Are Nearly all Tidal Stream
Turbines Designs Wrong
for the Pentland Firth?
Stephen Salter
Institute for Energy Systems
University of Edinburgh
S.Salter@ed.ac.uk
www.see.ed.ac.uk/~shs
No names, no pack drill.
EWTEC Patras 1998
Edinburgh vertical-axis, variable-pitch with rim power take off.
. . . just like wind turbines but under water.
P max
1
2
3 16
 AU 
27
Frederick Lanchester 1868-1946 Albert Betz 1885-1968
Turbine in a duct:
P max  gAUH
Open flow field
Duct
1
3 16
Pow   AU 
2
27
Pow   gAH U
3
.296U
gH U
1.4
B=0.59
1.2
B=0.47
1
CP at peak
Betz Limit
0.8
0.6
0.4
0.2
0
0.00
0.02
0.04
0.06
0.08
0.10
0.12
Froude number
0.14
0.16
0.18
0.20
McAdam RA, Houlsby GT, Oldfield MLG.
Experimental measurements of the hydrodynamic
performance and structural loading of the transverse horizontal
axis water turbine: part 1.
Renewable Energy vol. 59 pp. 105-114. 2013
3
 2.75  0.55


 3.35
O’Doherty DM. Mason-Jones, Morris, O’DohertyT, Bryne, Pricket, Grosvenor.
Interaction of Marine Turbines in Close Proximity. EWTEC 2011
D ow nst ream force on a 1 40 di amet er rot o r as a fract io n o f id eal
1.2
1.2
1
0.8
fds i 4
FDSi 4
0.6
0.4
0.2
0
0
 70  60  50  40  30  20  10
 DR
2
0
Xi
10
20
30
40
50
60
DR
2
70
NASA
EWTEC Patras 1998
Edinburgh vertical-axis, variable-pitch with rim power take off.
Flow Impedance
The determination of the water to flow despite the
introduction of obstacles.
Flow Impedance
The determination of the water to flow despite the
introduction of obstacles.
Ratio of head increase to flow-rate reduction.
Flow Impedance
The determination of the water to flow despite the
introduction of obstacles.
Ratio of head increase to flow-rate reduction.
m. sec sec
Z
 2
3
m
m
Flow Impedance
The determination of the water to flow despite the
introduction of obstacles.
Ratio of head increase to flow-rate reduction.
m. sec sec
Z
 2
3
m
m
sec 1
Z 2.
m rho. g
Flow Impedance
The determination of the water to flow despite the
introduction of obstacles.
Ratio of head increase to flow-rate reduction.
m. sec sec
Z
 2
3
m
m
sec 1
Z 2.
m rho. g
DeltaH
Z
2
Power
Flow Impedance
The determination of the water to flow despite the
introduction of obstacles.
Ratio of head increase to flow-rate reduction.
m. sec sec
Z
 2
3
m
m
sec 1
Z 2.
m rho. g
DeltaH
Z
2
Power
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 = ?
68 mm
bob
Pentland bed stills. P Hayes. Fisheries Research Aberdeen 2006-8
Friction coefficients for Fshear = 0.5 ρ U2 Cf
6.165 TW x 0.04 = 247 GW
GOOGLE IMAGES
MoD order the stretcher bearers to be at the same end ?
No tip-to-hub velocity reduction
No squeezing torque through a bearing.
On-line shirt-sleeve access at the surface.
Thousands of force lines.
Contact-free gutter seal.
Lots of space.
Are Nearly all Tidal Stream
Turbines Designs Wrong
for the Pentland Firth?
Stephen Salter
Institute for Energy Systems
University of Edinburgh
S.Salter@ed.ac.uk
www.see.ed.ac.uk/~shs
Google images
Google images
Speed up x 30
Range up x 6000
Payload up x 20,000
Cost per ton-mile down ÷ 100
Something for the simpletons
R.A. McAdam , G.T. Houlsby , M.L.G. Oldfield
Structural and Hydrodynamic Model Testing of the Transverse
Horizontal Axis Water Turbine
EWTEC 2011
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
No names, no pack drill.
R.A. McAdam, G.T. Houlsby, M.L.G Oldfield. Structural and Hydrodynamic Model
Testing of the Transverse Horizontal Axis Water Turbine. EWTEC 2011