Heriot-Watt University
ROS: The Research Output Service. Heriot-Watt University EdinburghNot a member yet
4689 research outputs found
Sort by
Energy yield enhancement of bifacial photovoltaic modules
Get PDFThe bifacial photovoltaic (BPV) module is an emerging renewable technology that
produces augmented energy yield due to its capability of receiving sunlight both on the
front and rear sides. This contrasts with conventional monofacial PV, which captures
sunlight only on the front side. The extensive deployment of bifacial PV is expected to
reduce the cost of solar energy considerably. However, there is limited evidence
regarding the field performance of bifacial PV. Uncertainty exists in modelling the
ground-reflected irradiance received by the rear side of BPV, which depends on ground
albedo and the view factor (VF) from solar PV to the ground. Existing research on the
view factor considers infinite lengths of the PV array, which prevents accurate
determination of ground-reflected irradiance for PV arrays with finite lengths.
In this research, the finite element method (FEM) is used to develop a view factor
computation model for the finite length of the PV array. The model can be utilised to
analyse the ground-reflected irradiance at the rear side of bifacial PV, which is necessary
to predict bifacial PV's energy generation correctly, adding scientific value to this
research. The developed model is verified with the analytical solution with an error
margin of ±2%. The model is validated by comparing calculated and measured reflected
irradiance, which shows a strong agreement at a root mean square error (RMSE) of 16
W/m2
and a mean bias error (MBE) of 7 W/m2
.
An investigation into the performance of BPV for four ground surfaces: soil, white
pebbles, concrete, and white tiles is undertaken to quantify the gain BPV can achieve.
Six empirical models are developed based on the measured data, which can be utilized
to estimate rear irradiance gain, bifacial energy gain and power output. A probability
distribution of bifacial energy gain data at a 95% confidence level shows that the bifacial
energy gain varies within 2%-25% depending on the reflectance of the ground surface
and the probability is low that the bifacial energy gain will be more than 30%. Based on
the annual bifacial energy gain analysis, the highest gain range is found for white tiles
ground surface, followed by concrete and white pebbles. Simulations have been
performed for various utility-scale PV arrays across the UK to verify the reliability of
measured field data. The results are found to be consistent with the measured bifacial
energy gain which showed a clear agreement of about 2%-5%. The findings of this
research will remove some uncertainty about BPV performance, which is crucial to
predict its energy generation accurately
Construction and application of adjusted higher gauge theories
Get PDFThis thesis investigates several aspects of nonabelian higher gauge theories, which appear
in many areas of physics, notably string theory and gauged supergravity. We show that
nonabelian higher gauge theory admits a consistent classical nonperturbative formulation
insofar as a higher nonabelian parallel transport exists consistently, without requiring
certain curvature components (fake curvature) to vanish.
Next, we explore examples of nonabelian higher gauge theories that naturally appear
in high-energy physics. Using a generalisation of L∞-algebras called EL∞-algebras, we
show that tensor hierarchies of gauged supergravity naturally admit a formulation in terms
of higher nonabelian gauge theories. Furthermore, toroidal compactifications of string
theory exhibiting T-duality also naturally contain higher gauge symmetry, which explain
several features of nongeometric compactifications (Q- and R-fluxes)
Improved carbonate reservoir characterisation : a case study from the mid-Cretaceous Mishrif reservoir in the giant West Qurna/1 oilfield, Southern Iraq
Get PDFThe mid-Cretaceous Mishrif carbonate reservoir in West Qurna/1 oilfield is characterized
by strong heterogeneity, tidal channels, and a complicated faults system which have very
strong effects on the fluid flow and can result in unrealistic forecasted behaviour of the
reservoir. The central hypothesis of this thesis is that two-dimensional seismic data and
well data do not delineate the reservoir channels sufficiently and their variable fairway
patterns. Hence, there is a need for a high-resolution 3D seismic dataset to explore
reservoir characterisation including channel geometries more accurately. This thesis
focuses mainly on porosity characterisation of the Mishrif channelized reservoir. It aims
to delineate the Mishrif channel fairways with their intrinsic complexity then characterize
the channel fairway’s reservoir properties, such as the porosity, and lithology, especially
in new areas that have no well control.
