Alireza Maheri

• PhD CEng
• Professor of Mechanical Engineering; Personal Chair at University of Aberdeen

Porous graded materials found in nature can be regarded as variable stiffness optimised load carrier elements that exhibit beneficial properties for real-life engineering designs. In order to investigate the nonlinear behaviour of variable stiffness bioinspired materials, the large deflection of functionally graded beams made from porous materials...

Multiobjective optimisation and integrated aerodynamic-structural design of wind turbine blades are emerging approaches, both requiring significant number of high fidelity analyses. Designer-in-the-loop blade modelling and pre/ post-processing using specialised software is the bottleneck of high fidelity analysis and therefore a major obstacle in p...

The recent steep decline in the cost of PV panels and wind turbines provides an opportunity to utilise Hybrid Renewable Energy Systems (HRES) to fulfil thermal loads as well as the electrical demand. Two coupled system architectures are proposed and studied along with the base case of uncoupled architecture for comparison. The coupled systems inclu...

A generic integrated configuration-size optimisation formulation for design of hybrid renewable energy systems (HRES) is presented in this paper. This formulation allows identifying the optimum configuration for a given site and the optimum size of each component in that configuration by solving only one optimisation problem. Single and multiobject...

This study investigates the influence of ambient conditions on cryogenic cooling times for medium-carbon steel-grade ISO EN 1.0456 (ASTM A333 Gr.6) processing pipes, focusing on the air velocity, ambient temperature, and cooling medium. Using MATLAB, baseline cooling times were computed for air velocities of 0–25 m s⁻¹, considering both in-air cool...

This paper presents a feasibility study of the Cryogenic Cooling and Cutting System (CCCS), an embrittlement-based technique for offshore wind monopile foundations. The CCCS employs cryogenic treatment of the monopile wall surface to significantly reduce its impact energy absorption capability significantly, aiming to achieve shorter overall cuttin...

This study delves into the significant area of low-energy impact fracturing within ISO EN 1.0577 (S355J2) mild carbon steel grade, exploring its cooling time depending on diverse temperature gradients across varying wall thicknesses. The cooling behavior is analyzed systematically to comprehend the material's structural dynamics under different the...

This study investigates the influence of ambient conditions on cryogenic cooling times for low-carbon steel-grade ISO EN 1.0456 (ASTM A333 Gr.6) processing pipes, focusing on air velocity, ambient temperature, and cooling medium. Utilising MATLAB, baseline cooling times were computed across air velocities ranging from 0 to 25 m/s, encompassing in-a...

This paper presents a feasibility study of the Cryogenic Cooling and Cutting System (CCCS), an embrittlement-based technique for offshore wind monopile foundations. The CCCS employs cryogenic treatment of the monopile wall surface to significantly reduce its impact energy absorption capability significantly, aiming to achieve shorter overall cuttin...

The wind energy sector has experienced a significant expansion during the past two decades. With the current global appetite for the further expansion of offshore wind farms (OWFs) as one of the main renewable energy resources, a vast number of OWFs are expected to enter the decommissioning stage in the near future which may potentially create seri...

Industry Challenge: One of the significant challenges for the decommissioning industry is to reduce the cutting time and carbon emissions through the removal of old carbon steel structures and pipes. Therefore, this research project aims to define the effect of different ambient conditions on the cooling time needed for different carbon steel grade...

In multi-energy systems the full utilisation of the generated energy is a challenge. Integrating heat and electricity supply at the system level design could provide an opportunity to address this challenge. In this paper we introduce and examine two coupled thermal-electrical dispatch strategies for grid-connected hybrid multi-energy systems suppl...

Figure 1-DBTT Curve for the low (mild) Carbon Steel Grade of: ISO EN 1.0577 (S355J2) The Aims and Objectives of the Conceptual Design: 1. Investigate a new cutting technique based on a low impact energy shattering method, which utilises the embrittlement concept of Ductile to Brittle Temperature Transition (DBTT) of ISO EN 1.0577 (S355J2). 2. Inves...

