Harnessing wave energy comes of harmful green house gases. This is the main motivation factor behind further development of this way of power generation. We need to find energy sources that will replace polluting ones (e.g. fossil fuels). Like with most green energy sources, wave power is also renewable. Since this energy source ultimately comes from the heat energy that is emitted from the sun, The amount power in that comes in waves is huge. The energy density is typically around 3040 kW for every meter (2.2 feet) of wave along the shore. As we go further into the ocean 100kW for every meter is not uncommon. Waves are hardly interrupted and almost always in motion. This makes generating electricity from wave energy a reasonable reliable energy source (at least when you compare them to solar and wind).
With considering the increasing of global temperature, and also the concern of global climate change, many policy makers worldwide have been accepted the importance of reducing greenhouse gas emissions, in particular from the power industries so the importance of the renewable energy is obvious. Wave energy is one of the renewable energy sources. And has the potential to play a valuable part in a sustainable energy future. Wave energy is also one of the predictable energy sources that depending on oscillating the surface of water. The wave energy system for generation electricity in the last few years has been growing rapidly.
Oceans cover more than 70% of Earth's surface, making them the world's largest solar collectors.
The oceans cover ¾ of the earth and contain a great store of energy. The world's largest solar collector absorbs a fantastic amount of the sun's energy: 4,000 times the amount of electricity used by all humans on the planet.
A typical square mile of the ocean contains more energy than 7,000 barrels of oil.
The ocean contains two types of energy: thermal energy from the sun's heat, and mechanical energy from the tides and waves.Ocean mechanical energy is quite different from ocean thermal energy. Even though the sun affects all ocean activity, tides are driven primarily by the gravitational pull of the moon, and waves are driven primarily by the winds.
The tidal rise and fall of the oceans is caused by the varying gravitational pull of the sun and the moon.
The incoming and outgoing tides of the sea can be harnessed to produce electrical power. Energy can be extracted from the temperature difference between the warmer and cooler layers in a process called Ocean Thermal Energy Conversion (OTEC). The heat energy is then used to generate electricity
Ocean wave energy is captured directly from surface waves or from pressure fluctuations below the surface. Wave power systems convert the motion of the waves into usable mechanical energy which in lump can be used to generate electricity. Waves are caused by wind blowing on the surface of the water.
Among different types of ocean waves, wind generated waves have the highest energy concentration. Wind waves are derived from the winds as they blow across the oceans. This energy transfer provides a natural storage of wind energy in the water near the free surface. Once created, wind waves can travel thousands of kilometres with little energy losses, unless they encounter head winds .
Nearer the coastline the wave energy intensity decreases due to interaction with the seabed.
Ocean waves encompass two forms of energy: the kinetic energy of the water particles, that in general follow circular paths; and the potential energy of elevated water particles.
On the average, the kinetic energy in a linear wave equals its potential energy. The energy flux in a wave is proportional to the square of the amplitude and to the period of the motion. The average power in long period, large amplitude waves commonly exceeds 40-50 kW per meter width of oncoming wave.
Wave power is the transport of energy by ocean waves, and the capture of that energy to do useful work — for example; electricity generation, water filtering, or the pumping of water into reservoirs. A machine able to exploit wave power is generally known as a wave energy converter (WEC). Harnessing the power in ocean waves is another way to extract energy from the seas. Wave power devices extract energy directly from surface waves or from pressure fluctuations below the surface. Renewable energy analysts believe there is enough energy in the ocean waves to provide up to 2 terawatts of electricity. (A terawatt is equal to a trillion watts.) Waves are powered largely by the wind and the tides. As wind blows across the surface of the ocean, it creates waves. In deep water waves oscillate up-and-down, while near the shore a surge of water results .
As most forms of renewables, wave energy is unevenly distributed over the globe. Increased wave activity is found between the latitudes of ~30o and ~60o on both hemispheres, induced by the prevailing western winds (Westerlies) blowing in these regions. Particularly high resources are located along the Western European coast, off the coasts of Canada and the USA and the southern coasts of Australia and South America.
India has a coastline of approximately 7500 km.The average wave potential along the Indian coast is around 5-10 kW/m and peak monsoon average is around 20 kW/m. Even 10% utilization would mean a resource of 3750 –7500 MW.
