Project

To transfer energy from collected offshore wind farms over a long distance, HVDC transmission is preferred over HVAC in terms of efficiency and economy. Several multi-stage configurations have been proposed in the literature. However, the multi-stage configuration generally results in a large size due to a large number of conversion stages, relatively high cost, and low efficiency and power density. Also, the independent control of several converters and communication among the sources make the system complex. To overcome these disadvantages, multi-port modular DC/DC topologies have been suggested. Multiport converters are highly non-linear MIMO systems with many control variables. Also, the coupling between the control variables makes modeling and control system design complicated. Despite such complexity, advanced control techniques have not been comprehensively studied. Moreover, most controller design work on multiport converters has not considered the uncertainties of the converter model. In this Ph.D. study, a robust controller is implemented for multi-port modular DC/DC converter for offshore wind farms application.

The pitch system of a wind turbine is one of the systems used for regulating the power production of the wind turbine. The Pitch system may turn the blades of the turbine from approximately 0 to 90 degrees around its own axis and thus regulate the energy input from the wind to the turbine. If the blades are turned into a 90 degree position the turbine will stop rotating and the energy production is stopped. If an error occurs in the turbine and it is necessary to shut the turbine down before extensive damage occurs, an emergency stop is performed by turning the blades to their 90 degree position. The pitch system is the primary safety system of the turbine.

As the pitch system has an essential function of the wind turbine it is extremely important that the system is reliable and available. Especially for offshore wind turbines it is extremely important that no other maintenance than the scheduled has to be performed. Research shows that pitch systems are currently responsible for 22% of wind turbines' total downtime.
A combination of lower cost and increased reliability and availability on the hydraulic pitch system will reduce both the total cost of ownership (TCO) and Total Cost of Energy (TCE).

This project aims to significantly increase the reliability and availability of the pitch systems compared to current hydraulic and electric pitch systems. This is done through a modular way of thinking in which the entire system is brought out in the rotating hub and distributed in three individual systems - one for each wing. Through this transformation it is the goal to reduce the price by 20% while the number of components is lowered by 10%.

To increase uptime for a hydraulic pitch system, external leakage from the hydraulic components must be eliminated. This will be achieved through reductions in external leakage paths to both the environment in the hub of the turbine and nature where the turbine is erected. In 2012, 74% of the offshore wind turbines were installed with hydraulic pitch systems. Of the total offshore capacity, 86% of the turbines are controlled by hydraulic pitch systems (2012). It is the goal for the new hydraulic pitch system that it must be in new offshore wind turbines already being installed with hydraulic pitch, but by the modular thinking and plug and play setup it is possible to access turbine manufacturers who use electric pitch and thus take greater market share.

The purpose of the project is to mature the idea of ​​a novel approach for establishing reliable digital twins of offshore wind turbines, which can be employed for improved operation and maintenance of these systems. Upon successful completion of this, the intention is to apply for an Innovation Fund project or EUDP project. The aim is to develop digital twins based on closed-loop model updating and incorporate them in a systematic procedure for structural health monitoring of wind turbines, and (2) aim To develop data-driven control strategies for vibration damping.

The purpose of this proof of concept project is to further investigate the WaveSpring technology and how it can benefit wave energy plants. The results from the project will increase the efficiency of wave energy plants and reduce the price of the energy produced from the plants.

An experimental study of float design is carried out with scale 1:40 models. Through tests in a wave laboratory, horizontal and vertical wave forces are measured under different influences for a wide range of float types. Initially, the effect of the float geometry is measured for a restrained float. Subsequently, the effect of the float's anchoring system is described where movements of the float under wave influence are possible.

Vessel propellers have reduced power efficiency with increased growth of barnacles and fouling, leading to an

increase in fuel consumption as high as 5%. SubBlue Robotics has developed an underwater propeller po-
lishing robot that allows for propeller polishing without the use of divers, and is capable of careful, precisepolishing of curved surfaces. As no divers are in the water, it can polish when the ship is loading and unloading

cargo, thus saving the shipowner valuable idling. Idling is the reason why the propeller polishing is often skip-
ped. The project will give technical robustness to the existing prototype, develop commercial grade components, and test the robot on commercial vessels. Leading partner is SubBlue Robotics, who has worked on

the designs and prototypes since 2016, the MMMI now IME institute at SDU provides knowledge on robots in harsh

enviroments, while shipowners DFDS and Maersk and diving company Odin Diving represent the market de-
mands the robot must meet. Three senior executives from CoGrow have invested in SubBlue Robotics, who

has just secured yet more capital and competences from two more investors.

The flow over ship propellers is under investigation. In particular propellers of unconventional geometry such as tip-fin propellers are being investigated, in particular with a view to improve efficiency and limit noise and vibration impacts. A comparative study of a tip-fin propeller and a conventional propeller is being carried out. Both propellers are designed for the same ship and the same service conditions. The examination is made theoretically as well as experimentally. The experiments include open water, self propulsion and cavitation tests.

The region of Southern Denmark has had a long historical tradition for a strong involvement in the maritime sector, but the region has for the last 50 years been especially known for its deep involvement in the offshore sector, with Esbjerg as a key location in Northern Europe. The sector is now well-established and continues to grow, currently undertaking a radical transformation. This development is influenced by different factors, including an increase in offshore oil and gas decommissioning, as well as the rapidly growing offshore wind farms and plans for building large energy islands. These islands will serve as electro fuel production and bunkering facilities but will also become hubs that facilitate better connections between the energy generated from offshore wind constructions and the zero emission energy systems ashore. These developments all lead to important challenges and opportunities for the maritime sector. For instance, a strong focus on the maritime offshore sector is essential to realize the plans for developing the energy offshore sector and the connected goals for costs, efficiency, sustainability, performance etc. in all stages of the life cycle, from design, construction, operation, and maintenance to the final decommissioning. The maritime offshore activities will therefore be essential for reaching the United Nations (UN) 2030 and 2050 climate targets. The idea of the project is to investigate multiple aspects of this transition.
The project portfolio consists of six interconnected work packages (WP 1-6) that serve as part of a holistic collaboration platform that will significantly energize the maritime research at SDU. The topics are interdisci-plinary and cover a wide range of maritime disciplines, such as:

• Sustainability, safety, and risks
• Energy efficiency, maintenance, propulsion technologies and fuels
• Business history
• Business and Logistics
• Regulation
• Human factors, health, socio-economic issues
• Naval architecture and maritime operations

All work packages, though separate in their research focus, are interconnected and important to the project, as the breadth and interdisciplinarity of the initiative is what makes it unique in a Danish context.

To further develop existing theoretical understanding on the concept of sustainable biomass with GHG neutrality when applied with a holistic integration across sectors

To coordinate the use of novel solutions to negative emissions (carbon storage solutions) across different sectors based on carbon captured in biomass, from point source emissions, and directly from the atmosphere

To develop crosscutting society system analysis methodologies, tools, and models allowing for an overarching holistic co-optimization of the carbon balance across all sectors of agriculture, forestry, energy, transport, industry, buildings, waste management, and materials

To use these models on the assessment and development of a sustainable co-optimized carbon management strategy for green fuels in the green transition of Denmark

To create an understanding of sustainable biomass availability and of the holistic carbon balance of a net zero society on the global scale to reveal the techno-economic feasibility of solutions, models and system designs and their scalability and applicability as models for a global climate solution.

This project intends to develop an indicator that can effectively reflect all attributes of a ship’s energy efficiency.