We have witnessed an energy transition movement towards low carbon sources which necessarily involves the implementation of large-scale electricity generation from renewable energy sources. Due to land area restriction, several countries will face limitations to their solar photovoltaic energy generation potential. In this way, wind energy will gai...

EMB Future Science Brief No. 9 provides an overview of the technology and European deployment status in the offshore renewable energy sector. It discusses the environmental and socioeconomic considerations, and presents the key knowledge, research, and capacity gaps that must be addressed to ensure sustainable delivery of the EU Green Deal. It clos...

This study presents an overall assessment of the current five most conventional cutting technologies in the offshore industry from the economic, production, safety, and environmental impact viewpoints. The applicability, advantages, and disadvantages of each cutting technique for cutting operations of jacket structures are summarised. The cutting t...

1. To investigate a new cutting technique based on an impact shattering method, which utilising the embrittlement concept of Ductile to Brittle Transition (DBT) of mild carbon steel types. 2. To investigate thermal distribution and fracture propagation in for the shattering process of Offshore Monopile Foundations (OMF). 3. To evaluate the effect...

There has been a rapid increase in government efforts to expand electric vehicle markets by deploying fast-charging stations, promoting uptake through greater investment, and by enacting supportive policies. Government support and private investment have contributed to the expansion of electric vehicles in many countries. The aim of this study is t...

One key stage common to most offshore decommissioning projects is the removal of a platform's topside. These large, complex structures require the use of highly specialized and expensive vessels to reach a suitable end-of-life state. Stakeholders, therefore, need accurate methods to assess the costs and durations of choosing different decommissioni...

The challenges presented by increased electricity generation from intermittent renewable energy sources can be minimized by incorporating energy storage systems (ESS). Despite the benefits, this is still an emerging technology with limited use in Brazil. The aim of the present study is to use a multiobjective optimization process to support the pla...

This paper investigates the performance of several meta-heuristic algorithms, including Particle Swarm Optimisation (PSO), different variants of Differential Evolution (DE), Biogeography-Based Optimisation (BBO), Cultural Algorithm (CA), Optics-Inspired Optimisation (OIO), and League Championship Algorithm (LCA), for optimum layup of laminated comp...

The lifespan for offshore wind farms (OWFs) is between 20 and 25 years, and with a growing demand for renewable energy, the number of OWFs approaching decommissioning phase will dramatically increase in the coming years. This paper presents a new cost model by adopting a bottom-up approach for the removal and transportation phases of OWF decommissi...

A differential evolution (DE)-based algorithm is used for discrete optimization of steel frames. DE is a simple yet efficient population-based search algorithm, originally proposed for continuous optimization problems. It is based on the same search philosophy as most evolutionary algorithms (EA), utilizing mutation, crossover and selection operato...

This paper presents a data protocol for storing the information which are required for the planning of windfarms decommissioning. The data protocol is the base of a decision support system software tool which allows its user to define various decommissioning scenarios and to evaluate them against cost, risk, and environmental impact measures. The p...

Cultural Algorithms (CAs) are evolutionary algorithms (EAs) inspired by the conceptual models of the human cultural evolution process. In contrast to the conventional EAs, which work only based on the population space, CAs employ an additional space, called belief space, to collect the information about the behaviour of individuals in the search sp...

Planning offshore oil & gas decommissioning requires decision making based on expert domain knowledge. As more tools are developed to assist planners in simulating operations, there is an increased need for data models that can accurately represent the domain. The application of semantic web technologies has recently been suggested as a possible me...

This paper presents the modeling and analysis of a wind energy conversion system with a stand-alone small-scale induction-generator based wind turbine. The wind turbine is connected to a buck converter to achieve maximum power point tracking under variable wind speed conditions and to charge a battery and feed a DC load. Also, this converter is res...

Two new methods for reducing the computational cost of the unsteady vortex lattice method are developed. These methods use agglomeration to construct time‐saving tree structures by approximating the effect of either a group of vortex rings or query points. A case study shows that combining the two new O(n·log n) tree methods together results in an...

In variable-pitch wind turbines, pitch angle control is implemented to regulate the rotor speed and power production. However, mechanical loads of the wind turbines are affected by the pitch angle adjustment. To improve the performance and at the same time alleviate the mechanical loads, a gain-scheduling fractional-order PID (FOPID), where a train...