The thesis project was divided into three stages. The first stage focuses on the seismic
reservoir characterisation of one of the Middle East's largest complex carbonate reservoirs
in the West Qurna/1 oilfield, which hosts a complex internal architecture characterized
by several tidal channels whose deposits may give good reservoir properties. In the
second stage, multisource data was used to establish the essential workflow elements for
characterizing Mishrif tidal channel fairways. The final stage incorporates 3D seismic
data as a secondary variable into the property modelling to explore a more channels
distribution using a combined dataset workflow.
It was concluded that the seismic inversion interpretation demonstrates promising results,
with the model-based inversion performing better than the linear programming sparse
spike (LPSS). We interpreted the lithological variation in the Mishrif mA zone based on
the model-based inversion, including high-energy corals, mounds, and rudist shoal facies
that were not observed previously. Also, we noticed that the seismically derived porosity
improved our understanding by providing the realistic distribution of the Mishrif
channel's porosity. A variety of approaches has been suggested to characterizing the
Mishrif carbonate tidal channels. It was observed that well data analysis and thin section
micrographs provided a good understanding of Mishrif channelized facies. Also, modern
channels and outcrop scales were highly valuable in acquiring information for the
comparison with channel fairways detected in the Mishrif reservoir. Our study found that
spectral decomposition with the colour blending of three frequency intervals provides a better geo-body extraction of the Mishrif mB1 channelized zone than the other seismic
attribute surfaces. We analysed the results of the probabilistic neural network PNN
algorithm and found that the Mishrif mB1 zone is clustered into two different
heterogeneity-quality lithofacies (channels and restricted lagoon facies). We incorporated
seismic inversion into the 3D property model with a different weighting of the correlation
coefficients in the mB1 channelized zone. Thus, we observed that the constrained model
combining well log data and seismic data as a secondary variable yields better channel
fairway delineation with a moderate correlation coefficient weighting, and high weighting
impacted the channel distribution. The findings of this thesis can be applied in other
scenarios, such as contaminant transport in groundwater resources, or CO2 storage
Numerical simulation of surfactant flooding with relative permeability estimation using inversion method
Get PDFSurfactant flooding attracts significant interest in the hydrocarbon industry, with a definite
promise to improve oil recovery from depleting oil reserves. In this thesis, surfactant flooding
is the primary area of focus as it has significant potential for integration with other chemical
enhanced oil recovery techniques, including polymer, nanofluid, alkali, and foam. This
combined approach has the potential to reduce interfacial tension to ultralow levels, decrease
adsorption, and offer other benefits. However, due to the various mechanism, surfactant
flooding poses a more complex model for simulators by encountering numerical issues (e.g.,
the appearance of spurious oscillations, erratic pulses, and numerical instabilities), rendering
the methods ineffective. To address these challenges, the analytical modelling technique of
surfactant flooding was studied, leading to the development of a novel inversion method in the
MATLAB programming environment.
Numerical accuracy issues were discovered in 1D models that used typical cell sizes found in
well-scale models, leading to pulses in the oil bank and a dip in water saturation, particularly
for low levels of adsorption, highlighting the need for more refined models. Based on these
findings, we examined the surfactant flooding technique in 2D models to recover viscous oil
in short reservoir aspect ratios. Instabilities such as viscous fingering and gravity tongue were
observed on the flood fronts, and the magnitude of the viscous fingers was influenced by
vertical dispersion, resulting in errors in computed mobility values at the fronts. Interestingly,
introducing heterogeneity only minimally affected the spreading of the front and did not
significantly impact viscous fingering or numerical artifacts. To optimize the nonlinearity of
flow behaviour and degree of mobility control at the fronts, a homogenous model was
considered to develop the inversion method.
