Renewable energy, including offshore wind power, is expected to play a significant role in mitigating climate change and meeting a growing demand on electricity. Fiji, a Small Island Developing Nation in the South Pacific, needs large quantities of additional renewable energy to achieve its NDC goals and has good natural resources for offshore wind power. The purpose of the study is to analyse the technical potential for fixed and floating offshore wind power, identify the most suitable site (s), perform economic feasibility analysesfor different-sized offshore wind farms and determine possible emission reductions from offsetting electricity generation based on fossil fuels. The objectives are achieved through a literature study, interviews, a GIS-based multi-criteria site suitability analysis and feasibility calculations. In the study it was concluded that there is great potential for offshore wind power in Fiji. There are large areas with technical potential for fixed and floating offshore wind power and the most suitable sites, both located in the Bligh waters, have average wind speeds of 8.6 m/s and 8.5 m/s. The potential for offshore wind power was concluded to be large enough for Fiji’s needs, economically feasible and potentially competitive to invest in. The simple payback time would be approximately 13.5 years and the cost of electricity would be 0.13 USD/kWh, which is lower than the feed-in tariff for Fiji’s national grid at 0.15 USD/kWh. Different-sized offshore wind farms and its possible emission reductions could contribute with between 12-37% of Fiji’s NDC goal to reduce emissions from the energy sector by 30% compared to a business as usual scenario as well as contribute to have 99% renewable grid-connected electricity generation by 2030. However, during the study, it was concluded an implementation of offshore wind power in Fiji would require large investments, large capacities of energy storage, frequency regulating services and there are potential environmental and social impacts have to be taken into consideration. There is also a need for further research on how to cyclone-proof offshore wind farms in Fiji. / Förnybar energi, inklusive havsbaserad vindkraft, förväntas spela en avgörande roll för att minska klimatförändringarna och för att möta en ökande efterfrågan på elektricitet. Fiji, en liten önation i Stilla havet, behöver stora mängder ytterligare förnybar energi för att nå sina NDC mål och har bra naturresurser för havsbaserad vindkraft. Syftet med studien är att analysera den tekniska potentialen för fixerad och flytande havsbaserad vindkraft, identifiera de mest lämpliga platserna, utföra ekonomiska lönsamhetsanalyser för olika stora havsbaserade vindkraftsparker och avgöra möjliga utsläppsminskningar genom att avsätta elproduktion baserad på fossila bränslen. Målen uppfylls genom en litteraturstudie, intervjuer, GIS-baserad multikriterie platslämplighetsanalys och genomförbarhetsberäkningar. I studien drogs slutsatsen att det finns stor potential för havsbaserad vindkraft i Fiji. Det finns stora områden med teknisk potential för fixerad och flytande havsbaserad vindkraft och de mest lämpliga platserna, båda belägna i Bligh waters, har genomsnittliga vindhastigheter på 8.6 m/s och 8.5 m/s. Potentialen för havsbaserad vindkraft bedöms vara stor nof för Fijis behov, ekonomsikt genomförbart och potentiellt konkurrenskraftigt att investera i. Återbetalningstiden bedöms vara ungeför 13.5 år och elektricitetskostnaden 0.13 USD/kWh, vilket är lägre än inmatningstaxan till Fijis nationella elnät som är på 0.15 USD/kWh. De 12-37% av Fijis mål om att minska utsläppen från energisektorn med 30% jämfört med ett business as usual scenario liksom bidra till att ha 99% förnybar elnätsansluten elgeneration till 2030. Men, i studien drog också slutsatsen att en implementering av havsbaserad vindkraft i Fiji skulle kräva stora investeringar, stora mängder energilagring, frekvensreglerande tjänster och det finns potentiella miljömässiga och sociala effekter som måste tas i hänsyn. Det finns också behov av ytterligare forskning om hur man kan cyklon-säkra havsbaserade vindkraftsparker i Fiji.

