Development of an ocean-current turbine for the Kuroshio ... · a Okinawa Institute of Science and...
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Development of an ocean-current turbine for the Kuroshio current Katsutoshi Shirasawa 1 * , Junichiro Minami 1 , Hidetsugu Iwashita 2 and Tsumoru Shintake 1 1 Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan 2 Graduate School of Engineering, Hiroshima University, Hiroshima 739-8527, Japan Abstract Ocean currents are a promising source of sustainable energy because the flow of water provides regular and predictable energy. Japan is in a suitable loca;on for harnessing the power of ocean currents because the Kuroshio ocean current runs steadily near the Japanese seaside. The current flow is approximately 500 m deep and 100 km wide with a flow speed of 1-1.5 m/s. In order to harness the kine;c energy of marine currents, we propose a novel ocean-current turbine. The turbines are moored to the seabed and func;on like kites in the water flow. To operate such turbines in the middle layer of a marine current, it is necessary to cancel the resul;ng rotor torque. Therefore, our turbine is designed with a float at its top and a counterweight at its boHom. Owing to buoyancy and gravita;onal force, the turbine body maintains its aItude stably by canceling the rotor torque. In other words, buoyancy and gravity act together as a righ;ng moment. Another advantage of working far from the sea surface is the lack of influence from waves and wind, especially in a typhoon. As a first step, we constructed a prototype turbine and conducted towing experiments in order to confirm the float and counterweight configura;on. Blade Torque (T) Buoyancy (F) Gravity (G) Counterweight Rotor Blade Float Nacelle Ocean Current 1-1.5 m/s Roll (θ) Major Diameter Minor Diameter Experimental verification of a floating ocean-current turbine with a single rotor for use in Kuroshio currents * Katsutoshi Shirasawa a, *, 1 , Kohei Tokunaga b , Hidetsugu Iwashita b , Tsumoru Shintake a a Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan b Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan article info Article history: Received 17 March 2015 Received in revised form abstract Ocean currents have excellent potential as future renewable energy resources. In order to harness the kinetic energy of marine currents, we propose a new ocean-current turbine. In general, ocean currents have sufficiently large cross sections. Thus, the turbines are moored to the seabed and function like kites Contents lists available at ScienceDirect Renewable Energy journal homepage: www.elsevier.com/locate/renene Renewable Energy 91 (2016) 189e195 Sinker Mooring Line Ocean Current Sea Level Turbine 100 m Seabed Over 500 m Float Nacelle Counterweight Pitch hHps://en.wikipedia.org/wiki/Kuroshio_Current Mo+va+on • Japan is suitable to harness the power of the ocean current. • Kuroshio Ocean Current runs steadily near Japan seaside. • Technical issues – Stability of a floa;ng body. • Cancel out a rotor torque. • Proposal of new ocean-current turbine – We started R&D in 2012. Prototype Turbine Energy Farm Kuroshio Current Principle Towing Experiment at Sea Reference Advantages • Stability – Ocean currents flow constantly. • Availability – The volume of the water flow is very large. • Predictability – The flow speeds and paths have been inves;gated thoroughly. • No visual impact – The turbine operates beneath the water surface. Measurement Result Ocean-current turbine system Rotor diameter 2 m Number of blades 3 Speed of flow 1~1.5 m/s Rated generator output 1 kW Cp (max.) 0.42 (TSR=4) Float volume 0.1 m 3 Counterweight( in air) 50 kg Conclusion • We have proposed a new ocean-current turbine. – Float and weight configura;on has worked very well. • We have developed the prototype turbine and performed towing test in the sea. • Output Ave. 300W(Peak 400 W) – good agreement with the expected value. – Moored floa;ng body has showed high body stability . • Mooring experiment using a scale model has been carried out with a circula;ng water channel. Parameters of the Prototype Turbine Float 390 g (Buoyancy 760gf) Nacelle + Blade 350 g Weight 520 g Scale model Dia. 250 mm Scale-model Test at Circula+on Water Channel Measured value Rotor diameter 1.46 m Number of blades 3 Tip speed ratio 4 C P (max.) 0.42 C T (max.) 0.63 Airfoil NACA642-415 Width 〜100 km, Depth 〜500 m, Speed 1〜1.5 m/s Rotor diameter 80 m, 1 Turbine: Output 3 MW @ 1.5 m/s Towing Tank Experiment Turbine Design Output Power Thrust Force
Transcript of Development of an ocean-current turbine for the Kuroshio ... · a Okinawa Institute of Science and...
