Optimization and Control of Power Flow in Distribution Networks

Climate change is arguably the most critical issue facing our generation and the next. As we move towards a sustainable future, the grid is rapidly evolving with the integration of more and more renewable energy resources and the emergence of electric vehicles. In particular, large scale adoption of residential and commercial solar photovoltaics (PV) plants is completely changing the traditional slowly-varying unidirectional power flow nature of distribution systems. High share of intermittent renewables pose several technical challenges, including voltage and frequency control. But along with these challenges, renewable generators also bring with them millions of new DC-AC inverter controllers each year. These fast power electronic devices can provide an unprecedented opportunity to increase energy efficiency and improve power quality, if combined with well-designed inverter control algorithms. The main goal of this dissertation is to develop scalable power flow optimization and control methods that achieve system-wide efficiency, reliability, and robustness for power distribution networks of future with high penetration of distributed inverter-based renewable generators.

Proposed solutions to power flow control problems in the literature range from fully centralized to fully local ones. In this thesis, we will focus on the two ends of this spectrum. In the first half of this thesis (chapters 2 and 3), we seek optimal solutions to voltage control problems provided a centralized architecture with complete information. These solutions are particularly important for better understanding the overall system behavior and can serve as a benchmark to compare the performance of other control methods against. To this end, we first propose a branch flow model (BFM) for the analysis and optimization of radial and meshed networks. This model leads to a new approach to solve optimal power flow (OPF) problems using a two step relaxation procedure, which has proven to be both reliable and computationally efficient in dealing with the non-convexity of power flow equations in radial and weakly-meshed distribution networks. We will then apply the results to fast time- scale inverter var control problem and evaluate the performance on real-world circuits in Southern California Edison’s service territory.

The second half (chapters 4 and 5), however, is dedicated to study local control approaches, as they are the only options available for immediate implementation on today’s distribution networks that lack sufficient monitoring and communication infrastructure. In particular, we will follow a reverse and forward engineering approach to study the recently proposed piecewise linear volt/var control curves. It is the aim of this dissertation to tackle some key problems in these two areas and contribute by providing rigorous theoretical basis for future work.

On the Distribution and Fishery Potential of the Japanese Red Crab Chaceon granulatus in the Palauan Archipelago, Western Caroline Islands

A deep-water trapping survey in the Palauan archipelago, Western Caroline Islands, has revealed an abundance of the Japanese red crab, Chaceon granulatus. The recorded depth range (250-900 m) is similar to that of other geryonids, but the large numbers of females caught below 700 m is atypical. Mean yields in excess of 5 kg crabs plus 1 kg shrimp, Heterocarpus laevigatus, by-catch per trap-night were attainable at optimum depths. Chaceon granulatus is apparently a very large geryonid, with maximum weights of 2.02 kg and 1.51 kg recorded for male and female specimens, respectively. A range of body colors was observed: Orange-red shades appear to dominate the deeper waters (below 500 m) while yellow-tan colors are more abundant in the upper reaches. Preliminary evidence suggests that Chaceon granulatus is highly marketable, and the infrastructure in Palau is such that crabs could either be marketed fresh locally or airfreighted to Japan as a quick-frozen product. The high post-trapping survival rates observed indicate that maintaining crabs in live-holding tanks may be a feasible option. The large catches and quality of deep-water crabs taken suggests that the Palauan population of Chaceon granulatus may be able to support a small-scale fishery. It is not yet known whether this population is unusually large or whether these findings typify the deep forereef fauna of the region.

Effects of ethanol on vehicle energy efficiency and implications on ethanol life-cycle greenhouse gas analysis.

