Developing control strategies for variable hydrogen production from offshore wind: enabling power to X applications

The global shift toward renewable energy relies heavily on integrating offshore wind energy with Power-to-X (PtX) technologies, particularly green hydrogen production. This thesis aims to explore and develop optimal operational strategies for hybrid offshore wind power plants, focusing on the balance between hydrogen production and electricity market sales. By examining different electrolyzer operational strategies ON/OFF, ON/Standby, and ON/OFF/Standby—under varying operational models namely Grid integrated PtX, Standalone PtX and Electricity only model, the research evaluates how these operational strategies influence system flexibility, operational efficiency, and overall profitability. The objective is to find a dynamic control strategy that maximizes both hydrogen output and economic returns. The results show that the ON/OFF/Standby operational strategy delivers the highest revenue across the evaluated models (Grid-integrated PtX and Standalone PtX) by effectively balancing production during periods of low electricity prices and reducing operational costs using standby states. In comparison, the ON/OFF and ON/Standby strategies generated slightly lower revenues. The research also highlights how weekly hydrogen dispatch via ship introduces operational complexity, resulting in cyclical variations in hydrogen storage levels that must be managed carefully to prevent bottlenecks and optimize output. The study leverages Mixed-Integer Linear Programming (MILP) and Economic Model Predictive Control (EMPC) frameworks to optimize the balance between hydrogen production, electricity sales, and electrolyzer state transitions. By accounting for key factors such as electrolyzer degradation, desalination requirements, and dynamic operational shifts, the research provides a comprehensive understanding of the real-world challenges involved in running hybrid systems. Time frame analysis further enhances this understanding by examining how operational states switch over time, offering deeper insights into system behavior. Sensitivity analysis demonstrates that higher hydrogen prices can significantly boost total revenue, while also showing that electrolyzer operational strategies can be flexibly adapted to prioritize either electricity or hydrogen production, depending on the asset owner's objectives. These findings underscore the profitability potential of PtX systems under favorable market conditions and provide actionable insights for optimizing hybrid wind-hydrogen systems, contributing to the broader global transition toward a sustainable, decarbonized energy future

Optimal sizing of hybrid diesel engine – photovoltaic and battery system for a marine vessel application

Environmental concerns have been motivating increased interest in the use of renewable energy sources as a result of diminishing of fossil fuel sources and the negative effect it has on the environment. Photovoltaic (PV) energy system is a renewable energy source with various applications and their implementation in energy production and saving are well documented in various research and applications. Installing these systems onto marine vessels or connecting it to marine vessel power plant through external connections could prove to be an efficient way of minimizing conventional fuel costs and simultaneously protecting the environment by significantly reducing carbon emission. In order to understand the technical and economic viability of using photovoltaic system for an offshore marine vessel, it is vital to determine the optimal sizing of PV system, battery, inverter and diesel generator. This project presents the proposed approach used in order to optimally size the power system components of hybrid system such as photovoltaic panels, inverter, battery and the conventional diesel generator. For this study, MATLAB software is used to develop a program to perform the power production calculation in order to meet the load demand pattern by utilizing power source from PV panel and conventional diesel generators. Probabilistic method is used to analyze the impact of random weather conditions to the sizing of the components. In addition, economic analysis was performed to optimize the sizing of the PV panels and batteries. Optimal sizing can save up to 1 percent of the Net Present Cost (NPC) with engine fuel price taken into consideration when comparison is made between 100 kW and 500 kW sized hybrid configuration. The conclusion of this project is that the developed algorithm is suitable to be used to optimally size hybrid diesel, PV and battery system

Challenges and prospects of renewable hydrogen-based strategies for full decarbonization of stationary power applications

The exponentially growing contribution of renewable energy sources in the electricity mix requires large systems for energy storage to tackle resources intermittency. In this context, the technologies for hydrogen production offer a clean and versatile alternative to boost renewables penetration and energy security. Hydrogen production as a strategy for the decarbonization of the energy sources mix has been investigated since the beginning of the 1990s. The stationary sector, i.e. all parts of the economy excluding the transportation sector, accounts for almost three-quarters of greenhouse gases (GHG) emissions (mass of CO2-eq) in the world associated with power generation. While several publications focus on the hybridization of renewables with traditional energy storage systems or in different pathways of hydrogen use (mainly power-to-gas), this study provides an insightful analysis of the state of art and evolution of renewable hydrogen-based systems (RHS) to power the stationary sector. The analysis started with a thorough review of RHS deployments for power-to-power stationary applications, such as in power generation, industry, residence, commercial building, and critical infrastructure. Then, a detailed evaluation of relevant techno-economic parameters such as levelized cost of energy (LCOE), hydrogen roundtrip efficiency (HRE), loss of power supply probability (LPSP), self-sufficiency ratio (SSR), or renewable fraction (fRES) is provided. Subsequently, lab-scale plants and pilot projects together with current market trends and commercial uptake of RHS and fuel cell systems are examined. Finally, the future techno-economic barriers and challenges for short and medium-term deployment of RHS are identified and discussed.This research is being supported by the Project ENERGY PUSH SOE3/P3/E0865, which is co-financed by the European Regional Development Fund (ERPF) in the framework of the INTERREG SUDOE Programme and the Spanish Ministry of Science, Innovation, and Universities (Project: RTI2018-093310-B-I00)

