scholarly journals Trend of OTEC (Ocean Thermal Energy Conversion) and Power Generation Technology Utilizing Small Temperature Difference

2016 ◽  
Vol 51 (1) ◽  
pp. 85-90
Author(s):  
Shin Okamura
Keyword(s):  
Power Generation ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Small Temperature ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Power Generation Technology ◽  
Ocean Thermal Energy ◽  
Generation Technology

scholarly journals Dynamic Simulation of System Performance Change by PID Automatic Control of Ocean Thermal Energy Conversion

2020 ◽  
Vol 8 (1) ◽  
pp. 59 ◽  
Author(s):  
Lim Seungtaek ◽  
Lee Hoseang ◽  
Kim Hyeonju
Keyword(s):  
Control System ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Pid Control ◽  
Seawater Temperature ◽  
Ocean Thermal Energy Conversion ◽  
Control Value ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Near infinite seawater thermal energy, which is considered as an alternative to energy shortage, is expected to be available to 98 countries around the world. Currently, a demonstration plant is being built using closed MW class ocean thermal energy conversion (OTEC). In order to stabilize the operation of the OTEC, automation through a PID control is required. To construct the control system, the control logic is constructed, the algorithm is selected, and each control value is derived. In this paper, we established an optimal control system of a closed OTEC, which is to be demonstrated in Kiribati through simulation, to compare the operating characteristics and to build a system that maintains a superheat of 1 °C or more according to seawater temperature changes. The conditions applied to the simulation were the surface seawater temperature of 31 °C and the deep seawater temperature of 5.5 °C, and the changes of turbine output, flow rate, required power, and evaporation pressure of the refrigerant pump were compared as the temperature difference gradually decreased. As a result of comparing the RPM control according to the selected PID control value, it was confirmed that an error rate of 0.01% was shown in the temperature difference condition of 21.5 °C. In addition, the average superheat degree decreased as the temperature difference decreased, and after about 6000 s and a temperature decrease to 24 °C or less, the average superheat degree was maintained while maintaining the superheat degree of 1.7 °C on average.

scholarly journals The extraction of power and fresh water from the ocean off the coast of KZN utilising ocean thermal energy conversion (OTEC) techniques

2021 ◽  
Author(s):  
◽  
Makhosonke Gumede
Keyword(s):  
Energy Conversion ◽  
Fresh Water ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Power Output ◽  
Warm Water ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Kwazulu Natal ◽  
Ocean Thermal Energy

Ocean thermal energy conversion (OTEC) is an electric power generation system which uses the temperature difference between warm water at the surface (26 oC) and cold water from the depths (5 oC) of the ocean. Generating electricity is not the only function of OTEC as it can also produce significant amounts of fresh water. This can be very important, for example on islands and in some regions, such as Port Edward, where fresh water is limited. This thesis sets out to harness this fluidic energy, thus generating significant amounts of useful electric power for insertion into the national grid, as well as fresh water in Port Edward on the KwaZulu-Natal (KZN), South Coast. The site of Port Edward is naturally suited to the establishment of alternate energy collection sources such as OTEC; the geographical location of this region is additionally suited to the development of Open Cycle - Ocean Thermal Energy Conversion (OC- OTEC). Port Edward lies just beneath the tropic of cancer and on the shore of the Indian Ocean thus two important elements needed for OTEC namely constant sunlight and large coastal areas can easily be found in this region. More importantly, the steep drop in water depth down to 3000 meters makes this an ideal research site for ocean thermal energy conversion in KwaZulu-Natal (KZN). If the proposed theories are correct, this can possibly be used for base generated energy capacity and fresh water. The results are presented with reference to the temperature difference between the sea surface and the sea bottom because it is an important parameter in choosing an actual plant site and system design of OC-OTEC. This research is mainly laboratory based concentrating on design, calculations, modelling and simulation of OC-OTEC. The thermodynamic fluid calculations were undertaken with a view to design the main mechanical components of an OC-OTEC system, i.e. flash evaporator, condenser and steam turbine. SOLID EDGE software was utilized to design OC-OTEC plant and ASPEN PLUS V8.6 software was used to simulate and model the experiment. An OC-OTEC demonstration plant was designed and constructed in an Electrical Power Laboratory at Durban University of Technology (DUT). The experimental study was carried out on the demonstration plant with consideration given to water temperature, mass flow rate of fluid, and pressure. The measurements were taken before and after each component. The selection of a good process modelling and simulation tool was of extreme importance for the success of this work. Throughout the measurements, we found that the thermal efficiency (%) and the power output increased with increasing temperature difference Δt = tw - tc. The power output was produced when the total temperature difference was sufficient to allow heat transfer within the evaporator and provide a pressure drop across the turbine. There was more heat transfer (steam produced) in the flash evaporator at a constant flow rate because the warm water continuously supplied heat energy to the evaporator without losing much energy through the process, therefore continuous feed to the turbine improved constant power output. The thermal efficiencies were increased with increasing pressure across the turbine. The increase of pressure drops across the steam turbine caused the output power to increase. The larger flow rates of the warm water lead to higher amounts fresh water produced from the condenser. The final step in this process was the design of the main components of a practical plant to be used as a pilot plant at a selected location on the KwaZulu-Natal South coast. This will address the problem of lack of water in the region.