Development of an ocean-current turbine for the Kuroshio current Katsutoshi Shirasawa1*, Junichiro Minami1, Hidetsugu Iwashita2 and Tsumoru Shintake1
1Okinawa Institute of Science and Technology Graduate University, Okinawa 904-0495, Japan 2Graduate School of Engineering, Hiroshima University, Hiroshima 739-8527, Japan
AbstractOceancurrentsareapromisingsourceofsustainableenergybecausetheflowofwaterprovidesregularandpredictableenergy.Japanisinasuitableloca;onforharnessingthepowerofoceancurrentsbecausetheKuroshiooceancurrentrunssteadilyneartheJapaneseseaside.Thecurrentflowisapproximately500mdeepand100kmwidewithaflowspeedof1-1.5m/s.Inordertoharnessthekine;cenergyofmarinecurrents,weproposeanovelocean-currentturbine.Theturbinesaremooredtotheseabedandfunc;onlikekitesinthewaterflow.Tooperatesuchturbinesinthemiddlelayerofamarinecurrent,itisnecessarytocanceltheresul;ngrotortorque.Therefore,ourturbineisdesignedwithafloatatitstopandacounterweightatitsboHom.Owingtobuoyancyandgravita;onalforce,theturbinebodymaintainsitsaItudestablybycancelingtherotortorque.Inotherwords,buoyancyandgravityacttogetherasarigh;ngmoment.Anotheradvantageofworkingfarfromtheseasurfaceisthelackofinfluencefromwavesandwind,especiallyinatyphoon.Asafirststep,weconstructedaprototypeturbineandconductedtowingexperimentsinordertoconfirmthefloatandcounterweightconfigura;on.
Blade Torque (T)
Buoyancy (F)�
Gravity (G)�
Counterweight�
Rotor Blade�
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Ocean Current 1-1.5 m/s �
(a) Side view� (b) Back view�
Roll (θ)�
Major Diameter�
Minor Diameter�
Experimental verification of a floating ocean-current turbine with asingle rotor for use in Kuroshio currents*
Katsutoshi Shirasawa a, *, 1, Kohei Tokunaga b, Hidetsugu Iwashita b, Tsumoru Shintake a
a Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japanb Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8527, Japan
a r t i c l e i n f o
Article history:Received 17 March 2015Received in revised form2 January 2016Accepted 6 January 2016Available online 28 January 2016
Keywords:Renewable energyOcean currentOcean-current turbineOcean energy
a b s t r a c t
Ocean currents have excellent potential as future renewable energy resources. In order to harness thekinetic energy of marine currents, we propose a new ocean-current turbine. In general, ocean currentshave sufficiently large cross sections. Thus, the turbines are moored to the seabed and function like kitesin the water flow. In the future, turbines will be installed approximately 100 m deep to avoid the in-fluence of surface waves; this is especially important during typhoons. To operate such turbines in themiddle layer of a marine current, it is necessary to cancel the resulting rotor torque. Therefore, ourturbine is designed with a float at its top and a counterweight at its bottom. Owing to buoyancy andgravity, the turbine maintains a stable position. We describe towing experiments carried out to confirmthe float and counterweight configuration and show that the results verify hydrostatic stability andelectric power generation for the proposed turbine.
© 2016 Elsevier Ltd. All rights reserved.
1. Introduction
There are several different oceanic energy forms: wave, marinecurrents, tidal currents, and thermal energy. Many studies arecurrently being carried out in order to realize commercial operationworldwide [1,2]. Ocean currents are also a promising source ofsustainable energy because the flow of water provides regular andpredictable energy. On the other hand, research and developmentare difficult technically and potentially costly. However, the de-mand for renewable energy sources has increased since theFukushima nuclear power plant disaster in 2011.
