PowerPoint Presentation: OCEAN ENERGY TECHNOLOGIES BY P.V.S CHAMAN LAL Introduction: Introduction Federal Agency for Science and Innovation, 2010 Moscow, Russia 2 The main overview is mainly related to study of ocean and its wave, the ways to harness energy and the technologies Why Ocean?: The ocean is the world's largest solar collector and can provide huge amount of energy (kinetic and thermal) which is absolutely clean (zero CO2 emission), sustainable, strategic, and predictable. Changes in salinity, thermal gradients, tidal sea level change and currents, or ocean waves can be used to generate electricity. The number of ocean energy technology concepts has increased to +100 known devices. Available global Ocean Energy resource is in the same order of magnitude of the present electricity production worldwide (even more!). Why Ocean? PowerPoint Presentation: Basic technique for producing electricity from ocean When this wind skims over the sea , an interaction is caused in which energy is exchanged between the wind and the sea surface. At first, little ripples arise on the surface. Then, the wind that skims along these ripples causes higher air pressure at the front of the wave than at the back. As a result the ripples change into small waves. As this process continues, the waves become higher and the distance between the tops (wave length) becomes longer . Wind is caused by differences in temperature due to the solar heating of the earth's atmosphere. PowerPoint Presentation: Table compiled from International Energy Agency, Policy Report, 2006 5 PowerPoint Presentation: Ocean energy mainly consists of the following 3 types 1] Tidal power:-due to high and low tides over a day. 2] Ocean current:-they are due to temperature gradient in the different part of sea. 3] Surface waves;-These are the waves due to wind over the surface of a sea. Tidal energy This technology has been in use since the 11th Century. When tides come into the shore, they can be trapped in reservoirs behind dams. Then when the tide drops, the water behind the dam can be let out just like in a regular hydroelectric power plant. There are two different means to harness tidal energy: first is to exploit the cyclic rise and fall of the sea level using barrages second is to harness local tidal currents, analogous to wind power also called ‘marine current turbine’. PowerPoint Presentation: Barrage An artificial dam to increase the depth of water for use in irrigation or navigation, or in this case, generating electricity. Flood The rise of the tide toward land (rising tide) Ebb The return of the tide to the sea (falling tide) TIDAL BARRAGE METHODS Two types of barrages: SINGLE BASIN BARRAGE DOUBLE BASIN SYSTEMS PowerPoint Presentation: SINGLE BASIN BARRAGE DOUBLE BASIN SYSTEMS PowerPoint Presentation: Marine current turbines work, in principle, much like submerged windmills, but driven by flowing water rather than air. The main difference is that marine current turbines of a given power rating are smaller, (because water is 800 times denser than air) and they can be packed closer together (because tidal streams are normally bi-directional whereas wind tends to be multi-directional). 750 kW – 1.5 MW 15 – 20 m diameter rotors 3 m monopile 10 – 20 RPM Deployed in multi-unit farms or arrays Like a wind farm, but Water 800x denser than air Smaller rotors More closely spaced AXIAL TURBINES PowerPoint Presentation: VERTICAL AXIS CROSS-FLOW TURBINES PowerPoint Presentation: Advantages & Disadvantages of Tidal Turbines Low Visual Impact Mainly, if not totally submerged. Low Noise Pollution Sound levels transmitted are very low High Predictability Tides predicted years in advance, unlike wind High Power Density Much smaller turbines than wind turbines for the same power High maintenance costs High power distribution costs Somewhat limited upside capacity Intermittent power generation PowerPoint Presentation: WAVE ENERGY Types of wave energy technologies Oscillating water column Pelamis Wave dragon Archimedes wave swing Mccabe wave pump Power buoy Aqua bouy PowerPoint Presentation: The Oscillating Water Column generates electricity in a two step process. As a wave enters the column, it forces the air in the column up the closed column past a turbine, and increases the pressure within the column. As the wave retreats, the air is drawn back past the turbine due to the reduced air pressure on the ocean side of turbine. Oscillating Water Column PowerPoint Presentation: The energy is produced when a wave runs on the length of the systems. Joints, connected to pump oil and to a hydraulic generator (smoothing systems), allow movement between each section and produce electricity as the wave moves by . THE PELAMIS Main features about the Pelamis : Overall length = 390x220 Diameter = 14000 m3 Overall power rating = 0.75MW Nominal wave power = 55kW/m Annual power production =2.7GWh Water depth = >50m PowerPoint Presentation: THE WAVE DRAGON The wave dragon is a system that temporarily stores water in a reservoir before falling into a turbine The waves reach the reservoir by way of a ramp. After going through an alternator, the water is released to the source. This means of generation can be comparable to a dam with three steps: absorption, storage and power take off. Main features about the largest Wave Dragon : Width and length = 