Floating Power Plant (FPP) develops a hybrid floating wind and wave energy device. Pitching Wave Energy Converters (WECs) interact with the supporting structure, amplifying the motion of the WECs within the design wave frequency range. In this work we focus on the effect of the chamber geometry – without the WEC – in amplifying the waves inside the chamber. The simulations are carried out using two-phase Navier-Stokes simulations. We investigate the wave propagation and the interaction between waves and the fixed support structure. The simulations are compared to experimental tests performed in the wave basin at Aalborg University.
To comply with regulations stated by the United Nation's International Maritime Organization, ballast water discharged by ships must be treated to avoid the spread of invasive organisms including algae. In this study, Raman spectroscopy and multivariate data analysis was used to make a Partial Least Squares Discriminant Analysis (PLS-DA) classification model for discrimination between viable (potential invasive) and UV exposed non-viable organisms. UV exposure is commonly used as a ballast water treatment strategy and a UV based exposure method was developed such that non-viable (and dying) algae consistently could be obtained. Raman spectra from both viable and UV treated algae of Rhodomonas salina and Tetraselmis suecica were measured. A PLS-DA model was obtained to form the normalized dataset, and Cross-Validated using Venetian blinds. Based on their individual Raman spectra, it was possible to obtain 100 % discrimination between the two algal species. The model classified 92 and 91 % of the viable algae correctly for R. salina and T. suecica, respectively, as opposed to 82 and 94 % for non-viable algae. In conclusion, in this proof of concept study, Raman spectroscopy was found to have a potential for algae species identification as well as discrimination between viable and non-viable algae.
Successful maritime spatial planning processes require stakeholder engagement and participation, thus requiring tools that support collaboration. Communication-driven spatial decision support systems are designed to facilitate decision making processes of complex spatial problems and are therefore suited for this task, but there are unresolved questions about user access control for these systems. In this study, user access control was designed for a spatial decisions support system for collaborative maritime spatial planning based on observation of two user tests. It was found that there were three distinct groups of users with special access needs to collaborative functionality. The level of access to functionality was organized into three groups: passive participants, actively contributing collaborators and managing moderators.
GreenHopper is the first Danish zero-emission ferry developed as a test platform for autonomous waterborne navigation technologies. The paper presents technology development within the innovation project ShippingLab Autonomy, which led to the commissioning of GreenHopper at Limfjorden (DK) in December 2022. The technology research resulted in a holistic system architecture for surface vessel autonomy, based on distribution of functionality and responsibility on software modules, similar to the structure observed in the International Maritime Organization (IMO) Seafarers Training Certification and Watch-keeping (STCW) regulatory framework. The paper shows how this approach results in an architecture that supports safe behaviours of individual modules and of autonomous navigation at a system level. The paper presents the individual modules, specific features and benefits. Elements of the regulatory framework are highlighted to poise technology approval by maritime authorities. The paper reflects on lessons learned, discusses continued technology validation in dedicated operational scenarios.
In the current transition of power industry from conventional sources to renewable energy sources, wind power generation is becoming one of the key sources of electrical energy. Although the development of wind power plants (WPPs) has made a significant contribution to addressing the demand for clean and cheap energy, the integration of large-scale WPPs introduces a series of technical challenges to power system operations. These challenges involved control, protection, and adherence to specified power quality standards. Particularly, power quality plays a vital role in utility systems and industries having direct technical and economic impact on both power consumers and suppliers. To tackle such issues, various grid codes have been initiated by regulation authorities. Moreover, different ancillary devices and control approaches have been adopted to comply with the established grid code. This article aims to review the state-of-the-art research and progress, while considering the main challenges related to dynamic performance and power quality enhancement of emerging grid-forming wind power plants. Various topologies of wind energy conversion systems (WECSs) are examined and compared, and their control strategies are investigated. A comprehensive review on power quality and dynamic response issues caused by large-scale wind power integration is presented. Moreover, the evolving grid code requirements for grid-connected WPPs in most leading countries including Denmark, U.K., Australia, Germany, and the USA are analyzed and compared. Furthermore, the improvement approaches proposed in the literature are investigated and classified on different basis and their pros and cons are discussed. A brief discussion on the solutions and future directions is presented. Finally, some conclusive considerations about the overall study are provided.
Physical wave basin tests with a focus on uncertainty estimation have been conducted on a sphere subjected to wave loads at Aalborg University as part of the effort of the OES Wave Energy Converters Modeling Verification and Validation (formerly, OES Task 10) working group to increase credibility of numerical modeling of WECs. The tests are referred to as the Kramer Sphere Cases, and the present note is dealing with wave excitation force tests on a fixed model. The present note is including details to facilitate CFD models which replicate the physical setup in detail.
Physical wave basin tests with a focus on uncertainty estimation have been conducted on a fixed sphere subjected to wave loads at Aalborg University as part of the effort of the OES Wave Energy Converters Modeling Verification and Validation (formerly, OES Task 10) working group to increase credibility of numerical modeling of WECs.
The present note defines an idealized test case formulated to accurately represent the physical tests in a simple way. The test case consists of a fixed, rigid sphere half submerged in water subjected to regular waves of three different levels of linearity. The objective of the present note is to allow for numerical tests of the idealized test case.
Floating Power Plant is, together with several partners, preparing to design, build and test a scaled version of the complete so-called P80 device. The scaled model is to be tested in AAU's wave basin, SSPA's facilities, followed by at least one external facility. The model will be tested in combinations of wave, wind and current conditions with a view to validating the numerical models and to further develop the understanding of the interactions within the device. The purpose of this document is to gather information that is relevant to designing and building the physically scaled model, and to designing and executing the test campaign.
Highly accurate and precise heave decay tests on a sphere with a diameter of 300 mm were completed in a meticulously designed test setup in the wave basin in the Ocean and Coastal Engineering Laboratory at Aalborg University, Denmark. The tests were dedicated to providing a rigorous benchmark dataset for numerical model validation. The sphere was ballasted to half submergence, thereby floating with the waterline at the equator when at rest in calm water. Heave decay tests were conducted, in which the sphere was held stationary and dropped from three drop heights: a small drop height, which can be considered a linear case, a moderately nonlinear case, and a highly nonlinear case with a drop height from a position where the whole sphere was initially above the water. The precision of the heave decay time series was calculated from random and systematic standard uncertainties. At a 95% confidence level, uncertainties were found to be very low — on average only about 0.3% of the respective drop heights. Physical parameters of the test setup and associated uncertainties were quantified. A test case was formulated that closely represents the physical tests, enabling the reader to do his/her own numerical tests. The paper includes a comparison of the physical test results to the results from several independent numerical models based on linear potential flow, fully nonlinear potential flow, and the Reynolds-averaged Navier–Stokes (RANS) equations. A high correlation between physical and numerical test results is shown. The physical test results are very suitable for numerical model validation and are public as a benchmark dataset.
The project "IEA OES Task 10 Phase III - WEC Modelling" is a publicly-funded research project under the Danish Energy Agency EUDP grant with Journal no. 134232-510153. As part of the initial period of the project, a selection of three test cases has been defined under WP2. The present report forms the deliverable for Milestone "M1: Case studies defined".