Japan is in a suitable location for harnessing the power of oceancurrents because the Kuroshio ocean current runs steadily near theJapanese seaside [3]. The Kuroshio current is a strong ocean currentin the western North Pacific Ocean. The current flow is approxi-mately 500mdeep and 100 kmwidewith a flow speed of 1e1.5m/s[4e6]. This appears to be a rather slow flow, but it is sufficient forgenerating electricity because the density of water is 800 timeshigher than that of air. The Kuroshio current has a power densityequivalent to that of a wind flow at 9e14 m/s. Moreover, the
Kuroshio current is an energy resource with only small fluctuationsin flow, regardless of the time of day or the season. As mentionedabove, an ocean-current turbine has many advantages for powerproduction; these include:
! Stability
Ocean currents flow constantly.
! Availability
The volume of the water flow is very large.
! Predictability
The flow speeds and paths have been investigated thoroughly.
! No visual impact
The turbine operates beneath the water surface.Tidal-current turbines have technologies in common with
ocean-current turbines. At the European Marine Energy Centre(EMEC), several tidal-current turbine projects are currently un-derway [7]. Most of these projects have adopted horizontal-axisturbines mounted onto the seabed. This means that, even though
* Fully documented templates are available in the elsarticle package on CTAN.* Corresponding author.
E-mail address: [email protected] (K. Shirasawa).1 Since 2012.
Contents lists available at ScienceDirect
Renewable Energy
journal homepage: www.elsevier .com/locate/renene
http://dx.doi.org/10.1016/j.renene.2016.01.0350960-1481/© 2016 Elsevier Ltd. All rights reserved.
Renewable Energy 91 (2016) 189e195
Sinker �
Mooring Line�
Ocean Current�
Sea Level�
Turbine�
�100 m�
Seabed�
Over 500 m�
Float�
Nacelle�
Counterweight�
Pitch�
hHps://en.wikipedia.org/wiki/Kuroshio_Current
Mo+va+on• Japanissuitabletoharnessthepoweroftheoceancurrent.
• KuroshioOceanCurrentrunssteadilynearJapanseaside.
• Technicalissues– Stabilityofafloa;ngbody.
• Canceloutarotortorque.
• Proposalofnewocean-currentturbine– WestartedR&Din2012.
PrototypeTurbine
EnergyFarm
KuroshioCurrent Principle
TowingExperimentatSea
Reference
Advantages
• Stability– Oceancurrentsflowconstantly.
• Availability– Thevolumeofthewaterflowisverylarge.
• Predictability– Theflowspeedsandpathshavebeeninves;gated
thoroughly.
• Novisualimpact– Theturbineoperatesbeneaththewatersurface.
MeasurementResult
Ocean-currentturbinesystem
Rotor diameter 2 m
Number of blades 3
Speed of flow 1~1.5 m/s
Rated generator output 1 kW
Cp (max.) 0.42 (TSR=4)
Float volume 0.1 m3
Counterweight( in air) 50 kg
Conclusion
• Wehaveproposedanewocean-currentturbine.– Floatandweightconfigura;onhasworkedvery
well.• Wehavedevelopedtheprototypeturbineand
performedtowingtestinthesea.• Output Ave.300W(Peak400W)
– goodagreementwiththeexpectedvalue.
– Mooredfloa;ngbodyhasshowedhighbodystability.
• Mooringexperimentusingascalemodelhasbeencarriedoutwithacircula;ngwaterchannel.
ParametersofthePrototypeTurbine
Scalemodel�
Float390g(Buoyancy760gf)
Nacelle+Blade350g
Weight520g
Scalemodel
Dia.250mm
Scale-modelTestatCircula+onWaterChannel
Measuredvalue�
Rotor diameter 1.46 m
Number of blades 3
Tip speed ratio 4
CP (max.) 0.42
CT (max.) 0.63
Airfoil NACA642-415
Width〜100km,Depth〜500m,Speed1〜1.5m/s
Rotordiameter80m,1Turbine:[email protected]/s
TowingTankExperiment TurbineDesign OutputPowerThrustForce
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