Inflow Measurement in a Tidal Strait for Deploying Tidal Current Turbines: Lessons, Opportunities and Challenges

Tidal energy has received increasing attention over the past decade. This increasing focus on capturing the energy from tidal currents has brought about the development of many designs for tidal current turbines. Several of these turbines are progressing rapidly from design to prototype and pre-commercial stages. As these systems near commercial development, it becomes increasingly important that their performance be validated through laboratory tests (e.g., towing tank tests) and sea tests. Several different turbine configurations have been tested recently. The test results show significant differences in turbine performance between laboratory tests, numerical simulations, and sea tests. Although the mean velocity of the current is highly predictable, evidence suggests a critical factor in these differences is the unsteady inflow. To understand the physics and the effect of the inflow on turbine performance and reliability, Verdant Power (Verdant) and the National Renewable Energy Laboratory (NREL) have engaged in a partnership to address the engineering challenges facing marine current turbines. As part of this effort, Verdant deployed Acoustic Doppler Current Profiler (ADCP) equipment to collect data from a kinetic hydropower system (KHPS) installation at the Roosevelt Island Tidal Energy (RITE) project in the East River in New York City. The ADCP collected data for a little more than one year, and this data is critical for properly defining the operating environment needed for marine systems. This paper summarizes the Verdant-NREL effort to study inflow data provided by the fixed, bottom-mounted ADCP instrumentation and how the data is processed using numerical tools. It briefly reviews previous marine turbine tests and inflow measurements, provides background information from the RITE project, and describes the test turbine design and instrumentation setup. This paper also provides an analysis of the measured time domain data and a detailed discussion of shear profiling, turbulence intensity, and time-dependent fluctuations of the inflow. The paper concludes with suggestions for future work. The analysis provided in this paper will benefit future turbine operation studies. In addition, this study, as well as future studies in this topic area, will be beneficial to environmental policy makers and fishing communities.

Improvement of Torque Performance of a Vertical Axis Type Marine Turbine for a Water Current Generation System

This paper describes the possibility of an improvement of torque performance and hydrodynamic forces on a vertical axis type water turbine, used for marine current generating system. The water turbine analyzed here is based on a Darrieus turbine with vertical blades. We considered possibilities of controlling the angle of attack of blades in order to improve the starting performance and to reduce energy loss during the rotation of the turbine. We used blade-element/ momentum theory in order to investigate the variations appearing in torque performance when the angle of attack were controlled. We also proved the validity of our predictions of hydrodynamic forces on the blade and the turbine, made through CFD calculation, by comparing them with the results of corresponding model tests in a current channel. In the corresponding model test we investigated not only the hydrodynamic forces on the turbine with three fixed blades, but also the inline force and the cross-flow force on the rotating turbine with three blades. Regarding the cyclic pitching of turbine blades, results suggest that significant increase in average turbine torque is possible.

Concept Design of Mining System of Seafloor Hydrothermal Deposit

Japan Deep Sea Technology Association had carried out concept design of the mining system for seafloor hydro-thermal deposit from 2008 through 2009. Through this concept design, the economic evaluation of the system with parameter of annual production of the ore was discussed, and it was clarified that more than 500 thousand tons annually would enable us to get positive balance. The environmental effect by mining was also discussed and was concluded that the active hydrothermal vents are not the targets of mining, instead, the dead vents are the targets. Then, the technological feasibility of each subsystem was discussed which constitutes the mining system, from the digger to the surface transporter. Finally, it was concluded that the mining system for hydrothermal deposits is feasible using the state-of-the-art technology even in rough sea around Japan.

An Integral Design Approach for Deep Sea Mining Systems Using Dredging Technology

Experience in the area of wet mining and the dredging industry learns that the excavation system cannot be seen separate from the slurry transportation system. These two key systems in a deep sea mining operation interrelate to such extend that they must be developed towards an integral solution. The nominal production, peak production and variability of these figures must match for all sub-systems in the overall mining system to optimize for mining efficiency; we call this the ‘game of capacities’. Also the configuration of the excavation and transport system has great consequences. For instance an important question is whether to place the first pump and its drive of the slurry transport system on the seafloor mining tool or in the riser system. The choices made impact amongst others on; the mining tool’s reach (and thus efficiency), the seafloor mining tool’s propulsion system and its geo-mechanical interaction, the slurry transport flow and pumping power requirements. This paper will discuss the several dependencies of the (producing) subsystems and important choices for configuration and their consequences regarding technology, capex, opex, reliability and maintainability.

Subsea Slurry Lift Pump for Deepsea Mining

Recent developments in subsea mining as well as oil & gas exploration and development drilling will require the use of a subsea pumping solution capable of handling slurries. These slurries are characterized by relatively large particle sizes and non-uniform flow conditions including fluctuating solids concentrations, densities, viscosities, and maximum particle size in both the mining and drilling applications. While challenging enough in surface applications, slurry transport problems are exacerbated by the vertical lift required in subsea use. This paper will first present the effect of each varying parameter on the overall horsepower required. Additionally, the pumping efficiency of some different pump types when responding to these changing conditions will be shown. From a control perspective, altering a pump’s speed in response to changing flow conditions presents some unique challenges. As an alternative to adjusting a rotary pump’s speed, an algorithm to control a positive displacement pumping solution to automatically adjust its output in this application is presented.