Variable-speed stall-regulated (VS-SR) wind turbines can be designed to produce power as efficiently as variable-speed pitch-controlled (VS-PC) systems. However, amongst the main drawbacks of VS-SR systems high transient power and low predictability have been the primary factors in favour of adopting VS-PC system for multi-MW wind turbines. Cyclic...

Machining operations are performed on composite parts to obtain the final geometry. However, machining composites is challenging due to their low machinability and high cost. Numerical modelling of machining presents a valuable tool for cost reduction and a better understanding of the cutting process. Meshfree methods are an attractive choice to mo...

A Chebyshev collocation method is presented for the free vibration analysis of geometrically exact nonlinear beams with fully intrinsic formulation. The intrinsic formulation of the governing equations of the beam contains neither displacement nor rotation variables. The proposed collocation discretization technique is based on the Chebyshev points...

The Element-Free Galerkin method (EFG) is a prominent member of the meshfree methods family. In this work, EFG is utilised to simulate the orthogonal cutting process of unidirectional composites. The mathematical model is derived from the weak form of the momentum conservation equation with frictional contact constraints based on penalty method. Sp...

This paper presents an empirical force model quantifying the effect of fibre volume fraction and fibre orientation on the cutting forces during orthogonal cutting of unidirectional composites. Glass fibre plates and high speed steel cutting tools are used to perform orthogonal cutting on shaping machine whereas cutting forces are measured using pla...

The use of active controls has shown to be of substantial help in supporting the increasing size of wind turbines by reducing peak stresses and fatigue loads. In this respect, this paper proposes the use of intuitive frequency-based control strategies for reducing loads in wind turbine blades equipped with multi-input multi-output (MIMO) active flo...

Storage systems are key components of standalone hybrid renewable energy systems due to intermittent nature of renewable resources. In design of standalone hybrid system, the storage system needs to be optimally sized to guarantee power quality, system reliability and cost effective energy supply. In this paper, the most mature and traditional long...

The optimum design of Hybrid Renewable Energy Systems (HRES) depends on different economical, environmental and performance related criteria which are often conflicting objectives. The Non-dominated Sorting Genetic Algorithm (NSGA-II) provides a decision support mechanism in solving multi-objective problems and providing a set of non-dominated solu...

This paper presents an empirical force model quantifying the effect of fibre volume fraction and fibre orientation on the cutting forces during orthogonal cutting of unidirectional composites. Glass fibre plates and high speed steel cutting tools are used to perform orthogonal cutting on shaping machine whereas cutting forces are measured using pla...

Hybrid Renewable Energy Systems (HRES) utilise local renewable resource to supply a local demand load. Traditional size optimisation methods of standalone HRES aim at finding solutions with highest reliability in power supply and producing energy at lowest levelised cost of energy (LCE). In these methods, irrespective of the actual user requirement...

This paper presents a variety of dispatch strategies for hybrid renewable systems including wind turbine, PV panel, fuel cell, and diesel generator and battery bank. These strategies are distinguished based on the priority of the usage of battery bank, fuel cell and diesel generator in case of power deficit and the precedence of charging of battery...

Nowadays, the usage of renewable energy has become popular. For the wind energy, as the wind turbine getting larger, more wind energy can be extracted. However, wind turbine components also became bulkier and hence increased the cost of installation. Furthermore, loads on the larger rotor also increased and made its life span shorter. As a result,...

Using fibre reinforced polymers (FRP) is increasing across many industries. Although FRP are laid-up in the near-net shape, several cutting operations are necessary to meet quality and dimensional requirements. Modelling of cutting is essential to understand the physics of the cutting phenomena and to predict quality and cost of products. This pape...

The need for high quality machining of composite materials is rising due to the increased utilisation of these materials across several applications. This paper presents experimental findings of orthogonal cutting of unidirectional glass fibre reinforced plastic (UD-GFRP) composites using HSS single-point cutting tools. Key process indicators inclu...

