e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:03/Issue:03/March-2021
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ANALYSIS OF WAVE POWER TECHNOLOGIES Dr JP Kesari*1, Siddharth Sharma*2, Chanda Singh*3 *1Professor,
Department of Mechanical Engineering, Delhi Technological University, Bawana Road, New Delhi-110042, India.
*2,3Undergraduate
Student, Department of Mechanical Engineering, Delhi Technological University, Bawana Road, New Delhi-110042, India.
ABSTRACT This paper involves the study of significant wave power technologies and their applications. As the energy consumption of the world is increasing exponentially, there is a need for renewable energy resources. Wave energy (power) is one such alternative. Various Wave Energy Converters (WECs) are studied in this paper along with their characteristics. The current status of development of wave power technologies in India is also discussed. Given the depletion of traditional energy sources and their impact on climate, the authors emphasize to try adopting wave power technologies.
I.
INTRODUCTION
Due to the depletion of the traditional sources of energy like fossil fuels and their harmful effects on the environment, there is a need for cleaner, safer and renewable energy sources. Since most of the earth is covered with water, wave energy is a promising renewable energy source. Wave energy (or wave power or ocean energy) is continuous (in the sense that waves are available 24 hours a day throughout the year), environmentally friendly, pollution free and predictable with high accuracy. Waves are formed on the ocean surface due to the interaction of wind with the water surface. Waves can store and transmit the kinetic energy which they carry from the wind thousands of kilometres with negligible loss. Wave power technologies have made remarkable progress in recent years but are still decades behind other renewable energy sources as huge amount of money is required for construction of structures in oceans and their maintenance. “A potential of 40,000 MW along the Indian coast has been concluded by a general research on wave nature.[1]”
II.
WAVE ENERGY CONVERTERS
Wave Energy Converters (WECs) are used to transform potential and kinetic energy of a moving ocean wave into electrical or mechanical energy. WECs can be generally classified based on three types: location, operating principle and direction of wave propagation. Location: Based on location, wave energy converter devices are classified into three types: onshore, nearshore and offshore devices. 1 Onshore Devices: Onshore devices are installed in the shallow water above sea. Waves are attenuated as they pass through shallow water. As a result, these devices are less prone to damage in severe weather conditions. They have less energy to utilise as shallow water results in reduced wave power. Since their location is mostly accessible, these are easy to install and maintain. 2 Nearshore Devices: Nearshore devices are installed in relatively shallow water “(there is lack of consensus for what defines shallow water). Nearshore constitutes an area within 2km from the coastline. [3]” Nearshore devices, like onshore devices, have reduced wave power due to shallow water. 3 Offshore Devices: Offshore devices are installed in deep water. As a result, they have higher amount of energy to exploit. Their installation and maintenance is difficult. Deep water waves have high energy content so offshore devices are designed to withstand extreme conditions which leads to higher cost.
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e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:03/Issue:03/March-2021
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Figure-1: Wave power characteristics for off-shore, near-shore and on-shore WECs Direction of Wave Propagation: Based on size and direction of wave propagation, wave energy converters are classified into three types: attenuator, point absorber and terminator. 1 Attenuator: These WECs are mounted parallel to the wave propagation direction. “They consist of a sequence of cylindrical sections in succession which are joined together by flexible hinged joints that allows the individual sections to rotate relative to each other.[2]” Pelamis which is developed by Ocean Power Delivery Ltd is a typical example. “The 750kW P2 (second generation) machine was successfully installed at the Billia Croo, Orkney wave test site for the first time in October 2010.[5]”
Figure-2: Pelamis (attenuator) 2 Point Absorber: These WECs are dimensionally considerably smaller relative to the incident wavelength. These devices generate electricity from the bobbing or pitching action of a device, by transforming the up-anddown pitching movement of the waves into rotary or oscillatory movements (depending on a particular device).They are able to generate power irrespective of the direction of wave propagation due to their small size. “150kW PowerBuoy technology developed by Ocean Power Delivery Ltd is an example of point absorber.[6]”
Figure-3: Power Buoy (point absorber) www.irjmets.com
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e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:03/Issue:03/March-2021
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3 Terminator: A terminator is a near-surface floating device like a point absorber. However, it absorbs energy in only one direction. These WECs are placed perpendicular to the direction of wave propagation. As the name suggests, they terminate or end the wave action. An example of this type of WEC is the Salter’s Duck which is developed at the University of Edinburgh.
Figure-4: Salter’s Duck (Terminator) Mode of Operation: Based on mode of operation, some significant classifications are: submerged pressure differential, oscillating wave surge converter, oscillating water column and overtopping device. 1 Submerged Pressure Differential: This type of WEC is a completely submerged point absorber. It uses the pressure difference formed between the wave crests and troughs over the device. “It consists of a sea bed fixed air-filled cylindrical chamber with a moveable upper cylinder. When the crest of the wave travels over the device, the air within the cylinder is compressed by the water pressure above the device. As a result the upper cylinder moves down. When the trough of the wave travels over, the water pressure over the device is reduced and the upper cylinder rises.[8]” An example of this type of WEC is the Archimedes Waveswing submerged wave power buoy developed by AWS Ocean Energy Ltd. “The system is suitable for deployment in water depths in excess of 25m and can be configured for ratings between 25kW and 250kW by selecting the appropriate scale.[9]”
Figure-5: Archimedes Wave Swing (Submerged Pressure Differential) 2 Oscillating Water Column: “Oscillating water columns (or OWCs) generally comprise of a partially submerged fixed or floating hollow structure, which forms an air chamber, having an opening to the sea below the water surface. When water rises inside the chamber, the air volume inside the chamber is compressed and driven through a turbine. When the water level inside the chamber decreases, the air is drawn back through the turbine.[10]” OWCs have been used as point absorbers as well as being installed into the shoreline to serve as a terminator. An example of a shoreline mounted device is the Wavegen Limpet which is installed on the island of Islay, Western Scotland, and generates power for the national grid.