390x220m Reservoir = 14,000 m3 Rated power/unit = 11MW Annual p ower production/unit =35GWh Water depth = >30m PowerPoint Presentation: THE ARCHIMEDES WAVE SWING (AWS) The working procedure is based on the principle of the float (Archimedes). The only moving part is an air-filled floater. Waves create an ‘up and down’ movement due to applied pressure on the floater which is located in a lower fixed cylinder. A linear generator based in the cylinder, this movement is converted into electricity and then transmitted to the shore Each unit is currently rated at 1.2 Megawatts, equal to the electrical demand of approximately 500 households’ energy . PowerPoint Presentation: MCCABE WAVE PUMP The McCabe Wave Pump has three pontoons linearly hinged together and pointed parallel to the wave direction. The center pontoon is attached to a submerged damper plate, which causes it to remain still relative to fore and aft pontoons. Hydraulic pumps attached between the center and end pontoons are activated as the waves force the end pontoons up and down. The pressurized hydraulic fluid can be used to drive a motor generator (rated at 250–500 kW) PowerPoint Presentation: THE AQUA BUOY The vertical movement of the buoy drives a broad, neutrally buoyant disk acting as a water piston contained in a long tube beneath the buoy. The water piston motion in turn elongates and relaxes a hose containing seawater, and the change in hose volume acts as a pump to pressurize the seawater PowerPoint Presentation: High capital costs for initial construction High maintenance costs Wave energy is an intermittent resource Requires favorable wave climate. Investment of power transmission cables to shore Degradation of scenic ocean front views Interference with other uses of coastal and offshore areas navigation, fishing, and recreation if not properly sited Reduced wave heights may affect beach processes in the littoral zone Onshore wave energy systems can be incorporated into harbor walls and coastal protection Reduce/share system costs Providing dual use Create calm sea space behind wave energy systems Development of mariculture Other commercial and recreational uses; Long-term operational life time of plant Non-polluting and inexhaustible supply of energy Wave Power Advantages & Disadvantages Ocean Thermal Energy Conversion: Ocean Thermal Energy Conversion OTEC Description: OTEC Description Oceanic Thermal Energy Conversion OTEC utilizes the ocean’s 20ºC natural thermal gradient between the warm surface water and the cold deep sea water to drive a Rankine Cycle OTEC utilizes the world’s largest solar radiation collector - the ocean. The ocean contains enough energy power all of the world’s electrical needs. OTEC Process: OTEC Process 1. Power input to pumps to start process 4. Expanding vapor drive the turbine, and electricity is created by a generator 5. Heat extraction from cold-water sink to condense the working fluid in the condenser. Cycle begins again Return to step 2 3. Heat addition from the hot-water source used to evaporate the working fluid within the heat exchanger (Evaporator) 2. Fluid pump pressurizes and pushes working fluid to evaporator Open-cycle OTEC: Open-cycle OTEC PowerPoint Presentation: 24 PowerPoint Presentation: Hybrid systems Hybrid systems combine the features of both the closed-cycle and open-cycle systems. In a hybrid system, warm seawater enters a vacuum chamber where it is flash-evaporated into steam, similar to the open-cycle evaporation process. The steam vaporizes a low-boiling-point fluid (in a closed-cycle loop) that drives a turbine to produces electricity. APPLICATIONS FOR OTEC PowerPoint Presentation: OTEC systems can produce fresh water as well as electricity. This is a significant advantage for an island, such as the Virgin Islands for example, where fresh water is limited. There is enough solar energy received and stored in the warm tropical ocean surface layer to provide most, if not all, of present human energy needs. DISADVANTAGES OTEC plants must be located where a difference of about 40 degrees Fahrenheit occurs year round. Ocean depths must be available fairly close to shore-based facilities for economic operation. Construction of OTEC plants and laying pipes in coastal waters may cause localized damage to reefs and near-shore marine ecosystems. OTEC ADVANTAGES PowerPoint Presentation: Ocean Thermal Energy Conversion (OTEC) The world's only Open Cycle OTEC facility at Keahole Point on the Kona coast of Hawaii (United States Department of Energy) 27 PowerPoint Presentation: CONCLUSION Each system has its own advantages and disadvantages. Several common points to these three main technologies stand out. The positive aspects of using ocean energy are: Reduction in dependence on fossil fuels. Source of energy is free, renewable and clean. Clean electricity is produced with no production of greenhouse gas or pollution (liquid or solid). Energy produced is free once the initial costs are recovered. These technologies are renewable sources of energy. The negative aspects of using ocean energy are: At present, electricity produced would cost more than electricity generated from fossil fuels at their current costs. It leads to the displacement of wild life habitats. Technologies are not fully developed. Problems exist with the transport of electricity to onshore loads.