Modelling and validation of energy storage components for dynamical analysis of offshore energy systems

Den økende integreringen av fornybar energi til havs og utvidelsen av overførings- og distribusjonsnett i maritime energisystemer krever en betydelig grad av pålitelighet og systemstabilitet. Spesielt viktig vil det være å opprettholde balansen mellom etterspørsel og produksjon, til tross for kontinuerlige systemendringer grunnet diskontinuitet fra fornybare kilder og markedsvariasjoner. Energilagring vist seg å være et effektivt alternativ for å løse disse utfordringene da det tillater mer elastisitet og robusthet da det kompenserer for systemendringer ved å bevare strømbalansen. I denne masteroppgaven undersøker jeg hvilken effekt energilagring, spesielt hybrid energilagringssystemer (HESS), har på forbedringer av det offshore strømnettets elastisitet og pålitelighet. Kraftsystemet som studeres her består av en HESS koblet til vekselstrømnettet til et offshore kraftsystem (RAPS) via en totrinns krafttransformerer. Hovedfokuset i dette prosjektet har vært å se på hvordan HESS kan brukes til å forbedre DC samleskinne spenningsstabilitet ved å redusere gjenopprettingstid og avvik. En batterisuperkondensator HESS er implementert på grunn av de komplementære energitetthet- og effekttetthetsegenskapene som er i bestanddelens lagringselementer. Resultatet av prosjektets evne til å oppnå stabilitet sammenlignes med stabiliteten av batterier utnyttet i tilsvarende bruk. Kontrollsystemene som brukes til hybridlagringstransformerere er avhengig hovedsakelig av responstiden til HESS-elementer. Nettoeffekten av etterspørselsvariasjoner er fraskilt fra høyfrekvente og lavfrekvente komponenter. På grunn av forskjellige kontrollbåndbredder kan superkondensatoren utligne høyfrekvente toppvariasjoner i løpet av noen millisekunder, og batteriet reagerer langsommere til systemvariasjoner. Denne HESS-kontrollstrategien opprettholder en konstant likestrøms samleskinnespenning under et manglende samsvar mellom produksjon og etterspørsel. Følgelig er batteriet beskyttet mot svingende toppstrømmer, noe som forbedrer dets levetid. I tillegg er superkondensators volumetriske effektivitet forbedres og kan operere innenfor et større frekvensspekter og absorbere høyfrekvente svingninger Simuleringsmodellen til systemet og dets komponenter er utviklet i MATLAB- og Simulink-programmene, hvor hvert HESS-element er koblet til DC-samleskinnen via en 2-kvadrant toveis DC/DC-omformer (BDC). DC-samleskinnen var deretter koblet til vekselstrømnettet via en 2-nivå-spenningskilde-omformer (2L-VSC) med et LCL-filter og i serie med en trappetransformator. En resistivt belastning og trefaset spenningskilde utgjør vekselstrømnettet i detteprosjektet. Frittstående modeller av DC-sidene og AC-sidene på kraftsystemet ble verifisert, der modelleringen av BDC-ene og 2L-VSC og deres kontrollutforming er av størst betydning. Andre komponenter i rutenettet har blitt modellert etter behov i løpet av simuleringsstudiene. Sammenlignende ytelsesevalueringer mellom HESS og batteri gjøres først i et frittstående DC-system og full simuleringsmodell (DC/AC hybrid-system). Undersøkelsene og resultatene som ble fremsatt i dette prosjektet fastslår fordelene med å implementere en fullstendig aktiv parallell hybridbatteri-superkondensator HESS-topologi i maritim strømforsyning til å redusere flyktige gjenopprettingstid og størrelsen på spenningsavviket, fremfor å benytte seg av enkeltenergilagring. Det konkluderes derfor med at bruk av en hybrid energilagringstopologi med en effektiv tidsskala/frekvensbasert