Ocean Thermal Gradient Research Articles

Assessment of Tidal and Wave Energy Resource Potential in Malaysia with Sea Level Rise Effects

Ocean energy, e.g., waves, tidal current, and thermal and salinity gradient, can be used to produce electricity. These marine-based renewable energy technologies are at relatively early stages of development and potentially deployed at various sea conditions. In the past, numerous studies were undertaken to explore the feasibility of harvesting of the marine energy in Malaysia; however, those studies were limited to a specific location (i.e., the east coast of Peninsular Malaysia and East Malaysia) and the consideration of sea level rise effect was not studied. This study assessed the potential of tidal and wave energy resources in Malaysia’s waters with the effect of projected sea level rise and was undertaken through numerical modeling using MIKE 21 software. The research outcomes were tidal and wave energy contours for Malaysia’s waters with an inclusion of the sea level rise projection for 2060 and 2100, as well as a potential site determined for tidal and wave energy harvesting. The simulation results highlight the significant potential of tidal and wave energy in specific locations around Malaysia and its coastal regions, as well as in the South China Sea’s offshore regions. By incorporating sea level rise projections into tidal and wave simulations, we revealed a notable increase in tidal and wave power.

Quantifying the Role of Ocean Dynamics in SST Variability across GCMs and Observations

Abstract Midlatitude SSTs forced by mesoscale oceanic processes can affect the large-scale atmosphere, pointing to the ocean’s crucial role outside the tropics. Previous studies have shown oceanic mesoscale processes’ effect on global and regional climate variability. This study quantifies the local contribution of ocean dynamics to mixed-layer temperature across the globe by directly estimating the ocean heat flux divergence resolved by state-of-the-art ocean reanalysis, eddy-resolving, and eddy-parameterized versions of two U.S. national climate models and indirectly from air–sea flux satellite-based estimates. Our results show that the eddy-resolving climate simulations resolve mixed-layer temperature variances that are larger and closer to those inferred from observations than both their eddy-parameterized counterparts and ECCO over much of the extratropics. The observations and the eddy-resolving models indicate a more significant role of ocean dynamics in the mixed-layer temperature variability than the surface fluxes over most extratropics compared to their eddy-parameterized versions. A frequency domain analysis shows that the better-resolved ocean mesoscale and thermal gradients enhance the variance over a time scale from 2 months to 30 years. Results show agreement in the ocean’s contribution among satellite-based estimates, ocean reanalysis products, and ocean eddy-resolving simulations. At the same time, differences emerge for ECCO and the eddy-parameterized models, suggesting that surface fluxes account for a larger fraction of the mixed-layer temperature variability in most of the extratropics.

Modeling and Optimization of a Phase Change Material-Based Ocean Thermal Energy Harvester for Powering Uncrewed Underwater Vehicles

Abstract As oceans cover over 70% of the planet's surface, they represent a large reservoir of resources that remain vastly untapped. Uncrewed underwater vehicles (UUVs) are becoming a key technology for ocean exploration. Ocean thermal gradient is a permanent and reliable energy source that can be used to power UUVs using phase change material (PCM)-based thermal engines. When using PCM-based thermal engines to power UUVs, there are different energy conversion stages: thermal, hydraulic, kinetic, and electrical, dependent on a wide variety of parameters. Thus, optimization of the overall energy conversion is still a challenge for powering the increasing energy demanding UUVs for long missions. The goal of this study is to propose a PCM-based ocean thermal energy harvesting system for powering float-type UUVs such as the SOLO-II float. This reduces the cost of battery replacement and expands the float's mission time. For this purpose, we developed a theoretical model consisting of hydraulic and electrical systems, designed to provide the electrical power needed by the UUV. The hydraulic and electrical systems are implemented using matlab/simulink. Parameter values from the literature and an accumulator size of 3.78 L are used. The mass of PCM calculated for the energy harvesting system is 5.73 kg, providing a theoretical volume change of 0.78 L. Varying the value of the electrical load connected to the electrical generator, the developed model can, theoretically, provide 13.66 kJ of electrical energy, which is more than 1.5 times the energy requirement per cycle for the SOLO-II float.

