Tide EnergyTechnologies

San Jose State University

FX RongèreApril 2008

Tidal Dams

Tidal Dam

The dam creates a difference of potential energy between the tide pond and the open sea

Δz

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Power Generation

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Power Generation

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Power Generation

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With:

τ : tidal period

η : Turbine conversion rate

AT: Area of the turbine

R : Range of the tide

Apool: Area of the tidal pool

)()(.)()(..2. 21211 tztzsigntztz

g

A

A

dt

dz

pool

T

Basin Management

To optimize power generation the flow gates are kept closed some time after high and low tides Tide and Basin Management

La Rance

0

2

4

6

8

10

12

0 4 8 12 16 20 24

Time (hour)

Wat

er lev

el (m

) Po

wer

(M

W)

Sea Level

Basin Level

Power

La Rance Tidal Power Plant

Tide mean range: 8.4m Tide basin area: 22 km2

10 m9 m8 m7m6m5m4m3m

La Rance Tidal Power Plant

24 Units of 10 MW each built between 1961 and 1967

700 m dam 480 GWh/y CF=23%

The Severn Barrage (UK) Capacity: 8,640 MW, 17 TWh, CF= 23%,

Length=15.9 km

In the Bristol Channel Range 8.2 m, Basin Area: 480 km2

The Severn Barrage (UK)

Economics

Severn Barrage costsMM MM

Civil Engineering 4,900£ 9,800$ Power Generation 2,400£ 4,800$ Power Control 380£ 760$ Management 300£ 600$ Land sea defences 30£ 60$ Effluent Discharge 80£ 160$

Total 8,090£ 16,180$ Additional cost (Grid) 1,230£ 2,460$

Total investment cost 9,320£ 18,640$ Annual Maintenance cost 70£ 140$ Generation 17 TWhAnnual Revenues ($60/MWh) 595£ 1,190$ Simple Payback Period 15 years

The Severn Barrage (UK)

Tidal Streams

There are generated by the difference of water levels

Golden Gate Currents

Current Golden Gate San Farncisco - 21-24 November 2007

1.8

6.6

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2.2

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Time (hours)

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rent

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Model

BasinOcean R

C

z1z2

tctm

tbtz

then

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If

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.cos.

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2z1 has the same period as z2 and a phase-shiftCurrent has the same period as z2 and is in quadrature with z1

Current Power

The power of the current is similar to the power of the wind

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Available energy is proportional to the cube of the current velocity

2..

3vAW Max

Power Density

(m/s) (Miles/h) (knots) (W/m2)1 2.2 1.9 5002 4.5 3.9 4,0003 6.7 5.8 13,5004 8.9 7.8 32,0005 11.2 9.7 62,500

Current Speed

Shear Effect

Current Velocity Profile (3 knots at

the surface - depth 10m - exp 0.16)

0

2

4

6

8

10

12

0.00 0.50 1.00 1.50 2.00 2.50 3.00

Velocity (Knots)

Altitude fro

m the b

otto

m (m

)

The Golden Gate Site

Golden Gate

maximum depth = 377 feet

Turbine main components

Rotor• Extracts power from flow• Turns at low RPM 10-30

rpm• Efficiency varies with flow

velocity (45% max)

Gearbox• Increase rotational speed

of shaft from turbine• 80-95% efficient

Foundation• Secure turbine to seabed• Resist drag on support

structure and thrust on rotor

Generator and Power Conditioning• Generate electricity• Condition electricity

for grid interconnection

• Turns at high RPM• 95-98% efficient

Source: Brian Polagye Tidal In-Stream Energy Overview March 6, 2007

General concept is similar to wind turbines

Turbines

2...

3vAW TT

η is the conversion rate of the turbine, typically 25% to 35%

300 kW, 6 m prototype developed by Marine Current Technologies in operation in the Bristol Channel since 2003

1 MW, 20m twin rotor prototype currently developed by Marine Current Technologies installed in Northern Ireland’s Strangford Lough (2008)

Marine Current Technologies

Strangford Lough project

Strangford Lough project

Turbines

Verdant Power

35 kW, 5m Diameter turbine developed by Verdant. Prototype installed in New York at Roosevelt Island (2006 2008). Project of 175 kW

Turbines

Lunar Energy

2 MW, 21m 7 blade rotor prototype currently in development

Gravity Foundation: concrete slab

Power augmentation by convergent-divergent ducting to increase conversion rate

Promising since 2

...3v

AW TT

Turbines

Clean Current Pile Mounted 4 bladed, 14 m, 1 MW A 65 kW prototype has

been Tested at Race Rocks from Sep 2006 to May 2007

Race Rock is a marine reserve run by Lester B.Pearson College on Vancouver Island (Canada)

Turbines

Open Hydro Open Center

Rotor Diameter 15 m rated at 1.5 MW

Operating Conditions: Current speed > 0.7 m/s Prototype under test at European Marine Energy Center (UK) – Dec. 2006

Source: Bruce H. Adee Tidal Power Technology Update August 9, 2007

Gorlov Different mounting

Prototype has been tested at Uldomok Strait in Korea in 2002

1 m diameter and 2.5 m high 1.5 kW

Enemar KoboldMoored – surface mounted3 vertical articulating blades vertical: 5.0 m diameter: 6 m chord: 0.4 m25 kW @ 2.0 m/sPrototype has been deployed in Straits of Messina 4 years operational experience

The Energy Business Limited

Foundation TechnologiesMonopile

• Small footprint• Established technology

used in offshore wind

Gravity Base

Chain Anchors

Tension Leg

Hollow steel pile driven or drilled into seabed

Pros:

• High cost in deep water• Installation expensive

for some types of seabed

Cons:

Heavy foundation of concrete and low cost aggregate placed on seabed

• Deep water installation feasible

Pros:

• Large footprint• Scour problems for some

types of seabed• Decommissioning

problems

Cons:

• Small footprint• Deep water

installation feasible

Chains anchored to seabed and turbine

Pros:

• Problematic in practice• Device must have high

natural buoyancy

Cons:

Submerged platform held in place by anchored cables under high tension

• Small footprint• Deep water

installation feasible

Pros:

• Immature technology now being considered for offshore wind in deep water

Cons:

(10-40m)

Source: Brian Polagye Tidal In-Stream Energy Overview March 6, 2007

Projects Worldwide

Gulf Stream Current

Florida Current Resource

2..

3vAW Max

1.9 2.4 2.8 3.1Current speed (knots)

Companies to follow Blue Energy Canada Clean Current Technology Marine Current Turbines GCK (Gorlov) Lunar Energy Open Hydro Enemar Kobold Verdant Power Seapower Tidal Electric Aquantis

Annapolis Tidal Generating Station (USA)