Numerical Study on Circulation and Thermohaline Structures With Effects of Icing Event in the Caspian Sea

A hydrostatic and ice coupled model was developed to analyze circulation and thermohaline structures in the Caspian Sea. The northern part of the Caspian Sea freezes in the winter. Waters start icing in November and ices spread during December and January. The northern part of the Caspian Sea is covered by ices in severe winters. Ice-covered area is at its maximum during January and February, and then ices begin melting in March and disappear in April. The occurrence of ices must have significant effects on circulation and thermohaline structures as well as ecosystem in the northern Caspian Sea. In the present study, formation of ices is modeled assuming that ices do not move but spread and shrink on water surface. Under the ices, it is assumed that the exchange of momentum flux is impeded and the fluxes of heat and brine salt are given at sea-ice boundary. The ice model was coupled with a hydrostatic model based on MEC (Marine Environmental Committee) Ocean Model developed by the Japan Society of Naval Architect and Ocean Engineers. Numerical simulation was carried out for 20 years to achieve stable seasonal changes in current velocity, water temperature, and salinity. The fluxes of momentum, heat, and salt were estimated by using measurement data at 11 meteorological stations around the Caspian Sea. Inflow of Volga River was taken into account as representative of all the rivers which inflow into the Caspian Sea. Effects of icing event on circulation and thermohaline structures were discussed using the results of numerical simulation in the last year. As a result, the accuracy of predicting water temperature in the northern Caspian Sea was improved by taking the effects of icing event into account. Differences in density in the horizontal direction create several gyres with the effects of Coriolis force. The differences were caused by differences in heat capacity between coastal and open waters, differences in water temperature due to climate, and inflow of rivers in the northern Caspian Sea. The water current field in the Caspian Sea is formed by adding wind-driven current to the dominant density-driven current, which is based on horizontal differences in water temperature and salinity, and Coriolis force.

Analysis of Practical Examples of Experienced-Based Marine Education for Marine Space Utilization

Environmental education is being promoted worldwide and is the subject of active effort in Japan as well. However, many environmental education programs focus on land-based systems, and currently only few schools have programs on the marine environment. Toward the goal of developing an educational game for advancing marine environmental education, we assessed the current state of environmental education and conducted basic research on existing educational games. The current state of environmental education indicated a need for developing educational games with a marine environmental theme to be linked with outdoor hands-on activities. As for the game itself, a card game is likely to be a suitable basic format because it can be used regardless of physical setting and also because the use of a variety of cards can be effective in maintaining continued interest and developing the capacity to understand the annual cycle of the natural environment. We also developed a region-specific card game whose objectives were to understand the region’s organisms and the relationship between people and the environment.

Study on Advanced Use and Social Value of Existing Fishing Port Space

In recent years, the fishery population in Japanese fishing ports has halved with a decline of the fishery industry, and the use of fishing port facilities has also been declining. Because of this, there is a demand for effective use of existing fishing ports, which have thus far served only for the primary industry, and there is a transition in their use to higher order industries, indicating a change in the social value of fishing ports. In this study, the social value for realizing the higher order use of fishing port space was analyzed based on the locations of the port, the value of the land, and social needs. Although, with the current classification, 2921 existing fishing ports can be classified into 5 categories, designated class III fishing ports (13 ports), class III fishing ports (114 ports), class II fishing ports (496 ports), class I fishing ports (2210 ports), and class IV fishing ports (101 ports), the findings of this study were applied to develop a new classification which incorporated new social conditions. In this paper, the social value of fishing ports in modern society is shown, and a new classification of fishing ports which differs from the current system based solely on the port size is discussed, taking their social value into consideration.

A Systematic Approach for Quantitative Environmental Assessment of Seafloor Massive Sulfide Mining

Seafloor massive sulfides have been a subject of interest for profitable commercial mining these ten years. However, less information is available for both the baseline ecosystems in the distribution areas and the environmental impacts on them caused by the mining. Owing to growing concern for the global and local environments, the quantitative understanding of the environmental impacts, the systematic environmental assessment, and the effective control and regulation methods of seafloor massive sulfide mining must be clarified. A systematic approach necessary for the clarification is discussed. An example design of artificial impact experiment and the monitoring are introduced. An international initiative is proposed.

Dynamic Model Development and Simulation Analysis of China’s Total Integrated Deep Ocean Mining Pilot System

A typical and may be the most prospective deep ocean mining system is an integration of a mining ship system, a hoist pipeline system and a self-propelled seafloor miner system. According to this representative system configuration, China has designed and developed a deep ocean mining pilot system. In order to evaluate and improve the design of the pilot system, and further to provide technical references for the practical system operation, dynamic simulation models of the subsystems and the total integrated system are developed. For the seafloor miner, a multi-body model with the scale of 1:1 to the actual size of the pilot miner is built, which can be used effectively to perform detailed design, analysis and optimization of the miner system. Meanwhile, to make the integration of the total mining system possible, a simplified 3D single-body model with 6 DOF of the miner is also developed, which is capable of real-time simulation and can be easily integrated with other subsystems. For the pipeline system including the rigid lifting pipe, submerged pump, buffer storage and flexible hose, finite element method (FEM) and discrete element method (DEM) are all proposed and developed. With the FEM model, the towing mining operation process, as well as the launching and retrieval process, can be analyzed. Whereas, the DEM model is preferred to perform the dynamic analysis of the total integrated mining system due to its relative high computation efficiency compared with that of the FEM model. To realize the dynamic analysis of the total integrated mining system with relative high efficiency and accuracy, the single body model of the miner and the DEM model of the pipeline are chosen to be integrated to form the total system and perform dynamic analysis, which in a way can provide specific guidance and suggestions for the practical deep ocean mining system analysis, operation and control. For further researches, more attention will be focused on the analysis of the launching and retrieval operation process of the total mining system, including the water entry of the miner, the launching process of the pipeline system and the final seafloor-touchdown of the miner.