The Potential of Viable Ocean Wave Mega Power Conversion


Several new technologies that convert ocean waves into electric power have appeared at test installations off the coasts of Ireland, Scotland, the Orkney Islands and Portugal. Technology that can convert ocean wave energy into electric power is still in its early prototype stage of development and its cost per kilowatt is high. As the technology evolves and is developed further over the next several years, its capital cost and long-term maintenance cost could likely decrease. Ocean wave energy is an indirect form of solar thermal energy that heats large masses of land and large expanses of ocean at different rates, thereby causing winds to blow over several thousand square miles of ocean surface and deliver energy in the form of ocean waves to coastal regions.

Throughout most of the world, ocean wave energy is diffuse. There are a few of locations where a variety of factors contribute to higher energy levels in ocean waves at select locations. These factors include strong winds blowing over very large surface areas of ocean and toward coastal regions that are very close to a steep continental shelf. Waves generated over ocean of great depth have small amplitude (height) and a long wavelength (distance between peaks). As these ocean waves propagate over a steep continental shelf to shallower water depths, wavelength decreases and wave height increases to levels that are favourable for ocean wave conversion into electrical energy.


Premium locations for viable ocean wave power conversion include:


1) Brazil's East Coast between Ilheus and Natal (700-miles): Southeast trade winds blow over deep Brazilian Basin and toward steep continental shelf that is very near the Brazilian coast.


2) Madagascar's East Coast (800-miles): Southeast trade winds blow over deep Southeastern Madagascar Basin in southern Indian Ocean and toward steep sub-oceanic shelf along Madagascar's East Coast. Cyclonic storm region exists over Indian Ocean east of Madagascar.


3) South Africa's "Wild Coast" between Port Elizabeth and Durban (400-miles); southern Southeast trade winds blow over southeastern Madagascar Basin as well as Natal Basin in south Indian Ocean and toward steep continental shelf off South Africa's east coast. South Equatorial current merges with Mozambique current and Agulhas current in this region.


Locations with potential for viable ocean wave power generation include:


-Southwest coast of Chile, south of Valdivia (800-miles); due to the Westerlies blowing over southern Indian Ocean, Southwestern Pacific Basin and Southeast Pacific Basin and pushing ocean waves toward multiple inlets and islands along southern Chile's rugged west coast.


-East coast of the Lesser Antilles and north coast of Guyana; Northeast trade winds blow over the Cape Verde Basin and Guiana Basin toward steep sub-oceanic shelf near the east coasts of the Lesser Antilles.


-Northwest coasts of Portugal and Spain (and Southwest coast of France in the Bay of Biscay); due to the Westerlies blowing over the Nova Scotia Basin, Newfoundland Basin and West European Basin in the north Atlantic.


-Northwest coastal regions of Ireland and Scotland; due to Westerlies blowing over the Nova Scotia Basin, Newfoundland Basin in the north Atlantic. Shape of entrances to the Bristol Channel, Dingle Bay, Shannon, Galway Bay, Donegal Bay and Firth of Lorne can increase amplitude of incoming ocean waves.


-East coasts of Australia’s Cape York Peninsula and Gulf of Papua: Southeast Trade winds and Southeast Monsoon blow over Pacific Ocean and Coral Sea. Narrowing waterway and steep undersea shelf east of Torres Strait increases amplitude of ocean waves in Gulf of Papua and northeastern Australian coast.


-West coast of Tasmania: Westerlies blow over large expanses of South Atlantic Ocean as well as southern Indian Ocean.


-Gulf of Guinea coast between Tabou, Ivory Coast and Lagos, Nigeria (600-miles): Southeast Trade winds and coastal winds blow over the Cape Basin and the Angola Basin toward steep continental shelf. Cold Benguala current collides with the warm Equatorial Counter current and Guinea current in this region


-Southwest coast of Alaska and west coast of Queen Charlotte Islands: Westerlies blow over North Pacific Ocean and pushing ocean waves toward multiple inlets and islands along this coastal region. Entrance to Bristol Bay and Dixon Entrance can increase ocean wave amplitude.