Structure of the eastern Arabian Sea upper water column in the middle Miocene: Implications for the development of the South Asian monsoon

Structure of the eastern Arabian Sea upper water column in the middle Miocene: Implications for the development of the South Asian monsoon

Computational fluid dynamics analysis of PCM-based ocean thermal engine with external rib turbulators

Computational fluid dynamics analysis of PCM-based ocean thermal engine with external rib turbulators

1 MW OTEC 플랜트의 키리바시 계통 연계 해석

Kiribati is an archipelagic state in the central Pacific Ocean. Its grid system operates independently like Korean grid system. Kiribati strives to provide renewable resources to reduce its dependence on fossil fuel imports. It uses solar energy as their principal renewable energy; however, a power generation method using ocean thermal gradient (OTEC) is considered more suitable for the country. In this article, the generator and PV systems were modeled, and then the entire system was simulated and analyzed before adding a new 1 ㎿ OTEC plant to the Kiribati system. After that, the simulated effective power and frequency values were verified to compare the values before and after the installation of the new 1 ㎿ OTEC power plant. In addition, the impact on the system was analyzed if the installed OTEC plant is not connected to the system due to a failure or repair. In conclusion, this study has proved that the load burden of the installed generator is reduced and the operation is stable in case Kiribati operates the OTEC plant.

Undersea Wireless Power and Data Transfer System With Shared Channel Powered by Marine Renewable Energy System

Marine renewable energy (i.e., wave, tidal or ocean current, thermal gradient, and salinity gradient), can revolutionize ocean observing capabilities and marine power supply method. Under the marine environment, as the conductive feature of seawater, it has big challenge for wireless power and signal transfer under marine environment. To deal with this issue, this paper provides an undersea wireless power and data transfer system with the shared channel which powered by renewable system. The power and data could be transferred with the same channel based on the time division multiplexing theory. In one switching cycle, the power is transferred in the first half switching cycle and the data is transferred in the second half switching cycle. The data is modulated by frequency-shift keying (FSK) modulation method. The frequency for power transfer is set as 240 kHz. With the FSK modulation method, the two signal carriers’ frequencies are respectively set 10 MHz and 2 MHz. The data could be completely transferred with the high bandwidth. The glass tank experimental platform is constructed with the 35‰ salinity water. The simulated and experimental results verify the theory analysis and the calculation very well.

Utilization and Linkage of Oceanic Energy in Natuna Island: A Review

Rachmayani, R.; Ningsih, N.S.; Ardiansyah, I.; Yani, L.F.; Rizal, A.M.; Kartadikaria, A.R.; Sari, N.T, and Park, H., 2021. Utilization and linkage of oceanic energy in Natuna Island: A review. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 599–603. Coconut Creek (Florida), ISSN 0749-0208. Natuna Regency is known as the northernmost regency in the Karimata Strait with its abundant captured fisheries up to 104.879,81 tons, oil up to 3.138.143 barrels and natural gas up to 34.772.019 MMBTU in 2019, respectively. Moreover, Natuna is famous for aquaculture fisheries of Napoleon (Cheilinus undulatus) with allowed-export capacity up to 30,000 kg. However, resource development in Natuna is often constrained by poor infrastructure such as limited fish unloading berths and natural gas pipelines, obscure electricity, and inadequate energy resources. Thus, the utilization of resources in Natuna has not been maximized. Currently, Natuna has been partially improved on distribution services through the sea toll and the establishment of the Integrated Marine and Fisheries Centre (SKPT) of the Lampa Strait. To carry out the challenge and manifest the resources in Natuna, researches on marine renewable energy in Natuna have been conducted and revealed significant wave height up to ∼1.5 m, ocean current velocity per year ranged from 0.255 to 0.340 m/s, and thermal gradient's Carnot efficiency up to 0.67. Despite these lacking numbers on ocean currents, waves, and thermal gradients for renewable energy development, this study exhibits that the Natuna region has a great energy potential from wind farm and solar power plant development. There are four recommended sites namely Pulau Tiga, Sabang Mawang, Sedanau Island, and SKPT Natuna as places to develop hybrid renewable energy development from pumped hydro storage system, wind farm, and/or solar power plant. The renewable energy development at these locations will support smart city concept in Natuna.

Upper ocean hydrographic changes in response to the evolution of the East Asian monsoon in the northern South China Sea during the middle to late Miocene

Upper ocean hydrographic changes in response to the evolution of the East Asian monsoon in the northern South China Sea during the middle to late Miocene

Half-precessional cycle of thermocline temperature in the western equatorial Pacific and its bihemispheric dynamics