In summary, the developed inversion method accurately estimated the two-phase relative
permeability curves, which were validated using fractional flow theory. The precision of the
inverted curves was further improved using the optimization algorithm, demonstrating the
method's ability to predict outcomes closer to the observed values for 2D models with
instabilities. The obtained results are of significant value for core flood analysis, interpretation,
matching, and upscaling, providing insights into the potential of surfactant flooding for
enhanced oil recovery. Additionally, the use of the developed MATLAB Scripts promotes open
innovation and reproducibility, contributing to the benchmarking, analytical, and numerical
method development exercises for tutorials aimed at improving the overall understanding of
surfactant flooding
Algebraic and geometric aspects of two-dimensional Artin groups
Get PDFIn this thesis we study the algebra and the geometry of two-dimensional Artin groups under various aspects. First, we solve the problem of acylindrical hyperbolicity, by proving that all the two-dimensional Artin groups that are not trivially non-acylindrically-hyperbolic are acylindrically hyperbolic. In particular, we prove that every non-spherical Artin group of dimension 2 has trivial centre. Then, we study the structure of parabolic subgroups of large-type Artin groups, and prove various results about their combinatorial structure. We notably show that any intersection of parabolic subgroups is again a parabolic subgroup. Finally, we study the isomorphisms between Artin groups of large-type, and we prove that the family of large-type free-of-infnity Artin groups is rigid. We also fully describe the automorphism groups of these Artin groups
Adventures in high dimensions : unveiling the power of high-dimensional entanglement
Get PDFIn today’s digital landscape, quantum communication is revolutionizing technology amidst
cyber threats. Extensive research aims to meet the primary requirement for a secure
quantum network: establishing quantum nonlocal correlations without assumptions. Photonic high-dimensional entanglement platforms have garnered attention due to their large
encoding capacity and noise resilience. Yet, tapping into their full potential requires
resource-efficient methods, both theoretically and experimentally. This thesis explores
the spatial properties of bi-photon states generated through spontaneous parametric down-conversion, a key source of photonic entanglement. We introduce theoretical, numerical,
and experimental techniques to analyze and measure joint spatial correlations of these
entangled pairs. Furthermore, we employ the quantum steering framework to certify entanglement, introducing two sets of quantum steering inequalities. The first set showcases
genuine high-dimensional quantum steering. We derive simple two-setting inequalities,
based on the mutually unbiased basis or MUB, for certifying the presence of genuine
high-dimensional steering. We experimentally validate these inequalities with macro-pixel
photon-pair entanglement, certifying genuine high-dimensional steering up to d = 15. The
other set of steering inequalities harnesses the advantages of high-dimensional entanglement to be simultaneously noise-robust and loss-tolerant. The second set capitalizes on
high-dimensional entanglement’s noise robustness and loss tolerance. We demonstrate
quantum steering in up to 53 dimensions, surpassing qubit-based systems, even under
challenging conditions equivalent to 79 km of telecommunication fibre loss and 36% white
noise. Surprisingly, high dimensions significantly reduce measurement time, achieving a
quantum steering violation nearly two orders of magnitude faster by doubling the Hilbert
space dimension. Building on this progress, we explore expanding dimensionality in the
temporal degree of freedom. We identify the challenges in certifying high-dimensional
time-bin entanglement due to the arduous nature of the current measurement techniques. To
overcome this, we introduce a novel technique for conducting generalized measurements
on high-dimensional time-bin states using a long multi-mode fibre. We experimentally
validate this approach in a 4-dimensional Hilbert space
Ultra-fast screening of stress-sensitive (naturally fractured) reservoirs using flow diagnostics
Get PDFQuantifying the impact of poro-mechanics on reservoir performance is critical to the
sustainable management of subsurface reservoirs containing either hydrocarbons,
groundwater, geothermal heat, or being targeted for geological storage of fluids (e.g., CO2
or H2). On the other hand, accounting for poro-mechanical effects in full-field reservoir
simulation studies and uncertainty quantification workflows in complex reservoir models
is challenging, mainly because exploring and capturing the full range of geological and
mechanical uncertainties requires a large number of numerical simulations and is hence
computationally intensive. Specifically, the integration of poro-mechanical effects in
full-field reservoir simulation studies is still limited, mainly because of the high
computational cost. Consequently, poro-mechanical effects are often ignored in reservoir
engineering workflows, which may result in inadequate reservoir performance forecasts.