Due to substantial generation and demand fluctuations in standalone green microgrids, energy management strategies are becoming essential for the power sharing purpose and regulating the microgrid voltage. The classical energy management strategies employ the maximum power point tracking (MPPT) algorithms and rely on batteries in case of possible e...

One of the major components of horizontal axis wind turbines is the tower, which supports the weight ofthe rotor and nacelle as well as the thrust force produced by therotor. Wind turbine towers are designed for static stability under the axial load, for strength to withstand the cantilever thrust force and for dynamic stability in interaction with...

This paper presents a variety of dispatch strategies for hybrid renewable systems including wind turbine, PV panel, fuel cell, diesel generator and battery bank. These strategies are distinguished based on the priority of the usage of battery bank, fuel cell and diesel generator in case of power deficit and the precedence of charging of battery ban...

This paper presents the results of an investigation into the performance of different controllers in active load control of wind turbine blades equipped with microtabs. A bang bang (BB) controller, a linear quadratic regulator (LQR) a proportional integral derivative (PID) and a sliding mode controller (SMC) are synthesised for load alleviation. Th...

It is well-known that, due to bimodal operation as well as existent discontinuous differential states of batteries, standalone microgrids belong to the class of hybrid dynamical systems of non-Filippov type. In this work, however, standalone microgrids are presented as complementarity systems(CSs) of the Filippov type which is then used to develop...

Due to the PV module simulation requirements as well as recent applications of model-based controllers, the accurate photovoltaic (PV) model identification method is becoming essential to reduce the PV power losses effectively. The classical PV model identification methods use the empirical data of the maximum power point (MPP) at the standard test...

In a decoupled design method for bend-twist adaptive blades the optimum induced twist at a reference operating condition is obtained in the aerodynamic design phase. In the structural design phase, the structural and material configuration need to be found such that the elastic coupling in the blade produces the desired induced twist obtained in th...

In a decoupled design method for bend-twist adaptive blades the optimum induced twist at a reference operating condition is obtained in the aerodynamic design phase. In the structural design phase, the structural and material configuration need to be found such that the elastic coupling in the blade produces the desired induced twist obtained in th...

The present paper is one of the first to investigate the use of bend-twist adaptive blades on a variable-speed pitch-controlled tidal turbine in order to reduce hydrodynamic loads. The realisation of the substantial unexploited hydrokinetic energy of tides is currently driving hydrokinetic turbine research. In contrast to wind turbines, tidal techn...

Modern wind energy industry is highly under the influence of the advances in aerospace and has borrowed and adopted many new and innovative concepts from that industry. With the aim of exploring potential benefits of flapping blades in wind turbines, this paper presents the preliminary results of the numerical simulation of a flapping-pitching rect...

The present paper investigates the aerodynamic design of wind turbine blades while considering manufacturing constraints. Blade topologies achieved by unconstrained optimisation methods are likely to lose optimality after manufacturing simplifications are applied. The present paper proposes and evaluates the performance of an optimisation method fo...

This paper presents the results of a study on the effect of the number of poles of AC induction motors (IM) on their performance in both propulsion and regenerative brake modes in eco-urban electric cars (EC). Since changing the number of poles affects the maximum motor speed, different transmission ratios are considered in modelling of the powertr...

Deterministic size optimisation methods are unreliable in design of reliable and cost effective wind–PV–battery hybrid renewable systems irrespective of selected worst-case-scenarios and safety factors.

As a result of the significant growth of wind turbines in size, blade load control has become the main challenge for large wind turbines. Many advanced techniques have been investigated aiming at developing control devices to ease blade loading. Amongst them, trailing edge flaps have been proven as effective devices for load alleviation. The presen...

Uncertainty in the strength of natural material, such as timber, is considerably higher than man-made construction materials which are produced through controlled and precise manufacturing processes. Adopting a classical deterministic design approach, designer usually employs high factor of safety to incorporate this material strength uncertainty i...

This paper presents the results of a systematic study on the effects of the cross-arm size (cross sectional diameter and thickness) and the cable stay cross sectional diameter on the maximum load carrying capacity of single cross-arm prestressed stayed column system. Due to the addition of cross-arms and prestressed cables, the traditional slendern...