-Southeast Newfoundland at Placentia Bay and St Mary's Bay: Westerlies blow over Northwest Atlantic Basin and Nova Scotia Basin. Cold Labrador Current meets warm North Atlantic Drift east of the Avalon Peninsula and causes rough seas with potential to generate electric power.


Technology capable of converting the energy of ocean waves into usable electric power may still undergo several years of design optimization and refinement. Over the long term, computer aided robotic manufacturing technology along with related mass-production technologies would likely reduce the capital cost of ocean power conversion technologies such as the Pelamis system. Ocean water has some 3400-times the density of air. Measurements taken off the coasts of Scotland and of Portugal have indicated that ocean-generated electric power has a density of 30-Mw per square kilometer, or15 to 20-times that of power generated from windfarms or solar photovoltaic installations.


The aforementioned east coast regions of Brazil, South Africa and Madagascar could offer over 50% more power density than the European locations. At a future time, cost competitive mega offshore ocean-wave power-conversion installations could be developed and located off the east coasts of these countries. They would likely have the potential to supply multi giga-watt levels of power to economies that would need and use increasing amounts of power. While Madagascar may remain an undeveloped economy for decades to come, a mega offshore ocean power generation system located off their East Coast could likely supply power via undersea cables to a Southern African power grid. Alternatively, a privately owned offshore installation could generate hydrogen for export to other nations.


Mega coastal power installations may appear at a future time along the southwest coast of Chile. This rugged coastal ocean region has a proliferation of islands, bays, ocean inlets, and valleys. Any of a variety of evolving ocean-wave energy conversion systems may be used in these locations. One wind energy proposal for southern Chile suggests using cable systems to suspend multiple wind turbines at high altitude across wide valleys that face the Pacific Ocean in the southern Andes Mountains. Ocean wave installations and wind energy installations both supply energy when demand is low. Both would require the use of energy storage systems. Chile would likely use fresh water hydraulic energy storage in the Andes Mountains and also pump small volumes of ocean water into sealed tanks located at very high altitude. Brazil would likely use hydraulic energy storage by pumping fresh water to higher elevations at hydroelectric installations.


South Africa is a nation that has faced drought conditions in recent years. Using fresh water hydraulic energy storage at high altitude may be a limited option. Ocean water may have to be pumped through piping systems into sealed tanks located at high altitude, a system that could be used in the coastal mountains near Cape Town. A similar energy storage system may be used in Madagascar. The relative absence of a natural gas industry in South Africa allows any large salt domes (5,000’ diameter by 25,000’ high) that may be found deep underground, to be used for compressed air energy storage (CAES).


One suggested modification that may be made to CAES would be to include thermal energy storage technology so as to raise thermal energy efficiency. When air is compressed, its temperature increases and the heat may be transferred into storage tanks containing eutectic salts or eutectic metal oxides (eg: O=Al-O-Al=O). An alternative would be to use metallic-carbonates that decompose when heated (eg: CaCO3 + heat > CaO + CO2) and produce heat up to 1,000-degrees C when re-mixed (CaO + CO2 > CaCO3 + heat). Heat from external sources may also be added to the storage system. Compressed air from underground mega-storage (2,000-psia) would enter a lower-pressure running tank (constant pressure of 300-psia over a prolonged duration) then be heated prior to being expanded in a turbine.


The islands of the Lesser Antilles are presently heavily dependant on diesel generated electric power. Ocean wave power generation could become more cost-competitive over the long-term future and eventually replace diesel-electric power generation. Solar thermal power conversion and even wind energy could eventually gain greater acceptance in this region. These technologies will require the use of energy storage technology. Flow batteries or hydrogen technology may be the most likely candidates to store ocean wave and wind generated energy while metallic-carbonates, eutectic salts or eutectic metal oxides may be used to store thermal energy.


The fact that the world’s premium locations for ocean wave energy generation are outside the United States increases the likelihood that progress in developing and refining this technology would likely remain private. While this lack of government funds may appear to be a disadvantage, it would likely reduce malinvestment in developing the technology. Over the long-term future, ocean wave power conversion (as well as ocean tidal power conversion) could likely become more cost effective, more reliable, more cost competitive and offer higher energy density over equal area than wind power conversion or solar photovoltaic power conversion. It could come to play a significant role in the economic future of several nations.