Bioethanol is the world's largest-produced alternative to petroleum-derived transportation fuels due to its compatibility within existing spark-ignition engines and its relatively mature production technology. Despite its success, questions remain over the greenhouse gas (GHG) implications of fuel ethanol use with many studies showing significant impacts of differences in land use, feedstock, and refinery operation. While most efforts to quantify life-cycle GHG impacts have focused on the production stage, a few recent studies have acknowledged the effect of ethanol on engine performance and incorporated these effects into the fuel life cycle. These studies have broadly asserted that vehicle efficiency increases with ethanol use to justify reducing the GHG impact of ethanol. These results seem to conflict with the general notion that ethanol decreases the fuel efficiency (or increases the fuel consumption) of vehicles due to the lower volumetric energy content of ethanol when compared to gasoline. Here we argue that due to the increased emphasis on alternative fuels with drastically differing energy densities, vehicle efficiency should be evaluated based on energy rather than volume. When done so, we show that efficiency of existing vehicles can be affected by ethanol content, but these impacts can serve to have both positive and negative effects and are highly uncertain (ranging from -15% to +24%). As a result, uncertainties in the net GHG effect of ethanol, particularly when used in a low-level blend with gasoline, are considerably larger than previously estimated (standard deviations increase by >10% and >200% when used in high and low blends, respectively). Technical options exist to improve vehicle efficiency through smarter use of ethanol though changes to the vehicle fleets and fuel infrastructure would be required. Future biofuel policies should promote synergies between the vehicle and fuel industries in order to maximize the society-wise benefits or minimize the risks of adverse impacts of ethanol.

Briefing: Re-Engineering the City 2020-2050 - Urban Foresight and Transition Management

Cities may be responsible for up to 70% of global carbon emissions and 75% of global energy consumption and by 2050 it is estimated that 70% of the world's population could live in cities. The critical challenge for contemporary urbanism, therefore, is to understand how to develop the knowledge, capacity and capability for public agencies, the private sector and multiple users in city regions systemically to re-engineer their built environment and urban infrastructure in response to climate change and resource constraints. Re-Engineering the City 2020-2050: Urban Foresight and Transition Management (Retrofit 2050) is a major new interdisciplinary project funded under the Engineering and Physical Science Research Council's (EPSRC) Sustainable Urban Environments Programme which seeks to address this challenge. This briefing describes the background and conceptual framing of Retrofit 2050 project, its aims and objectives and research approach.

Wireless and Physical Security via Embedded Sensor Networks

Wireless Intrusion Detection Systems (WIDS) monitor 802.11 wireless frames (Layer-2) in an attempt to detect misuse. What distinguishes a WIDS from a traditional Network IDS is the ability to utilize the broadcast nature of the medium to reconstruct the physical location of the offending party, as opposed to its possibly spoofed (MAC addresses) identity in cyber space. Traditional Wireless Network Security Systems are still heavily anchored in the digital plane of "cyber space" and hence cannot be used reliably or effectively to derive the physical identity of an intruder in order to prevent further malicious wireless broadcasts, for example by escorting an intruder off the premises based on physical evidence. In this paper, we argue that Embedded Sensor Networks could be used effectively to bridge the gap between digital and physical security planes, and thus could be leveraged to provide reciprocal benefit to surveillance and security tasks on both planes. Toward that end, we present our recent experience integrating wireless networking security services into the SNBENCH (Sensor Network workBench). The SNBENCH provides an extensible framework that enables the rapid development and automated deployment of Sensor Network applications on a shared, embedded sensing and actuation infrastructure. The SNBENCH's extensible architecture allows an engineer to quickly integrate new sensing and response capabilities into the SNBENCH framework, while high-level languages and compilers allow novice SN programmers to compose SN service logic, unaware of the lower-level implementation details of tools on which their services rely. In this paper we convey the simplicity of the service composition through concrete examples that illustrate the power and potential of Wireless Security Services that span both the physical and digital plane.

A benchmark comparison between reconfigurable, intelligent and autonomous wireless inertial measurement and photonic technologies in rehabilitation

Advanced sensory systems address a number of major obstacles towards the provision for cost effective and proactive rehabilitation. Many of these systems employ technologies such as high-speed video or motion capture to generate quantitative measurements. However these solutions are accompanied by some major limitations including extensive set-up and calibration, restriction to indoor use, high cost and time consuming data analysis. Additionally many do not quantify improvement in a rigorous manner for example gait analysis for 5 minutes as opposed to 24 hour ambulatory monitoring. This work addresses these limitations using low cost, wearable wireless inertial measurement as a mobile and minimal infrastructure alternative. In cooperation with healthcare professionals the goal is to design and implement a reconfigurable and intelligent movement capture system. A key component of this work is an extensive benchmark comparison with the 'gold standard' VICON motion capture system.