styringsstrategi forbedrer kortvarig stabilitet av DC-busspenningen sammenlignet med utnyttelse av en enkelt energilagringsenhet.The increasing growth in renewable energy integration and the expansion of transmission and distribution networks in offshore energy systems necessitates an optimal level of system stability and reliability. An important issue in this regard is maintaining generation-demand balance to mitigate the effects of intermittency of renewable sources and variations in load demand. Energy storage is a proven effective solution to enhance grid resiliency by compensating for power mismatch due to the factors mentioned above. This master’s thesis investigates the contribution of energy storage, specifically hybrid energy storage systems (HESS), to the improvement of grid resiliency against load variations. The power system under study is made up of a HESS connected to an AC offshore remote area power system (RAPS) via a two-stage power converter. The focus of this project is the utilisation of the HESS to improve DC bus voltage stability by reducing the load-transient recovery time and mitigating deviation magnitudes. A battery-supercapacitor HESS is implemented considering the complementary energy density and power density characteristics of the constituent storage elements. Its effectiveness in achieving the stability objective is compared with that of a battery in the same application. Control employed for the hybrid storage converters relies mainly on the response time of the HESS elements. System net power due to load demand variation is decoupled into high and low-frequency components. Due to the difference in the control bandwidths, the supercapacitor compensates high-frequency peak variations, mainly within the first few milliseconds of a transient event, and the battery responds to slower system variations. This HESS control strategy aims to maintain a constant DC bus voltage during a generation-demand mismatch. Consequently, the battery is protected from fluctuating peak currents, improving its lifetime. Furthermore, the supercapacitor’s volumetric efficiency is increased, operating within a broader voltage range and absorbing high-frequency peak fluctuations. The simulation models used for the investigations are developed in the MATLAB and Simulink environments. In the full power system, each HESS element is connected to the DC bus via a 2-quadrant bidirectional DC/DC converter (BDC). The DC bus is then interfaced to the AC grid via 2-level voltage source converter (2L-VSC) with an LCL filter and in series with a step-up transformer. Making up the AC downstream system is a resistive load and three-phase voltage source acting as an infinite busbar. Standalone models of the DC and AC-sides of the power system are verified, where the modelling of the BDCs and 2L-VSC and their control designs are most critical. Other components of the grid are modelled as required for the simulation studies. Comparative performance evaluations between the HESS and battery are made first in a standalone DC system model and then in a full system model (DC/AC hybrid system). The investigations and results obtained establish the advantages of implementing a full active parallel hybrid battery-supercapacitor HESS topology over single energy storage in reducing transient recovery time and magnitude of voltage deviation. It is finally established that the stability of the DC bus voltage is improved relatively by utilising a hybrid energy storage system employing an effective time-scale/frequency-based control strategy, as compared to a single energy storage unit