This thesis hence develops an alternative approach that couples hydrodynamics using
existing flow diagnostics simulations for single- and dual-porosity models with poro mechanics to screen the impact of coupled poro-mechanical processes on reservoir
performance. Due to the steady-state nature of the calculations and the effective proposed
coupling strategy, these calculations remain computationally efficient while providing
first-order approximations of the interplay between poro-mechanics and hydrodynamics,
as we demonstrate through a series of case studies. This thesis also introduces a new
uncertainty quantification workflow using the proposed poro-mechanical informed flow
diagnostics and proxy models. These computationally efficient calculations allow us to
quickly screen poro-mechanics and assess a broader range of geological, petrophysical,
and mechanical uncertainties to rank, compare, and cluster a large ensemble of models to
select representative candidates for more detailed full-physics coupled reservoir
simulations.James Watt Scholarshi
Visual place recognition for improved open and uncertain navigation
Get PDFVisual place recognition localises a query place image by comparing it against a reference database of known place images, a fundamental element of robotic navigation.
Recent work focuses on using deep learning to learn image descriptors for this task
that are invariant to appearance changes from dynamic lighting, weather and seasonal
conditions. However, these descriptors: require greater computational resources than
are available on robotic hardware, have few SLAM frameworks designed to utilise
them, return a relative comparison between image descriptors which is difficult to interpret, cannot be used for appearance invariance in other navigation tasks such as
scene classification and are unable to identify query images from an open environment that have no true match in the reference database. This thesis addresses these
challenges with three contributions. The first is a lightweight visual place recognition
descriptor combined with a probabilistic filter to address a subset of the visual SLAM
problem in real-time. The second contribution combines visual place recognition and
scene classification for appearance invariant scene classification, which is extended
to recognise unknown scene classes when navigating an open environment. The final contribution uses comparisons between query and reference image descriptors to
classify whether they result in a true, or false positive localisation and whether a true
match for the query image exists in the reference database.Edinburgh Centre for Robotics and Engineering and Physical Sciences Research Council (EPSRC) fundin
Examining the influence of the social context in the perception, provision, and receipt of social support in sport : a multi-method approach
Get PDFThe purpose of this thesis was to investigate how social support works by
examining the social context that underpins the perception, provision, and receipt of
social support in sport. This thesis makes an original and distinct contribution to the
field by adopting a multi-method investigation of the role of the physical (i.e., spatial
centrality) and social (i.e., social identity) environments in the experience of social
support. Four original studies are reported in three empirical chapters. In Chapter 3, two
cross-sectional studies are reported in which the moderating role of social identity in the
relationship between spatial centrality and social support was explored. Findings
indicated that individuals who were spatially peripheral to their group were at risk of
perceiving and receiving lower levels of social support. In Chapter 4, a laboratory
experiment is reported in which the effects of social identity on the perception of
support, self-efficacy, and the receipt of support were examined. Findings indicated that
shared social identity structured the perception of available support, the interpretation of
received support (i.e., experimentally provided support), and provided a source from
which self-efficacy beliefs were derived. In Chapter 5, a longitudinal mixed-methods
study is reported in which the temporal relationships between social identity, perceived
support, and received support were investigated. Findings indicated a bi-directional
relationship between social identity and perceived support across three time points.