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Figure-6: Limpet (Oscillating Water Column) 3 Overtopping Device: “Overtopping devices (OTDs) depend on the capture of water from waves. The incident waves would overtop the WEC's edge and be trapped in the reservoir, which is a few meters above sea level. The water is released to the sea from the reservoir through low-head turbines, which are responsible for generation of electricity. To increase the amount of energy captured by the WEC, an OTD can use collectors to concentrate incident waves and increase wave height. [12].” A typical example is the wave dragon. A pair of large curved reflectors collect waves in the central receiving section, 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 through a number of low-head turbines.
Figure-6: Wave Dragon (Overtopping Device) 4 Oscillating Wave Surge Converter: An oscillating wave surge converter generally consists of a hinged deflector which is positioned perpendicular to the wave direction (a terminator). The hinged deflector moves back and forth exploiting the horizontal particle velocity of the wave. “Aquamarine Power Oyster (a near-shore device) is a common example of an oscillating wave surge converter. In this device, the top of the deflector is above the water surface and is hinged from the sea bed.[14]”
Figure-7: Aquamarine Power Oyster (Oscillating Wave Surge Converter) www.irjmets.com
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III.
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STATUS OF WECS IN INDIA
“With the present state of technology, India’s potential of wave energy is estimated to be 40-60 GW. The wave energy potential is estimated to be 5-15 MW/m along the coastline. Except for the pilot plant at Vizinjham Fisheries Harbour near Trivandrum in Kerala, India has no large wave energy plants. The Maharashtra Government has built a project which would lead to the generation of 15-20 kW of electricity located at Borya and Budhal villages in the coastal Ratnagiri district. The wave energy potential along the Indian coast was examined in depth in a report published by the Indian Renewable Energy Development Agency (2014). Their results depicted that higher wave power is available along the west coast which is likely due to strong waves during the south-west monsoon. However, due to very powerful winds, the highest wave power can be obtained at the southern tip of the Indian peninsula (Kanyakumari, Nagercoil district, Koodankulam). Based on wave statistics, five possible sites for the deployment of wave energy devices were identified. These locations and their wave power are shown in Table 1.[15], [16]” Table-1: Favourable locations for WECs in India State
Location
Wave power (in kW/m)
Andhra Pradesh
Kaviti
14.96
Tamil Nadu
Puducherry
10.59
Tamil Nadu
Kanyakumari
23.39
Kerala
Trivandrum
25.08
Maharashtra
Kudal
21.95
IV.
CONCLUSION
Wave power has enormous potential in electricity generation. The ocean is an enormous resource and harnessing ocean wave energy is a significant step towards achieving the renewable energy targets. Wave power (or energy) conversion technologies have made significant progress over the past decade. Despite the remarkable progress, these technologies still remain immature as shown by a large number of different technologies and device sizes. Also the initial cost of construction is quite high for WECs. Currently, investment in wave power is considered risky due to lack of operational experience and high capital cost. A combination of focused research and the establishment of government incentives for an early adopter market would be required to move the technological progress forward.
ACKNOWLEDGEMENT Authors wish to acknowledge Delhi Technological University for their complete support throughout the work.
V. [1] [2]
[3] [4] [5] [6] [7] [8]
REFERENCES
https://www.mahaurja.com/meda/en/new_technologies/wave_power López, I., Andreu, J., Ceballos, S., Martínez de Alegría, I., & Kortabarria, I. (2013). Review of wave energy technologies and the necessary power-equipment. Renewable and Sustainable Energy Reviews, 27, 413–434. Blackledge, Jonathan & Coyle, Eugene & Kearney, Derek & McGuirk, Ronan & Norton, Brian. (2013). Estimation of Wave Energy from Wind Velocity. Engineering Letters. 21. 158-170. https://waveenergyconversiontamu15.weebly.com/theory-of-wave-energy--availability.html http://www.emec.org.uk/about-us/wave-clients/pelamis-wave-power/ https://oceanpowertechnologies.com/pb3-powerbuoy/ https://coastalenergyandenvironment.web.unc.edu/ocean-energy-generating-technologies/waveenergy/overtopping-terminator/ Drew, B., Plummer, A. R., & Sahinkaya, M. N. (2009). A review of wave energy converter technology. Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy, 223(8), 887–902.
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e-ISSN: 2582-5208 International Research Journal of Modernization in Engineering Technology and Science Volume:03/Issue:03/March-2021 [9] [10] [11] [12] [13] [14] [15] [16]
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https://tethys.pnnl.gov/organization/archimedes-wave-swing Alves, M. (2016). Frequency-Domain Models. Numerical Modelling of Wave Energy Converters, 11–30. http://wavesycys.blogspot.com/2008/05/case-study-limpet-wave-power-generator.html H. Polinder and M. Scuotto, ‘‘Wave energy converters and their impact on power systems,’’ in Proc. Int. Conf. Future Power Systems, Nov. 18, 2005, pp. 9–18. https://tethys.pnnl.gov/project-sites/wave-dragon-pre-commercial-demonstration-project https://tethys-engineering.pnnl.gov/technology/oscillating-wave-surge-converter https://inpressco.com/wp-content/uploads/2016/10/Paper38179-182.pdf Khojasteh, D., Mousavi, S. M., Glamore, W., & Iglesias, G. (2018). Wave energy status in Asia. Ocean Engineering, 169, 344–358.
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