George A. Aggidis

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• Professor
• Head of Energy Engineering at Lancaster University

The untapped potential of wave energy offers another alternative to diversifying renewable energy sources and addressing climate change by reducing CO2 emissions. However, development costs to mature the technology remain significant hurdles to adoption at scale and the technology often must compete against other marine energy renewables such as of...

The technologically advanced learning ocean system—wave energy converter (TALOS-WEC) project addresses the urgent need for sustainable and efficient energy solutions by leveraging the vast potential of wave energy. This project presents a pioneering approach to wave energy capture through its unique multi-axis and omnidirectional point absorber des...

Oscillating water column (OWC) wave energy converters (WECs) are very popular types of wave energy converters due to their practical implementations, their versatility in deployment in different marine environments, and their high reliability in wave energy conversion. In development, different forms of OWCs have been proposed and advanced, such as...

Fuel cells (FCs) offer several operational advantages when integrated as a power source in electric vehicles (EVs). Since the voltage of these cells is typically low, usually less than 1 V, the power conversion system requires a DC–DC converter capable of providing a high voltage conversion ratio to match the input voltage of the motor propulsion s...

This study examines the TALOS wave energy converter that is equipped with multiple PTOs to enable multi-axis wave energy capture. In order to optimize the control of multiple PTOs, a WEC-Sim model of TALOS has been used to quantify the impact of PTO stiffness and damping and to understand the influence of separately actuating individual PTOs rather...

The west coast of Great Britain has the potential for barrages to create tidal range reservoirs that both facilitate electricity generation and prevent flooding from sea level rise. Seawater flows into and out of the reservoir, or impoundment, through turbines and sluices. The impounded water follows the natural tidal sequence but with a delay whic...

The efficient and sustainable supply and transport of water is a key component to any functioning civilisation making the role of urban water systems (UWS) inherently crucial to the wellbeing of its customers. However, managing water is not a simple task. Whether it is aging infrastructure, transient flows, air cavities or low pressures; water can...

The Pelton turbine has been widely regarded as the most efficient hydro turbine for high head applications. However, the Pelton turbine buckets, especially the area commonly referred to as the ‘splitter’, are highly susceptible to erosion, drastically reducing efficiency over prolonged periods of time. This paper demonstrates a novel turbine idea t...

Tidal range electricity generation schemes are designed to have a minimum operational life of at least 120 years, making it important to plan for changes such as Sea Level Rise (SLR). Previous studies have shown that schemes can maintain the existing tidal range within the impoundment and protect areas from flooding. Here it is demonstrated that ti...

As the world strives towards its goal of net zero carbon emissions, it is vital that renewable energy sources be optimized to their full potential. A key source of renewable energy is hydropower, more specifically, the Pelton turbine—a highly efficient, widely used, and well-researched piece of turbomachinery. This review proposes a methodology tha...

The Lancaster in-house code is a time-domain analysis code, developed especially for the TALOS wave energy converter, a novel wave energy conversion technology. The TALOS wave energy converter is a point absorber-like wave energy converter, but with a unique power take-off (PTO) system. The whole PTO system is fully enclosed within the structure, h...

In this study, we present the development of a numerical model of the TALOS Wave Energy Converter (WEC) in WEC-Sim and compare it with existing numerical in-house models from Lancaster and results from DNV's Sesam code. The objective of this work is to validate the performance of the TALOS WEC using WEC-Sim and compare the results with those obtain...

As global energy demands and climate concerns continue to grow, the need for renewable energy is becoming increasingly clear and wave energy conversion (WEC) systems are receiving growing interest. Over the years, many WEC systems have emerged but most of these systems are designed to extract energy from a single direction of motion. In reality, th...

With the current increase in demand for animal and agricultural products, management of agrowaste has become critical to avoid greenhouse gas emissions. The present article investigates the applicability of ammonium bicarbonate synthesis via flash distillation to valorize and stabilize several types of anaerobic digestates which are produced from i...

