Identifying calendar-correlated day-ahead price profile clusters for enhanced energy storage scheduling

Optimising the scheduling of energy storage systems with respect to multiple revenue streams is crucial to the business case for installations in the UK and other countries with high electrical grid penetration. In this work we use hierarchical clustering for the first time to correlate groupings of UK day-ahead electricity price profiles with calendar period. We observe that there are three primary clusters in the 2017–2019 dataset, and hypothesise that these arise from the interplay of winter/summer variations in demand along with longer term variations in the wholesale gas price. Looking at finer detail, we find that in summer 2018 there is a clear split in weekday/ weekend price profiles, with the latter showing a significantly delayed price peak, and higher night time prices. These findings demonstrate the usefulness of the approach for revenue stacking, as the optimal bidding for ancillary services to fit around the performance of peak shaving will be influenced by the knowledge of such patterns, especially when the horizon for bidding is beyond the day ahead

CFD modelling of outflow and ductile fracture propagation in pressurised pipelines

This thesis describes the fundamental extension, development and testing of a mathematical model for predicting the transient outflow following the failure of pressurised pipelines. The above encompasses improvements to the theoretical basis and numerical stability, reduction in the computational runtime and the modelling of fracture propagation with particular reference to CO2 pipelines. The basic model utilises the homogeneous equilibrium model (HEM), where the constituent phases in two-phase mixtures are assumed to be in thermodynamic and mechanical equilibrium. The resultant system of conservation equations are solved numerically using the Method of Characteristics (MOC) coupled with a suitable Equation of State to account for multi-component hydrocarbon mixtures. The first part of the study involves the implementation of the Finite Volume Method (FVM) as an alternative to the MOC. In the case of gas and two-phase hydrocarbon pipeline ruptures, both models are found to be in excellent accord producing good agreement with the published field data. As compared to the MOC, the FVM shows considerable promise given its significantly shorter computation runtime and its ability to handle non-equilibrium or heterogeneous flows. The development, testing and validation of a Dynamic Boundary Fracture Model (DBFM) coupling the fluid decompression model with a widely used fracture model based on the Drop Weight Tear Test technique is presented next. The application of the DBFM to an hypothetical but realistic CO2 pipeline reveals the profound impacts of the line temperature and types of impurities present in the CO2 stream on the pipeline’s propensity to fracture propagation. It is found that the pure CO2 and the postcombustion pipelines exhibit very similar and highly temperature dependent propensity to fracture propagation. An increase in the line temperature from 20 – 30 oC results in the transition from a relatively short to a long running propagating facture. The situation becomes progressively worse in moving from the pre-combustion to the oxy-fuel stream. In the latter case, long running ductile fractures are observed at all the temperatures under consideration. All of the above findings are successfully explained by examining the fluid depressurisation trajectories during fracture propagation relative to the phase equilibrium envelopes. Finally, two of the main shortcomings associated with previous work in the modelling of pipeline ruptures are addressed. The first deals with the inability of Oke’s (2004) steady state model to handle non-isothermal flow conditions prior to rupture by accounting for both heat transfer and friction. The second removes the rupture plane instabilities encountered in Atti’s (2006) model when simulating outflow following the rupture of ultra high pressure pipelines. Excellent agreement between the new nonisothermal model predictions and the published data for real pipelines is observed

Stresses and deformations in flexible layered pavement systems subjected to dynamic loads

