scholarly journals Hydrodynamic Effects of Tidal-Stream Power Extraction for Varying Turbine Operating Conditions

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3240
Author(s):  
Lilia Flores Mateos ◽  
Michael Hartnett
Keyword(s):  
Thrust Force ◽  
Operating Conditions ◽  
Blockage Ratio ◽  
Stream Power ◽  
Power Extraction ◽  
Tidal Stream ◽  
Electrical Generation ◽  
Hydrodynamic Effects ◽  
Turbine Wake ◽  
Tidal Stream Power

Realistic evaluation of tidal-stream power extraction effects on local hydrodynamics requires the inclusion of the turbine’s operating conditions (TOC). An alternative approach for simulating the turbine’s array energy capture at a regional scale, momentum sink-TOC, is used to assess the impact of power extraction. The method computes a non-constant thrust force calculated based on the turbine’s operating conditions, and it uses the wake induction factor and blockage ratio to characterise the performance of a turbine. Additionally, the momentum sink-TOC relates the changes produced by power extraction, on the velocity and sea surface within the turbine’s near-field extension, to the turbine’s thrust force. The method was implemented in two hydrodynamic models that solved gradually varying flows (GVF) and rapidly varying flows (RVF). The local hydrodynamic effects produced by tidal-stream power extraction for varying the turbine’s operating conditions was investigated in (i) the thrust and power coefficient calculation, (ii) flow rate reduction, and (iii) tidal currents’ velocity and elevation profiles. Finally, for a turbine array that operates at optimal conditions, the potential energy resource was assessed. The maximisation of power extraction for electrical generation requires the use of an optimum turbine wake induction factor and an adequate blockage ratio, so that the power loss due to turbine wake mixing is reduced. On the other hand, the situations where limiting values of these parameters are used should be avoided as they lead to negligible power available. In terms of hydrodynamical models, an RVF solver provided a more accurate evaluation of the turbine’s operating conditions effect on local hydrodynamics. Particularly satisfactory results were obtained for a partial-fence. In the case of a fence configuration, the GVF solver was found to be a computationally economical tool to pre-assess the resource; however, caution should be taken as the solver did not accurately approximate the velocity decrease produced by energy extraction.

scholarly journals The impact of seabed rock roughness on tidal stream power extraction

Energy ◽  
2016 ◽  
Vol 112 ◽  
pp. 762-773 ◽  
Author(s):  
Nicolas Guillou ◽  
Jérôme Thiébot
Keyword(s):  
Stream Power ◽  
Power Extraction ◽  
Tidal Stream ◽  
The Impact ◽  
Tidal Stream Power

scholarly journals The available power from tidal stream turbines in the Pentland Firth

2013 ◽  
Vol 469 (2157) ◽  
pp. 20130072 ◽  
Author(s):  
Thomas A. A. Adcock ◽  
Scott Draper ◽  
Guy T. Houlsby ◽  
Alistair G. L. Borthwick ◽  
Sena Serhadlıoğlu
Keyword(s):  
Numerical Model ◽  
Large Fraction ◽  
Field Measurements ◽  
Stream Power ◽  
Power Extraction ◽  
Actuator Disc ◽  
Tidal Stream ◽  
Set Up ◽  
Swept Area ◽  
Tidal Stream Power

This paper assesses an upper bound for the tidal stream power resource of the Pentland Firth. A depth-averaged numerical model of the tidal dynamics in the region is set-up and validated against field measurements. Actuator disc theory is used to model the effect of turbines on the flow, and to estimate the power available for generation after accounting for losses owing to mixing downstream of the turbines. It is found that three rows of turbines extending across the entire width of the Pentland Firth and blocking a large fraction of the channel can theoretically generate 1.9 GW, averaged over the spring–neap cycle. However, generation of significantly more power than this is unlikely to be feasible as the available power per additional swept area of turbine is too small to be viable. Our results differ from those obtained using simplified tidal channel models of the type used commonly in the literature. We also use our numerical model to investigate the available power from rows of turbines placed across various subchannels within the Pentland Firth, together with practical considerations such as the variation in power over the spring–neap tidal cycle and the changes to natural tidal flows which result from power extraction.