Identification and assessment of potential wind energy project sites in the State of Maryland

Gemstone Team Renewables

Finance for water and sanitation as a public service

Drawing on empirical evidence gathered through the PSIRU database, this contribution aims at addressing the potential of public finance to enhance the provision of water supply and sanitation as a public service. It highlights the problems associated with (and the disappointing results obtained from) resort to Private Sector Participation and private finance, both historically and in the last 15-20 years, in developed and developing countries. It also addresses the advantages of using public finance as a more cost-effective and equitable instrument to achieve developmental objectives such as the expansion of service coverage and development of water and sanitation infrastructure. The potential of public operations in maximising developmental impact from the social, economic and environmental points of view is then explored referring to specific examples from a variety of countries and regions. These include the in-house restructuring of public operations to enhance transparency, accountability and effectiveness, as well as the use of Public-Public Partnerships (PUPs) to build capacity. Attention is devoted to the specific financial requirements of expanding sewerage services at global level to achieve MDGs or broader developmental goals. These requirements are revisited in light of a regional breakdown of coverage gaps, available resources and development aid flows. These findings challenge the established view among international and bilateral agencies that expanding sewerage services in developing countries is excessively costly and should be abandoned as a priority because unaffordable. This contribution draws on a number of PSIRU Reports, and particularly the following. - http://www.psiru.org/reports/2008-03-W-sewers.pdf - http://boell-latinoamerica.org/download_es/agua08_privatizacion_LA_2007.pdf - http://boell-latinoamerica.org/download_es/agua08_agua_un_servicio_publico.pdf - http://www.psiru.org/reports/2006-03-W-investment.pdf All PSIRU Reports are accessible at http://www.psiru.org/publicationsindex.asp.

Development and application of a multiple linear regression model to consider the impact of weekly waste container capacity on the yield from kerbside recycling programmes

The paper describes the development and application of a multiple linear regression model to identify how the key elements of waste and recycling infrastructure, namely container capacity and frequency of collection affect the yield from municipal kerbside recycling programmes. The overall aim of the research was to gain an understanding of the factors affecting the yield from municipal kerbside recycling programmes in Scotland. The study isolates the principal kerbside collection service offered by 32 councils across Scotland, eliminating those recycling programmes associated with flatted properties or multi occupancies. The results of a regression analysis model has identified three principal factors which explain 80% of the variability in the average yield of the principal dry recyclate services: weekly residual waste capacity, number of materials collected and the weekly recycling capacity. The use of the model has been evaluated and recommendations made on ongoing methodological development and the use of the results in informing the design of kerbside recycling programmes. The authors hope that the research can provide insights for the ongoing development of methods to optimise the design and operation of kerbside recycling programmes.

Financial Taxes and the Sand in the Wheels of Financialization:Legal Challenges for the EU Directive Implementing Enhanced Cooperation in the Area of Financial Transaction Tax

One of the many results of the Global Financial Crisis was the insight that the financial sector is under-taxed compared to other industries. In light of the huge bailouts and continued subsidies for financial institutions that are characterized as too-big-to-fail demands came on the agenda to make finance pay for the mega-crisis it caused. The most prominent examples of such taxes are a Financial Transaction Tax (FTT) and a Financial Activities Tax (FAT). Possible effects of such taxes on the economic constitution and increasingly in particular on the European Single Market have been discussed controversially over the last decades already. Especially with the decision of eleven EU member states to adapt an FTT using the enhanced cooperation procedure a number of additional legal challenges for implementing such a tax have emerged. This paper analyzes how tax measures of indirectly regulating the financial industry differ, what legal challenges they pose, and what their overall contribution would be in making the financial system more stable and resilient. It also analyzes the legal arguments against enhanced cooperation in this area and the legal issues related to the British lawsuit against the Commission’s Directive proposal in the European Court of Justice on grounds of the extra-territoriality application of tax. The paper concludes that the feasibility of an FTT is legally sound and given the FTT’s advantages over a FAT the EU Directive should be implemented as a first step for a European-wide FTT. However, significant uncertainties about its implementation remain at this stage.