Many of the proposed rational design methods for flexible pavements are concerned with the stresses and strains which occur in the various layers of the structure. The purpose of the work reported is to investigate, in the laboratory, the complete stress and strain distributions set up in the different layers under dynamic loads. Two systems have been investigated, a single layer of clay and a two layer system consisting of a granular base on a clay subgrade. The loading in each case consisted of a single pulse having a duration of loading between 0.1 and 2 sec. The load was uniformly distributed over a circular area and of varying magnitude. In-situ measurements of stress and strain were made using pressure and strain cells, -, at various orientations. Surface deflection was measured with a rectilinear potentiometer. Stress and strain distributions were determined by moving the load relative to the buried transducers. By superimposing results, values of principal stresses and strains and maximum shear were derived. By combining stress and strain measurements, values of in-situ elastic modulus and Poisson's ratio were calculated. Results were compared with elastic theory, both Boussinesq and layered system, the latter being computed using a recently developed program. Stresses showed good agreement with theory in both systems, but strains, being dependent on modulus, were less easy to predict theoretically. In-situ values of modulus were stress dependent for both materials. For the clay, at low stress levels, the modulus increased sharply with decreasing stress, while for the granular material modulus increased with stress level. In the two layer system results compared less favourably with theory, but the important values of tensile horizontal stress above the interface and vertical strain below the interface appear to be predicted adequately. The values of modular ratio were near to unity and hence Boussinesq theory was equally as adequate as the layered system approach for most effects. Strains were predicted with fair accuracy when local values of modulus were used i.e., those in the neighbourhood of the points concerned. The assumption of perfect roughness at the interface, used in most theoretical solutions, was shown to be valid. The stress dependence of modulus is thought to be one of the main problems at present in the application of layered system theory and, for the calculation of strains, in the use of the Boussinesq approach also

United Kingdom minerals yearbook 2014 : statistical data to 2013

The United Kingdom Minerals Yearbook is an annual publication providing comprehensive statistical data on minerals production, consumption and trade, and includes commentary on the UK's minerals industry. It contains: • essential guidance for decision makers • reliable and up–to–date information • authoritative commentary on current developments It is of value to all those interested in the many facets of Britain's minerals industry and its contribution to the national economy. This publication forms part of Britain's continuous mining and quarrying record

United Kingdom Minerals Yearbook 2013 : statistical data to 2012

The compilers of this volume are grateful for the help received from the Office for National Statistics, the Department for Business, Innovation and Skills, the Department for Communities and Local Government, the Department of Energy and Climate Change, the Crown Estate Commissioners, The Crown Mineral Agent, the Northern Ireland Department of Enterprise, Trade and Investment and the Isle of Man Department of Trade and Industry. They would also like to acknowledge the valuable assistance given by the World Bureau of Metal Statistics, the UK Iron and Steel Statistics Bureau, the Mineral Products Association, The Coal Authority and the numerous companies that have generously provided additional information

An analytical and experimental assessment of flexible road ironwork support structures

This paper describes work undertaken to investigate the mechanical performance of road ironwork installations in highways, concentrating on the chamber construction. The principal aim was to provide the background research which would allow improved designs to be developed to reduce the incidence of failures through improvements to the structural continuity between the installation and the surrounding pavement. In doing this, recycled polymeric construction materials (Jig Brix) were studied with a view to including them in future designs and specifications. This paper concentrates on the Finite Element (FE) analysis of traditional (masonry) and flexible road ironwork structures incorporating Jig Brix. The global and local buckling capacity of the Jig Brix elements was investigated and results compared well with laboratory measurements. FE models have also been developed for full-scale traditional (masonry) and flexible installations in a surrounding flexible (asphalt) pavement structure. Predictions of response to wheel loading were compared with full-scale laboratory measurements. Good agreement was achieved with the traditional (masonry) construction but poorer agreement for the flexible construction. Predictions from the FE model indicated that the use of flexible elements significantly reduces the tensile horizontal strain on the surface of the surrounding asphaltic material which is likely to reduce the incidence of surface cracking

Pursuing safer batteries: Thermal abuse of LiFePO4 cells

In this paper, accelerated rate calorimetry (ARC) and oven exposure, are used to investigate thermal runaway (TR) in lithium-ion cells. Previous work shows that lithium iron phosphate (LFP) cells have a lower risk of TR over other Li-ion chemistries. ARC is carried out on cells at various SOC to identify which decomposition reactions are contributing to the TR behaviour of a cell at different SOC. Results show, at SOC of 100% and 110%, the negative and positive electrode reactions are the main contributors to TR, while at lower SOC it is the negative electrode reaction that dominates. Cells at 100% SOC exposed to high temperatures during oven tests show, along with the ARC analysis, that the presence of the cathode and electrolyte reactions leads to an increase in the severity of a TR event for oven temperatures above . By comparing the heat generated in ARC and oven testing, it is shown that ARC does not fully capture the self-heating and TR safety hazard of a cell, unlike oven testing. This work gives new insight into the nature of the decomposition reactions and also provides an essential data set useful for model validation which is of importance to those studying LFP cells computationally

