Project

The ocean covers over 70% surface of the earth, however, we have to say that so far human being knows still very little under these waters, although we believe there should be plenty of resources we could adopt if we could find out some safe and cost-effective technology to do so. Subsea robotics has been helping human beings to extend their capabilities in recent decades, thanks to the rapid technology development. Subsea robots can commit difficult and/or dangerous tasks beyond human's natural capability, such as deepwater sea floor scanning, oil & gas exploitation and exploration, subsea pipeline installation and inspection, as well as handling some catastrophic disasters.

The proposed equipment can certainly provide us with a solid and professional subsea robotic platform, not only to verify our so-far obtained results, but also to inspire new thinking and ideas, as well as to provide relevant industries a lab-sized testing robot protocol.

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.

A more and more widespread way to protect the coast against ongoing erosion is to build so-called Low Crested Structures (LCSs). Despite a large number of coast parallel LCSs exist, the structural performance of these structures are not fully clarified. The LCSs dealt with are coast parallel detached rubble mound structures, either emerging slightly above the water surface or somewhat submerged like a reef.

Initially results of a study of the geometry of existing LCSs are presented. The geometry and structural performance of existing LCSs form the basis of the limits for new design equations. New improved design formulas for calculation of static stability of LCSs are developed on the basis of new 2D and 3D laboratory experiments with scale models. The formulas are specially designed for breakwaters subject to shallow water waves and/or depth limited waves, as the majority of existing LCSs are exposed to such conditions. The formulas are validated against prototype experience. Ecological aspects in relation to structural stability are important, and design guidance on how to consider ecology in the design is therefore given. The new design guidance adds practical and helpful knowledge to the toolbox of the designing engineer.

The Danish wave energy sector consists of several large floating and loosely anchored wave power plants. These plants require specially designed anchoring systems, as “standard” solutions (largely coming from the offshore oil and gas industry) are not designed for the conditions and specifications applicable to wave power plants. For these wave power plants, it is necessary to reduce the resulting anchoring and structural loads, which can be done by making the anchoring solutions more compliant. This will reduce the costs of the anchoring solution and the structure of the plant and thereby the overall costs of the plant and its produced energy, while making the systems more reliable.

The four plants selected to be part of this project are all at a stage of development where they have either completed, or are about to complete, testing of the plants at sea. The four plants are Floating Power Plant, Wave Dragon, Weptos and Leancon. They all require comparable anchoring solutions, as the plants are large, floating, loosely anchored structures operating in water depths of around 30 – 100 m at full commercial scale. This project investigates and compares different anchoring solutions that are useful for these wave power plants. The anchoring solutions are assessed step by step, in order to carry out a systematic and thorough evaluation. The project is organised in the following work packages:

- WP 1: Design practices and tools.
- WP 2: Anchoring solutions.
- WP 3: Preliminary design.
- WP 4: Full analysis.
- WP 5: Cost evaluation.
- WP 6: Selection and results.
- WP 7: Dissemination and project management.

Throughout the project, reports will be produced presenting the results of the selected studies and milestones according to the project Gantt chart. Each of them is crucial for the next step of the analysis and will thus be of great importance. The final results of this project are numerous. It will provide experience and insight into the development of anchoring solutions for all project partners. Furthermore, it will provide the developers with detailed analyses of the various anchoring solutions, and evaluate their prices and practical applicability. Aalborg University will build up experience and know-how in the field, which will enable them, and/or a possible spin-off company, to offer design services in the field to companies in the future. It is also expected to be significant cost and reliability benefits, in addition to having an effective anchoring solution, for the partner plants.

Description
100 kW EXOWAVE wave energy testing in Hanstholm.

Key results
• Design, build and demonstrate an Exowave wave energy converter (WEC) block at a 14-meter water depth in the Danish North Sea in conjunction with a hydro turbine driven electrical generator connected to the grid. The power generation would be +100 kW.
• Include learnings from EUDP1: numerical model verified by tank test (AAU) and CFD analysis (Delft University), feasibility study: wind and wave plant in very large scale, WEC detailed design and engineering, FAT and demonstration at DanWEC site.
• Assess the environmental impact and improve animal life by shaping the WEC foundation for fish breeding grounds.
• Life cycle analysis and include eco-friendly materials as waste materials from wind turbine blade waste materials.
• Assess supply chain in the North Sea region with special focus in Denmark and its raw material, production facilities, knowledge provider for fulfilling the aim above LOI target and support the Danish national energy target in 2030 and 2050. And to include the results in the design phase. The overall KPI here is to lower LCOE.
• TRL improve from 6 to 7

This project aims at designing mooring system for floating wave energy converters (WECs) using a design approach based on numerical uncertainty quantification to estimate loads to a given tolerance level. This approach is to be compared to traditional deterministic approach with safety factors in terms of cost of the designed system. This is to be achieved by: (i) using an uncertainty quantification (UQ) toolbox based on general polynomial chaos (gPC) into a state-of-the-art mooring dynamics solver; (ii) to perform detailed numerical investigation on the influence on snap-loads on the mooring design. All parts aim at providing a base for lowering the economic cost of the mooring system.