Dear Colleagues, Promoting a circular economy is essential for our society to thrive, however the proposed strategies for valorization of the biomass are often not coherent. From a holistic perspective, all steps of bioenergy processes should also contribute to the fractionation of the nutrients (i.e., C, N, P, S and K) for better management of the...

Optimal control techniques can oversee the power take off (PTO) operation of wave energy conversion systems to ensure that the overall power output is maximized, but optimization in real-time poses difficulties given the wave variability and the underlying constraints of the system. This study examines several different model predictive control (MP...

The present study provides details on the power capture performance of TALOS WEC based on PTO system parameters. Considering that only surge, heave and pitch modes of motions are directly coupled to the incident sea waves. Hence, the model is defined to be a 3 DOF model. The PTO system is modelled by using ideal elements. The study focuses on surge...

Most creatures are highly adapted to the environment for survival through the evolutionary process and developing useful biological features for design inspirations could improve the performance of Wave Energy Converters (WECs), such as the TALOS WEC. A method of obtaining biological inspiration to conceive novel design is provided in this paper. T...

This paper presents and discusses the performance of a new cascaded modular power electronic converter for Wave Energy Conversion (WEC) systems. The proposed electrical power converter employs submodule units to replace the central conventional power converter aiming to bring additional benefits of scalability, lower voltage and current stresses, b...

This paper explores the variability of wave power in space and time using a 42-year high-resolution hindcast wave model from the Copernicus Marine Environment Monitoring Service for the North-West European shelf. We calculate the wave energy flux using significant wave height and wave energy period. To improve wave power assessment, we use knowledg...

Currently, there are many different wave energy converters. Their levelized cost of energy of extracting wave energy are still much higher than other matured renewables. The findings of the review show that disagreements of levelized cost of energy are due to the different cost constitutions and their measuring method of capital expenditure and ope...

Wave energy shows potential to provide electricity in a renewable manner. The TALOS WEC (Wave Energy Converter) is a unique design with six PTO (Power Take-Off) elements to provide six Degrees of Freedom (DOFs), which is potentially able to harvest energy more efficiently than traditional single-DOF devices. As a step towards its optimisation and c...

TALOS wave energy converter is a point absorber proposed at Lancaster University (UK), with its main advantage being its ability to absorb energy from all motion modes (i.e. multi-axis Power-Take-Off system). Following previous computational studies in the frame of device development (including frequency-domain modelling), here we present a motion...

The TALOS Multi Axis Wave Energy Converter (WEC) research project recommends investigations into key aspects of WEC technology and global deployment potential, requiring the integration of novel methodologies across optimisation, control, condition monitoring and resource forecasting, thus producing advances that will drive evidenced reductions in...

Panel methods based on potential flow theory have been widely employed for wave-structure interactions, since these methods could provide fast, reliable and accurate predictions for the forces acting on and the motions of the marine structures if the strong nonlinear forces are not included in the analyses. In reality, some panel methods can be reg...

This paper focuses on the preliminary time-domain analysis of a multi-mode Wave Energy Converter (WEC), the so-called TALOS WEC, by deploying two different computational tools. The device consists of an internal sphere attached to its floater with springs and dampers, and power is captured through the sphere's motions relatively to the floater. The...

The recent global urbanization problem has set the industry and researchers sights to the importance of safe, effective water distribution due to the unprecedent demand placed on our aging water networks. Our current water practices often increase the degradation of assets through heightened pressures causing more failures and leakage. Whilst the h...

Financial viability and political will ultimately determine if tidal range power schemes are developed. This research aims to demonstrate a robust system to make initial estimates of capital costs for tidal range schemes that can be compared between systems and options. A levelised cost of energy (LCOE) is used to compare a tidal range barrage (Mor...

Wave energy provides a renewable and clear power for the future energy mix and fights against climate change. Currently, there are many different wave energy converters, but their costs of extracting wave energy are still much higher than other matured renewables. One of the best indicators of calculating the generating cost of wave energy is the ‘...

