Wave Energy Converters

This paper addresses a fundamental study of a floating type shrouded wind turbine on the design, mathematical model and motion analysis. Several novel concepts are introduced to the system for cost reduction: a revolute hinge is applied between the tower and the nacelle to maintain the orientation of the nacelle even in a large tower inclination, a swashplate mechanism with cyclic control is employed for blade pitch regulation to improve the system control-lability, a novel mooring system with a slewing bearing is utilized to build the passive yawing system, and an advanced spar-type floater is used to obtain high restoring performance with a short spar. Firstly, the design aspects of the main components of the system are given. Then, the numerical model including the structural model, hydrodynamic/aerodynamic model, and the control system is presented. The static and dynamic responses under both the operational situation and survival conditions are finally studied. The paper illustrates the probability of the shrouded wind turbine on floating offshore application, and can provide critical information for the optimization design in next stage.

The aim of this study was to develop a model of ocean wave energy converter based on water mass gravity force (WEC-WGF) to overcome the flaws of existing wave energy converter that rely on water buoyancy force. This paper presented physical model experiment result of wave energy converter based on water mass gravity force. The harvested energy were compared with calculated theoretical energy based on linear wave theory. The physical model investigation was carried out at wave simulator (flume) in Hydraulics Laboratory Department of Civil Engineering, Hasanuddin University Indonesia on February-March 2016. The physical model consists of a series of one-way gear connected with plastic container as an interface between converter and regular generated wave. Investigation was carried out to observe the influence of gravity weight mass and wave height variations on converters harvested power. The experiment result indicated that the amount of converter Power Take Off (PTO) were strongly influenced by variation of gravity weight mass (M gw), followed by wave height (H) and wave period (T) respectively. These results outperform the calculated power by means of linear wave theory. The result of this experiment could be used as a reference to develop theoretical or analytical model of wave energy converter based on water mass gravity force. Keywords— Wave, Gravity Force, Renewable Energy, Wave Energy Converter I. INTRODUCTION Energy, water and food are essential needs to support the continuation of human activities. In the last few decades, the main source of energy depends on the burning of fossil fuel. Since the depletion of oil resources, most countries in the world started to realize the importance of environmental conservation and efficient use of fossil fuel reserves. Moreover, the reduction of fossil fuel as a main source of energy hopefully could reduce the level of CO2 emissions which are considered as a main source of global air pollution. The total global CO2 emissions in 2013, comprised of; power plants contribute 42%, transportation 23%, industrial activities 19%, households 6%, services and other sectors produced 3% to 7%. The amount of CO2 released into the atmosphere in the last 42 years increased by approximately 230% from 13.995 million tons in 1971 increased to 32.190 million tons in 2013 [1] [2]. Efforts to reduce CO2 emissions has been carried out through the utilization of renewable energy sources such as wind energy (wind), hydropower plants, solar power, ocean currents and wave energies. In term of energy density, wave energy poses the greatest energy content that is available for 24 hours. However it has not been fully utilize due to the cost per kWh did not economically feasible due to the flaws of existing wave energy converter technologies [3].

A detailed review of wave energy resource assessment and the state-of-the-art of deployed wave energy converters (WECs) in real environmental conditions in the Mediterranean Sea have been analysed in this study. The installed power of the several deployed WECs in the Mediterranean Sea varies between 3–2500 kW. Ten project cases of deployed WECs in the basin are presented, with their analysis of the essential features. Five different types of WEC have already been tested under real environmental conditions in Italy, Greece, Israel and Gibraltar, with Italy being the Mediterranean country with the most deployed WECs. The main questions of the relevant studies were the ongoing trends, the examination of WECs in combination with other renewable sources, the utilising of WECs for desalination, and the prospects of wave energy in the Mediterranean islands and ports. This paper is the first comprehensive study that overviews the recent significant developments in the wave energy sector in the Mediterranean countries. The research concludes that the advances of the wave energy sector in the Mediterranean Sea are significant. However, in order to commercialise WECs and wave energy exploitation to become profitable, more development is necessary

As long as it is economical, Turkey, which is encircled on three sides by the seas, should have the utmost benefit of using her existing potential of the wave motion. This paper presents our assessment on whether it is feasible to integrate the wave energy systems into the current Turkish Energy Program. The data required for calculating the approximate wave energy densities at many sites along the Turkish coasts have been derived from “Wind and Deep Water Wave Atlas of the Turkish Coast”, MEDCOAST Publications, have been used in a wave energy project analysis, which has been conducted by using RETScreen® International, “Small Hydro” in order to find out the cost effectiveness of a wave power converter system to harness the sea power from Turkish waters having a mild climate. The technically available resource has been estimated approximately 10 TWh/year with an annual wave power between 4 and 17 kW/m. This is 7.8 % of the economically feasible potential of current Turkish hydroelectrical energy. The regions in the west of the Black Sea in the north of Istanbul Straits and off the southwestern coasts of Aegean Sea between Marmaris and Finike have been suggested as the best sites to harness the wave energy.

Sea waves carry 1000-10000 gigawatts (GWs) of power. Although there are a large number of different approaches to harness offshore wave energy they could be expensive, practically challenging and vulnerable to storms. Therefore, this paper explain how nearshore waves could be used and converged to increase the energy density and generate electricity using a smaller wave energy converter (WEC) than would otherwise be necessary. To illustrate the effectiveness of this approach, some tests were carried out with a physical model of a manipulator both in steady, uniform waves and in random waves created in a wave flume representing different sea states. The results include comparisons between theoretical predictions and wave flume tests with respect to incident wave energy, loss in manipulation and increase in energy density for different settings of the manipulator. The paper also presents the brake torque and angular velocity of two single duct, axial flow turbines placed in manipulated waves. It is found that wave manipulation creates energetic off shore waves close to nearshore which makes it suitable for typical offshore WECs. The paper also discusses morphodynamics and ecological issues and outlines the advantages of building coastal structures for wave manipulation.