Power generation of the future will be dominated by renewable energy sources. This is a positive trend as society aims to improve sustainability, energy security, and reduce CO2 emissions. This progress however bears challenges for the power systems of the future. One area of particular concern is the blackstart recovery capability of the power systems following blackout events that disrupt electricity supply, as traditional blackstart suppliers have originated from unsustainable power sources. As new sustainable technologies are explored to fill the void, offshore wind power has been identified as a potential suitor to address future blackstart deficiencies. However, following a blackout event that leaves an offshore wind farm isolated, the current technology does not allow for start-up of the wind farm in an islanded mode without assistance from the onshore grid. Hence, a STATCOM with active power storage, known as an ES-STATCOM, is the proposed solution to energize the offshore wind farm to operate in an islanded mode, in preparation for assisting the onshore grid with blackstart. An EMT model and simulation of an ES-STATCOM with grid forming control capabilities and the surrounding offshore wind farm export system were developed in this thesis to assess the viability of the STATCOM solution in energization. The results are promising and show that the ES-STATCOM is in fact able to energize the offshore system to a stable voltage, while avoiding high order harmonics and large overvoltages that have the potential to cause damage to expensive subsea power system components. Ultimately, this thesis serves as a proof-of-concept for blackstart technology, providing useful insights towards the maturity of offshore wind-based blackstart providers of the future. / Framtidens elproduktion kommer att domineras av förnybara energikällor. Detta är en positiv trend eftersom samhället strävar efter att förbättra hållbarheten, tryggheten gällande energiförsörjning samt minska koldioxidutsläppen.. Denna utveckling innebär dock utmaningar för framtidens kraftsystem. Ett område som är särskilt oroande är kraftsystemens förmåga att återhämta sig efter blackout som stör elförsörjningen, eftersom de traditionella leverantörerna av ett strömavbrott har sitt ursprung i ohållbara kraftkällor. I takt med att man utforskar ny hållbar teknik för att fylla tomrummet har havsbaserad vindkraft identifierats som en potentiell kandidat för att åtgärda framtida brister vid svartstart. Efter ett strömavbrott som gör att en havsbaserad vindkraftpark blir isolerad från kraftnätet kan vindkraftparken inte startas upp i ett ö-läge utan hjälp från landnätet med nuvarande teknik. Därför föreslås en STATCOM med aktiv energilagring, en så kallad ES-STATCOM, som lösning för att ge energi till havsbaserade vindkraftparker så att de kan fungera i ö-läge, som en förberedelse för att hjälpa landnätet med svartstart. En EMT-modell och simulering av en ES-STATCOM med nätbildande kontrollfunktioner och det omgivande exportsystemet för havsbaserade vindkraftparker utvecklades i denna avhandling för att bedöma lönsamheten hos STATCOM-lösningen för energitillförsel. Resultaten är lovande och visar att ES-STATCOM kan försörja det havsbaserade systemet med den en energi som krävs för en stabil spänning, samtidigt som man undviker harmoniska övertoner av hög ordning och stora överspänningar som har potential att skada dyra komponenter i det havsbaserade kraftsystemet. I slutändan tjänar denna avhandling som ett proof-of-concept för blackstart-teknik och ger användbara insikter om hur mogna framtida leverantörer av svartstart-teknik för havsbaserad vindkraft är.

Previous research has displayed that multi-source farms provide an opportunity to reduce the cost of energy and improve the energy output quality. This thesis assesses the cost competitiveness of co-located wind-wave farms, specifically floating offshore wind (FLOW) turbines and CorPower’s wave energy converters (WEC). This research was conducted in collaboration with CorPower, a Swedish WEC developer. A cost model is generated, which calculates the levelized cost of energy (LCOE) utilizing a life-cycle cost analysis. The model is developed by combining CorPower’s existing cost model with an agglomeration of FLOW cost models from previous studies. An in depth literature research informs about synergies, which are translated into shared costs within the model. The cost model is applied to a site on the Northern