scholarly journals Finite-Time Thermodynamic Model for Evaluating Heat Engines in Ocean Thermal Energy Conversion

Entropy ◽  
2020 ◽  
Vol 22 (2) ◽  
pp. 211 ◽  
Author(s):  
Takeshi Yasunaga ◽  
Yasuyuki Ikegami
Keyword(s):  
Energy Conversion ◽  
Thermal Energy ◽  
Temperature Difference ◽  
Thermal Efficiency ◽  
Atmospheric Condition ◽  
Ocean Thermal Energy Conversion ◽  
Dead State ◽  
Heat Engines ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Ocean thermal energy conversion (OTEC) converts the thermal energy stored in the ocean temperature difference between warm surface seawater and cold deep seawater into electricity. The necessary temperature difference to drive OTEC heat engines is only 15–25 K, which will theoretically be of low thermal efficiency. Research has been conducted to propose unique systems that can increase the thermal efficiency. This thermal efficiency is generally applied for the system performance metric, and researchers have focused on using the higher available temperature difference of heat engines to improve this efficiency without considering the finite flow rate and sensible heat of seawater. In this study, our model shows a new concept of thermodynamics for OTEC. The first step is to define the transferable thermal energy in the OTEC as the equilibrium state and the dead state instead of the atmospheric condition. Second, the model shows the available maximum work, the new concept of exergy, by minimizing the entropy generation while considering external heat loss. The maximum thermal energy and exergy allow the normalization of the first and second laws of thermal efficiencies. These evaluation methods can be applied to optimized OTEC systems and their effectiveness is confirmed.

Multi-Energy System Based on Ocean Thermal Energy Conversion

2020 ◽  
Author(s):  
Zhihao Li ◽  
Jiapeng Su ◽  
Hui Yu ◽  
Anjun J. Jin ◽  
Jing Wang
Keyword(s):  
Power Generation ◽  
Energy Conversion ◽  
Thermal Energy ◽  
System Level ◽  
Energy Output ◽  
System Efficiency ◽  
Ocean Thermal Energy Conversion ◽  
Complementary System ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy

Abstract The ocean thermal energy is abundant and is ready for clean energy output. Firstly, the global total is about 40 billion kW. The ocean thermal energy conversion (OTEC) is clean and renewable, the power generation is stable, and the energy stored capacity is high. Active exploitation of ocean thermal energy resources is of great significance to realize the strategy of maritime power. Next, in view of the efficiency limit of a traditional OTEC, authors propose an approach of multi-energy complementary system to improve the system efficiency based on OTEC. This approach integrates solar energy, wind energy and energy storage into a complementary OTEC system; this complementary system sets parameters at the system level. For example, a 1 MW integrated power generation system is designed. Moreover, by calculating a theoretical model, researchers investigate the system with computer aided design and simulation. The efficiency of the complementary OTEC system with solar heating can reach 12.8% and the comprehensive efficiency can reach 18.6%. Furthermore, there are many favorable by-products of OTEC that are considered beneficial for the eco-system. Finally, in this paper, the basic principle and working process of the approach are analyzed, and the system efficiency is calculated. The results show that in comparison to the traditional OTEC, the complementary system can improve the ratio of power generation output efficiency, stability and ocean energy utilization.

Ocean Thermal Energy Conversion (OTEC) as Base Load Renewable Power

2014 ◽  
Author(s):  
Laurence J. Shapiro
Keyword(s):  
Power Generation ◽  
Energy Conversion ◽  
Thermal Energy ◽  
Technology Development ◽  
Rankine Cycle ◽  
Solar Pv ◽  
Ocean Thermal Energy Conversion ◽  
Thermal Energy Conversion ◽  
Ocean Thermal Energy ◽  
Base Load

Ocean Thermal Energy Conversion (OTEC) is a form of renewable solar energy that has the capability to provide 24 hour base load, dispatchable power to electrical systems. This is a major advantage over solar PV and wind, which are intermittent and can have significant adverse effects on grid stability once penetration exceeds 10% of grid capacity. This paper describes OTEC technology, suitable areas for implementation, current levels of technology development, regulatory barriers, problems posed by intermittent power generation as well as how it is differentiated from intermittent renewable technologies and can enhance grid stability. The discussion of the OTEC technology will include the underlying thermodynamics, critical heat transfer requirements and efficiency issues associated with low temperature Rankine Cycle applications. The discussion of suitable areas for implementation will include required ocean temperatures, ocean topography, current fuel dependence and regulatory issues to be addressed. The discussion of problems posed by intermittent power generation on networks will include transient response of grids to sudden changes in production as well as ramp rate requirements as solar PV comes on and off line on a daily cycle. OTEC, as a base load generation source, will be discussed in terms of market factors and reserve requirements.

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