The conservation of water is, justifiably, a huge concern to water companies, regulatory bodies, environmentalist and more but, unfortunately, water loss through leakage can remain undetected for long periods of time without effective leakage detection. Leakage detection in water distribution networks has taken many forms through investigating vary...

Renewable energy resources such as offshore wind and wave energy are environment friendly and omnipresent. A hybrid offshore wind-wave energy (HOWWE) system produces a more efficient, economical and sustainable form of energy than exploitation of the individual resources. The objective of this paper is to give a detailed review of co-generation tec...

Ocean energy systems (OESs) convert the kinetic, potential, and thermal energy from oceans and seas to electricity. These systems are broadly classified into tidal, wave, thermal, and current marine systems. If fully utilized, the OESs can supply the planet with the required electricity demand as they are capable of generating approximately 2 TW of...

Tidal range power is gaining recognition as a globally important power source replacing unsustainable fossil fuels and helping mitigate the climate change emergency. Great Britain (GB) is ideally situated to exploit tidal power but currently has no operational schemes. Schemes are large and expensive to construct, assessment of their costs is usual...

The potential power from coastal tidal range is becoming better appreciated due to the need to mitigate global warming. Great Britain (GB) is ideally situated to exploit tidal power but currently has no operational systems. Historically, estuaries have been proposed as sites for barrages, but more recently coastal lagoons are favoured due to a lowe...

This book provides the materials and examples for understanding the fundamentals of the fluid-structure interactions, especially on the wave-structure interaction, which is based on the potential flow theory, and the applications of the wave-structure interaction in wave energy conversion, such as the optimisation and control of the PTO for maximis...

Wood bottom and fly ashes were added to the anaerobic digestate using sulfuric, hydrochloric, nitric, and lactic acids, as pH conditioners and sorption activating agents. Minimum (pH of zero-point charge), mild, and severe acidification of the samples were tested. The solid-liquid separation achieved was accounted visually and with the measurement...

The depletion of world´s mineral resources increases the cost of production of chemical fertilisers for agriculture, due to the need for extraction of raw materials in poorly accessible and inconvenient sites. An enhancement of the circular economy by means of reprocessing clean nutrient-rich waste materials will also address environmental challeng...

The corresponding presentation to the conference paper 'Review of Leakage Detection in Water Distribution Networks' presented in the International Water Association's Hydroinformatics Conference 2022 held in Bucharest, Romania. This presentation includes a quick summary walk-through of the contents of the review paper. This includes a novel classif...

The study of wave-structure interactions involving nonlinear forces would often make use of the popular hybrid frequency–time domain method. In the hybrid method, the frequency-domain analysis could firstly provide the reliable and accurate dynamic parameters and responses; then these parameters and responses are transformed to the parameters to es...

Design inspiration comes from the continuous stimulation of external information and the continuous accumulation of knowledge. In order to obtain an ideal design inspiration from nature, researchers have proposed a large number of biological information retrieval and knowledge acquisition methods. But how to purposefully acquire valuable biological...

The valorization of low pollutant bioenergy waste streams as fertilizers is key for a more circular economy. In addition to supplementing nutrients, the wood fly ash could be used as stabilizing agent of an agrowaste digestate, to minimize the pollution of the environment. A two-stage experimental design with series of mild and severe acidification...

Current panel methods for wave-structure interactions employ the potential flow theory, which provide fast, reliable and relatively accurate predictions for the marine structures, and now some open source packages, NEMOH and HAMS, are available. In this research, the relative utility and performance of NEMOH and HAMS is compared with the well-known...

Biomimetics and creatures could contribute to novel design inspiration for wave energy converters, as we have seen numerous examples in applications of other branches of engineering. However, the issue of how to obtain valuable biological entities, or bionic design cases, that could produce inspiration for novel designs, may be challenging for the...