coast of Portugal; the location of a FLOW farm project under development. Including wave energy, improves the annual energy production of the farm by up to 10%. However, the effects on power smoothing are negligible, due to the high seasonal variability of the wave resource and the minimal complementarity of the two energy sources. The LCOE of a 1GW 50% wind - 50% wave farm is 63€/MWh. The high initial investment costs of the wind farm results in the standalone wind LCOE of 73€/MWh. The strong capacity factor of the WECs cause the LCOE to reduce to 55€/MWh, when evaluating a standalone wave farm. In all co-location configurations, savings for FLOW and wave farm developers are exhibited. The highest savings are identified for small wind/wave arrays co-located in large farms. This results in an LCOE reduction of up to 4.5% for both wind and wave farm developers. The largest relative savings are found in the DEVEX costs and the electrical transmission installation costs. The identified cost calculations and savings are inline with previous studies. The savings are in the lower range compared to other studies, due to the conservative estimations of the degree of shared costs. The cost model provides a tool, that can be continuously updated with the most recent findings of cost inputs and wind-wave synergies, i.e. shared cost opportunities. This thesis’ results reflect how co-locating wind and wave farms can improve the cost-competitiveness of both technologies. Nevertheless, more in depth research is required to comprehend the full potential of co-located wind-wave farms. There is a necessity of collaboration between wind and wave industry members to ensure that the synergies and shared cost-opportunities identified, are fully exploited. / Tidigare forskning har visat att parker med flera källor ger möjlighet att minska energikostnaderna och förbättra energiproduktionens kvalitet. I den här avhandlingen utvärderas kostnadskonkurrenskraften hos samlokaliserade vind- och vågkraftsparker, särskilt flytande havsbaserade vindkraftverk (FLOW) och CorPowers vågenergiomvandlare (WEC). Denna forskning genomfördes i samarbete med CorPower, en svensk WEC-utvecklare. En kostnadsmodell genereras, som beräknar den nivellerade energikostnaden (LCOE) med hjälp av en livscykelkostnadsanalys. Modellen är utvecklad genom att kombinera CorPowers befintliga kostnadsmodell med en agglomeration av FLOW-kostnadsmodeller från tidigare studier. En djupgående litteraturstudie ger information om synergier, som översätts till delade kostnader i modellen. Kostnadsmodellen tillämpas på en plats på Portugals norra kust, där ett FLOW-anläggningsprojekt är under utveckling. Genom att inkludera vågenergi förbättras parkens årliga energiproduktion med upp till 10%. Effekterna på effektutjämningen är dock försumbara, på grund av vågresursens stora säsongsvariationer och de två energikällornas minimala komplementaritet. LCOE för en 1GW 50% vind - 50% vågkraftspark är 63€/MWh. De höga initiala investeringskostnaderna för vindkraftsparken resulterar i en LCOE för fristående vindkraft på 73 €/MWh. Den starka kapacitetsfaktorn för WECs gör att LCOE minskar till 55€/MWh, vid utvärdering av en fristående vågkraftspark. I alla samlokaliseringskonfigurationer uppvisas besparingar för FLOW och vågparksutvecklare. De största besparingarna identifieras för små vind-/vågkraftsparker som samlokaliseras i stora parker. Detta resulterar i en minskning av LCOE med upp till 4,5% för både vind- och vågparksutvecklare. De största relativa besparingarna finns i DEVEX-kostnaderna och installationskostnaderna för elektrisk överföring. De identifierade kostnadsberäkningarna och besparingarna är i linje med tidigare studier. Besparingarna ligger i det lägre intervallet jämfört med andra studier, på grund av de konservativa uppskattningarna av graden av delade kostnader. Kostnadsmodellen är ett verktyg som kontinuerligt kan uppdateras med de senaste rönen om kostnadsingångar och synergier mellan vind och våg, dvs. möjligheter till delade kostnader. Resultaten i denna avhandling visar hur samlokalisering av vind- och vågkraftsparker kan förbättra kostnadskonkurrenskraften för båda teknikerna. Det krävs dock mer djupgående forskning för att förstå den fulla potentialen hossamlokaliserade vind- och vågparker. Det finns ett behov av samarbete mellanvind- och vågkraftsindustrin för att säkerställa att de identifierade synergierna ochgemensamma kostnadsmöjligheterna utnyttjas fullt ut.