The sea wave’s motion can be converted into mechanical energy by using proper wave power mechanisms. There are currently about 40 types of mechanisms for exploiting the energy available in waves, several of which are now being constructed. These devices are generally categorized by location installed and power take-off system. Locations are shoreline, near shore and offshore. Power take-off systems can be oscillating column of water, underwater pneumatic systems, wave dragon system and oscillating bodies system. Also these mechanisms can be lying on the bottom of the sea, on the shoreline and on sea level.
Onshore wave power systems, as their name suggests, are those built along shorelines to extract the energy in breaking waves. These devices are fixed to or embedded in the shoreline itself, which has the advantage of easier maintenance and/or installation. In addition these would not require deep water moorings or long lengths of underwater electrical cable. There are three general varieties of onshore system technologies: The Oscillating Water Column. The Tapchan. The Pendulor Device.
Shoreline devices have the advantage of being close to the utility network, are easy to maintain, and as waves are attenuated as they travel through shallow water they have a reduced damaged in extreme conditions. Tidal range can also be an issue. In addition,by nature of their location, there are generally site specific requirements including shoreline geometry and geology, and preservation of coastal scenery, so devices cannot be designed for mass manufacturing.
Offshore devices are generally in deep water although in deep water is that it can harvest greater amounts of energy because of the higher energy content in deep water waves . offshore devices are more difficult to construct and maintain, and because of the greater wave height and energy content in the waves, need to be designed to survive the more extreme conditions adding cost to construction.
Near shore devices are defined as devices that are in relatively shallow water , but it has been suggested that this could be a depth of less than one quarter wavelength . waves with reduced power, limiting the harvesting potential.
Oscillating Water C olumns (OWCs) are devices that generate energy from the rise and fall of water caused by waves and tides in the ocean. As water rises and falls around and inside an OWC, air is displaced by the water in a collecting chamber and pushed back and forth past a Power-Take-Off (PTO) system. The PTO system converts the airflow into energy. In models that convert airflow to electricity, the PTO system consists of a bidirectional turbine. This means that the turbine always spins the same direction regardless of the direction of airflow, allowing for energy to be continuously generated. Basic OWC Components. Collecting chamber,Power take-off,Wells turbine
Due to the tapering of the horizontal channel,water is lifted to reservoir 3m above.The water in the reservoir flows back into the sea from the behind it and turbine house through a conventional low pressure water turbine rinning a 350 kw generator connected to the local grid.
The Pendulor, which consists of a rectangular box, which is open to the sea at one end (Figure ). A pendulum flap is hinged over this opening, so that the actions of the waves cause it to swing back and forth. This small schemes (≥ 5 kW) have been built in Japan and there are plans to develop a larger plan
An overtopping device captures sea water of incident waves in a reservoir above the sea level, then releases the water back to sea through turbines. An example of such a device is the Wave Dragon, which is shown in Fig. This device uses a pair of large curved reflectors to gather waves into the central receiving part, where they flow up a ramp and over the top into a raised reservoir, from which the water is allowed to return to the sea via a number of low-head turbines. The Wave Dragon system was the world’s first nearshore wave energy converter producing power for the grid . Wave Dragon is a very simple construction and only the turbines are the moving parts.
This system utilizes the Power Buoy technology which consists of modular ocean-going buoys, as shown in Figure. The rising and falling of the waves moves the buoy-like structure creating mechanical energy which is converted into electricity and transmitted to shore by means a secure, undersea transmission line. A buoy with 40 kW power has a diameter of 4 m and is 16 m long, with approximately 5 m of the unit rising above the ocean surface. Using the three-point mooring system, they are designed to be installed about 8 km offshore in water 40 to 60 m deep.
The Pelamis system looks like a ‘sea snake.’ It is a succession of floated empty segments in 50m or more water depth. The segments are linked to each others by hinged joints. 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. Above fig show the internal structure mechanism of pelamis hydraulic cylinder, motor genetator,actuator are the main components.
The Archimedes Wave Swing (AWS) is a submerged cylinder shaped buoy, moored to the seabed, at least six metres below the sea surface. Passing waves move an air filled upper casing against a lower fixed cylinder, with the up and down movement converted into mechanical energy, as shown in figure. The mechanical energy is converted into electrical energy by means a linear synchronous generator.
