Bond graph modelling of exergy in integrated energy systems

Ph. D. Thesis.Integrated municipal or district energy systems are one facet of the effort to support sustainable energy systems that work towards reducing anthropogenic climate change emissions. Current energy systems — including electricity, heat, and cooling — operate mostly independently, under the control of domain-distinct industries and regulatory bodies. Operating these separate systems in a cooperative or integrated manner promises improvements in efficiency, the ability of networks to absorb renewable energy sources and storage, emissions reductions and community-based benefits. The nature of district energy systems is that they cannot easily be modified or built upon without severe disruption to the communities they serve, so assessments of their behaviour and performance caused by potential changes must be modelled. This thesis investigates what methods can model integrated energy systems and develops a bond graph-based approach to constructing a fully-integrated system model. Although energy based methods for integrated energy system modelling exist, this thesis demonstrates that exergy can form the basis of integrated energy system models. Exergy being a measure of the usefulness of energy allows the equivalence of energy domains in a single model form, permitting development of a genuine, physically-founded integrated energy system model. An integrated model of a residential district supplied by heat and electrical networks, based on a real UK urban area, is demonstrated in OpenModelica using the developed modelling approach. The concept of an exergy storage device is introduced to provide a mechanism for mediating energy flows between the networks. The model is used to evaluate the performance of the test network, using trial cases to investigate how transferring exergy between energy domains through the mediating storage affects the overall system energy and exergy efficiencies. Operational regimes that transfer energy from the electrical to the thermal sub-system using the mediating storage are found to improve the exergy efficiency of the system.Newcastle University, Siemen

ECOS 2012

The 8-volume set contains the Proceedings of the 25th ECOS 2012 International Conference, Perugia, Italy, June 26th to June 29th, 2012. ECOS is an acronym for Efficiency, Cost, Optimization and Simulation (of energy conversion systems and processes), summarizing the topics covered in ECOS: Thermodynamics, Heat and Mass Transfer, Exergy and Second Law Analysis, Process Integration and Heat Exchanger Networks, Fluid Dynamics and Power Plant Components, Fuel Cells, Simulation of Energy Conversion Systems, Renewable Energies, Thermo-Economic Analysis and Optimisation, Combustion, Chemical Reactors, Carbon Capture and Sequestration, Building/Urban/Complex Energy Systems, Water Desalination and Use of Water Resources, Energy Systems- Environmental and Sustainability Issues, System Operation/ Control/Diagnosis and Prognosis, Industrial Ecology

Energy. A continuing bibliography with indexes, issue 36, January 1983

This bibliography lists 1297 reports, articles, and other documents introduced into the NASA scientific and technical information system from October 1, 1982 through December 31, 1982

Fast temperature programmed gas chromatography coupled to supercritical fluid chromatography (SFC×GC)

The topic of this thesis is the development of comprehensively coupled (supercritical fluid × gas) chromatography and its application to the chemical analysis of biodiesel and biodiesel blends. A future low-carbon economy might still have a need for large, high-efficiency diesel engines fueled with a high-quality carbon neutral fuel such as biodiesel. The quality of fuels are judged according to technical standards: documents that detail the requirements of compliance. Liquid fuels are complex mixtures that challenge the separation science used to ensure compliance. Chromatographic separations that use different separation mechanisms can be combined to meet those challenges, culminating in comprehensive coupling, where every fraction of a first separation is subjected to a second separation. The fundamental difference between the separation mechanisms of supercritical fluid chromatography (SFC) and gas chromatography (GC) allows for a powerful, technically feasible, coupled technique. To make the coupling practical the GC separation must be fast and temperature-programmed. A coaxial resistive heater for short capillary columns with active cooling by liquid carbon dioxide was constructed, with which hundreds of consecutive fast temperature-programmed GC separations were performed at a rate of four per minute. These chromatograms of fractions of SFC separations were combined to construct two-dimensional SFC×GC chromatograms. When biodiesel and biodiesel blends are analysed by SFC×GC, separation in the first dimension is by polarity and degree of unsaturation and in the second dimension by volatility. The resulting chromatograms contain powerful patterns of peaks, with the aromatic hydrocarbons separated from the alkanes, and the fatty acid methyl esters (FAMEs) of the biodiesel separated from the hydrocarbons of the petrodiesel. Because the flame ionization detector (FID) is used, quantification should be straightforward and reliable. The FID remains compatible with SFC×GC even when organic modifiers are added to the SFC mobile phase, because the volatile modifiers elute on the GC as a solvent peak, separate from the less-volatile analytes of interest. SFC×GC can be used for research and quality control in the liquid fuels and vegetable oil industries.Thesis (PhD (Chemistry))--University of Pretoria, 2020.ChemistryPhD (Chemistry)Unrestricte