The El Niño-Southern Oscillation (ENSO), which is tightly coupled to the equatorial thermocline in the Pacific, is the dominant source of interannual climate variability, but its long-term evolution in response to climate change remains highly uncertain. This study uses Mg/Ca in planktonic foraminiferal shells to reconstruct sea surface and thermocline water temperatures (SST and TWT) for the past 142 ky in a western equatorial Pacific (WEP) core MD01-2386. Unlike the dominant 100-ky glacial-interglacial cycle recorded by SST and δ18O, which echoes the pattern seen in other WEP sites, the upper ocean thermal gradient shows a clear half-precessional (9.4 ky or 12.7 ky) cycle as indicated by the reconstructed and simulated temperature (ΔT) and δ18O differences between the surface and thermocline waters. This phenomenon is attributed to the interplay of subtropical-to-tropical thermocline anomalies forced by the antiphased meridional insolation gradients in the two hemispheres at the precessional band. In particular, the TWT shows greater variability than SST, and dominates the ΔT changes which couple with the west-east SST difference in the equatorial Pacific at the half-precessional band, implying a decisive role of the tropical thermocline in orbital-scale climate change.

On the Marine Energy Resources of Mexico

The Atlantic and Pacific coasts of Mexico offer a variety of marine energy sources for exploitation. Although the Mexican government has made important efforts to reduce its dependence on fossil fuels, national participation in clean energies is still limited in terms of electricity production. This paper presents a practical theoretical assessment of marine energy sources around Mexico, with the aim of identifying potential zones for subsequent, more detailed, technical evaluations and project implementations. The energy sources considered are ocean currents, waves, salinity, and thermal gradients. Using global databases, the percentages of energy availability for the defined thresholds were computed to establish the prospective regions with the most persistent power availability. This approach proved to offer more meaningful information than simple averaged values. Moreover, some environmental and socio-economic factors to be considered for future ocean energy resource assessments in Mexico were also discussed. The results show that the wave energy potential is highest in the northwest of Mexico (~2–10 kW/m for more than 50% of the time), and that there is a constant source of ocean current energy off Quintana Roo state (~32–215 W/m2 for more than 50% of the time). The thermal gradient power is more persistent in the southwest and southeast of the country, where ~100–200 MW can be found 70% of the time. The salinity gradient energy is strongest in the southeast of Mexico. The practical approach presented here can be extended to perform preliminary resources assessments in regions where information is scarce.

Study of available thermal energy on OTEC

Thermal efficiency is commonly applied in the power plants for the purpose of evaluating heat engines. However, the maximization of the thermal efficiency does not lead the maximization of the available power output from ocean thermal energy conversion (OTEC), which converts the finite thermal energy stored between different temperature seawaters into work. The maximum work efficiency based on the theoretical maximum work from the ideal heat engine has been identified for evaluation; however, the implication in the available thermal energy has not yet been substantially identified. This paper theoretically reveals the available thermal energy from the ocean thermal gradient and the effective energy, which is known as the exergy, using the reference of the equilibrium temperature as the dead state. By employing the finite-time thermodynamics, the available energy and the exergy calculation methods for OTEC are obtained. For the evaluation of the systems, the normalized thermal efficiency is proposed instead of the conventional thermal efficiency and the exergy efficiency for OTEC is proposed as well. The results indicated that increases in the normalized thermal efficiency increase the power output from the OTEC system and the maximum normalized thermal efficiency conditions correspond to the maximum power output heat balance. They also showed the effectiveness of the proposed exergy for OTEC derived by entropy generation minimization.

Application of Finite-time Thermodynamics for Evaluation Method of Heat Engines

Application of Finite-time Thermodynamics for Evaluation Method of Heat Engines

OTECの有効熱エネルギーに関する研究

For the evaluation of the heat engines, the thermal efficiency is commonly applied in the power plants. However, the maximization of the thermal efficiency do not lead the maximization of the available power output from OTEC, which converts into the work from the finite thermal energy stored between different temperature seawaters. The maximum work efficiency based on the theoretical maximum work from the ideal heat engine has been counseled for the evaluation, however, the implication in the available thermal energy has not identified substantially. This paper theoretically reveals the available thermal energy from the ocean thermal gradient and the effective energy, which is called the exergy, using the reference of the equilibrium temperature as the dead state. By employing the finite-time thermodynamics, the available energy and the exergy calculation methods are obtained and the normalized thermal efficiency for OTEC and the exergy efficiency are proposed.

