the beat oscillation resulting from constant frequency excitation. Specically, a least squares estimate of the slope of the Teager-Kaiser instantaneous frequency versus time plot for the rising half-cycle of the beat response to a stationary drive provides a near-optimal estimate of the linear drive sweep rate that sustains resonance in the pendulum, Dung and Dung-Van der Pol oscillators. These predictions are confirmed with model-based numerical simulations. A closed-form approximation to the AM-FM nonlinear resonance beat response of a Dung oscillator driven at its low-amplitude oscillator frequency is obtained from a solution to an associated Mathieu equation. AR time responses are found to evolve along a Mathieu equation primary resonance stability boundary. AR breakdown occurs at sweep rates just past optimal and map to a single stable point just off the Mathieu equation primary resonance stability boundary. Optimal AR sweep rates produce oscillating phase dierences with extrema near 90 degrees, allowing extended time in resonance. AR breakdown occurs when phase difference equals 180 degrees. Nonlinear resonance of the van der Pol type may play a role in the extraordinary sensitivity of the human ear. / The mechanism for maintaining the cochlear amplifier at its critical point is currently unknown. The possibility of open-loop control of cochlear operating point, maintaining criticality on average through periodically varying damping (super-regeneration) motivates a study of spontaneous otoacoustic emission (SOAE) amplitude modulation on a short (msec) time scale. An example of periodic amplitude modulation within a wide filter bandwidth is found that appears to be a beat oscillation of two SOAEs. / by Carey Witkov. / Thesis (Ph.D.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web.