Further, the receipt of support appeared to bolster levels of social identity. Qualitative
evidence indicated that while groups norms were crucial to developing a shared
understanding of support expectations, the receipt of support was contingent on
individual approaches to seeking it. Overall, this thesis makes several original and
distinct contributions to the field by demonstrating that the physical and social
environments appear to underpin the perception, provision, and receipt of social
support
The application of ruthenium phosphinine complexes in catalysis and aluminium amino bis(phenolate) complexes for the ROCoP of CO2
Get PDFThis thesis consists of two parts.
Part 1
This work describes the synthesis of ruthenium phosphine and phosphinine hydrides
without the requirement for high pressured hydrogen gas. Firstly, several ruthenium
phosphine chlorides were synthesised successfully as starting materials. Hydrogen/
hydride donors were trialled for the source of hydrogen with cis-[Ru(H)2(dppm)2] able to
be synthesised using NaOH/ROH mixtures (ROH = MeOH, EtOH and iPrOH) or two
equivalents of Na[HBEt3]. [RuCl2(tetraphos)] (tetraphos = PP3 = P(CH2CH2PPh2)3) and
[RuCl2(PP´)2] (PP´ = 2-phosphinophosphinine, 2-PPh2-3-Me-6-SiMe3-PC5H2) were
converted into their analogous dihydrides using two equivalents of Na[HBEt3]. The first
metal dihydride supported by phosphinophosphinine ligands, cis-[Ru(H)2(PP´)2], was
synthesised successfully and fully characterised. Ruthenium dichloride tridentate
phosphine complexes featuring etp (bis(diphenylphosphinoethyl)phenylphosphine) and
triphos (1,1,1-tris(diphenylphosphinomethyl)ethane) were synthesised as ionic triply chloride-bridged dimers, but addition of Na[HBEt3] did not lead to well characterised
hydride complexes, despite 1H NMR spectroscopy revealing the presence of hydride
resonances. The hydride complexes that proved difficult to isolate were therefore
generated for use in catalysis by in-situ reactions. These hydride complexes were utilised
in H-atom catalytic reactions. The different phosphine ligand systems were compared
with respect to their performance in catalysis and revealed that cis-[Ru(H)2(PP´)2] was a
successful catalyst for the acceptorless dehydrogenation of benzyl alcohol to benzyl
benzoate, albeit at similar rates to [Ru(H)2(dppm)2].
Part 2
The ROCoP (Ring Opening CoPolymerisation) of cyclohexene oxide (CHO) and CO2
performed well with three aluminium bis(phenolate) compounds in the presence of an
activating agent PPNCl. Interestingly, a switchable polymer system could be achieved
by the addition or removal of the activating agent. When present, PPNCl successfully
incorporated CO2 into the polymer chain producing a polycarbonate and in the absence
of PPNCl, the methyl group present on the Al-ABP complexes polymerised the CHO
forming a polyether. The ROCoP of limonene oxide and CO2 proved futile with the Al-ABP complexes; therefore, the focus of the polymerisations was on cyclohexene oxide.
CHO performed well at the ROCoP of CHO and CO2 at low pressures of CO2 down to 5
bar and at moderate temperature of 60 °C without impacting the percentage incorporation
of carbonate linkages. The conversion of CHO and CO2 with one of the Al-ABP
complexes was not affected by lowering the reaction temperature from 75 °C to 60 °C.
Due to the viscosity of the reaction solution, there was a conversion limit of 60% for the
formation of poly(cyclohexene carbonate). To overcome this toluene was added to the
reaction mixture which led to increased molecular weights.EPSRC Centre for Doctoral Training in Critical Resource Catalysis (CRITICAT) Fundin
Access Repository Dashboard
Do you manage ROS: The Research Output Service. Heriot-Watt University Edinburgh ? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!