The Bristol Cylinder consists in a floating cylinder that collected the wave’s movement. The cylinder is mechanically connected to the energy unit by flexible joints and rods. The rods are moving slowly with cylinder and the reciprocating motion is transferred to the axels in converter unit. The Bristol Cylinder operates under the sea level as shown in figure. Two or more Bristol cylinders could be connected in parallel. It is also possible to make wave parks near shore or wind power units connected together like float offshore. This method of collector wave energy is in the process of pending patents in Finland
The Anaconda is a new wave power (1) generator which could soon be harnessing the vast amounts of clean power around Britain's coasts. Anaconda is simply a large long rubber tube filled with water, closed at both ends, with its head anchored to face the oncoming waves. As the motion of the waves underneath the rubber tube causes the tube to rise and fall, it sqeezes the tube in some places and causing bulges of water to form in other places. The bulges are pushed through the tube at the same speed as the waves passing below the tube with the bulges effectively surfing on the front of the waves carrying energy. The bulges of high pressure water are collected in an accumulator before being released into a conventional hydraulic turbine which in turn drives an electricity generator. When the water leaves the turbine it is fed back around into the main tube again (in a low pressure region). The advantage of the Anaconda over say the Pelamis (3) system is that the Anaconda is so cheap to make (relatively), and has no hinges or joints to break . The designers predict that the cost of an Anaconda which will generate an average of 1 Megawatt of electricity (12 month average) will be around GBP 23 million. Such a tube would need to be 7 metres in diameter, and 150 metres long, and would be installed a couple of miles off the UK coast in the North Atlantic.
A wave farm – or wave power farm or wave energy park – is a collection of machines in the same location and used for the production of electricity.It can be either offshore or near shore, for the production of large quantities of electricity for the grid.
The Indian wave energy programme started in 1983 at the Institute of Technology, Madras and has concentrated almost exclusively on the OWC concept.
The initial research conducted by the Wave Energy Group, IIT Chennai focused on the choice of the wave energy device (Raju, Ravindran 1987, Raju, Ravindran 1989).
A 150 kW prototype OWC With harbor walls was built onto the breakwater of the Vizhinjam Fisheries Harbor, near Trivandrum in India.
The energy in the waves is converted by the OWC caisson into pneumatic energy.
The power take-off mechanism is the Wells turbine connected to a generator.
The generator delivers the electrical power to the grid.
The prototype turbine design specifications were as follows: a)Type Constant chord, wells b)Profile NACA 0021 c)Chord 380 mm d)No. of rotor blades8 e)Hub/tip ratio0.6
The turbine was coupled directly to a 110 kW squirrel cage induction generator with a rated speed of 1000 rotations per minute (rpm) and slip of eight per cent.
The plant was first commissioned in October 1991.
As the cost of production is comparably less and the harnessing of wave energy is more economical than the wind energy.
Harnessing wave energy comes of harmful green house gases. This is the main motivation factor behind further development of this way of power generation. We need to find energy sources that will replace polluting ones (e.g. fossil fuels). Like with most green energy sources, wave power is also renewable. Since this energy source ultimately comes from the heat energy that is emitted from the sun, The amount power in that comes in waves is huge. The energy density is typically around 3040 kW for every meter (2.2 feet) of wave along the shore. As we go further into the ocean 100kW for every meter is not uncommon. Waves are hardly interrupted and almost always in motion. This makes generating electricity from wave energy a reasonable reliable energy source (at least when you compare them to solar and wind). It should be mentioned that the amount of energy that is being transported through waves does vary every year and from season to season. On the northern hemisphere, the average value of November and May could be different with a factor of two or more. Wave and wind energy has a larger potential during the winter which is a nice synergistically effect with solar energy where the largest potential is in the summer. A wave farm that is occupying less than a half square mile of an ocean would generate more than 30 MW of power – the equivalent of 20.000 British homes. Ocean wave energy plants can be put offshore, solving several of the issues that come with power plants closer to the land. The first benefit of offshore wave power is that there is a larger energy potential in these waves.
