A design of Darrieus vertical axis tidal turbine using modified airfoil was studied numerically in this work. The turbine design was evaluated in 2D CFD model using kω turbulence model, upwind interpolation scheme and simulated using OpenFOAM. The turbine had three blades which were arranged symmetrically. The blades were of NACA 0012 airfoil which had been modified in the trailing edge region to increase its lift performance. The modification was made by truncating the trailing edge at the 15% of chord length from the trailing edge. Single normal and blunt airfoil were modelled and investigated prior to the turbine design evaluation. For generating the mesh, Cstructured grid was employed to the single airfoil model and hybrid mesh to the vertical axis tidal turbine model. From the single airfoil simulations, it was found that blunt NACA0012 had 12% higher lift coefficient than normal airfoil and the pressure coefficient magnitude of blunt vertical axis tidal turbine significantly rise two times from vertical axis tidal turbine using normal NACA0012 airfoil.  Index Terms-vertical axis tidal turbine, Darrieus turbine, truncated Naca0012, blunt airfoil

No abstract

Improving the reliability of marine renewable energy devices such as wave and tidal energy convertors is an important task, primarily to minimize the perceived risks and reduce the associated cost for operation and maintenance. Marine systems involve a wide range of uncertainties, due to the complexity of failure mechanism of the marine components, scarcity of data, human interactions and randomness of the sea environment. The fundamental element of a probabilistic risk analysis necessarily needs to rely on operational information and observation data to quantify the performance of the system. However, in reality it is difficult to ascertain observation of the precursor data according to the number of component failures that have occurred, mainly as a result of imprecision in the failure criterion, record keeping, or experimental and physical modelling of the process. Traditional reliability estimation approaches such as Fault Tree, Event Tree and Reliability Block Diagram analysis offer simplified, rarely realistic models of this complex reliability problem. The main reason is that they all rely on accurate prior information as a perquisite for performing reliability assessment. In this paper, a hierarchical Bayesian framework is developed for modelling marine renewable component failures encountered the uncertainty. The proposed approach is capable to incorporate the conditions, which lack reliable observation data (e.g. unknown/uncertain failure rate of a component). The hierarchical Bayesian framework provides a platform for the propagation of uncertainties through the reliability assessment of the system, via Markov Chain Monte Carlo (MCMC) sampling. The advantages of using MCMC sampling has proliferated Bayesian inference for conducting risk and reliability assessment of engineering system. It is able to use hyper-priors to represent prior parameters as a subjective observations for probability estimation of the failure events and enable an updating process for quantitative reasoning of interdependence between parameters. The developed framework will be an assistive tool for a better monitoring of the operation in terms of evaluating performance of marine renewable system under the risk of failure. The paper illustrates the approach using a tidal energy convertor as a case study for estimating components failure rates and representing the uncertainties of system reliability. The paper will be of interest to reliability practitioners and researchers, as well as tidal energy technology and project developers, seeking a more accurate reliability estimation framework.

The depletion of fossil fuels and the worsening environment motivate engineers and researchers to explore renewable energy resources. One of the promising renewable energy is wind energy. The wind turbine extracts wind energy to generate electricity. This study aims to modify a wind turbine blade using Clark Y foil to improve the lift force. The modification is employed by forming a winglet profile with a 30° angle on the foils tip. The result shows that the 30° winglet enlarges the lift coefficient to 1.3253 from 1.2795 of the original blade lift coefficient.

No abstract