Three-dimensional finite element modelling of stack pollutant emissions

In this paper we propose a finite element method approach formodelling the air quality in a local scale over complex terrain. The area of interest is up to tens of kilometres and it includes pollutant sources. The proposed methodology involves the generation of an adaptive tetrahedral mesh, the computation of an ambient wind field, the inclusion of the plume rise effect in the wind field, and the simulation of transport and reaction of pollutants. The methodology is used to simulate a fictitious pollution episode in La Palma island (Canary Island, Spain).Peer ReviewedPostprint (published version

Mercury emissions from coal-fired power plants : a local or a global pollutant?

This dissertation tests whether or not mercury emissions from electric power plants are not a significant contributor to mercury measurements in rainfall and argues that the current United States (U.S.) Environmental Protection Agency (EPA) proposed regulatory scheme for controlling mercury from electric power plants, the Clean Air Mercury Rule (CAMR), is an effective regulatory mechanism by using a number of ordinary least square (OLS) and spatial regression models. Two dependent variables are tested, mercury concentration (the average mercury concentration measured in rainfall in nanograms per liter, ng/L) and mercury deposition (the total annual mercury falling at each measurement site in nanograms per square meter, ng/m 2 ), with mercury concentration determined to be the more valid dependent variable. The source for the mercury concentration and deposition data is the Mercury Deposition Network (MDN), part of the National Atmospheric Deposition Program (NADP), with the data obtained for between 46 and 75 sites operating from 2001 through 2005. Independent variables include: (1) emissions to the air from power plants, (2) emissions to the air from other industrial sites, (3) emissions to the land from the mining industry, (4) population as a proxy variable for vehicle emissions, (5) burned area from wildfires, (6) precipitation and (7) dummy variables for year and EPA region. Data for independent variables 1, 2, and 3 were obtained from the EPA\u27s Toxic Release Inventory (TRI) program. Population for each county in the U.S. was obtained from the Census Bureau, and wildfire data was obtained from the U.S. Department of Agriculture satellite based fire mapping system, Moderate Resolution Imaging Spectroradiometer (MODIS). Microsoft Access was utilized to summarize and total the independent variables within a variable radius of the MDN measurement sites, ranging from 25 to 500 miles. The software tool GeoDa 0.95i, made available by the University of Illinois, was used to perform the OLS, spatial lag, and spatial error regressions. After changing the functional form of the equation to a log-linear model (using the natural log form of the dependent variable and the linear forms of the independent variables) to deal with heteroskedasticity, the results indicate a strong spatial component to the model. Other than precipitation, the most significant predictor of mercury concentration is fire area burned between 50 and 75 miles of the MDN measurement site (z = 3.08, p \u3c 0.01). Other positive and significant predictors in this model include all other industry emissions between 25 and 50 miles (z = 2.71, p \u3c 0.01), fire area burned between 75 and 100 miles (z = 2.64, p \u3c 0.01), population within 25 miles (z = 1.91, p \u3c 0.10), utility emissions between 25 and 50 miles (z = 1.88, p \u3c 0.10), and population between 50 and 75 miles (z = 1.71, p \u3c 0.10). Two of the independent variables are significant and have negative coefficients. These are utility emissions between 50 and 75 miles (z = -2.49, p \u3c 0.05), and fire area burned between 25 and 50 miles (z = -2.12, p \u3c 0.05). Several conclusions are drawn from this research, including: (1) that utility mercury emissions are marginally significant as a predictor of mercury concentration in rainfall, but only at distances under 50 miles from the measurement point, (2) that there is no known best method for controlling mercury emissions from all utility plants at high levels of collection efficiency (90 percent) although research is ongoing, and (3) that the cap-and-trade provisions of CAMR would be unlikely to result in the creation of new or the exacerbation of existing mercury hotspots. Given that the U.S. District of Columbia Circuit Court of Appeals set aside the CAMR rule in early 2008, two policy prescriptions are provided. One approach makes an economic argument for revising the cap-and-trade provisions of CAMR to include transfer coefficients. The second suggestion involves a less complicated and mor

End-of-life management of solid oxide fuel cells

This thesis reports on research undertaken to investigate the end-of-life management of solid oxide fuel cells (SOFC), through the definition of a framework and the development of a multicriteria evaluation methodology which together support comparison of alternative end-of-life scenarios. The primary objective of this research is to develop an understanding of the challenges and opportunities arising during the end-of-life phase of the technology, such that any conflicts with end-of-life requirements might be addressed and opportunities for optimising the end-of-life phase fully exploited. The research contributions can be considered in four principal parts. The first part comprises a review of SOFC technology and its place in future sustainable energy scenarios, alongside a review of a growing body of legislation which embodies concepts such as Extended Producer Responsibility and Integrated Product Policy. When considered in the context of the life cycle assessment literature, which clearly points to a lack of knowledge regarding the end-of-life phase of the SOFC life cycle, this review concludes that the requirement for effective end-of life management of SOFC products is an essential consideration prior to the widespread adoption of commercial products. The second part of the research defines a framework for end-of-life management of SOFCs, which supports clarification of the challenges presented by the SOFC stack waste stream, as well as identifying a systematic approach for addressing these challenges through the development of alternative end-of-life management scenarios. The framework identifies a need to evaluate the effectiveness of these end-of-life scenarios according to three performance criteria: legislative compliance; environmental impact; and economic impact. The third part of the research is concerned with the development of a multi-criteria evaluation methodology, which combines conventional evaluation methods such as life cycle assessment and cost-benefit analysis, with a novel risk assessment tool for evaluating compliance with current and future legislation. A decision support tool builds on existing multi-criteria decision making methods to provide a comparative performance indicator for identification of an end of-life scenario demonstrating low risk of non-compliance with future legislation; low environmental impact; and a low cost-benefit ratio. Finally, the validity of the framework for end-of-life management is tested through the completion of two case studies. These case studies demonstrate the flexibility of the framework in supporting a reactive end-of-life management approach, whereby end-of-life management is constrained by characteristics of the product design, and a proactive approach, whereby the impact of design modification on the end-of-life phase is explored. In summary, the research clearly highlights the significance of the end-of-life stage of the SOFC life cycle. On the one hand, failure to manage end-of-life products effectively risks undermining the environmental credentials of the technology and is likely to lead to the loss of a high-value, resource-rich material stream. On the other hand, the early consideration of aspects identified in the research, especially while opportunities remain to influence final product design, represents a real opportunity for optimising the end-of-life management of SOFC products in such a way as to fully realise their potential as a clean and efficient power generation solution for the future