The overarching objective of VALID (Verification through Accelerated testing Leading to Improved wave energy Designs) is to de-risk the whole WEC design process in terms of components reliability and survivability by developing an integrated and open platform for the testing of critical components and subsystems, proposing novel testing procedures going beyond current testing practices. As a consequence, it will facilitate developers to take sound design decisions at early stages of technology developments.

Wave power is one of the most reliable resources for renewable energy utilisation. However, the development of high-performance wave energy converters (WECs) is a complex challenge and requires a solid framework of evaluation tools. The EU-funded VALID project will focus on developing and validating a new test rig platform and methodology for accelerated hybrid testing that can be used across the wave energy sector. By improving the reliability and survivability of the components and subsystems that form WECs, the project aims to establish a standard for future use.

Moorings of floating oil and gas (O&G) structures present surprisingly large failure rates. A top solution is a redundancy in the design. However, marine renewables cannot afford such redundancy in the mooring design to obtain a competitive levelised cost of energy (LCOE). The EU-funded ISLINGTON project will reduce uncertainties in the estimated fatigue damage of mooring cables due to soil-cable interaction in the touch-down zone (TDZ) and the economic cost for marine renewables. ISLINGTON will improve the numerical modelling of the cable-soil interaction in the TDZ for mooring cables, generate experimental data for mooring line trenching and perform a numerical investigation of the effect of trenching on the fatigue of mooring cables.

In an effort to minimize the costs of offshore wind parks, the present research deals with optimizing a certain aspect of the support structure, namely the approach to scour. Scour is the phenomenon of seabed changes in the vicinity of the support structure that arises when the support structure disturbs the local flow sufficiently much. Scour is particularly evasive because in case of current, the flow disturbance can be intense and dig a hole comparable to the horizontal extent of the support structure. This usually implies a considerable loss of stiffness, ultimate strength or lifetime of the support and super structure. In case of waves, however, the flow disturbance can be much weaker and even backfill the hole with soil. The ability to accurately forecast this development of the geometry of the scour hole becomes central for obtaining both a safe and cost-effective solution. In practice, scour forecasts facilitate the comparison between a scour design based on either deployment of scour-protection or enhanced structural design. The broad goal is to develop a method that produces accurate scour forecasts for offshore wind parks. The present research investigates more specifically which parameters are suitable for characterizing the scour geometry during both scouring and backfilling and how the parameters develop in time for a given sea state. The present research is restricted to treat a monopile in sand since this is a common and potentially cost-saving case.

In Europe, coastal areas are great zones of settlement and play a vital role in the wealth of many nations. Over the past 50 years, the population living in European coastal municipalities has more than doubled and in 2001, it reached 70 million inhabitants. The total value of economic assets located within 500 meters of the European coastline was estimated at between € 500 and 1,000 billion in 2000. [THESEUS, 2010]

This PhD stipend is affiliated with the 4 year research project THESEUS (“Innovative technologies for safer European coasts in a changing climate”) funded by the European Commission (6.5 million Euro). The objective of the project is to study the application of innovative combined coastal mitigation and adaptation technologies generally aiming at delivering a safe (or low-risk) coast for human use/development and healthy coastal habitats as sea levels rise and climate changes (and the European economy continues to grow). The general aim of this PhD project is to develop and evaluate innovative methods for mitigation of flooding and coastal erosion hazard in the context of increasing storminess and sea level rise.

The PhD project will be related mainly to experimental testing of various innovative methods for improving the safety of European coasts in a changing climate. These methods will among others be upgrade of existing defences (dikes, breakwaters etc.) and reduction of wave energy at the coasts by utilization of wave energy converters placed offshore. Concerning the use of wave energy converters for coastal protection, an additional numerical study will be performed, where the numerical model is calibrated and validated against the experimental test-data. Thereby, it is possible to apply the evaluated wave energy converters at any shoreline. Moreover, the consequence of overtopping waves on dikes will be investigated in oblique- and short-crested waves which can be used to more realistically evaluate the consequence of sea water level rise.