Recognizing the imperative transition towards renewable energy sources to combat climate change, this study explores the outlooks for offshore wind power in Norway, a country endowed with extensive coastlines and favourable wind conditions. The thesis sets out to support decision-making processes by synthesizing contemporary research and applying context-specific insights to the southern half of the Norwegian economic zone (NEZ) into a comprehensive Spatial-Multi-criteria Analysis (SMCA). Through meticulous research, sub-criteria relevant to the geographical information systems-based SMCA are identified across four major categories: Wind, Techno-economic, Environ-mental, and Social considerations. Through the adoption of the Analytic hierarchy process (AHP) framework, the analysis generates suitability maps for all identified sites within the NEZ, facilitating a ranking procedure for both floating and bottom-fixed sites. By, among else, incorporating potential grid connection points and distance to suitable ports, this thesis offers a novel contribution to the limited body of literature on offshore wind power SMCA in the NEZ. Additionally, through state of the art data sets on mammal presence and cumulative impact on seabirds, the study not only advances the academic discourse on offshore wind power planning but also offers practical tools for policymakers and industry practitioners. The findings underscore the complexity of offshore wind farm siting, highlighting the impor-tance of a balanced consideration of various criteria to ensure sustainable and economically viable energy production. Significantly, amongst sites suitable for floating foundations, Ves-tavind A emerges as the prime location for wind farm development. The bottom rankings, however, are claimed by different sites depending on which weighting schema is applied. For future studies on the topic, important building blocks include incorporating data on seabed conditions such as geology and sloping into the SMCA alongside including more sub-criteria linked to met-ocean conditions (e.g., cut-out periods of the wind turbines caused by extreme weather). / Mot bakgrund av den globala omställningen till en alltmer grön energimix utforskar denna studie utsikterna för havsbaserad vindkraft i Norge, ett land med vidsträckta kustlinjer och gynnsamma vindförhållanden. Uppsatsen syftar till att stödja beslutsprocesser genom att sammanställa samtida forskning och tillämpa insikter anpassade till den södra halvan av Norges ekonomiska zon (NEZ) i en omfattande rumslig analys. Slutprodukten blir en relativ rangordning av en uppsättning områden som alla, enligt norska myndigheter, lämpar sig för installation av havsbaserad vindkraft. Genom noggrann efterforskning identifieras olika faktorer (subkriterier) som anses rel-evanta för den rumsliga analysen, dessa delas up i fyra övergripande kategorier: Vind, Tekno-ekonomiska faktorer, Miljöaspekter och Sociala aspekter. Med hjälp av en särskild viktningsmodell, där faktorerna ställs mot varandra och prioriteras utifrån deras relativa betydelse, genereras lämplighetskartor för alla platser inom studieområdet. Denna process ligger sedermera till grund för den ovannämnda rangordningen och görs både för platser som är tänkta för flytande och bottenfast havsbaserad vindkraft. Genom att bland an-nat inkludera potentiella anslutningspunkter till elnätet och avstånd till hamnar, som speficifkt lämpars sig för vindturbininstallationer, bidrar detta forskningsarbete med nytt innehåll till den vetenskapliga litteraturen. Därtill kan studien, utöver att bidra till den akademiska diskursen, komma att fungera som ett praktiskt verktyg för beslutsfattare och yrkesverksamma inom industrin. Resultaten påminner läsaren om komplexiteten i placeringen av havsbaserade vindkraftverk, vilket bekräftar vikten av en balanserad beaktning av olika kriterier. Detta för att kunna säkerställa att nya energiprojekt presterar bra utifrån ett miljömässigt och socialt perspektiv samtidigt som den ekonomiska lönsamheten säkras. Sett till de områden som studien utreder framstår Vestavind A som det bäst lämpade området för utveckling av havsbaserad vindkraft. De lägsta placeringarna upptas emellertid av olika platser beroende på hur de olika kriterierna viktas. Några förslag på hur denna studie kan utvecklas för att fortsatt kunna bidra till nya insikter inom forskningsområdet är att inkludera data om bottenförhållanden (exempelvis geologi och lutning) i den rumsliga analysen, samt att addera subkriterier med en naturlig koppling till meteorologiska aspekter såsom avbrottsperioder för vindturbiner till följd av extremväder.

This thesis investigates the impact of resonant overvoltages and their origin. Series and parallel resonances are present in any electrical grid. The frequency of which this resonance occurs is called resonance frequency. For parallel resonance, which is mainly being studied in this thesis, a high impedance peak can be found at the resonance frequency. This impedance peak in conjunction with a harmonic rich current cause a kind of temporary overvoltages called resonant overvoltages. The harmonic content of the current is high following a fault clearing in the grid, due to transformer saturation. The resonance frequency is heavily dependent on the amount of reactance present in the grid, which entail that a change in reactance causes a change in the resonance frequency. The electromagnetic transient tool PSCAD has been used to investigate resonant overvoltages following transformer energization caused by faults and switching in Stockholm. Secondly, a model was created of a grid connecting off-shore wind power to the mainland via long AC submarine transmission cables. These cables, having a high capacitance, lower the resonance frequency. Faults in this model were simulated to investigate the phenomenon of resonant overvoltages in such a grid. This was especially interesting due to Swedens planned expansion of wind power in the Baltic sea. While resonant overvoltages were found in Stockholm they were not deemed significant due to their low magnitude and longevity. However, severe resonant overvoltages were found in the off-shore wind farm model. The worst resonant overvoltages had a maximum amplitude of the 2nd order harmonic voltage of 130 kV which, while eventually damped, were significant for up to 50 periods. Lastly, the phenomenon of an increased resonance frequency during the saturation of a transformer was studied. The most severe resonant overvoltages occured in a model where the frequency scans showed a resonance frequency of 98 Hz. Indicating, caution needs to be had during EMT-studies of resonant overvoltages while choosing what resonance frequency to study.