Intercontinental transport of nitrogen oxide pollution plumes

We describe the first satellite observation of intercontinental transport of nitrogen oxides emitted by power plants, verified by simulations with a particle tracer model. The analysis of such episodes shows that anthropogenic NO_x plumes may influence the atmospheric chemistry thousands of kilometers away from its origin, as well as the ocean they traverse due to nitrogen fertilization. This kind of monitoring became possible by applying an improved algorithm to extract the tropospheric fraction of NO₂ from the spectral data coming from the GOME instrument.<br> <br> As an example we show the observation of NO₂ in the time period 4--14 May, 1998, from the South African Plateau to Australia which was possible due to favourable weather conditions during that time period which availed the satellite measurement. This episode was also simulated with the Lagrangian particle dispersion model FLEXPART which uses NO_x emissions taken from an inventory for industrial emissions in South Africa and is driven with analyses from the European Centre for Medium-Range Weather Forecasts. Additionally lightning emissions were taken into account by utilizing Lightning Imaging Sensor data. Lightning was found to contribute probably not more than 25% of the resulting concentrations. Both, the measured and simulated emission plume show matching patterns while traversing the Indian Ocean to Australia and show great resemblance to the aerosol and CO₂ transport observed by Piketh et al. (2000)

A multi-output AC/DC energy conversion system for grid integration of bioelectrochemical power-to-gas storage

Bioelectrochemical Energy Storage (BES) systems are able to convert electrical power into biomethane and resemble the structure of fuel cells, as several low voltage modules are connected in series creating stacks, which are in turn parallelized to reach the desired power. However, in this case, BES modules act as gas energy storage/load that generate storable biomethane as a product. This paper proposes a multi-output multilevel AC/DC power conversion system for BES stacks. The proposed topology has a structure like a modular multi-level converter (MMC) wherein BES stacks are connected to submodules and only a capacitor exists in the DC link. Therefore, it needs only a small filter on the AC side while voltages and powers of all BES stacks are simultaneously under control. A mathematical model of the proposed power conversion system is presented, and then a control scheme has been designed in order to achieve the following goals: 1) simultaneous control of all output voltages; 2) independent control of the active and reactive power interchanged with the grid; 3) control the quality of grid current; 4) suppression of circulating current. For verification of the system performance, OPAL-RT real-time simulation results that are obtained from a 10-kW BES system containing 18 stacks are presented.© 2022 The Authors. Published by Elsevier Ltd, under a Creative Commons license https://creativecommons.org/licenses/by/4.0/fi=vertaisarvioitu|en=peerReviewed

Energy efficiency opportunities in the service plants of cast iron foundries in Italy

Though in a foundry most of the energy is used in the process plants and particularly in energizing furnaces, service plants require absolutely large amounts of energy, above all as electricity. The most energy consuming service is compressed air preparation, but large amounts are due to lighting, HVAC, pumps and fans. These energy users are common to most of industrial branches with different weights both in absolute and relative terms. This paper reports on the experience of some energy audits carried out in five Italian cast iron foundries allowing to identify the relative importance of different services in this industrial branch. The analysis is based on real data measured during the audits. Energy saving actions were then conceived, comparing the results of new technologies applied in some factory sectors and the energy usage of the previous equipment

A chronology of global air quality

Air pollution has been recognized as a threat to human health since the time of Hippocrates, ca 400 BC. Successive written accounts of air pollution occur in different countries through the following two millennia until measurements, from the eighteenth century onwards, show the growing scale of poor air quality in urban centres and close to industry, and the chemical characteristics of the gases and particulate matter. The industrial revolution accelerated both the magnitude of emissions of the primary pollutants and the geographical spread of contributing countries as highly polluted cities became the defining issue, culminating with the great smog of London in 1952. Europe and North America dominated emissions and suffered the majority of adverse effects until the latter decades of the twentieth century, by which time the transboundary issues of acid rain, forest decline and ground-level ozone became the main environmental and political air quality issues. As controls on emissions of sulfur and nitrogen oxides (SO2 and NOx) began to take effect in Europe and North America, emissions in East and South Asia grew strongly and dominated global emissions by the early years of the twenty-first century. The effects of air quality on human health had also returned to the top of the priorities by 2000 as new epidemiological evidence emerged. By this time, extensive networks of surface measurements and satellite remote sensing provided global measurements of both primary and secondary pollutants. Global emissions of SO2 and NOx peaked, respectively, in ca 1990 and 2018 and have since declined to 2020 as a result of widespread emission controls. By contrast, with a lack of actions to abate ammonia, global emissions have continued to grow