NUI Maynooth Eprint Archive
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Real-time control of oscillating water column wave energy converters
No full textIn order to build a carbon-free society, the production of clean and affordable
electric energy is vital. Furthermore, to reduce variability and minimise the need
for potentially expensive energy storage systems, the diversification of renewable
energy resources is essential. To this end, wave energy is a significant and almost
untapped source of renewable energy, which can considerably contribute to the
renewable energy mix and, ultimately, to decarbonisation.
Wave energy converters (WECs) harness wave power by exploiting different
operating principles. However, due to the relatively high levelised cost of energy
(LCoE) associated with wave energy projects, WECs struggle to penetrate in the
electric power industry market. A key step to minimise the LCoE, and therefore
improve WEC commercialization, is to develop high-performance, real-time, control
strategies to maximise the electric energy produced over the WEC lifetime. In
particular, this thesis focuses on enhancing the economic viability of a specific
type of WEC, known as the oscillating water column (OWC) WEC, by improving
state-of-the-art OWC control techniques.
The OWC system is one of the most promising WECs, especially due to its
simplicity of operation, the possibility to easily dissipate excessive power, and the
fact that all the moving parts are above the water level, meaning that maintenance
operations are potentially less complex and expensive. To date, due to the critical
importance of turbine performance, OWC control strategies mainly focus on an
oversimplified control objective, namely turbine efficiency maximisation, ignoring
hydrodynamic and electric generator performance. In this thesis, possible staticefficiency-
based and dynamic control strategies to optimise the (overall) wave-towire
(W2W) energy conversion process of OWC WECs are designed. Furthermore,
as an alternative to relatively laborious model determination from first principles,
the potential of data-based modelling techniques to provide parsimonious, controloriented,
OWC hydrodynamic models, is investigated. Finally, to maximise OWC
WEC profitability, it is important to consider peak-shaving (or rated power) control,
to extend the OWC operational range and, consequently, improve the capacity
factor. Since peak-shaving control affects the optimal sizing problem for an OWC
PTO, a control co-design approach is devised in this thesis to assess the benefit
of rated power control. Ultimately, peak-shaving control, used in combination
with control co-design techniques, can significantly reduce the LCoE by improving
the capacity factor
Investigating the Roles of the N-Degron Pathway in Regulating the Crosstalk Between Hypoxia and the Innate Immune Responses.
No full textHow plants integrate and respond to multiple simultaneous or consecutive stresses is an increasingly pressing question with the advent of Climate Change. Presented in this Ph.D. thesis is an exploration of the crosstalk between hypoxia and immune responses and the role of the N-degron pathway in its regulation. Transcriptomic analyses using RNA-Seq facilitated dissection of Arabidopsis responses to combined hypoxia and flg22, uncovering interactions between responses to these stresses. It was discovered that hypoxia represses flg22-induced responses at the gene level and also dampens cellular immune responses (e.g. MAPK signalling and callose deposition). This work also found combined hypoxia/flg22 treatments induce novel responses which may point towards pathways that antagonise multi-stress resistance but also those which lie at the intersection of multiple stresses. One pathway which was particularly enriched under combined treatments was jasmonic acid (JA) signalling. The phytohormone JA is well known for its involvement in plant stress responses and this study further highlighted its role as a potential point of intersection for hypoxia and flg22 responses. Further, a potential