The present study investigated the acidification treatment of an agrowaste digestate and a food waste digestate, which is necessary before the addition of the wood ashes to attain the pH of zero point of charge in the blend intended to behave as a slow-release fertilizer. The 336-h acidification treatments of the 2.39 ± 0.35 g of digestates were pe...

The wood ash-based treatment of anaerobic digestates is a novel technology to achieve the stabilization and improve the properties of organic amendments as slow-release fertilizers. The present work evaluated 3 strategies to optimize the blending of these materials under minimum acidification. The first strategy consisted in the titration of 2 samp...

The detection of cavitation formation in hydraulic turbomachinery has been widely investigated due to its significant impact on their steady and dynamic operation. The aim of this study is the application of Spectral Kurtosis tool in order to effectively detect the impulsive shock waves generated during the implosion of vapour bubbles. The methodol...

In the Global South, pico- and micro-hydropower turbines are often made by local workshops. Despite several advantageous features, e.g., a high power density and capacity to handle silt, there is no commonly available Turgo turbine design appropriate for local manufacture. Technological developments including the internet, CAD, and additive manufac...

About 50% of all hydropower plants (HPPs) worldwide were originally commissioned more than 40 years ago, so that the advanced age of the fleet is a major concern across all continents, and especially in Europe. The modernization of HPPs can generate several benefits in terms of generation, flexibility, safety, operation, and may have neutral or eve...

The present study combined two nutrient management strategies to improve the marketability of a waste-derived fertilizer: (a) isolation of ammoniacal nitrogen and (b) preparation of a bulk soil amendment. The wood fly ash with low content of pollutants was added to an agrowaste anaerobic digestate as alkaline stabilizer, which promoted the volatili...

Handling of food waste and agro-industrial waste digestates, and fly and bottom wood ashes represents an economic and environmental problem for society and industries where they are produced due to the requirement of large capacity storage facilities with special conditions. Since both materials contain important nutrients for crops, two different...

Water disinfection is an essential process for drinking water use. One of the water treatment process stages includes the application of Ultraviolet (UV) light to assist with the removal of pathogens and viruses such as Cryptosporidium. The previous review in the UV treatment system explores the optical and reaction of microorganisms to the technol...

The addition of wood bottom ash to an agrowaste anaerobic digestate has been proposed for improving the carbon to nutrient ratio of the soil organic amendment (C/N/P < 100/10/1). The ash-based treatment also aimed to improve properties of the anaerobic digestate as controlled-release fertilizer by decreasing the availability of nitrogen, carbon, an...

An important flow mechanism that can affect the performance and efficiency, as also the maintenance cost of centrifugal pumps is cavitation. Scientific research has been focusing on the mechanisms that govern cavitation in order to develop experimental and numerical tools that are able either to detect the phenomenon or to anticipate its appearance...

Wave energy converter technologies continue to show good progress in worldwide research. One of the most researched technologies, the Oscillating Water Column (OWC), is arguably one of the most popular categories within the converter technologies due to its robustness, simplicity and versatility. However, the versatility of the OWC is still largely...

Ocean wave energy continues to develop through innovation and a growing number of collaborations around the world. With the vast resource of wave energy on our doorstep it remains a focal point in ocean energy engineering with great potential. In order for wave energy to become more competitive and a serious player in the renewable energy mix, such...

Anaerobic digestate is a waste product of biogas generation which is produced in large amounts and, because of its high water content, it is expensive to store, transport, and spread to land. Additionally, special conditions are required for land application to minimise the losses of nutrients. This material is primarily used as source of organic m...

The experimental investigation of the corrosion resistance of welded shipbuilding and submarine steels with the optimum weld quality which can be used in the future for the improvement of the quality of already existing underwater marine systems (including oil platforms, bridge columns and ships) and for the construction of new and unfamiliar under...

Many consider the Pelton turbine a mature technology, nevertheless the advent of Computational Fluid Dynamics (CFD) in recent decades has been a key driver in the continued design development. Impulse turbine casings play a very important role and experience dictates that the efficiency of a Pelton turbine is closely dependent on the success of kee...