CO2 capture and storage (CCS) cost reduction via infrastructure right-sizing

Carbon capture and storage (CCS) will be a critical component of a portfolio of low-carbon energy technologies required to combat climate change (Technology Roadmap, 2013). As such, an extensive transportation infrastructure will be required to transport captured CO2 from different sources to the available sinks. Several studies in the literature suggest that shared oversized pipeline networks may be the most efficient long term option compared to single source to sink pipelines, based on increased CCS deployment over the years and therefore increased CO2 flowrate to the transport network. However, what is neglected in this vision is that the deployment of intermittent renewable energy tends to displace thermal power generation. This directly reduces the amount of fossil fuel burned, CO2 produced, captured and transported through the network. This paper presents an optimisation methodology to “right-size” CO2 transport infrastructure, explicitly accounting for the transient flow of CO2 arising from the co-deployment of intermittent renewable energy generators. By application of this methodology, we demonstrate that capital cost reductions of up to 28% are possible relative to a business-as-usual design case

Stresses and deformations in flexible layered pavement systems subjected to dynamic loads

Many of the proposed rational design methods for flexible pavements are concerned with the stresses and strains which occur in the various layers of the structure. The purpose of the work reported is to investigate, in the laboratory, the complete stress and strain distributions set up in the different layers under dynamic loads. Two systems have been investigated, a single layer of clay and a two layer system consisting of a granular base on a clay subgrade. The loading in each case consisted of a single pulse having a duration of loading between 0.1 and 2 sec. The load was uniformly distributed over a circular area and of varying magnitude. In-situ measurements of stress and strain were made using pressure and strain cells, -, at various orientations. Surface deflection was measured with a rectilinear potentiometer. Stress and strain distributions were determined by moving the load relative to the buried transducers. By superimposing results, values of principal stresses and strains and maximum shear were derived. By combining stress and strain measurements, values of in-situ elastic modulus and Poisson's ratio were calculated. Results were compared with elastic theory, both Boussinesq and layered system, the latter being computed using a recently developed program. Stresses showed good agreement with theory in both systems, but strains, being dependent on modulus, were less easy to predict theoretically. In-situ values of modulus were stress dependent for both materials. For the clay, at low stress levels, the modulus increased sharply with decreasing stress, while for the granular material modulus increased with stress level. In the two layer system results compared less favourably with theory, but the important values of tensile horizontal stress above the interface and vertical strain below the interface appear to be predicted adequately. The values of modular ratio were near to unity and hence Boussinesq theory was equally as adequate as the layered system approach for most effects. Strains were predicted with fair accuracy when local values of modulus were used i.e., those in the neighbourhood of the points concerned. The assumption of perfect roughness at the interface, used in most theoretical solutions, was shown to be valid. The stress dependence of modulus is thought to be one of the main problems at present in the application of layered system theory and, for the calculation of strains, in the use of the Boussinesq approach also

A closed-loop analysis of grid scale battery systems providing frequency response and reserve services in a variable inertia grid

With increasing penetration of wind and solar generation the deployment of fast response plant, principally batteries, is currently considered necessary to mitigate reduced system inertia and the possibility of demand-supply imbalances. In this work the impact of these factors on battery cycling rates, taking into account the input from the batteries themselves, are analysed by applying the swing equation to a future inertia based on forecast generation mix. The operational capacity of batteries is a determining factor in their cycling rate, though the depth of discharge appears to be less well correlated. It is found that reducing system inertia does not, of itself, significantly impact on frequency volatility where the volatility of the generation to load imbalance is unchanged. However, the potential for a reduction in the damping of frequency deviations as a result of an increase in inverter connected motor drives may have a large impact on battery cycling characteristics. Provision of reserve services from battery systems requires a more complex operational strategy to ensure services are always deliverable and results in a significantly different cycling profile that may lead to greater battery degradation and consequently higher operational costs