Modelling Scenarios for Low Carbon Heating Technologies in the Domestic Sector Towards a Circular Economy

The UK Government’s Net Zero strategy requires strong commitments to avoid catastrophic impacts of climate change. The built environment puts major pressure on the natural environment, especially with space heating-related emissions; therefore, transitioning to a circular economy is vital. In this direction, the heat pump market in the UK has been growing gradually whereas the number is still low (43,000 units in 2021). The UK Government aims to reach 600,000 heat pump installations per year by 2028, and according to the Climate Change Committee (CCC), this number should reach 1 million by 2030. In order to accelerate the transition, the Boiler Upgrade Scheme (BUS) has been introduced to provide a £5,000 grant in the UK, and the Scottish Government granted Home Energy Scotland (HES) loan and cashback scheme providing a £7,500 grant and a £2,500 interest-free loan for heat pumps. Islands are facing environmental, economic and social pressure due to the lack of connection to the mainland and dependency on fossil fuel imports. Exploring the benefits of renewable energy and low carbon heating technologies is crucial to overcome these issues. Orkney has a huge potential for renewable energy by producing electricity more than its needs. Therefore, this study chooses Orkney as a case study to explore potential heat pump uptake scenarios in line with government targets towards Circular Economy (CE). The study aims to create a comprehensive holistic approach to evaluate the environmental, energy and economic impacts of heat pump deployment scenarios. The consequences of replacing conventional heating technologies with heat pumps have been assessed through (i) comparative life cycle assessment (LCA) of heat pumps with gas boilers in UK houses, (ii) energy systems modelling (ESM) to optimise the performance of a heat pump coupled with thermal energy storage (TES) tank to reduce use phase related impacts in Orkney, (iii) building stock modelling (BSM) of Orkney’s domestic sector to understand the housing condition, (iv) economic modelling to analyse life cycle cost of an air source heat pump and potential savings when existing conventional heating systems are replaced with heat pumps in Orkney, and (v) heat pump diffusion model to quantify hourly electric load curves of variable heat pump operation optimised by the energy model. The integrated methodology creates a more holistic and life cycle-wide approach to both demand, supply and end-user side of the system; therefore, the results are illustrated in both individual house archetypes level to provide guidance to the end-users and at the Orkney level to calculate cumulative savings for the policymakers. The results show that the use phase is the major contributor to the environmental impacts; therefore, increasing the renewable share in the UK’s electricity mix could help to reduce negative impacts in most of the categories. However, the high deployment of wind farms also creates toxicity and metal depletion problems. The heat pump uptake scenarios in Orkney shows that 82% reductions in energy supply could be achieved when ambitious energy efficiency improvement measures are taken in the CE scenario. The use phase-related emissions could be reduced by 98% when the heat pump becomes the only heating technology in Orkney. However, the life cycle-wide approach suggests that strong commitments are required in the manufacturing stage of these technologies through implementing circular principles such as including the use of secondary materials, eco-design and reusability of all components. Moreover, a market introduction program should be provided before shifting from one technology to another so greener production lines could be achieved. Total heating costs paid by consumers in Orkney could be reduced by 84% in the CE scenario when heat pump uptake is coupled with energy efficiency improvement measures; however, it requires a £130 million investment to insulate the unrefurbished housing stock of Orkney. Therefore, subsidies and incentives are also required for efficiency improvements such as reductions in VAT on equipment and labour costs, grants similar to BUS/HES and interest-free loans for the remaining costs. Future scenarios indicate that decision-making has significant importance on overall results; therefore, CE standards for heat pump manufacturing and deployment are crucial to reduce the negative impacts of fuel poverty and reach the Net Zero target

Using genetic algorithm for optimal sizing of stand-alone hybrid energy system

When planning a hybrid energy system (HES) that incorporates both renewable and non-renewable energy sources—those that rely on fossil fuels—the primary considerations are the total cost of the system and the CO? emissions. In this paper, we will investigate the typical hybrid energy system (HES) that incorporates both renewable and non-renewable energy sources involving a detailed simulation process that may require specific inputs, models, and data. Then, we employed dual optimization methods: genetic algorithm (GA) and particle swarm optimization (PSO). The consequences of GA and PSO execution in the bus timetabling problem depict that the GA algorithm is better at finding the optimal solution in terms of accuracy and iteration. Additionally, the GA algorithm is also superior to the straightforwardness of the techniques used. So, in this work, we employed a Genetic Algorithm Optimization (GA)–-based optimal sizing technique for HES configurations that include sustainability wind turbines (WTs), battery storage (BS), and diesel generators (DGs). HES improved power delivery to a rural community in the Wasit Province, Iraq, situated at 46° - 36° and 32° - 31° in the country's southeastern central region. Throughout the project's 25-year lifespan, the optimization primarily aims to minimize the total cost (CT) and total CO? emissions (ECO2T). The outcomes demonstrate that the GA algorithm may, with continuous electricity supply, minimize the objectives while meeting the load demand

Modeling, Simulation and Optimization of Wind Farms and Hybrid Systems

The reduction of greenhouse gas emissions is a major governmental goal worldwide. The main target, hopefully by 2050, is to move away from fossil fuels in the electricity sector and then switch to clean power to fuel transportation, buildings and industry. This book discusses important issues in the expanding field of wind farm modeling and simulation as well as the optimization of hybrid and micro-grid systems. Section I deals with modeling and simulation of wind farms for efficient, reliable and cost-effective optimal solutions. Section II tackles the optimization of hybrid wind/PV and renewable energy-based smart micro-grid systems

Modeling, Simulation and Optimization of Wind Farms and Hybrid Systems

The reduction of greenhouse gas emissions is a major governmental goal worldwide. The main target, hopefully by 2050, is to move away from fossil fuels in the electricity sector and then switch to clean power to fuel transportation, buildings and industry. This book discusses important issues in the expanding field of wind farm modeling and simulation as well as the optimization of hybrid and micro-grid systems. Section I deals with modeling and simulation of wind farms for efficient, reliable and cost-effective optimal solutions. Section II tackles the optimization of hybrid wind/PV and renewable energy-based smart micro-grid systems