Transient safety assessment of hydroelectric generation systems is a major challenge for engineers specialized in hydropower stations around the world. This includes two key scientific issues: the dynamic risk quantification in a multi-factors coupling process, and the identification of elements with highest contribution to system stability. This p...

The paper reviews recent research and development activities in the field of hydropower technology. It covers emerging and advanced technologies to mitigate flow instabilities (active and passive approach) as well as emerging magneto-rheological control techniques. Recent research findings on flow instabilities are also presented , especially conce...

Currently there is renewed interest in harnessing the vast tidal resource to combat the twin challenges of climate change and energy security. However, within the UK no tidal barrage proposals have passed the development stage, this is due to a combination of high cost and environmental concerns. This paper demonstrates how a framework, such as the...

Hydraulic generating systems are widely modeled in the literature for investigating their stability properties by means of transfer functions representing the dynamic behavior of the reservoir, penstock, surge tank, hydro-turbine, and the generator. Traditionally, in these models the electrical load is assumed constant to simplify the modeling proc...

Wave energy development continues to advance in order to capture the immense ocean energy available globally. A large number of wave energy conversion concepts have been developed and researched to date but we are still not able to see a convergence of technologies. This provides the requirement and additional opportunity for further research. This...

Impulse turbine casings play a very important role and experience dictates that the efficiency of a Pelton turbine is closely dependent on the success of keeping vagrant spray water away from the turbine runner and the water jet. Despite this overarching purpose, there is no standard design guidelines and casing styles vary from manufacturer to man...

This paper reports the initial results of three dimensional CFD simulations of the jet – runner interactions in a twin jet horizontal axis Pelton turbine. More specifically, the analysis examines the impact of the nozzle and spear valve configuration on the performance of the runner. Previous research has identified that injectors with notably stee...

The material selection for the improvement of the quality of already existing underwater marine systems (including oil platforms) and for the construction of new and unfamiliar underwater sea-structures (including the submerged parts of Wave Energy Converters and Tidal Energy Converters) in many countries like Greece is an essential parameter from...

The experimental determination of the optimum values of welding parameters and consequently the optimum weld quality of shipbuilding and submarine steels which can be used in the future for the improvement of the quality of already existing underwater marine systems (including oil platforms, bridge columns and ships) and for the construction of new...

Some animals and plants have special functions and structures. They are the result of biological evolution and Nature's ideas. The question to answer is how to use these biomimetic ideas to design the next generation of wave energy converters. In this paper, the characteristics of the existing wave energy converters are analyzed using biomimetic id...

In previous works, the authors presented computational fluid dynamics (CFD) results, which showed that injectors with noticeably steeper nozzle and needle tip angles 110 deg & 70 deg and 150 deg & 90 deg, respectively, attain higher efficiency than the industry standard, which, according to available literature on the public domain, ranges from 80...

The continuously increasing industrial productivity has resulted in a great breakthrough in the field of maintenance on centrifugal pumps in order to ensure their optimum operation under different operating conditions. One of the important mechanisms that affect the steady and dynamic operation of a pump is cavitation, which appears in the low stat...

Progress in wave energy lags behind most other forms of renewable energy despite there being strong technological capabilities across all engineering fields. As true fuel reserve figures become uncertain, prices begin to rise and global pressure to reduce carbon emissions increases, renewable energy development becomes a much larger priority. The p...

Impulse turbine casings play a very important role and experience dictates that the efficiency of a Pelton turbine is closely dependent on the success of keeping vagrant spray water away from the turbine runner and the water jet. Despite this overarching purpose, there is no standard design guidelines and casing styles vary from manufacturer to man...

This paper reports the initial results of three dimensional CFD simulations of the jet-runner interactions in a twin jet horizontal axis Pelton turbine. More specifically, the analysis examines the impact of the nozzle and spear valve configuration on the performance of the runner. Previous research has identified that injectors with notably steepe...