This study aims to explore the ability of a multi-criteria decision making with analytical hierarchy process (MCDM-AHP) model to emulate the results of a cost benefit analysis (CBA) model in the context of offshore wind farm siting within the Swedish exclusive economic zone (EEZ). The research question addressed is whether the MCDM-AHP analysis produces similar results to the CBA analysis. In addition to this, the strengths and weaknesses of each model is explored. The MCDM-AHP model employs the spatial criteria in a more basic manner compared to the CBA model, simplifying the evaluation process while still explaining 89.5% of the variation in the CBA model and defining similar areas as suitable. Thus, it can be concluded that the MCDM-AHP model adequately emulates the CBA model within the context of offshore wind farm siting within the Swedish EEZ. However, it is crucial to note that the two models produce outputs on different scales. While the CBA model provides levelized cost of energy (LCOE) values that can be thresholded for investment viability comparisons, the suitability score generated by the MCDM-AHP model remains a relative and arbitrary score within the model. Both models entail uncertainties, limiting their usage beyond making general assumptions or identifying areas of interest. The findings reveal that the CBA model demonstrates greater robustness when confronted with changes in spatial input parameters compared to the MCDM-AHP model. This discrepancy is attributed to the iterative computation process and consideration of flat cost inputs in the CBA model, whereas the MCDM-AHP model represents a linear combination of various spatial parameters. However, the calculated LCOE values in the CBA model are highly sensitive to changes in modeling assumptions regarding external parameters, resulting in significant linear variations. The LCOE values obtained from the CBA model baseline case fall within a range of 52.1 - 98.9 EUR/MWh, which aligns with similar studies, validating the CBA model. Nonetheless, caution should be exercised when considering these results as an accurate representation of the real world due to inherent uncertainties in cost inputs and the LCOE measure. The strengths of the MCDM-AHP model lie in its robustness when the order of relative importance remains stable for key spatial evaluators. It is sensitive to significant changes in water depth and wind speed, which heavily influence its output. The model's simplicity allows for a quick overview of the problem, but it requires assumptions that introduce uncertainties. Validation of the MCDM-AHP model using existing and planned offshore wind farms within the Swedish EEZ was possible but limited by the arbitrary scale and limited validation areas. The comparison between the two models could be enhanced with more comprehensive spatial and economic data for an in-depth CBA model, which could serve as a ground truth for the MCDM-AHP model. Nevertheless, the comparison made in this study considers the CBA model to be closer to the truth, acknowledging the underlying assumptions that should be considered during evaluation. In conclusion, within the context of offshore wind farm siting, the MCDM-AHP model produces outputs that are similar to the CBA model.

There has recently been an increased interest in hydrogen, both as a solution for seasonal energy storage but also for implementations in various industries and as fuel for vehicles. The transition to a society less dependent on fossil fuels highlights the need for new solutions where hydrogen is predicted to play a key role. This project aims to investigate technical and economic outcomes of different strategies for production and storage of hydrogen based on hydrogen demand and source of electricity. This is done by simulating the operation of different systems over a year, mapping the storage level, the source of electricity, and calculating the levelized cost of hydrogen (LCOH). The study examines two main cases. The first case is a system integrated with offshore wind power for production of hydrogen to fuel the operations in the industrial port Gävle Hamn. The second case examines a system for independent refueling stations where two locations with different electricity prices and traffic flows are analyzed. Factors such as demand, electricity prices, and component costs are investigated through simulating cases as well as a sensitivity analysis. Future potential sources of income are also analyzed and discussed. The results show that using an alkaline electrolyzer (AEL) achieves the lowest LCOH while PEM electrolyzer is more flexible in its operation which enables the system to utilize more electricity from the offshore wind power. When the cost of wind electricity exceeds the average electricity price on the grid, a higher share of wind electricity relative to electricity from the grid being utilized in the production results in a higher LCOH. The optimal design of the storage depends on the demand, where using vessels above ground is the most beneficial option for smaller systems and larger systems benefit financially from using a lined rock cavern (LRC). Hence, the optimal design of a system depends on the demand, electricity source, and ultimately on the purpose of the system. The results show great potential for future implementation of hydrogen systems integrated with wind power. Considering the increased share of wind electricity in the energy system and the expected growth of the hydrogen market, these are results worth acknowledging in future projects.