Closed Cycle Ocean Thermal Energy Research Articles

Theoretical design for ascertaining sustainability of energy systems with special reference to the competing renewable energy schemes

A single criterion assessment tool for gradation of the competing energy devices, was considered important for advancing R&D for improving upon their performance efficiency, particularly for the renewable energy systems. It was therefore outlined a theoretical design for ascertaining their individual sustainability percent achievable, from identification of the indices to be considered and a sustainability scale development for quantitative assessment. Case studies were thereafter made illustrating the modus operandi of using the developed model, for comparing the sustainability percentage achievable for different renewable energy systems, against a coal-based power plant as the referral energy unit. The competing renewable energy schemes studied were — solar PV, wind energy (both on-shore and off-shore), bio-fuel, and wave schemes like wave dragon, closed cycle ocean thermal energy conversion system (CC-OTEC) and a proposed barrage scheme (Severn barrage, UK). The study revealed that coal-based fossil fuel plant could hardly meet 40% sustainability against all other renewable energy schemes, achieving much more than 60% sustainability. In addition to the scope of use of the model for comparing the relative merits of the individual energy devices, it may find use for indexing a product with its environmental signature, on necessary modification and extension of the model. • A theoretical model designed for ascertaining total sustainability of energy systems. • Renewable energy (RE) schemes have >>60% sustainability but coal-fired power <<40%. • Single criterion assessment tool for ranking competing energy devices on sustainability. • Useful in R&D in improving performance efficiency of energy devices. • Indexing a product with environmental impact signature with extension of the model.

소형 LNG 재기화 시스템의 기화열을 열침으로 하는 해수온도차발전 사이클 성능분석

Demand for LNG, mainly in Asia, continues to increase in order to achieve the reduction of greenhouse gas emission and decarbonization goals. For the convenience of transport, natural gas is stored in a liquefied state and needs to be vaporized for reuse. A huge amount of cold heat is generated through the process of LNG re-gasification. In this study, the performance analysis of the closed cycle ocean thermal energy conversion (CC-OTEC) system using the vaporization cold heat of a small LNG regasification system as heat sink and warm surface seawater as a heat source was performed. After configuring the CC-OTEC with the working fluid as R32 in the LNG regasification system at 10 kg per second, the turbine inlet pressure changed from 15 bar to 17 bar. Gross power, net power, efficiency and parasitic load were analyzed. At the turbine inlet presusure of 16.2 bar, we exhibited the maximum net power of 198.5 kW and the maximum efficiency 2.78%.

Ocean Thermal Energy Conversion

A closed cycle ocean thermal energy conversion basically involves a working fluid which has a boiling point just low below ambient temperature. This fluid is then evaporated using warm sea water and then used to run turbines. This evaporated gas is then condensed using cold seawater. In this paper a study is being made to install a super heater between the evaporator and the turbine. The various consequences due to this technical advancement have been discussed taking into consideration all the components in the OTEC plant. As the energy requirement to run pumps cannot be avoided, to increase the overall efficiency of the plant an effort is being made to increase the net energy output of the turbine. This can be achieved by heating the working fluid above its saturation temperature thus increasing its enthalpy indirectly increasing the net output of the turbine. Along with a super heater a pre-heater has been installed which helps to compensate the heat losses in heat exchangers. Both the super heater and pre-heater have been developed using non-conventional energy resources and no external energy input is required. Along with this an economic study has also been made which supports the proposed idea.

Performance Analysis of 15 kW Closed Cycle Ocean Thermal Energy Conversion System With Different Working Fluids

Closed cycle ocean thermal energy conversion (CC-OTEC) is a way to generate electricity by the sea water temperature difference from the upper surface to the different depth. This paper presents the performance of a 15 kW micropower CC-OTEC system under different working fluids. The results show that both butane and isobutane are not proper working fluids for the CC-OTEC system because the inlet stable operating turbine pressure is in a very narrow range. R125, R143a, and R32, especially R125, are suggested to be the transitional working fluids for CC-OTEC system for their better comprehensive system performance. Moreover, it is recommended that propane should be a candidate for the working fluid because of its excellent comprehensive properties and environmental friendliness. However, propane has inflammable and explosive characteristics. As for the natural working fluid ammonia, almost all performance properties are not satisfactory except the higher net output per unit sea water mass flow rate. But ammonia has relative broader range of the stable operating turbine inlet pressure, which has benefits for the practical plant operation.