Tidal energy is one of the most predictable forms of renewable energy. Although there has been much commercial and R&D progress in tidal stream energy, tidal range is a more mature technology, with tidal range power plants having a history that extends back over 50 years. With the 2017 publication of the "Hendry Review" that examined the feasibilit...

Tidal energy is one of the most predictable forms of renewable energy. Although there has been much commercial and R&D progress in tidal stream energy, tidal range is a more mature technology, with tidal range power plants having a history that extends back over 50 years. With the 2017 publication of the "Hendry Review" that examined the feasibilit...

The impact of the nozzle and spear valve configuration on the performance of a Pelton turbine is investigated both experimentally and computationally. A previously published computational fluid dynamics (CFD) study has shown that injectors with noticeably steeper nozzle and spear angles, 110° and 70° respectively, attain a higher efficiency than th...

Several numerical investigations into the impact of the spear and nozzle configuration of impulse turbine injectors can be found in the literature, however there is little or no experimental data available for the effect on Turgo impulse turbine performance. A recent 2D numerical Design of Experiments (DoE) study found that much steeper nozzle and...

The first part of the article provides an overview of both single-axis and multi-axis wave energy converter (WEC) technology, with a particular focus on present and past prototype devices. The second part of the article considers a multi-axis concept device that has been developed and tank tested at Lancaster University by successive Master of Engi...

Centrifugal pumps are considered as machines of high importance in a wide range of industries, hence several strategies and methods have been developed in order to ensure their optimum performance under different operating conditions. An important mechanism that can affect pump's steady and dynamic operation is cavitation, which appears in the low...

Tidal range technology has seen much development and interest in recent years. The times when a barrage scheme would be rejected due to environmental and cost concerns is coming to an end. A large variety of new lower cost and less invasive methods have since emerged in the forms of tidal lagoons, reefs and fences. Since the construction of La Ranc...

Global energy focus is turning more and more towards renewable energy. With legally binding agreements requiring a drastic increase in the percentage of national energy demand created with renewable sources, tidal energy holds an important advantage – predictability. The UK is fortunate, having the greatest potential for this energy in the world, w...

The Turgo Impulse turbine provides a unique and novel solution to increasing the capacity of a hydraulic impulse turbine while maintaining the nozzle and spear injector system (as used in Pelton turbines) for flow regulation. This has produced a turbine which operates in the higher flow ranges usually reserved for Francis machines while maintaining...

The regenerative liquid ring (RLR) pump is a type of rotodynamic machine which has the ability to develop high heads at relatively low flow rates in only one impeller stage. Although the exact principle of operation of this type of pump has been a phenomenon not fully understood, it has nevertheless been widely applied for over a century in areas o...

This paper examines the optimum power output of a pitching-surge point absorber wave energy converter in irregular wave climates. A mathematical model based on frequency domain is used as the first step to estimate the hydrodynamic parameters of the device and its potential power output in realistic sea waves. The numerical results predict that the...

The Archimedes pump is one of the oldest feats of engineering still being used today. In recent times, it has seen a major revival in modern engineering, by reversing it for use as a turbine. This is now an established turbine, being used in Europe since 1994. It has been found this new turbine device has a plethora of advantages over current exist...

The recent development of Computational Fluids Dynamics (CFD) has allowed the flow modelingin impulse hydro turbines that includes complex phenomena like free surface flow, multi fluid interaction, and unsteady, time dependent flow. Some commercial and open-sourceCFD codes,which implement Eulerian solving methods, have been validated against experi...

Two computational methodologies – computational fluid dynamics (CFD) and the numerical modelling using linear potential theory based boundary element method (BEM) are compared against experimental measurements of the motion response of a pitching wave energy converter. CFD is considered as relatively rigorous approach offering non-linear incorporat...

This paper uses two modern commercial CFD software packages to compare the performance of a standard and improved impulse turbine injector developed in a previous study. The two injector designs are compared by simulating the two-dimensional (2D) axis-symmetric cases as well as full three-dimensional (3D) cases including the bend in the branch pipe...