role for the N-degron pathway in the removal of repression of JA signalling by the repressor protein, JASMONATE ZIM-DOMAIN 8 (JAZ8), was proposed by this work, with an N-degron pathway component, ARGINYL-TRANSFERASE 1 (ATE1), binding JAZ8 and mediating its destabilization. This further supports JA as a point of crosstalk between hypoxia and flg22 responses with the N-degron pathway potentially playing a regulatory role. Similar work to that in plants was attempted in mammals to allow direct comparison of conserved roles of the N-degron pathway in innate immunity and its role in the interplay between hypoxia and immunity. Aims to generate ATE1 knockout RAW264.7 macrophages were however unsuccessful, halting this work
How do we think in movements? Learning, knowledge and struggle
No full textIn June 2003, I was standing over a photocopier running off programmes for an activist
get-together in inner-city Dublin. Over that weekend, perhaps 150 activists crowded
into the rooms of an old Georgian house, now a trade union social club, to share their
experiences of organising – how to carry out direct action, how to make alliances
between movements, how to deal with burnout, how to work with internal diversity,
how to build alternative media, in the fifth of a series of “Grassroots Gatherings
Belgium
No full textBelgium has a small East Asian diaspora, within which the Chinese community is the largest,
as well as a long local reception of Chinese and Japanese art, philosophy and religion which led
to some Belgians identifying as Buddhist from the 1950s onward. Today there are a significant
number in particular of Belgian Buddhist converts in various East Asian traditions, with centres
identifying as “Zen” (sometimes in practice Ch’an, Thiền or Sŏn) the most visible, alongside
East Asian-led groups. East Asian Christianities, new religious movements, holistic healing and
martial arts are all also visible. Research on East Asian religiosities in Belgium is constrained
both by a shortage of statistical data and limited scholarly interest
Model-Free Linear Noncausal Optimal Control of Wave Energy Converters via Reinforcement Learning
No full textThis article introduces a novel reinforcement learning (RL) method for wave energy converters (WECs), which
directly generates linear noncausal optimal control (LNOC)
policies on continuous action space. Unlike other existing WEC
RL algorithms looking at the problem mainly from a learning
perspective, the proposed RL approach adopts a control-theoretic
approach by delving into the underlying WEC energy maximization (EM) optimal control problem (OCP). This leads to
control-informed decisions on choosing the RL state, as well as
developing the RL structure. The proposed model-free LNOC
(MF-LNOC) offers substantial advantages, including significantly
improved performance due to the use of noncausal information,
a simplified RL with linear actor and quadratic critic structures,
and remarkable fast convergence speeds, achieved using less than
150 s of data points, for a benchmarked point absorber, which can
be further shortened using the replay technique. This reduction
in training time allows for controller reconfiguration in pace with
sea changes. Demonstrative numerical simulations are presented
to verify the efficacy of the proposed methods. The proposed
MF-LNOC also shows robustness against wave prediction inaccuracies and changing sea conditions. The MF-LNOC methodology
can be highly attractive for WEC developers who want to design
an efficient and reliable controller for WECs but also hope to
avoid the challenge of establishing a control-oriented model that
can preserve high fidelity over a wide range of sea condition
On the Effective Implementation of Control Structures to Multi-DoF wave Energy Converters
No full textMaximising energy output through advanced control strategies is pivotal for the economic viability of wave
energy converters (WECs). However, most existing literature
primarily focuses on theoretical case studies, where WECs are
constrained to operate in a single degree of freedom (DoF).
