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Energy extraction and conversion
Published in Kornelis Blok, Evert Nieuwlaar, Introduction to Energy Analysis, 2020
Kornelis Blok, Evert Nieuwlaar
Ocean energy. A number of renewable energy sources are lumped together as ocean energies or marine energy sources: Tidal energy can be utilised in a number of places on Earth where the difference between high tide and low tide is large enough. In addition, if tidal currents are strong enough these currents can be used for power generation using generators that resemble wind turbines. Tidal energy originates from the gravitational forces of the moon and to some degree the sun.Wave energy can utilise the high power densities that occur in wind generated ocean waves.Ocean-thermal-energy-conversion (OTEC) makes use of the temperature differences between surface water and deep ocean water.Osmotic energy conversion makes use of the differences in salinity between fresh water and sea water.
The Role of The Oceans
Published in Kojima Toshinori, Harrison Brian, The Carbon Dioxide Problem, 2019
Toshinori Kojima, Brian Harrison
Finally, let us consider the merits of adopting a system that makes multiple use of the oceans. As was previously mentioned, the generation of electricity due to temperature differences in the ocean is a technique which is related to the raising of deep water (although there are inherent economic problems). If the deep ocean water were pumped up, electricity could be generated from the temperature difference between the deep water and the surface water (“ocean thermal energy conversion”). A preliminary evaluation by the author and colleagues (Tahara et al., 1994) showed that as a result of this electricity generation the consumption of fossil fuels would decrease by an equivalent amount, and carbon dioxide emissions would decrease. Furthermore, an amount of carbon dioxide equivalent to 10% of this reduction in carbon dioxide emissions would be physically absorbed by the deep water. Here again, though, it is necessary to consider the rates of diffusion and mixing in the surface layers.
Power and Energy Directly from Water
Published in Yatish T. Shah, Water for Energy and Fuel Production, 2014
Aquaculture is the best-known by-product of OTEC because it reduces the financial and energy costs of pumping large volumes of water from the deep ocean. Nonnative species such as salmon, lobster, abalone, trout, oysters, and clams can be raised in pools supplied by OTEC-pumped water. This extends the variety of fresh seafood products available for nearby markets and provides a low-cost refrigeration that can be used to maintain the quality of harvested fish [75]. In Kona, Hawaii, aquaculture companies working with an OTEC plant (Natural Energy Laboratory of Hawaii Authority [NELHA]) generate about $40 million annually, a significant portion of Hawaii’s gross domestic product (GDP) [77]. Deep-ocean water can also be combined with surface water to deliver water at an optimal temperature.
Recent development of integrating CO2 hydrogenation into methanol with ocean thermal energy conversion (OTEC) as potential source of green energy
Published in Green Chemistry Letters and Reviews, 2023
Mohd Hizami Mohd Yusoff, Lau Kok Keong, Nor Hafizah Yasin, Mohammad Syamzari Rafeen, Amiruddin Hassan, Geetha Srinivasan, Suzana Yusup, Azmi Mohd Shariff, A. Bakar Jaafar
Interestingly, the renewable hydrogen produced from ocean thermal energy conversion (OTEC) is a potential source to produce value-added green hydrocarbons upon reaction with the captured CO2. The increase in global warming and commitment toward energy security also led to the exploration of renewable energy technologies from various sources such as solar, wind, hydro, biomass and geothermal. Among them, OTEC is one of the promising green technologies that can fulfill global energy demand and reduce global warming due to excessive CO2 emission. By utilizing a stable temperature difference between warm surface water and cold deep ocean water, a huge potential of thermal energy can be produced from the thermodynamic cycle and support electricity generation. Malaysia has great potential to harness ocean thermal energy via OTEC technology based on its deep water depth of more than 700 m (8,9). By 2050, as the entry to OTEC potential, it is projected that Malaysia could consider growth of its OTEC resources to at least 12,000,0000 W or 12,000,000 KW, i.e. less than 50% of its minimum total potential of 26,000000 KW over its deep waters of 131,000 km2 at 700 m isobath or deeper up to 2900 m. By 2050, the amount of hydrogen that could be generated would be 2.1 million tons of H2/year assuming, (12,000,000 kW, 8750 h/year with 50 kWh/kgH2 = 2.1 million tons of H2/year]. Furthermore, the huge capacity for OTEC potential in Malaysia is comparable to other tropical and subtropical countries like Fiji, Philippines and Nauru Island (10). Of the State of Sabah, Malaysia, there exists number of sites for the deep-water production (DWP) of oil & gas, including Shell @Malikai (565 m), Shell @Gumusut-Kakap (1220 m), Murphy @Kikeh (1300 m), and PETRONAS Carigali @Rotan (1500 m). There also exists the potential of generating power (11), by converting the heat stored in the warm surface water into electrical energy with OTEC Technology by installing OTEC plants with Electrolyzers, gas Compressors, and compressed hydrogen gas storage on a floating platform, the like of the re-used Ultra Large Crude Carrier (ULCC), anchored adjacent to, but not within the 500 m limit in compliance with the safety requirements of, the DWP oil & gas production units. The generated renewable power, being the net of running OTEC plants, would be taken up in the production of green hydrogen by water electrolysis. Thus, for the conversion of the captured 13.5 MMSCFD of CO2 into green methanol, 204,000 KW of OTEC power capacity would be required to be developed and installed in order generate 97.82 MTPD of hydrogen, as stated herein.