Power farms on shore that are visible from land may cause conflicts with tourism and local acceptance. Due to this, coastal installations and facilities on land has to meet higher restrictions in terms of size and location. We don’t yet know exactly how wave power affects sea life. We will hopefully in the next following years have more data in this area.
wave energy technology
PREPARED BY – TARUN B PATEL
ME ENERGY ENGINEERING
GUIDED BY - Dr K V MODI
• Wave Energy Physics
• Wave power
• World resources of wave energy
• Types of Wave energy Technologies
• Major Project of Wave energy
• India’s wave Energy Programme
• Advantages n Disadvantages
Wave energy physics
What Is Wave Power
Source – “http://oceanenergy.wikidot.com”
Wave energy Resources
Western European coast
The coasts of Canada and the USA
The southern coasts of Australia and South
Source -“ http://www.wavepower.pdf/wiki”
Types of Wave Energy Technologies
• location installed
• The Oscillating Water Column.
• The Tapchan.
• The Pendulor Device
• Near shore
• Wave Dragon System
• Off Shore
• Power Buoy
• The Archimedes Wave Swing
• Bristol Cylinder
The Oscillating Water Column.
LIMPET, Isle of Islay, Scotland Opened in 2001, this
OWC power plant generates 500 kW with a single 2.6-
meter diameter Wells turbine.
Mutriku, Spain,Opened in 2011, this OWC power plant
generates approximately 300 kW with its 16 Wells
A demonstration device was built in 1985 at
Toftesfallen, in Norway
The Pendular Device.
small schemes (≥ 5 kW) have been built in
Japan and there are plans to develop a larger
Wave Dragon System.
7 MW device to be deployed in 2011 off Pembrokeshire,
Wales, to be tested 3 to 5 years.
1 MW wave park deployed for the U.S. Navy in Oahu, Hawaii.
5 MW wave station for Cornwall, United Kingdom, as part
of the Cornwall Wave Hub .
2.25 MW Agucadoura wave project off the coast of Portugal.
3 MW project under development off the coast of Orkney for
Scottish Power Renewables. 5 MW wave station for Cornwall,
United Kingdom, as part of the Cornwall Wave Hub.
The Archimedes Wave Swing.
The AWS machine was installed off Orkney in
2007 by AWS Ocean Energy with eventual plans
to create 250 kW.
This method of collector wave energy is in the
process of pending patents in Finland
7 metres in diameter, and 150 metres long,
and would be installed a couple of miles off the
UK coast in the North Atlantic.
The first wave farm was in Portugal, the
Aguçadoura Wave Farm, consisting of three
The world's largest is planned for Scotland.
The farm will be the world's largest with a
capacity of 3MW generated by four Pelamis
Major Wave Power Plant
Orkney Wave Power
United King Dom 2.4 Proposed
Portugal 2.25 2008
United King Dom
Spain 0.3 2009
Azura wave power
United state 0.2 2015
SDE Sea Waves
Israel 0.04 2009
Indian Wave Energy Programme
• The potential along the 6000 Km of coast is about 40,000 MW.
• Available in more northern and southern latitudes.
• Ocean Engineering Centre, Indian Institute of Technology,
Madras in 1982.
• wave energy potential along the Indian coast is between 5 MW to
15 MW per meter.
OWC technology has been tried at Vizhinjam along the Kerala coast, near
Thiruvananthapuram by National Institute of Ocean Technology, Chennai.
The power plant delivers 75 kW during April – November ,25 kW from
December - March. During June - September, it has peaks of 150 kW. The
monsoon month's average power production was 120 kW.
The cost of construction of the power plant was 99 lakhs Indian rupees. it
produces 4.45 lakhs units of electricity per year.
The unit cost stands 0.73 rupees, while the power from hydroelectric generators
cost around 1.5 rupee per unit.
Source – “http://Raj_CA-OE_15.pdf”
The plant was first commissioned in October 1991
Technical Specification OWC
Capacity 150 kW
power take-off mechanism is the Wells turbine
electrical power to the grid
The turbine design specifications :
a)Type Constant chord, wells
b)Profile NACA 0021
c)Chord 380 mm
d)No. of rotor blades8
The turbine was coupled directly to a 110 kW squirrel cage induction generator with
a rated speed of 1000 rpm.
Wave power potential around Indian coast
Source – “V Sanil Kumar et al 2013”
• Enormous Energy Potential
• Area Efficient
• Offshore Wave Power