Holocene variations of thermocline conditions in the eastern tropical Indian Ocean

Holocene variations of thermocline conditions in the eastern tropical Indian Ocean

Cross-front phytoplankton pigments and chemotaxonomic groups in the Indian sector of the Southern Ocean

Cross-front phytoplankton pigments and chemotaxonomic groups in the Indian sector of the Southern Ocean

Terrigenous input off northern South America driven by changes in Amazonian climate and the North Brazil Current retroflection during the last 250 ka

Abstract. We investigate changes in the delivery and oceanic transport of Amazon sediments related to terrestrial climate variations over the last 250 ka. We present high-resolution geochemical records from four marine sediment cores located between 5 and 12° N along the northern South American margin. The Amazon River is the sole source of terrigenous material for sites at 5 and 9° N, while the core at 12° N receives a mixture of Amazon and Orinoco detrital particles. Using an endmember unmixing model, we estimated the relative proportions of Amazon Andean material ("%-Andes", at 5 and 9° N) and of Amazon material ("%-Amazon", at 12° N) within the terrigenous fraction. The %-Andes and %-Amazon records exhibit significant precessional variations over the last 250 ka that are more pronounced during interglacials in comparison to glacial periods. High %-Andes values observed during periods of high austral summer insolation reflect the increased delivery of suspended sediments by Andean tributaries and enhanced Amazonian precipitation, in agreement with western Amazonian speleothem records. Increased Amazonian rainfall reflects the intensification of the South American monsoon in response to enhanced land–ocean thermal gradient and moisture convergence. However, low %-Amazon values obtained at 12° N during the same periods seem to contradict the increased delivery of Amazon sediments. We propose that reorganizations in surface ocean currents modulate the northwestward transport of Amazon material. In agreement with published records, the seasonal North Brazil Current retroflection is intensified (or prolonged in duration) during cold substages of the last 250 ka (which correspond to intervals of high DJF or low JJA insolation) and deflects eastward the Amazon sediment and freshwater plume.

해양 신재생에너지의 고찰

With the prospect of an increasing shortage of energy resources, there has been a growing interest in renewable alternative sources of energy. An increasing effort is being directed towards resolving the problems of extracting energy from the world's oceans, as they represent a vast potential source of renewable energy. This paper summarizes the extraction and conversion techniques of the ocean's energy resources, namely, energy derived from the ocean waves, tides, thermal gradients, and currents. For each energy extraction and conversion technique, case studies are discussed. 핵심용어: ocean energy, renewable energy from the sea, waves, tides, ocean current, thermal gradient, Ocean Thermal Energy Conversion, 해양 에너지, í•´ì–‘ì‹ ìž¬ìƒì—ë„ˆì§€, 파랑, 조석, 해류, 온도경사, í•´ì–‘ì˜¨ë„ì°¨ë°œì „

Global Review of Recent Ocean Energy Activities

AbstractOcean energy is regarded as an important future source of energy generation in many countries for transition to a low-carbon future. While commercial interest in ocean energy is growing significantly at a global level, there are considerable investment costs and bottlenecks that will need to be overcome. Research and funds are spread over many different wave and marine current energy concepts under development, and there is still no technology convergence, in contrast to what happened in wind energy. Although an important marine energy resource, discussion of offshore wind energy is not included in this manuscript. This article focuses on the latest developments in ocean energy—in particular, open-sea testing facilities set up by several countries as a measure to encourage deployment and streamlining procedures—and gives an overview of projects going into the water this past year. In addition, the article highlights the importance of collaborative research and development on ocean energy projects and the unique role of the Ocean Energy Systems Implementing Agreement as an intergovernmental organization promoting the use of ocean energy (wave, marine currents, tidal, ocean thermal gradients and salinity gradients) for energy extraction.

Performance Analysis of OTEC Plants With Multilevel Organic Rankine Cycle and Solar Hybridization

Among the renewable energy sources, ocean energy is encountering an increasing interest. Several technologies can be applied in order to convert the ocean energy into electric power: among these, ocean thermal energy conversion (OTEC) is an interesting technology in the equatorial and tropical belt, where the temperature difference between surface warm water and deep cold water allows one to implement a power cycle. Although the idea is very old (it was first proposed in the late nineteenth century), no commercial plant has ever been built. Nevertheless, a large number of studies are being conducted at the present time, and several prototypes are under construction. A few studies concern hybrid solar-ocean energy plants: in this case, the ocean thermal gradient, which is usually comprised in the range 20–25 °C in the favorable belt, can be increased during daytime, thanks to the solar contribution. This paper addresses topics that are crucial in order to make OTEC viable, and some technical solutions are suggested and evaluated. The closed cycle option is selected and implemented by means of an organic Rankine cycle (ORC) power plant, featuring multiple ORC modules in series on the warm water flow; with a three-level cycle, the performance is approximately 30% better if compared to the single-level cycle. In addition, the hybrid solar-OTEC plant is considered in order to investigate the obtainable performance during both day and night operation; this option could provide efficiency benefit, allowing one to almost triplicate the energy produced during daytime for the same prescribed water flow.