scholarly journals Incorporation of a Non-Constant Thrust Force Coefficient to Assess Tidal-Stream Energy

Energies ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 4151 ◽  
Author(s):  
Lilia Flores Mateos ◽  
Michael Hartnett
Keyword(s):  
Near Field ◽  
Regional Scale ◽  
Resource Assessment ◽  
Operating Conditions ◽  
Force Coefficient ◽  
Thrust Coefficient ◽  
Power Extraction ◽  
Energy Assessment ◽  
Tidal Stream ◽  
Tidal Stream Energy

A novel method for modelling tidal-stream energy capture at the regional scale is used to evaluate the performance of two marine turbine arrays configured as a fence and a partial fence. These configurations were used to study bounded and unbounded flow scenarios, respectively. The method implemented uses turbine operating conditions (TOC) and the parametrisation of changes produced by power extraction within the turbine near-field to compute a non-constant thrust coefficient, and it is referred to as a momentum sink TOC. Additionally, the effects of using a shock-capture capability to evaluate the resource are studied by comparing the performance of a gradually varying flow (GVF) and a rapidly varying flow (RVF) solver. Tidal-stream energy assessment of bounded flow scenarios through a full fence configuration is better performed using a GVF solver, because the head drop is more accurately simulated; however, the solver underestimates velocity reductions due to power extraction. On the other hand, assessment of unbounded flow scenarios through a partial fence was better performed by the RVF solver. This scheme approximated the head drop and velocity reduction more accurately, thus suggesting that resource assessment with realistic turbine configurations requires the correct solution of the discontinuities produced in the tidal-stream by power extraction.

Counter-Rotating Type Tidal-Stream Power Unit Playing Favorable Features in Various Ocean Circumstances

2013 ◽  
Author(s):  
Yuta Usui ◽  
Kohei Takaki ◽  
Toshiaki Kanemoto ◽  
Koju Hiraki
Keyword(s):  
Power Unit ◽  
Axial Force ◽  
Wire Rope ◽  
Stream Velocity ◽  
Vertical Force ◽  
Stream Power ◽  
Tidal Stream ◽  
Tandem Propellers ◽  
Tidal Stream Power ◽  
Cable Wire

The authors have invented the unique counter-rotating type tidal-stream power unit, which is composed of the tandem propellers and the double rotational armature type peculiar generator without the traditional stator. In the unit of the downstream type, the front and the rear propellers counter-drive the outer and the inner armatures of the peculiar generator respectively, in keeping the rotational torque counter-balanced between both propellers/armatures. This paper discusses and verifies experimentally the almighty features of the power unit. The axial force acting on the pillar increases naturally with the increase of not only the stream velocity but also the drag of the tandem propellers. Besides, the tandem propellers bring the symmetrical vertical force from side to side though the single propeller brings the force in one direction. The counter-balanced torque makes it possible to moor the power unit with only one cable/wire/rope, and the behavior of the submerged unit was confirmed experimentally.

scholarly journals Performance Research of Counter-rotating Tidal Stream Power Unit

2016 ◽  
Vol 9 (2) ◽  
pp. 129-136 ◽  
Author(s):  
Xuesong Wei ◽  
Bin Huang ◽  
Pin Liu ◽  
Toshiaki Kanemoto
Keyword(s):  
Power Unit ◽  
Stream Power ◽  
Tidal Stream ◽  
Performance Research ◽  
Tidal Stream Power

scholarly journals 1001 Development of Counter-Rotating Type Tidal Stream Power Unit

2013 ◽  
Vol 2013 (0) ◽  
pp. _1001-01_-_1001-02_
Author(s):  
Kohei TAKAKI ◽  
Yuta USUI ◽  
Toshiaki KANEMOTO
Keyword(s):  
Power Unit ◽  
Stream Power ◽  
Tidal Stream ◽  
Tidal Stream Power
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