Project

The long-term goals of this task are:
1. To assess the accuracy and establish confidence in the use of numerical WEC models
2. To determine a range of validity of existing computational modeling tools
3. To identify uncertainty related to simulation methodologies in order to:
a. Reduce risk in technology development
b. Improve WEC energy capture estimates
c. Improve loading estimates
d. Reduce uncertainty in LCOE models
4. To define future research and develop methods of verifying and validating the different types of numerical models required depending on the conditions

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 Ocean Energy Scale-up Alliance (OESA) is an accelerator project aiming to develop and deploy large scale marine energy pilots. The transnational partnership under the lead of the Dutch Marine Energy Centre (DMEC) combines expertise from 6 European countries from the North Sea Region.

The following three goals will accommodate a larger number of technology deployments in the future:

To develop a transnational scale-up offer for marine energy technologies, in which the services of large European service providers in offshore and marine energy are combined.
To accelerate the development of four technologies, leading to the deployment of 20 MW in large scale pilots.
To bring together stakeholders from the offshore industry, investment business and policy makers in a stakeholder platform and show the collaborative potential of marine energy in order to secure their support for future deployments in the ocean energy sector.

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 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).

The Wave Star wave energy machine converts the energy of waves into electricity. Wave Star is under development and model tests are being carried out at Aalborg University. The tests are carried out with a view to optimising the efficiency in different wave conditions and mapping effects such as the orientation of the plant in relation to the waves. The tests are supplemented with computer calculations. The project is being carried out in collaboration with Wave Star Energy.