This simplification is made due to the added complexity of
optimizing across multiple DoFs. In this study, we assess the
necessity of incorporating multiple DoFs within the control
framework, evaluating its effectiveness in a numerical simulation environment that replicates WEC performance across
multiple DoFs. To provide a basis for comparison, we contrast
the conventional PI controller with the innovative LiteCon
controller. Our study reveals two key findings: (i) Single DoF
control may suffice when the primary DoF of the power takeoff system is accurately identified, and (ii) the straightforward
LiteCon controller outperforms the traditional PI controller by
a significant margin
Historical trends of floating wind turbine fatigue loads (Ireland 1920–2010)
No full textWe present a new method for analysing the fatigue loads of offshore floating wind turbines over the long term. In this method, bias-corrected wind and wave data from the 20th century (ERA20C versus ERA5 reanalysis) is used for an energetic sea location in western Ireland. To reduce the computational cost and theoretical complexity, the sea states were clustered into categories to indicate how these categories evolve over three climate periods during a period of 30 years (1921–1950, 1951–1980, and 1981–2010). OpenFAST aeroelastic code simulation in floating mode was then conducted at each sea state for spar-type 5-MW and semi-submersible 15-MW wind turbines. This shows the damage loads and fatigue increments over the century, with some relevant cases (rotor torque, blade pitch and flapping, and tower side–side and fore–aft moments) showing fatigue increments of 5%–8%. Thus, in the new method, historical data are used to create a model to represent the evolution of sea states and corresponding fatigue over the long term, which can be applied globally to future projections
Wave Energy Optimal Control Structure With Second-Order Sliding Mode Tracking: Hardware-in-the-Loop Assessment
No full textThis article presents a hardware-in-the-loop assessment of a moment-based optimal controller including a robust
super-twisting tracking term. The aim of the overall control structure is to maximise the energy extracted by a flap-type wave
energy converter. An experimental assessment is performed via
hardware-in-the-loop testing, which allows experiments in a controlled environment and repeatable conditions. Key aspects of
the control structure are analysed in the results, with particular
focus on the behaviour of the second-order sliding mode tracking term. Robustness against modelling uncertainties and finitetime convergence are evaluated, initially for a single sea state,
and then across three different sea conditions. Excellent tracking
performance is observed for all considered operating conditions.
Finally, the super-twisting algorithm in the tracking loop is compared with the performance of a linear controller synthesised
based on Youla-Kuˇcera parametrisation, observing that the former
presents better tracking capabilities, also outperforming in terms of
energy extraction
Policy, planning practice and the lived experience in a changing Ireland: Provoking thoughts for/of change?
No full textRecent planning frameworks and policies have formally recognised the significance of the urban in contemporary Ireland and put in place the groundwork to accommodate, facilitate, and accelerate ‘metropolitanisation.’ If implemented, this new strategic positioning can move Ireland in the direction of more balanced development. However, the new spatial arrangements pose profound implications for existing modes of organisation and economic activity in cities and towns, as well as the rural sphere. Additionally, implementation of the new spatial and economic strategies are challenged by certain factors unique to the Irish context raised in this paper in the form of three provocations: 1) Ireland’s colonial legacies and mindsets hinder appropriate planning and development; 2) the historically grounded idealisation of the rural flattens lived experiences; and 3) moving beyond post-colonial confines requires a new and variegated politics of the urban and rural commons. These provocations serve to to open up a collective dialogue on the contours of a more mature approach to planning practice and policy development in Ireland that more closely resonates with lived experiences
Achieving Regional Equality
No full textGoverning from the metropolitan scale is not a
concept that is widely comprehended in Ireland.
And yet, the 2018 National Planning Framework
(NPF) statutorily mandates Ireland’s three regional
assemblies to develop what they term Metropolitan
Area Strategic Plans (MASP) for each of their
respective regional cities. This is a challenge for the
three regional assemblies because the purpose and
power of the metropolitan scale and its designation
is little understood amongst planners, policymakers
and the general public. Additionally in a staunchly
centralised Ireland, the regional assemblies as
governance bodies are under-recognised and underappreciated.
When done correctly, various opportunities can
stem from city-regional governance. Amongst
development scholars, strengthening lower tiers
of governance is beneficial particularly to identify
places in need of policy attention. However, in order
to effectively legitimise meso-level governance and
to successfully implement the Regional Spatial and
Economic Strategies (RSES) and MASPs, people’s
awareness of how the city-regional scale can benefit
them and their locality must first be addressed.
This policy report is based on research that took
place between September 2021 – December 2022.
Funded jointly by the Irish Research Council (IRC)
and the Southern Regional Assembly (SRA), the
research focuses on Ireland’s Southern Region, its
Assembly (SRA) and its executive (SRA Executive)
as a case study to observe and document the
relatively new process of ‘metropolitanisation’ in
Ireland in order to offer insight into implementatio