Wind turbine smart blades change their aerodynamic characteristics in response to changes in operating condition, aiming at enhancing the power capture capability or controlling the power and aerodynamic load. Smart blades span a wide range of technologies. Some of these technologies have been proposed and developed specially for wind turbines, whi...

This paper presents three case studies on structural optimisation. In the first case study a nonconventional approach is adopted to deliver an integrated design of trusses. This integrated design method, compared to traditional integrated design methods, while is significantly less demanding in terms of computational power, produces reasonable solu...

Optimal design of a standalone wind-PV-diesel hybrid system is a multi-objective optimisation problem with conflicting objectives of cost and reliability. Uncertainties in renewable resources, demand load and power modelling make deterministic methods of multi-objective optimisation fall short in optimal design of standalone hybrid renewable energy...

A dynamic model characterising the effect of microtab deployment on the aerodynamics of its base aerofoil is presented. The developed model predicts the transient aerodynamic coefficients consistent with the experimental and computational data reported in the literature. The proposed model is then used to carry out investigation on the effectivenes...

Finite element model for vibration and buckling of functionally graded sandwich beams based on a refined shear deformation theory is presented. The core of sandwich beam is fully metal or ceramic and skins are composed of a functionally graded material across the depth. Governing equations of motion and boundary conditions are derived from the Hami...

In the design of the controllers of hybrid renewable energy system (HRES), the system dynamics and constraints need to be modelled and simulated in conjunction with the controller itself. This paper presents mathematical and equivalent electrical models taking into consideration all system dynamics and constraints for the solar branch of HRES. This...

Performance of a HRES (hybrid renewable energy system) is highly affected by changes in renewable resources and therefore interruptions of electricity supply may happen in such systems. In this paper, a method to determine the optimal size of HRES components is proposed, considering uncertainties in renewable resources. The method is based on CCP (...

The objective of this study is to introduce aerofoils distribution as a design variable in wind turbine blade optimisation process. Aerodynamic optimisation is performed using a genetic algorithm (GA). An aerofoil-pairing database is developed to define a heuristic used in the GA rather than using a random selection in order to improve the GA perfo...

Design of hybrid renewable energy systems (HRES) contains many uncertainties such as uncertainties in resources, loads and component price variations. During the initial component-sizing phase, the system components brand and make are not known yet, thus, an accurate estimate of prices is not possible. This paper utilises design under uncertainties...

Wind turbines installed in cold climates are at risk of blade icing and required to be equipped with systems preventing the build-up of ice and/or ice removal. This paper presents the results of a preliminary investigation on the feasibility and suitability of using carbon fibres as resistive heating elements implanted in the structure of the compo...

This paper presents a goal programming algorithm utilising a weight-free aggregate function for producing enhanced design alternatives and a knowledge-based procedure for the selection of the final solution from a pool of enhanced alternatives. Normally, in a multi-disciplinary design problem several teams of designers with different preference and...

In order to design model-based controllers applicable to hybrid renewable energy systems (HRES), it is essential to model the HRES mathematically. In this study, a standalone HRES, consisting of a photovoltaic (PV) array, a lead-acid battery bank, a pitch-controlled wind turbine, and a three-phase permanent magnet synchronous generator (PMSG), supp...

Due to the presence of algebraic constraints as well as existing of different modes of operation, a standalone hybrid renewable energy system (HRES) is becoming complex as it can no longer be modelled using the conventional causal approach. The standalone HRES in this study supplies a variable DC load demand with a hybrid solar- and wind-generator...

This paper investigates the performance of a multiple-deme genetic algorithm (GA) with modified reproduction operators, in optimal design of planar steel frames according to the AISC-LRFD specification. The design objective is to minimise the weight of frame subject to strength, displacement and constructability constraints. A number of new crossov...

Uncertainties in renewable energy resources are the main challenges in maintaining a high quality of supply in stand-alone Hybrid Renewable Energy Systems (HRES). Conventionally, a battery bank is used as an auxiliary source to reduce the vulnerability of HRES to the climate changes and maintain the desired quality of supply. Considering the uncert...