387,936 research outputs found
Development of Laboratory Based Smart Micro Grid To Be Used As An Educational Tool
The increasing trend of the energy industry to move towards a new smart power grid has pushed researchers to address the challenges that this represents. Universities all around the world are also under pressure to better prepare their students to meet the challenges that await them with this new technology and techniques. The work presented on this thesis was motivated by the current need of the electrical engineering curriculum to include new material into their current courses. A laboratory based smart micro grid was created by applying several concepts and techniques currently being adopted by the energy industry to make their distribution systems smarter. A series of experiments were conducted in order to test the functionality of both hardware equipment as well as software implementation. The results indicate that the experimental setup has proven to be adequate to introduce students to new concepts of the smart grid
Water and sanitation provision in a low carbon society: The need for a systems approach
In the face of climate change threatening to cause major alterations to hydrological cycles and taking into account the relationship between water, energy use, and food production, water management challenges today prove more complex than ever to address. This paper, recognising the progress made through science and engineering in the last century, reflects on the need to manage water resources more sustainably. It proposes that a change in mindsets is required in order to reconsider our approach in applying established solutions and utilising current technologies and tools to deliver them, with a renewed focus on re-assessing what the real problems are from a systems perspective. Focusing on the water-energy-food nexus, water reuse using desalination processes as a management option is revisited. Findings demonstrate that interdisciplinary, integrated and holistic solutions have the potential to deliver benefits across different sectors, disciplines, and systems, with a real potential for taking us a bit closer to sustainability
Towards monolithic integration of germanium light sources on silicon chips
Germanium (Ge) is a group-IV indirect band gap semiconductor, and therefore bulk Ge cannot emit light efficiently. However, the direct band gap energy is close to the indirect one, and significant engineering efforts are being made to convert Ge into an efficient gain material monolithically integrated on a Si chip. In this article, we will review the engineering challenges of developing Ge light sources fabricated using nano-fabrication technologies compatible with Complementary Metal-Oxide-Semiconductor (CMOS) processes. In particular, we review recent progress in applying high-tensile strain to Ge to reduce the direct band gap. Another important technique is doping Ge with donor impurities to fill the indirect band gap valleys in the conduction band. Realization of carrier confinement structures and suitable optical cavities will be discussed. Finally, we will discuss possible applications of Ge light sources in potential photonics-electronics convergent systems
Application of entropy analysis in the prediction of flow distribution in parallel channels
Multiphase flow in parallel channels is often an efficient approach to manage
heat and energy distribution in engineering systems. However, two-phase flow
with heating in parallel channels is prone to maldistribution, resulting in
sub-optimal performance and in some cases, permanent damage. This challenge
requires accurate flow modeling in parallel channels to mitigate or design
against the adverse effect of two-phase flow maldistribution. The nonlinear
nature of multiphase flow results in a multiplicity of predicted solutions for
the same condition, thereby creating significant challenges in modeling flow
distribution. Therefore, this study focuses on solving this challenge by
applying entropy generation analysis and the conservation of mass, momentum
balance, and energy balance to predict two-phase flow distribution in a
two-parallel-channel assembly with a numerical model. Both model predictions
and experimental data show that equally distributed flow becomes severely
maldistributed with a decrease in flow rate, resulting in significant change
(>30%) in the entropy generation rate. We show that the entropy analysis can be
applied in distinguishing between stable and unstable flow distribution, like
the linear stability analysis used in previous studies. We also surpass the
limit of applying linear stability analysis by using entropy analysis to
identify the most feasible end state in a maldistribution process
On Using Blockchains for Safety-Critical Systems
Innovation in the world of today is mainly driven by software. Companies need
to continuously rejuvenate their product portfolios with new features to stay
ahead of their competitors. For example, recent trends explore the application
of blockchains to domains other than finance. This paper analyzes the
state-of-the-art for safety-critical systems as found in modern vehicles like
self-driving cars, smart energy systems, and home automation focusing on
specific challenges where key ideas behind blockchains might be applicable.
