second oxford tidal stream workshop 2013 are nearly all tidal stream turbines designs wrong? stephen...

Second Oxford Tidal stream Workshop 2013

Are Nearly all Tidal Stream Turbines Designs Wrong?

Stephen Salter

Institute for Energy Systems

University of Edinburgh

S.Salter@ed.ac.uk

www.see.ed.ac.uk/~shs

S.Salter@ed.ac.ukS.Salter@ed.ac.uk

No names, no pack drill.S.Salter@ed.ac.uk

. . . just like wind turbines but under water.

Pmax1

2 A U

316

27

Frederick Lanchester 1868-1946 Albert Betz 1885-1968

Unswept flow passage ≡ leaky pipes

≡ Vortex wake pollution

≡ Ignorance of flow angles

O’Doherty DM. Mason-Jones A, Morris C, O’DohertyT, Bryne C, Pricket PW, Grosvenor RI.

Interaction of marine turbines in close proximity.

EWTEC 2011

2.75

3.35

3

0.55

O’Doherty DM. Mason-Jones, Morris, O’DohertyT, Bryne, Pricket, Grosvenor. Interaction of Marine Turbines in Close Proximity. EWTEC 2011

R.A. McAdam, G.T. Houlsby, M.L.G Oldfield. Structural and Hydrodynamic Model Testing of the Transverse Horizontal Axis Water Turbine. EWTEC 2011

R.A. McAdam , G.T. Houlsby , M.L.G. OldfieldStructural and Hydrodynamic Model Testing of the Transverse

Horizontal Axis Water Turbine EWTEC 2011

Pow1

2 A U

316

27 Pow g A H U

.296 U3 g H U

Open flow field Duct

Bending moment atblade root

http://www.google.co.uk/search?q=Tidal+stream+turbine+Alstom&hl=en&client=safari&rls=en&tbm=isch&tbo=u&source=u

niv&sa=X&ei=BOBOUbPSJY6o0wXh2ICIBw&ved=0CEIQsAQ&biw=1042&bih=1505

GOOGLE IMAGES

NASA

Edinburgh vertical-axis, variable-pitch with rim power take off.

EWTEC Patras 1998

Pitch variation gives control of rotor forces

Contra-rotation cancels cross force and torque reaction in wake

70 60 50 40 30 20 10 0 10 20 30 40 50 60 700

0.2

0.4

0.6

0.8

1

1.2Downstream force on a 140 diameter rotor as a fraction of ideal

1.2

0

fdsi 4

FDSi 4

DR

2

DR2

Xi

Work goes through restricted passage to congested generation space

Second Oxford Tidal stream Workshop 2013

Are Nearly all Tidal Stream Turbines Designs Wrong?

Stephen Salter

Institute for Energy Systems

University of Edinburgh

S.Salter@ed.ac.uk

www.see.ed.ac.uk/~shs

Google images

Speed up x 30Range up x 6000

Payload up x 20,000Cost per ton-mile down ÷ 100

Google images

Something for the simpletons

Laminaria Hyperborea (kelp) are found along the

edges of the Pentland Firth at depths up to 30 m.

Length can reach 3.5 metres.

Cf = ?

Google images.

Pentland bed stills. P Hayes. Fisheries Research Aberdeen 2006-8

68 mm bob

Friction coefficients for Fshear = 0.5 ρ U2 Cf

6.165 TW x 0.04 = 247 GW

Edinburgh vertical-axis, variable-pitch with rim power take off.

EWTEC Patras 1998