Project

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.

This Bubble Project aims to assess the feasibility of revamping offshore oil and gas infrastructures transforming them into units producing methane from wind power.

Turkey is one of the fastest-growing energy markets in the world, with an annual 8% increase in energy demand. By the end of 2018, the total installed capacity and electricity production of Turkey was 88.5 GW and 300.7 TWh, respectively. Nowadays, more than 70% of all electricity production is supplied by fossil resources, and almost 30% of all electricity production comes from renewables, mainly hydro, while wind constitutes only 6.6% of the total electricity mix.

The wind and solar energy rate in total consumption are planned to be increased by at least 30% in the coming five years according to the 2023 vision plan of Turkey. However, due to the intermittent nature of wind energy, large-scale wind power integration may pose some serious challenges to Turkey's power system. Therefore, planning analysis and designing efforts are required to ensure the smooth, secure and reliable operation of Turkey's power system and electricity markets considering large-scale wind power integration. WindFlag aims to solve relevant challenges of large scale OWPP deployment and integration into the Turkish grid, such as extreme weak-grid situations, islanding conditions, and large harmonics and resonances.

The goal of the project is to significantly strengthen the scientific basis for the wind power industry in general and specifically the Danish wind power industry’s position in offshore applications.

To meet the goal the proposed research must have a significant potential for reduction of cost of energy from large offshore wind farms, and for contributing to reduction of the economic risks arising from inadequately founded design.

The key design driver for most offshore structures is safety. For offshore wind turbines/farms, however, the main design driver is economy and therefore there is a strong requirement for enhancing design tools and avoiding conservatism. Consequently, focus is on the following issues:

1. Mutual shadow effect between large blocks of wind turbines – ignorance of the effect may have disastrous consequences for the economy.
2. Extreme structural loading of offshore wind turbines – detailed understanding and description of extreme winds and gusts and resulting loads is crucial for the safety and economics of the wind turbines.
3. Interaction of large wind farms with waves and current – understanding and modeling may lead to reduced design loads on wind turbine units placed in the downwind end of the wind farms.
4. Grid connection and reliability – An unreliable grid caused by high wind energy penetration is an obvious barrier for the dissemination of the technology.
5. Optimized operation and maintenance for offshore wind farms – presently more than a third of the cost of energy from offshore wind farms relates to O&M and the potential for reductions is therefore large.

The project is sponsored by The strategic Research council and have participant from Risø National Laboratory, Elsam Engineering, Insitut for Mekanik, Energi og Konstruktion DTU, DHI, Svend Ole Hansen and Institute of Energy Technology AAU.

The institute of Energy Technology is especially involved in issue 4 in this project, by Birgitte Bak-Jensen, and also a Ph.D project is set up together with Risø and Elsam Engineering, with the title: Offshore Wind Power – Grid Connection and Reliability, see this project.

This Ph.D. project is carried out at Dong Energy in cooperation with Risø National Laboratory and Aalborg University.

The aim of the PhD project is to investigate the influence of wind generation on the reliability of power systems. This task is particularly important for large offshore wind installations, because failure of a large wind farm will have significant influence on the balance in the power system, and because offshore sites are normally more difficult to access than onshore installations. The reliability of power production from a wind farm depends on wind speed conditions, the wind turbines themselves, the system layout and the grid connection; besides, the offshore environment poses new challenges to face for the installers.

The project has been divided into three parts. Firstly, a model for yearly generation assessment of offshore wind farms has been developed: this model includes wind speed randomness and variability, components (e.g. wind turbines, internal cables and connectors to shore) failures, influence of site environment and some minor aspects of relevance. Secondly, this model has been used for evaluating the so-called HLI analysis (Hierarchical Level I), where the system adequacy to supply the load is assessed. The power system under study includes conventional power plants, an aggregated load and distributed generation together with offshore wind generation, whereas transmission facilities are neglected in this type of simulation. These two assessments are performed considering a sequential Monte Carlo simulation: this approach has shown more flexibility and completeness in the analysis of wind generation than analytical techniques.

With these two models, that are currently available, some sensitivity analyses will be carried out in the next months. Besides, some of the models will be used for performing an HLII analysis: in this type of study, the transmission facilities are included in the power system model and the adequacy of the system generation is evaluated including the availability of transmission lines and cables.

All analyses in the project are carried out by the use of the software Matlab and the power system analysis tool Power Factory from DigSILENT: simulations will include steady-state conditions as well as dedicated reliability analyses.

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.

The general aim of the 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 defenses (dikes, breakwaters etc.) and reduction of wave energy at the coasts by utilization of wave energy converters placed near-shore.

In connection with the construction of the Nysted (Rødsand) offshore wind farm, an experimental study of the erosion protection around the turbine foundations has been carried out. The project has determined comparative erosion depths around different foundation types placed on sand. In addition, tests have been carried out with the proposed erosion protection. The project has been carried out for SEAS Distribution, the Wind Power Department and Carl Bro Anlæg A/S. (Peter Frigaard, Morten Kramer, Tue Hald).