Next, potential benefits unlocked by applying such ideas are presented and
discussed for the respective usage scenario. Finally, a research agenda is
outlined to summarize remaining challenges for successfully applying
blockchains to safety-critical cyber-physical systems
Energy-Efficient NOMA Enabled Heterogeneous Cloud Radio Access Networks
Heterogeneous cloud radio access networks (H-CRANs) are envisioned to be
promising in the fifth generation (5G) wireless networks. H-CRANs enable users
to enjoy diverse services with high energy efficiency, high spectral
efficiency, and low-cost operation, which are achieved by using cloud computing
and virtualization techniques. However, H-CRANs face many technical challenges
due to massive user connectivity, increasingly severe spectrum scarcity and
energy-constrained devices. These challenges may significantly decrease the
quality of service of users if not properly tackled. Non-orthogonal multiple
access (NOMA) schemes exploit non-orthogonal resources to provide services for
multiple users and are receiving increasing attention for their potential of
improving spectral and energy efficiency in 5G networks. In this article a
framework for energy-efficient NOMA H-CRANs is presented. The enabling
technologies for NOMA H-CRANs are surveyed. Challenges to implement these
technologies and open issues are discussed. This article also presents the
performance evaluation on energy efficiency of H-CRANs with NOMA.Comment: This work has been accepted by IEEE Network. Pages 18, Figure
Making useful knowledge for heat decarbonisation:Lessons from local energy planning in the United Kingdom
Heat decarbonisation is challenging in many countries, but few studies address its âwicked problemâ qualities and the implications for producing useful knowledge. This paper elucidates the challenges by applying insights from science and technology studies, especially Callonâs concept of knowledge âframesâ, to explain the fate of a prominent UK innovation â the EnergyPath Networks (EPN) and Local Area Energy Planning (LAEP) tool of the Smart Systems and Heat programme. The aim of the tool, which coupled an engineering model with local planning, was to provide authoritative knowledge to support local decision making. However, after six years of piloting with local authorities the future take-up of EPN and LAEP remained uncertain, for two key reasons. First the techno-economic knowledge frame encountered numerous overflows emanating from more potent political-economic and technological perspectives governing local priorities. Second the framing of local decision making neglected the marginality of energy planning at local government level. Our analysis shows the problems that arise when lab-based research and development prematurely frame energy system problems, before encountering societal and political contexts of use. Problem definitions and solutions for heat decarbonisation based predominantly on technicalâeconomic knowledge lack requisite authority to progress this wicked problem, and must become more context-responsive
Municipal wastewater treatment with pond technology : historical review and future outlook
Facing an unprecedented population growth, it is difficult to overstress the assets for wastewater treatment of waste stabilization ponds (WSPs), i.e. high removal efficiency, simplicity, and low cost, which have been recognized by numerous scientists and operators. However, stricter discharge standards, changes in wastewater compounds, high emissions of greenhouse gases, and elevated land prices have led to their replacements in many places. This review aims at delivering a comprehensive overview of the historical development and current state of WSPs, and providing further insights to deal with their limitations in the future. The 21st century is witnessing changes in the way of approaching conventional problems in pond technology, in which WSPs should no longer be considered as a low treatment technology. Advanced models and technologies have been integrated for better design, control, and management. The roles of algae, which have been crucial as solar-powered aeration, will continue being a key solution. Yet, the separation of suspended algae to avoid deterioration of the effluent remains a major challenge in WSPs while in the case of high algal rate pond, further research is needed to maximize algal growth yield, select proper strains, and optimize harvesting methods to put algal biomass production in practice. Significant gaps need to be filled in understanding mechanisms of greenhouse gas emission, climate change mitigation, pond ecosystem services, and the fate and toxicity of emerging contaminants. From these insights, adaptation strategies are developed to deal with new opportunities and future challenges
International White Book on DER Protection : Review and Testing Procedures
This white book provides an insight into the issues surrounding the impact of increasing levels of DER on the generator and network protection and the resulting necessary improvements in protection testing practices. Particular focus is placed on ever increasing inverter-interfaced DER installations and the challenges of utility network integration. This white book should also serve as a starting point for specifying DER protection testing requirements and procedures. A comprehensive review of international DER protection practices, standards and recommendations is presented. This is accompanied by the identiïŹ cation of the main performance challenges related to these protection schemes under varied network operational conditions and the nature of DER generator and interface technologies. Emphasis is placed on the importance of dynamic testing that can only be delivered through laboratory-based platforms such as real-time simulators, integrated substation automation infrastructure and ïŹ exible, inverter-equipped testing microgrids. To this end, the combination of ïŹ exible network operation and new DER technologies underlines the importance of utilising the laboratory testing facilities available within the DERlab Network of Excellence. This not only informs the shaping of new protection testing and network integration practices by end users but also enables the process of de-risking new DER protection technologies. In order to support the issues discussed in the white paper, a comparative case study between UK and German DER protection and scheme testing practices is presented. This also highlights the level of complexity associated with standardisation and approval mechanisms adopted by different countries
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