Planning, Devolution and the Territorialisation of Wind Energy in the UK

The decarbonisation of energy systems draw a new set of stakeholders into debates over energy generation, engage a complex set of social, political, economic and environmental processes and impact at a wide range of geographical scales, including local landscape changes, national energy markets and regional infrastructure investment. This paper focusses on a particular geographic scale, that of the regions/nations of the UK (Scotland, Wales, Northern Ireland), who have been operating under devolved arrangements since the late 1990s, coinciding with the mass deployment of wind energy. The devolved administrations of the UK possess an asymmetrical set of competencies over energy policy, yet also host the majority of the UK wind resource. This context provides a useful way to consider the different ways in which geographies of "territory" are reflected in energy governance, such through techno-rational assessments of demand or infrastructure investment, but also through new spatially-defined institutions that seek to develop their own energy future, using limited regulatory competencies. By focussing on the way the devolved administrations have used their responsibilities for planning over the last decade this paper will assess the way in which the spatial politics of wind energy is giving rise to renewed forms of territorialisation of natural resources. In so doing, we aim to contribute to clarifying the questions raised by Hodson and Marvin (2013) on whether low carbon futures will reinforce or challenge dominant ways of organising relationships between the nation-state, regions, energy systems and the environment.

An overview of waste crime, its characteristics, and the vulnerability of the EU waste sector

While waste is increasingly viewed as a resource to be globally traded, increased regulatory control on waste across Europe has created the conditions where waste crime now operates alongside a legitimate waste sector. Waste crime,is an environmental crime and a form of white-collar crime, which exploits the physical characteristics of waste, the complexity of the collection and downstream infrastructure, and the market opportunities for profit. This paper highlights some of the factors which make the waste sector vulnerable to waste crime. These factors include new legislation and its weak regulatory enforcement, the economics of waste treatment, where legal and safe treatment of waste can be more expensive than illegal operations, the complexity of the waste sector and the different actors who can have some involvement, directly or indirectly, in the movement of illegal wastes, and finally that waste can be hidden or disguised and creates an opportunity for illegal businesses to operate alongside legitimate waste operators. The study also considers waste crime from the perspective of particular waste streams that are often associated with illegal shipment or through illegal treatment and disposal. For each, the nature of the crime which occurs is shown to differ, but for each, vulnerabilities to waste crime are evident. The paper also describes some approaches which can be adopted by regulators and those involved in developing new legislation for identifying where opportunities for waste crime occurs and how to prevent it.

Power Modeling and Capping for Heterogeneous ARM/FPGA SoCs

Low-power processors and accelerators that were originally designed for the embedded systems market are emerging as building blocks for servers. Power capping has been actively explored as a technique to reduce the energy footprint of high-performance processors. The opportunities and limitations of power capping on the new low-power processor and accelerator ecosystem are less understood. This paper presents an efficient power capping and management infrastructure for heterogeneous SoCs based on hybrid ARM/FPGA designs. The infrastructure coordinates dynamic voltage and frequency scaling with task allocation on a customised Linux system for the Xilinx Zynq SoC. We present a compiler-assisted power model to guide voltage and frequency scaling, in conjunction with workload allocation between the ARM cores and the FPGA, under given power caps. The model achieves less than 5% estimation bias to mean power consumption. In an FFT case study, the proposed power capping schemes achieve on average 97.5% of the performance of the optimal execution and match the optimal execution in 87.5% of the cases, while always meeting power constraints.

Technical and allocative efficiency of irrigation water use in the Guanzhong Plain, China

Due to increasing water scarcity, accelerating industrialization and urbanization, efficiency of irrigation water use in Northern China needs urgent improvement. Based on a sample of 347 wheat growers in the Guanzhong Plain, this paper simultaneously estimates a production function, and its corresponding first-order conditions for cost minimization, to analyze efficiency of irrigation water use. The main findings are that average technical, allocative, and overall economic efficiency are 0.35, 0.86 and 0.80, respectively. In a second stage analysis, we find that farmers’ perception of water scarcity, water price and irrigation infrastructure increase irrigation water allocative efficiency, while land fragmentation decreases it. We also show that farmers’ income loss due to higher water prices can be offset by increasing irrigation water use efficiency.